Santander Uk 20-F 5 Mar 24 2023 FY Annual report (foreign) Financial data

Cover Page

Cover Page	12 Months Ended
	Dec. 31, 2023 shares
Document And Entity Information [Line Items]
Document Type	20-F
Document Registration Statement	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Document Shell Company Report	false
Entity File Number	001-37595
Entity Registrant Name	Santander UK Group Holdings plc
Entity Incorporation, State or Country Code	X0
Entity Address, Address Line One	2 Triton Square
Entity Address, Address Line Two	Regent’s Place
Entity Address, City or Town	London
Entity Address, Postal Zip Code	NW1 3AN
Entity Address, Country	GB
Entity Common Stock, Shares Outstanding	7,060,000,000
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Document Accounting Standard	International Financial Reporting Standards
Entity Shell Company	false
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Central Index Key	0001649373
Business Contact
Document And Entity Information [Line Items]
Entity Address, Address Line One	2 Triton Square
Entity Address, Address Line Two	Regent’s Place
Entity Address, City or Town	London
Entity Address, Postal Zip Code	NW1 3AN
Entity Address, Country	GB
Contact Personnel Name	Lee Grant
City Area Code	+44
Local Phone Number	800 085 1491
Contact Personnel Email Address	lee.grant@santander.co.uk
1.089% Fixed Rate/Floating Rate Notes due 2025
Document And Entity Information [Line Items]
Title of 12(b) Security	1.089%  Fixed Rate/Floating Rate Notes due 2025
Trading Symbol	SAN/25C
Security Exchange Name	NYSE
1.532% Fixed Rate Resetting Notes due 2026
Document And Entity Information [Line Items]
Title of 12(b) Security	1.532%  Fixed Rate Resetting Notes due 2026
Trading Symbol	SAN/26
Security Exchange Name	NYSE
1.673% Fixed Rate/Floating Rate Notes due 2027
Document And Entity Information [Line Items]
Title of 12(b) Security	1.673%  Fixed Rate/Floating Rate Notes due 2027
Trading Symbol	SAN/27A
Security Exchange Name	NYSE
3.823% Fixed Rate/Floating Rate Notes due 2028
Document And Entity Information [Line Items]
Title of 12(b) Security	3.823%  Fixed Rate/Floating Rate Notes due 2028
Trading Symbol	SAN/28
Security Exchange Name	NYSE
2.896% Fixed Rate/Floating Rate Notes due 2032
Document And Entity Information [Line Items]
Title of 12(b) Security	2.896%  Fixed Rate/Floating Rate Notes due 2032
Trading Symbol	SAN/32
Security Exchange Name	NYSE
2.469% Fixed Rate/Floating Rate Notes due 2028
Document And Entity Information [Line Items]
Title of 12(b) Security	2.469%  Fixed Rate/Floating Rate Notes due 2028
Trading Symbol	SAN/28A
Security Exchange Name	NYSE
6.833% Fixed Rate/Floating Rate Notes due 2026
Document And Entity Information [Line Items]
Title of 12(b) Security	6.833%  Fixed Rate/Floating Rate Notes due 2026
Trading Symbol	SAN/28B
Security Exchange Name	NYSE
6.534% Fixed Rate/Floating Rate Notes due 2029
Document And Entity Information [Line Items]
Title of 12(b) Security	6.534%  Fixed Rate/Floating Rate Notes due 2029
Trading Symbol	SAN/29B
Security Exchange Name	NYSE

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Audit Information [Abstract]
Auditor Firm ID	876
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	London, United Kingdom

Consolidated Income Statement

Consolidated Income Statement - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Profit (loss) [abstract]
Interest and similar income	£ 11,853	£ 6,822	£ 4,830
Interest expense and similar charges	(7,186)	(2,350)	(833)
Net interest income	4,667	4,472	3,997
Fee and commission income	801	836	694
Fee and commission expense	(505)	(512)	(414)
Net fee and commission income	296	324	280
Other operating income	213	210	267
Total operating income	5,176	5,006	4,544
Operating expenses before credit impairment charges, provisions and charges	(2,485)	(2,370)	(2,540)
Impairment Loss On Financial Assets 1	(206)
Credit impairment (charges)/write-backs		(321)	233
Provisions for other liabilities and charges	(336)	(421)	(379)
Total operating credit impairment charges, provisions and charges	(542)	(742)	(146)
Profit from continuing operations before tax	2,149	1,894	1,858
Tax on profit from continuing operations	(553)	(471)	(485)
Profit from continuing operations after tax	1,596	1,423	1,373
Profit from discontinued operations after tax	0	0	32
Profit after tax	1,596	1,423	1,405
Attributable to:
Equity holders of the parent	1,596	1,406	1,369
Non-controlling interests	0	17	36
Profit after tax	£ 1,596	£ 1,423	£ 1,405

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of comprehensive income [abstract]
Profit after tax	£ 1,596	£ 1,423	£ 1,405
Movement in fair value reserve (debt instruments):
- Change in fair value	89	(278)	(111)
- Income statement transfers	(105)	247	110
- Taxation	5	11	(2)
Other comprehensive income, fair value reserve (debt instruments)	(11)	(20)	(3)
Cash flow hedges:
- Effective portion of changes in fair value	(147)	436	(875)
- Income statement transfers	1,231	(2,130)	357
- Taxation	(302)	468	142
Other comprehensive income, cash flow hedges, total	782	(1,226)	(376)
Net other comprehensive income/(expense) that may be reclassified to profit or loss subsequently	771	(1,246)	(379)
Pension remeasurement:
- Change in fair value	(598)	(723)	1,263
- Taxation	167	267	(419)
- Pension remeasurement	(431)	(456)	844
Own credit adjustment:
- Change in fair value	(15)	29	0
- Taxation	4	(9)	0
Own credit adjustment, total	(11)	20	0
Net other comprehensive (expense)/income that will not be reclassified to profit or loss subsequently	(442)	(436)	844
Total other comprehensive income/(expense) net of tax	329	(1,682)	465
Total comprehensive income/(expense)	1,925	(259)	1,870
Attributable to:
Equity holders of the parent	1,925	(276)	1,834
Non-controlling interests	0	17	36
Total comprehensive income/(expense)	£ 1,925	£ (259)	£ 1,870

Consolidated Balance Sheet

Consolidated Balance Sheet - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets
Cash and balances at central banks	£ 40,523	£ 46,635
Derivative financial instruments	1,472	2,439
Other financial assets at fair value through profit or loss	602	434
Loans and advances to customers	211,222	223,840
Loans and advances to banks	1,216	1,105
Reverse repurchase agreements - non-trading	12,468	7,348
Other financial assets at amortised cost	152	156
Macro hedge of interest rate risk	(630)	(2,654)
Financial assets at fair value through other comprehensive income	8,481	6,024
Interests in other entities	245	252
Intangible assets	1,548	1,550
Property, plant and equipment	1,512	1,526
Current tax assets	507	484
Retirement benefit assets	723	1,051
Other assets	2,029	2,004
Assets held for sale	13	49
Total assets	282,083	292,243
Liabilities
Derivative financial instruments	891	1,008
Other financial liabilities at fair value through profit or loss	899	803
Deposits by customers	195,149	197,313
Deposits by banks	20,357	28,543
Repurchase agreements - non-trading	8,411	7,982
Debt securities in issue	35,778	36,420
Subordinated liabilities	2,386	2,332
Macro hedge of interest rate risk	86	95
Other liabilities	2,501	2,601
Provisions	405	380
Deferred tax liabilities	188	30
Retirement benefit obligations	66	25
Total liabilities	267,117	277,532
Equity
Share capital	7,060	7,060
Other equity instruments	2,196	2,196
Retained earnings	6,047	6,563
Other reserves	(337)	(1,108)
Total equity	14,966	14,711
Total liabilities and equity	£ 282,083	£ 292,243

Consolidated Cash Flow Statemen

Consolidated Cash Flow Statement - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Profit before tax	£ 2,149	£ 1,894	£ 1,902
Non-cash items included in profit:
– Depreciation and amortisation	290	297	506
– Provisions for other liabilities and charges	336	421	383
– Impairment losses	196	285	(228)
– Other non-cash items	(799)	1,363	(244)
– Pension charge for defined benefit pension schemes	13	28	38
Non-cash items included in profit	36	2,394	455
Net change in operating assets and liabilities:
– Cash and balances at central banks	(87)	274	(659)
– Derivative assets	967	(719)	1,731
– Other financial assets at fair value through profit or loss	27	1,064	1,143
– Loans and advances to banks and customers	12,538	(10,683)	(960)
– Reverse repurchase agreements - non-trading	(3,224)	6,818	7,024
– Other assets	(144)	(571)	327
– Deposits by banks and customers	(10,982)	(1,373)	12,747
– Repurchase agreements - non-trading	704	(4,145)	(7,550)
– Derivative liabilities	(117)	(11)	(902)
– Other financial liabilities at fair value through profit or loss	102	(973)	(1,109)
– Debt securities in issue	(219)	(1,352)	(330)
– Other liabilities	(1)	(41)	(608)
Net change in operating assets and liabilities	(436)	(11,712)	10,854
Corporation taxes paid	(539)	(397)	(418)
Effects of exchange rate differences	(616)	2,354	(640)
Net cash flows from operating activities	594	(5,467)	12,153
Cash flows from investing activities
Purchase of property, plant and equipment and intangible assets	(393)	(504)	(615)
Proceeds from sale of property, plant and equipment and intangible assets	175	159	437
Purchase of financial assets at amortised cost and financial assets at FVOCI	(10,899)	(2,884)	(1,256)
Proceeds from sale and redemption of financial assets at amortised cost and financial assets at FVOCI	8,362	3,023	4,509
Net cash flows from investing activities	(2,755)	(206)	3,075
Cash flows from financing activities
Issue of other equity instruments	0	750	450
Issuance costs of other equity instruments
Issue of debt securities and subordinated notes	6,415	8,683	2,853
Issuance costs of debt securities and subordinated notes	(18)	(16)	(6)
Repayment of debt securities and subordinated notes	(6,409)	(4,522)	(13,728)
Disposal of non-controlling interests	0	(235)	(181)
Repurchase of other equity instruments	0	(750)	(500)
Dividends paid on ordinary shares	(1,538)	(1,013)	(1,346)
Dividends paid on other equity instruments	(133)	(143)	(143)
Dividends paid on non-controlling interests	0	(17)	(17)
Principal elements of lease payments	(48)	(26)	(25)
Net cash flows from financing activities	(1,731)	2,711	(12,643)
Change in cash and cash equivalents	(3,892)	(2,962)	2,585
Cash and cash equivalents at beginning of the year	48,945	51,787	49,221
Effects of exchange rate changes on cash and cash equivalents	(122)	120	(19)
Cash and cash equivalents at the end of the year	44,931	48,945	51,787
Cash and cash equivalents consist of:
Cash and balances at central banks	40,523	46,635	50,494
Less: restricted balances	(2,327)	(2,241)	(2,515)
Cash and bank balances at central banks less regulatory minimum cash balances	38,196	44,394	47,979
Other cash equivalents: Loans and advances to banks - Non-trading	1,014	938	1,270
Other cash equivalents: Reverse repurchase agreements	5,721	3,613	2,538
Cash and cash equivalents at the end of the year	£ 44,931	£ 48,945	£ 51,787

Consolidated Statement of Chang

Consolidated Statement of Changes in Equity - GBP (£) £ in Millions	Total	Total	Share capital	Other equity instruments	Fair value	Cash flow hedging	Currency translation	Retained earnings	Non-controlling interests
Beginning balance at Dec. 31, 2020	£ 16,245	£ 15,848	£ 7,060	£ 2,241	£ 29	£ 486	£ 2	£ 6,030	£ 397
Profit after tax	1,405	1,369						1,369	36
Other comprehensive (expense)/income, net of tax:
- Fair value reserve (debt instruments)	(3)	(3)			(3)
- Cash flow hedges	(376)	(376)				(376)
- Pension remeasurement	844	844						844	0
- Own credit adjustment	0
Total other comprehensive income/(expense) net of tax	465	465			(3)	(376)		844
Total comprehensive income/(expense)	1,870	1,834			(3)	(376)		2,213	36
Issue of other equity instruments	450	450		450
Disposal of non-controlling interests	(181)								(181)
Repurchase of other equity instruments	(500)	(500)		(500)
Dividends on ordinary shares	(1,346)	(1,346)						(1,346)
Dividends on other equity instruments	(143)	(143)						(143)
Dividends on non-controlling interests	(17)								(17)
Ending balance at Dec. 31, 2021	16,378	16,143	7,060	2,191	26	110	2	6,754	235
Profit after tax	1,423	1,406						1,406	17
Other comprehensive (expense)/income, net of tax:
- Fair value reserve (debt instruments)	(20)	(20)			(20)
- Cash flow hedges	(1,226)	(1,226)				(1,226)
- Pension remeasurement	(456)	(456)						(456)
- Own credit adjustment	20	20						20
Total other comprehensive income/(expense) net of tax	(1,682)	(1,682)			(20)	(1,226)		(436)
Total comprehensive income/(expense)	(259)	(276)			(20)	(1,226)		970	17
Issue of other equity instruments	750	750		750
Disposal of non-controlling interests	(235)								(235)
Repurchase of other equity instruments	(750)	(750)		(745)				(5)
Dividends on ordinary shares	(1,013)	(1,013)						(1,013)
Dividends on other equity instruments	(143)	(143)						(143)
Dividends on non-controlling interests	(17)								(17)
Ending balance at Dec. 31, 2022	14,711	14,711	7,060	2,196	6	(1,116)	2	6,563	0
Profit after tax	1,596	1,596						1,596
Other comprehensive (expense)/income, net of tax:
- Fair value reserve (debt instruments)	(11)	(11)			(11)
- Cash flow hedges	782	782				782
- Pension remeasurement	(431)	(431)						(431)
- Own credit adjustment	(11)	(11)						(11)
Total other comprehensive income/(expense) net of tax	329	329			(11)	782		(442)
Total comprehensive income/(expense)	1,925	1,925			(11)	782		1,154	0
Other	1	1						1
Dividends on ordinary shares	(1,538)	(1,538)						(1,538)
Dividends on other equity instruments	(133)	(133)						(133)
Ending balance at Dec. 31, 2023	£ 14,966	£ 14,966	£ 7,060	£ 2,196	£ (5)	£ (334)	£ 2	£ 6,047	£ 0

Company Balance Sheet

Company Balance Sheet - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets
Other financial assets at fair value through profit or loss	£ 602	£ 434
Loans and advances to banks	1,216	1,105
Other financial assets at amortised cost	152	156
Current tax assets	507	484
Other assets	2,029	2,004
Total assets	282,083	292,243
Liabilities
Other financial liabilities at fair value through profit or loss	899	803
Debt securities in issue	35,778	36,420
Subordinated liabilities	2,386	2,332
Total liabilities	267,117	277,532
Equity
Share capital	7,060	7,060
Other equity instruments	2,196	2,196
Retained earnings	6,047	6,563
Total equity	14,966	14,711
Total liabilities and equity	282,083	292,243
Santander UK Group Holdings plc
Assets
Other financial assets at fair value through profit or loss	9,591	7,888
Loans and advances to banks	1,816	4,800
Other financial assets at amortised cost	1,633	942
Interests in other entities	13,640	13,640
Current tax assets	22	19
Other assets	4	2
Total assets	26,706	27,291
Liabilities
Other financial liabilities at fair value through profit or loss	9,591	7,888
Debt securities in issue	1,911	4,898
Subordinated liabilities	1,633	942
Total liabilities	13,135	13,728
Equity
Share capital	7,060	7,060
Other equity instruments	2,196	2,196
Retained earnings	4,315	4,307
Total equity	13,571	13,563
Total liabilities and equity	£ 26,706	£ 27,291

Company Cash Flow Statement

Company Cash Flow Statement - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Adjustments for:
Non-cash items included in profit	£ 36	£ 2,394	£ 455
Net change in operating assets and liabilities	(436)	(11,712)	10,854
Effects of exchange rate differences	(616)	2,354	(640)
Net cash flows from operating activities	594	(5,467)	12,153
Cash flows from investing activities
Purchase of financial assets at amortised cost and financial assets at fair value	(10,899)	(2,884)	(1,256)
Net cash flows from investing activities	(2,755)	(206)	3,075
Cash flows from financing activities
Issue of other equity instruments	0	750	450
Issue of debt securities and subordinated notes	6,415	8,683	2,853
Repayment of debt securities and subordinated notes	(6,409)	(4,522)	(13,728)
Repurchase of other equity instruments	0	(750)	(500)
Issuance costs of debt securities and subordinated notes	(18)	(16)	(6)
Dividends paid on ordinary shares	(1,538)	(1,013)	(1,346)
Dividends paid on other equity instruments	(133)	(143)	(143)
Net cash flows from financing activities	(1,731)	2,711	(12,643)
Change in cash and cash equivalents	(3,892)	(2,962)	2,585
Cash and cash equivalents at beginning of the year	48,945	51,787	49,221
Cash and cash equivalents at the end of the year	44,931	48,945	51,787
Santander UK Group Holdings plc
Cash flows from operating activities
Profit from continuing operations before tax	1,675	1,202	1,495
Adjustments for:
Non-cash items included in profit	0	9
Net change in operating assets and liabilities	3,558	363
Effects of exchange rate differences	(513)	980
Net cash flows from operating activities	4,720	2,554
Cash flows from investing activities
Purchase of financial assets at amortised cost and financial assets at fair value	(2,394)	(3,802)
Investments in other entities	0	(50)
Net cash flows from investing activities	(2,394)	(3,852)
Cash flows from financing activities
Issue of other equity instruments	0	750
Issue of debt securities and subordinated notes	2,582	3,898
Repayment of debt securities and subordinated notes	(3,230)	(1,446)
Repurchase of other equity instruments	0	(750)
Issuance costs of debt securities and subordinated notes	(4)	(9)
Dividends paid on ordinary shares	(1,538)	(1,013)
Dividends paid on other equity instruments	(133)	(143)
Net cash flows from financing activities	(2,323)	1,287
Change in cash and cash equivalents	3	(11)
Cash and cash equivalents at beginning of the year	41	52
Cash and cash equivalents at the end of the year	£ 44	£ 41	£ 52

Company Statement of Changes in

Company Statement of Changes in Equity - GBP (£) £ in Millions	Total	Share capital	Other equity instruments	Retained earnings	Santander UK Group Holdings plc	Santander UK Group Holdings plc Share capital	Santander UK Group Holdings plc Other equity instruments	Santander UK Group Holdings plc Retained earnings
Beginning balance at Dec. 31, 2020	£ 16,245	£ 7,060	£ 2,241	£ 6,030
Profit after tax	1,405			1,369	£ 1,499
Issue of other equity instruments	450		450
Repurchase of other equity instruments	(500)		(500)
Dividends on ordinary shares	(1,346)			(1,346)
Dividends on other equity instruments	(143)			(143)
Ending balance at Dec. 31, 2021	16,378	7,060	2,191	6,754	13,513	£ 7,060	£ 2,191	£ 4,262
Profit after tax	1,423			1,406	1,206			1,206
Issue of other equity instruments	750		750		750		750
Repurchase of other equity instruments	(750)		(745)	(5)	(750)		(745)	(5)
Dividends on ordinary shares	(1,013)			(1,013)	(1,013)			(1,013)
Dividends on other equity instruments	(143)			(143)	(143)			(143)
Ending balance at Dec. 31, 2022	14,711	7,060	2,196	6,563	13,563	7,060	2,196	4,307
Profit after tax	1,596			1,596	1,679			1,679
Dividends on ordinary shares	(1,538)			(1,538)	(1,538)			(1,538)
Dividends on other equity instruments	(133)			(133)	(133)			(133)
Ending balance at Dec. 31, 2023	£ 14,966	£ 7,060	£ 2,196	£ 6,047	£ 13,571	£ 7,060	£ 2,196	£ 4,315

Company Income Statement

Company Income Statement - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement [Line Items]
Interest and similar income	£ 11,853	£ 6,822	£ 4,830
Interest expense and similar charges	(7,186)	(2,350)	(833)
Net interest income	4,667	4,472	3,997
Other operating income	213	210	267
Total operating income	5,176	5,006	4,544
Operating expenses before credit impairment charges, provisions and charges	(2,485)	(2,370)	(2,540)
Tax on profit	(553)	(471)	(485)
Profit after tax	1,596	1,423	1,405
Santander UK Group Holdings plc
Statement [Line Items]
Interest and similar income	176	192	221
Interest expense and similar charges	(179)	(196)	(225)
Net interest income	(3)	(4)	(4)
Dividend income	1,685	1,212	1,497
Other operating income	0	0	8
Total operating income	1,682	1,208	1,501
Operating expenses before credit impairment charges, provisions and charges	(7)	(6)	(6)
Tax on profit	4	4	4
Profit after tax	1,679	1,206	1,499
Profit from continuing operations before tax	£ 1,675	£ 1,202	£ 1,495

Risk Framework

Risk Framework	12 Months Ended
	Dec. 31, 2023
Risk Framework [Abstract]
Risk Framework	Our risk governance structure We are committed to the highest standards of corporate governance in every part of our business, including risk management. For details of our governance, including the Board and its Committees, see the ‘Governance’ section of this Annual Report. The Board delegates certain responsibilities to Board Level Committees as needed and where appropriate. Our risk governance structure strengthens our ability to identify, assess, manage and report risks, as follows: – Committees: A number of Board and Executive committees are responsible for specific parts of our Risk Framework – Key senior management roles: A number of senior roles have specific responsibilities for risk management – Risk organisational structure: We have the ‘three lines of defence’ model built into the way we run our business. Committees The Board and Board Level Committee responsibilities for risk are: Board Level Committee Main risk responsibilities The Board (including the Santander UK plc Board) – Has overall responsibility for business execution and for managing risk – Reviews and approves the Risk Framework and Risk Appetite Board Risk Committee (BRC) – Assesses the Risk Framework and recommends it to the Board for approval – Advises the Board on our overall Risk Appetite, tolerance and strategy – Oversees our exposure to risk and our strategy and advises the Board on both – Reviews the effectiveness of our risk management systems and internal controls – Reviews reports from the Chief Compliance Officer (CCO) on the adequacy and effectiveness of the compliance function – Responsible for oversight of cybersecurity risks and receives regular updates on cybersecurity risk position including cybersecurity incidents – Receives regular updates on financial crime compliance and risks including money laundering, bribery and corruption and sanctions compliance and monitors KPIs in line with approved Board risk appetite Board Responsible Banking Committee – Responsible for culture and operational risk from conduct, compliance, competition & legal matters – Ensures that adequate and effective control processes are in place to identify and manage reputational risks – Oversees our Sustainability and Responsible Banking programme and how it impacts on employees, communities, the environment including sustainability and climate change, reputation, brand and market positioning – Reviews updates on key risk issues, customer, reputational and conduct matters Board Audit Committee – Monitors and reviews the financial statements integrity, and any formal announcements on financial performance – Reviews the adequacy and effectiveness of the internal financial controls and whistleblowing arrangements – Monitors and reviews the effectiveness of the internal audit function – Receives regular updates from the internal audit function which performs reviews of cybersecurity risk and controls – Oversees the independence and performance of the external auditors Board Remuneration – Oversees implementation of remuneration policies, ensuring they promote sound and effective risk management The Executive Level Committee responsibilities for risk are: Executive Level Committee Main risk responsibilities Executive Committee (ExCo) – Reviews business plans in line with our Risk Framework and Risk Appetite before they are sent to the Board to approve – Receives updates on key risk issues managed by CEO-level committees and monitors the actions taken Senior Management Committee – Focuses on the responsibilities of the Executive Committee Senior Management Function holders and how they are discharged – Reviews updates on key risk issues, customer, reputational and conduct matters Executive Risk Control Committee (ERCC) – Reviews Risk Appetite proposals before they are sent to the BRC and the Board to approve – Ensures that we comply with our Risk Framework, Risk Appetite and risk policies – Reviews and monitors our risk exposures and approves any corrective steps we need to take Asset and Liability Committee (ALCO) – Reviews liquidity risk appetite (LRA) proposals – Ensures we measure and control structural balance sheet risks, including capital, funding and liquidity, in line with the policies, strategies and plans set by the Board – Reviews and monitors key asset and liability management activities to ensure we keep our exposures within our Risk Appetite Pensions Committee – Reviews pension risk appetite proposals – Approves actuarial valuations and reviews the impact they may have on our contributions, capital and funding – Consults with the pension scheme trustees on the scheme’s investment strategy Capital Committee – Puts in place reporting systems and risk control processes to make sure capital risks are managed within our Risk Framework – Reviews capital adequacy and capital plans, including the ICAAP, before they are sent to the Board to approve Incident Accountability Committee – Considers, calibrates, challenges and agrees any appropriate individual remuneration adjustments – Presents recommendations to the Board Remuneration Committee Credit Approval Committee – Approves corporate and wholesale credit transactions which exceed levels delegated to lower level forums or individuals Economic Crime Committee – Ensures due reporting, consideration, oversight and informed decision making regarding compliance with financial crime laws and regulations, fraud, and best industry practice aligned to our Risk Appetite Key senior management roles Senior roles with specific responsibilities for risk management are: Role Main risk responsibilities Chief Executive Officer (CEO) The Board delegates responsibility for our business activities and managing risk on a day-to-day basis to the CEO. The CEO proposes our strategy and business plan, puts them into practice and manages the risks involved. The CEO must also ensure we have a suitable system of controls to manage risks and report to the Board on them. Chief Risk Officer (CRO) Oversees and challenges risk activities, and ensures that the business activity is conducted within our risk appetite. Responsible for control and oversight of all risk types with regulatory responsibility to report on these risk types to Executive and Board Committees. Chief Financial Officer (CFO) Responsible for developing strategy, leadership and management of the CFO Division. The CFO is responsible for managing interest rate, liquidity, pension and capital risks. The CFO also aims to maximise the return on Regulatory and Economic Capital. Chief Internal Auditor (CIA) Designs and uses an audit system that identifies key risks and evaluates controls. The CIA also develops an audit plan to assess existing risks that involve producing audit, assurance and monitoring reports. Chief Compliance Officer (CCO) Responsible to the CRO for control and oversight of conduct & regulatory, reputational and economic crime risk, but has direct responsibility to report on conduct & regulatory and reputational risk to Executive and Board Committees and the regulator. Money Laundering Reporting Officer (MLRO) Responsible to the CCO for control and oversight of economic crime risk but has regulatory responsibility to report on this risk type to Executive and Board Committees and the regulator.

Credit Risk

Credit Risk	12 Months Ended
	Dec. 31, 2023
Disclosure of credit risk exposure [abstract]
Credit Risk	Credit risk Overview Credit risk is the risk of financial loss due to the default or credit quality deterioration of a customer or counterparty to which we provided credit, or for whom we have assumed a financial obligation. We set out how our exposures arise and our approach to credit risk across the credit risk lifecycle. We discuss our ECL approach and the key inputs to our ECL model. We then analyse our key metrics, credit performance and forbearance. Key metrics Stage 3 ratio of 1.49% ( 2022 : 1.24% ). Loss allowances of £994m ( 2022 : £1,007m ). Balance weighted average LTV of 66% ( 2022 : 69% ) on new mortgage lending. CREDIT RISK MANAGEMENT Exposures (audited) Exposures to credit risk arise in our business segments from: Retail and Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre In Mortgages: – Residential mortgages for customers with good credit quality (prime lending). – We provide these mostly for owner- occupiers, with buy-to-let mortgages for non-professional landlords. In Everyday Banking: – Unsecured lending to individuals, such as loans, credit cards and overdrafts. – Banking services to businesses with turnover up to £ 6.5 m per annum and simpler borrowing needs. We offer loans, credit cards and overdrafts. – Financing for cars, vans, motorbikes and leisure vehicles through Santander Consumer (UK) plc (SCUK). – Through our joint ventures, Hyundai Capital UK Ltd and Volvo Car Financial Services UK Limited, we provide retail point of sale customer finance and wholesale finance facilities (stock finance). – Loans, bank accounts, treasury services, invoice discounting, cash transmission, trade finance and asset finance. – We provide these to SMEs and mid- sized corporates with turnover up to £ 500 m per annum, Commercial Real Estate and Social Housing associations. – Asset and liability management of our balance sheet. – Exposures include financial institutions (derivatives and other treasury products), structured products, and sovereign and supranational assets chosen for diversification and liquidity. – Crown Dependencies - mainly residential mortgages to individuals in Jersey and the Isle of Man. Our approach to credit risk We manage our portfolios across the credit risk lifecycle, from drawing up our risk strategy and planning, through assessment and origination, monitoring, arrears management and debt recovery. We make sure the actual risk profile of our exposures stays in line with our business plans and within our Risk Appetite. We tailor the way we manage risk to the type of product and regularly review our approach and refine it when we need to. 1. Risk strategy and planning ( audited) All relevant areas of the business work together to create our business plans. We aim to balance our strategy, goals, and financial and technical resources with our Risk Appetite. To do this, we focus on economic and market conditions and forecasts, regulations, conduct matters, profitability, returns and market share. 2. Assessment and origination (audited) Managing credit risk begins with lending responsibly. That means only lending to customers who are committed to paying us back and can afford to, even if their circumstances change. We perform a thorough risk assessment to make sure a customer can meet their obligations before we approve a loan. We take proportionate steps to assess whether a customer will be able to repay the money borrowed. We do this by a series of initial affordability and credit risk assessments. We access each customer’s credit profile and signs of how reliable they are at repaying credit. When a customer applies, we assess the data they provide, plus data from credit reference agencies (for Retail and Business Banking and Consumer Finance) and performance on their other Santander UK accounts (if they have any) against our Credit Policy. Retail and Business Banking In Mortgages, for secured loans, we assess affordability by reviewing the customer’s income and spending, their other credit commitments, and what would happen if interest rates went up. Many of our decisions are automated as we use data available to us. We tailor our process and application assessment based on the product. More complex transactions often need greater manual assessment using our credit underwriters’ skill and experience. In Everyday Banking and Business Banking, many of our decisions are automated. We assess affordability by reviewing the customer’s income and spending, including other credit commitments and adjusting for future inflation and expected interest rates. Credit risk mitigation The types of credit risk mitigation, including collateral, across each of our portfolios are: Portfolio Description Residential mortgages Collateral is in the form of a first legal charge over the property. Before we grant a mortgage, the property is valued either by a surveyor or using automated valuation methodologies where our confidence in the accuracy of this method is high. Unsecured lending There is no collateral or security tied to the loan that can be used to mitigate any potential loss if the customer does not pay us back. Business banking services Business banking lending is unsecured. When lending to incorporated businesses, we typically obtain personal guarantees from each director, but we do not treat these as collateral. We consider the UK Government guarantee supporting losses on amounts lent under its Coronavirus Loan Schemes as collateral with 100% for Bounce Back Loan Scheme (BBLS) and 80% for Coronavirus Business Interruption Loan Scheme (CBILS). Consumer Finance In Consumer Finance, similar to Retail and Business Banking, many decisions are automated and we tailor the process to the product. Residual value risk is one of our top risks. Credit risk mitigation The type of credit risk mitigation, including collateral, is: Portfolio Description Consumer (auto) finance Collateral is in the form of legal ownership of the vehicle for most loans, with the customer being the registered keeper. Only a very small proportion of business is underwritten as a personal loan. In these cases, there is no collateral or security tied to the loan. We use a leading vehicle valuation company to assess the LTV at the proposal stage to ensure the value of the vehicle is appropriate. Corporate & Commercial Banking We assign each customer a credit rating according to the internal rating threshold, using our internal rating scale (see ‘Credit quality’ in ‘Santander UK group level – credit risk review’ section). To do this, we look at the customer’s financial history and trends in the economy, backed up by the expert judgement of a risk analyst. We review our internal ratings on a dynamic basis and at least once a year for those clients that are rated. We also assess the underlying risk of the transaction, taking account of any mitigating factors (see the tables below) and how it fits with our risk policies, limits and Risk Appetite. Responsible lending, including climate change and the transition to a low carbon economy As part of the Banco Santander group, we comply with the Equator Principles to factor social, ethical and environmental impacts into our risk analysis and decision making for qualifying financial transactions. We are committed to supporting clients and economies in their transition to a low carbon economy, providing financial products and/or services to business activities that are environmentally and socially responsible. Our Environmental, Social and Climate Change (ESCC) policy sets out how we identify, assess, monitor and manage environmental and social risks and other climate change related activities in the Oil and Gas, Power Generation and Mining and Metals sectors and those arising from businesses engaged in soft commodities. Our ESCC policy prohibits project-related financing for new coal-fired power plants (CFPP) worldwide and we will only work with new clients with CFPPs to provide specific financing for renewable energy projects. In line with Banco Santander's commitment, by 2030 we will eliminate all exposure to thermal coal mining and stop providing financial services to power generation clients with more than 10% of revenue from thermal coal. For more on our approach to responsible lending, see the Sustainability and Responsible Banking section. Credit risk mitigation The types of credit risk mitigation, including collateral, across each of our portfolios are as follows. In addition, from time to time, at a portfolio level we execute significant risk transfer transactions, which typically reduce RWAs. Portfolio Description SME and mid corporate Includes secured and unsecured lending. We can take mortgage debentures or a first charge on commercial property as collateral. Before agreeing the loan, we get an independent professional valuation of the property. Loan agreements typically allow us to obtain revaluations during the term of the loan. We can also take guarantees, but we do not treat them as collateral unless they are supported by a tangible asset charged to us. We also lend against assets (like vehicles and equipment) and invoices for some customers. We value assets before we lend. For invoices, we review the customers' ledgers regularly and lend against debtors who meet agreed criteria. Commercial Real Estate We take a first charge on commercial property as collateral. The loan is subject to criteria such as the property condition, age and location, tenant quality, lease terms and length, and the sponsor’s experience and creditworthiness. Before advancing the loan and where appropriate, a bank representative visits the property. We also get an independent professional valuation which typically includes a site visit. Loan agreements typically allow us to obtain revaluations during the term of the loan. Social Housing We take a first charge on portfolios of residential real estate owned and let by UK Housing Associations as collateral, in most cases. We revalue this every three to five years (in line with industry practice), using the standard methods for property used for Social Housing. Corporate Centre Credit risk mitigation The types of credit risk mitigation, including collateral, across each of our portfolios are as follows. In addition, from time to time, at a portfolio level we execute significant risk transfer transactions, which typically reduce RWAs. Portfolio Description Sovereign and Supranational In line with market practice, there is no collateral against these assets. Structured Products These are our High Quality Liquid Assets (HQLA) in our Eligible Liquidity Pool. They are mainly Asset Backed Securities (ABS) and covered bonds, which hold senior positions in the creditor hierarchy. Their credit rating reflects over-collateralisation in the structure and the assets that underpin their cash flows. Financial Institutions We use standard legal agreements to reduce credit risk via netting and collateralisation on derivatives, repos and reverse repos, and stock borrowing/lending. We also reduce risk by clearing trades through central counterparties (CCPs) where possible. Crown Dependencies We manage the risk on this portfolio in a similar way as for mortgages in Retail and Business Banking. 3. Monitoring (audited) We measure and monitor changes in our credit risk profile on a regular and systematic basis against our budgets, limits and benchmarks. Credit concentrations A core part of our monitoring and management is a focus on credit concentrations, such as the proportion of our lending that goes to specific borrowers, groups or industries. We set and monitor concentration limits in line with our Risk Appetite and review them on a regular basis. – Geographical concentrations: We set exposure limits to countries and geographies, with reference to the country limits set by Banco Santander and our own Risk Appetite. For more geographical information, see ‘Country risk exposures’. – Industry concentrations: We also set exposure limits by industry sector. We set these limits based on the industry outlook, our strategic aims and desired level of concentration, and relevant limits set by Banco Santander. We analyse committed exposures in the ‘Credit risk review’ section that follows. Retail and Business Banking We use IT systems and data available to us to monitor accounts. The main parts are: – Behavioural scoring: we use statistical models that help predict whether a customer will have problems repaying, based on how they use their accounts – Credit reference agencies: we often use data from agencies on how the borrower is handling credit from other lenders in our behaviour scoring models – Other Santander UK accounts: each month, we also look at how the customer uses their other accounts with us, so we can identify problems early. Our day-to-day retail credit risk monitoring relies on a mix of product, customer and portfolio performance measures as described above. However, changes in the wider UK economy also impact our Mortgages and Everyday Banking portfolios. As part of our day-to-day risk monitoring, we use a Retail Risk Playbook tolerance framework that sets out the most relevant macroeconomic variables to retail portfolio performance. We monitor these variables against our forecasts. If the economy deviates materially from our forecasts, such as due to the effects of the cost of living crisis or high inflation, we formally review our retail risk management policy and strategy. We also use the Retail Risk Playbook tolerance framework and management judgements to ensure that portfolio quality remains within our Risk Appetite by measuring against trigger values for key risk profile and performance metrics. For secured lending, our monitoring also takes account of changes in property prices. We estimate the property’s value every three months. In most cases, we use statistical models based on recent sales prices and valuations in that local area. Use of this model is subject to Model Risk Governance. Where a lack of data means the model’s valuation is not available, we use the original surveyor valuation with a House Price Index (HPI) adjustment as needed. For unsecured personal lending like credit cards and overdrafts, monitoring might lead us to raise or lower credit limits. For business banking services, we review revolving credit facilities each year to ensure the facilities remain appropriate for the customer's financial circumstances. Consumer Finance In Consumer Finance, similar to Retail and Business Banking, we use IT systems and data available to us to monitor accounts, and we use the Retail Risk Playbook tolerance framework and management judgements to ensure that portfolio quality remains within Risk Appetite. We also check the Residual Value of our portfolio each month, using triggers set to identify any material change in trends. Corporate & Commercial Banking and Corporate Centre We regularly monitor and report our credit risk by portfolio, segment, industry, location and customer. We monitor detailed analyses of our credit exposures and risk trends each month. We also report our larger exposures and risks to the BRC each month. Our Watchlist We also use a Watchlist for exposures subject to annual reviews to help identify potential problem debt early. Just because a customer is on our Watchlist does not mean they have defaulted. It just means that their probability of default has increased, such as they have breached a covenant or lost a major contract. We classify Watchlist cases as: – Enhanced monitoring: for less urgent cases. We monitor these cases more often and where appropriate may consider more collateral. – Proactive management: for more urgent or serious cases. We may take steps to restructure debt including extending the term, taking more collateral, agreeing a lower credit limit, or seeking repayment of the loan through refinancing or other means. We assess Watchlist cases for impairment as set out in the ‘Significant Increase in Credit Risk (SICR)’ section. When a customer is in enhanced monitoring, we do not consider it has suffered a SICR for ECL purposes, so it remains in Stage 1 for our loss allowance calculations. When a customer is in proactive management, we consider it has suffered a SICR, so we transfer it to Stage 2 and apply a lifetime ECL for our loss allowance calculations. We take into account any forbearance we offer. This includes any extra security, guarantees or equity available and the potential to enhance value by asset management. In Corporate & Commercial Banking, as part of our annual reviews, for loans nearing maturity, we look at the prospect of refinancing the loan on current market terms and applicable credit policy. If this is unlikely, we put the case on our Watchlist. We manage exposures not subject to annual reviews, mainly high volume and low value cases, using early warning indicators including credit reference agency data, supported by teams of expert analysts. In Corporate Centre, we typically monitor the credit quality of our exposures daily. We use internal and third-party data to detect any potential credit deterioration. In addition, we manage the credit quality of our Crown Dependencies mortgages in a similar way as for mortgages in Retail and Business Banking. 4. Arrears management ( audited) Retail and Business Banking and Consumer Finance We have several strategies to manage arrears that we can use as early as the day after a missed payment. We also reach out to up-to-date customers who may be at risk of going into arrears for support purposes. We assess the financial difficulties a customer is having, so we can offer them the right support to manage their agreement whilst in arrears. The strategy we use depends on the risk and the customer’s circumstances. Corporate & Commercial Banking and Corporate Centre We identify problem debt by close monitoring, supported by our Watchlist process for exposures subject to annual review. We aim to identify warning signs early by monitoring customers’ financial and trading data, checking to see they do not breach covenants, and having regular dialogue with them. We tailor our strategy to the type of customer, their circumstances and the level of risk. We try to help our customers find their own way out of financial difficulty and agree on a plan that works for both of us. We engage our Restructuring & Recoveries team as needed on Watchlist cases and we may hand over more serious cases to them. For exposures not subject to annual review, we have strategies to manage arrears that we can use as early as the day of the missed payment. If a case becomes more urgent or needs specialist attention, and if it transfers to Stage 3, we transfer it to our Restructuring & Recoveries team. For more, see the Forbearance section. 5. Debt recovery (audited) Sometimes, even when we have taken all reasonable and responsible steps to manage arrears in our Financial Support area, they are not effective. If this happens, we may choose to end our agreement with the customer and try to recover the outstanding balance (with recourse to any associated collateral), or as much of it as we can. Retail and Business Banking In Mortgages and Everyday Banking, we may use a debt collection agency, sell the debt, or take the customer to court. For retail mortgages, we may repossess the property as a last resort or to protect it from damage or third-party claims. We make sure our estimated losses from repossessed properties are realistic by getting two independent valuations and the estimated selling costs, and using them in our loss allowances calculations. Where we repossess a property, we do not take ownership. We use agents to realise the value and settle the debt. Any surplus funds are returned to the borrower or dealt with in line with insolvency rules. Consumer Finance In Consumer Finance, similar to Retail and Business Banking, we may use a debt collection agency or a specialist law firm to recover the balance outstanding. We may also consider the sale of debt where all avenues have been explored. Corporate & Commercial Banking and Corporate Centre Where we look for an exit, we aim to do this, if we can, by agreeing with the borrower that they will sell some or all their assets on a voluntary basis or agreeing to give them time to refinance their debt with another lender. Where we cannot reach an agreement, we consider recovery options. This can be through an insolvency proceeding, enforcing over any collateral or selling debt on the secondary market. We may also consider other legal action to recover what we are owed. If there is a shortfall, we write it off against our loss allowances. In very rare cases, we may act as mortgagee in possession of assets held as collateral against non-performing commercial lending. In such cases, we carry the assets on our balance sheet and classify them in line with our accounting policies. Loan modifications (audited) We sometimes change the terms of a loan when a customer gets into financial difficulty (this is known as forbearance), or for other commercial reasons. Forbearance (audited) We can change the terms of a customer's loan, temporarily or permanently, to help them through temporary periods of difficulty so they can get back on to sustainable terms. We assess what we offer to make sure the customer can afford it. Forbearance improves our customer relationships and we review our approach regularly to make sure it is still effective. We try to offer forbearance before a customer defaults and we only foreclose or repossess as a last resort. The main types of forbearance we offer are: Action Description Term extension We can extend the loan term, making each monthly payment smaller. We may offer this if the customer is up to date with payments but shows signs of financial difficulties. We may also offer this if the loan is about to mature and refinancing is not possible on market terms. Interest-only Historical interest-only payments due to financial difficulties are classed as forborne. For corporate customers, interest-only concessions are considered on a case by case basis. Concessions are only granted if the nature of the financial difficulties is assessed to be temporary. Counterparties are expected to recover in full and resume making full capital and interest payments once they are in a stronger financial position. Other payment rescheduling, including capitalisation For retail customers, we may add the arrears to the mortgage balance (this is known as capitalisation) if they cannot afford to increase their monthly payment to pay off their arrears in a reasonable time but have been making their monthly payments, usually for at least six months. We can also capitalise property charges due to a landlord. We pay them for the customer to avoid the lease being forfeited. We may combine this help with term extensions and, in the past, interest-only concessions. In certain cases, we may offer interest rate concessions. For corporate customers, we may lower or stop their payments until they have time to recover. We may reschedule payments to better match the customer’s cash flow – for example if the business is seasonal - or provide a temporary increase in facilities to cover peak demand ahead of their trading improving. We might do this by arrears capitalisation or drawing from an overdraft. We may also offer to provide new facilities, interest rate concessions and interest roll-up. In rare cases, we agree to forgive or reduce part of the debt. When we agree forbearance, we consider the account has suffered a significant increase in credit risk (SICR), as we explain later on, and we classify it as Stage 2 or 3. A non-performing forborne account is one that has forbearance carried out in Stage 3, and a performing forborne account is one that has forbearance carried out in Stage 2. If an account is already in Stage 2, we keep it in Stage 2 unless the account is deemed unlikely to pay, involves forgiving fees and interest or debt, or is being granted multiple forbearances. In these cases, we move it into Stage 3. If an account is already in Stage 3, we keep it in Stage 3. A loan moves out of forbearance once the exit criteria below are met. We monitor the performance of all forborne loans. We signed up to the HM Treasury Mortgage Charter published in June 2023, that aims to provide more support for customers who may be struggling to maintain their mortgage repayments. We made more customer support solutions available from July 2023, allowing customers who are up-to-date with their payments to make interest-only payments for six months or extend their mortgage term to reduce their monthly payments. Volumes of accounts seeking more support were less than 1% of active mortgage account stock. Mortgage Charter support solutions are not automatically classed as forbearance, unless other forbearance criteria are met. Exit from forbearance criteria Exit from Conditions to be met Cure Stage 3 to Stage 2 For an account in Stage 3 to exit non-performing forbearance, all the following conditions must be met: If the account was classed as Stage 3 due to being more than 90 days past due, then the account should be 90 days or less past due The customer has no other material default debt with us more than 90 days past due If the account was classed as Stage 3 due to being unlikely to pay, then the account should no longer be deemed unlikely to pay Account has exited its forbearance trigger for 12 consecutive months If all the conditions are met, the account is re-classed as Stage 2 forbearance until the Stage 2 forbearance exit conditions set out below are also met Stage 2 to Stage 1 For an account in Stage 2 to exit forbearance, all the following conditions must be met: The account is no longer in arrears, and the customer has no other material debts with us which are more than 30 days in arrears The account no longer triggers SICR The account has been classed as Stage 2 for at least two years since the end of the latest forbearance strategy If an account fails whilst in probation to cure, i.e. in the 12 months backstop in Stage 3 or the two years in Stage 2, the probation period is reset and the account is moved back to Stage 3. Other forms of debt management and modifications Retail and Business Banking In Mortgages, apart from forbearance, we have sometimes changed the contract terms to keep a good relationship with a customer. In Mortgages and Everyday Banking, we do not classify insolvency solutions for any unsecured retail customers as forbearance. This is in line with industry guidelines. Consumer Finance We do not classify insolvency solutions for any unsecured retail customers as forbearance. This is in line with industry guidelines. Corporate & Commercial Banking and Corporate Centre When customers are in financial difficulty, we can also manage debt in other ways, depending on the facts of the specific case: Action Description Waiving or changing covenants If a borrower breaks a covenant, we can either waive it or change it, taking their latest and future financial position into account. We may also add a condition on the use of any surplus cash (after operating costs) to pay down their debt to us. Asking for more collateral or guarantees If a borrower has unencumbered assets, we may accept more collateral in return for revised financing terms. We may also take a guarantee from companies in the same group and/or major shareholders. We only do this where we believe the guarantor can meet their commitment. Asking for more equity Where a borrower can no longer pay the interest on their debt, we may accept fresh equity capital from new or existing investors to change the capital structure in return for better terms on the existing debt. Risk measurement and control We measure and control credit risk at all stages across the credit risk lifecycle. We have a range of tools, processes and approaches. Retail and Business Banking and Consumer Finance These businesses involve managing large numbers of accounts, so they produce a huge amount of data. This allows us to take a more analytical and data intense approach to measuring risk. This is reflected in the wide range of statistical models we use across the credit risk lifecycle. We use: – Risk strategy and planning: econometric models – Assessment and origination: application scorecards, and attrition, pricing, loss allowance and capital models – Monitoring: behavioural scorecards and profitability models – Arrears management: models to estimate the proportion of cases that will result in possession (known as roll rates) – Debt recovery: recovery models. We assess and review our loss allowances regularly and have them independently reviewed. We look at factors such as the cash flow available to service debt. We also use an agency to value any collateral – mainly mortgages. Corporate & Commercial Banking and Corporate Centre We measure the credit risk on treasury products by adding their potential future exposure to market movements over their lives to their fair value. Then we add it to any other exposure and measure the total against our credit limits for each client. In Corporate Centre, we manage the credit risk on our Crown Dependencies mortgages in a similar way as for mortgages in Retail and Business Banking. We assess our loss allowances regularly by looking at factors such as the cash flow available to service debt and the value of collateral based on third-party professional valuations. Key metrics (audited) We use a number of key metrics to measure and control credit risk, as follows: Metric Description Expected Credit Loss (ECL) ECL tells us what credit risk is expected to cost us either over the next 12 months or over the lifetime of the exposure where there is evidence of a SICR since origination. We explain how we calculate ECL below. Stages 1, 2 and 3 We assess each facility’s credit risk profile to determine which stage to allocate them to, and we monitor where there is a SICR and transfers between the Stages including monitoring of coverage ratios for each stage. Stage 3 ratio The Stage 3 ratio is the sum of Stage 3 drawn and Stage 3 undrawn assets divided by the sum of total drawn assets and Stage 3 undrawn assets. The Stage 3 ratio is a key indicator used to monitor underlying asset performance. Expected Loss (EL) EL is based on the CRD IV regulatory capital rules and gives us another view of credit risk. It is the product of the probability of default, exposure at default and loss given default, and we include direct and indirect costs. We base it on our risk models and our assessment of each customer’s credit quality. The rest of our Risk review, impairments, losses and loss allowances refer to calculations in accordance with IFRS, unless we specifically say they relate to CRD IV. For our IFRS impairment accounting policy, see Note 1 to the Consolidated Financial Statements. We also assess risks from other perspectives, such as geography, business area, product and process to identify areas to focus on. We also use stress testing to establish vulnerabilities to economic deterioration. Our business segments tailor their approach to credit risk to their customers, as we explain later on. Key differences between regulatory EL and IFRS 9 ECL models There are differences between the regulatory EL and IFRS 9 ECL approaches. Although our IFRS 9 models use the existing Basel advanced IRB risk components, we make adjustments to ensure the outcome is in line with IFRS 9, i.e. the financial reporting standard we use, as follows. Basel advanced IRB EL IFRS 9 ECL Rating philosophy Mix of point-in-time, through-the-cycle or hybrid Point-in-time, forward-looking. Considers a range of economic scenarios Parameters calibration Contains regulatory floors and downturn calibration Unbiased estimate, based on conditions known at the balance sheet date Calculation timing Considers aggregation of possible default events in the next 12 months Considers monthly calculation of parameters, for all possible future default dates. First 12 months are used for Stage 1, full lifetime for Stages 2 and 3 Probability of Default (PD) PD in the next 12 months Includes forward-looking economic data and removes conservatism. PD in next 12 months for Stage 1, lifetime for Stages 2 and 3 Loss Given Default (LGD) Lifetime LGD for defaults in the next 12 months Modelled without regulatory floors and exclusion of indirect costs Exposure at Default (EAD) Exposure at the point of default if the customer defaults in the next 12 months Recognises ability for exposure to reduce from balance sheet date to default date SICR Does not inc

Market Risk

Market Risk	12 Months Ended
	Dec. 31, 2023
Disclosure Of Market Risk Exposure [Abstract]
Market Risk	BALANCE SHEET ALLOCATION BY MARKET RISK CLASSIFICATION (AUDITED) We classify all our assets and liabilities exposed to market risk as non-traded market risk, except for certain portfolios that we must classify as trading books for regulatory purposes (such as selling derivatives or derivative-based products to clients), of which we must fair value for accounting reasons (such as assets in the eligible liquidity pool). For accounting purposes, we classify all derivatives as held for trading unless they are designated as being in a hedging relationship. For more, see Note 11 to the Consolidated Financial Statements. NON-TRADED MARKET RISK OUR KEY NON-TRADED MARKET RISKS (audited) Non-traded market risk mainly comes from providing banking products and services to our customers, as well as our structural balance sheet exposures. It arises in all our business segments. In Retail and Business Banking, Consumer Finance and Corporate & Commercial Banking, it is a by-product of us writing customer business and we transfer most of these risks to Corporate Centre to manage. The only types of non-traded market risk that we keep in Retail and Business Banking, Consumer Finance and Corporate & Commercial Banking are short-term mismatches due to forecasting variances in prepayment and launch risk. This is where customers repay their loans earlier than their expected maturity date or do not take the expected volume of new products. Corporate Centre also manages our structural balance sheet exposures, such as foreign exchange and Income Statement volatility risk. Our key non-traded market risks are: Key risks Description Interest rate risk Yield curve risk: comes from timing mismatches in repricing fixed and variable rate assets, liabilities and off-balance sheet instruments. It also comes from investing non-rate sensitive liabilities in interest-earning assets. Basis risk: comes from pricing assets using a different rate index to the liabilities that fund them. We are exposed to basis risks associated with Bank of England bank rate, reserve rate linked assets we deposit with central banks, and the Sterling Overnight Index Average (SONIA) rate. Since the cessation of LIBOR at the end of 2021, basis risk exposure has been immaterial. Spread risk Spread risk arises when the value of assets or liabilities which are accounted for at fair value (either through Other Comprehensive Income or through Profit and Loss) are affected by changes in the credit spread. We measure these spreads as the difference between the discount rate we use to value the asset or liability, and an underlying interest rate curve. Foreign exchange risk Our banking businesses operate mainly in sterling markets, so we do not create significant foreign exchange exposures. The only exception to this is money we raise in foreign currencies. For more on this, see ‘Wholesale funding’ in the ‘Liquidity risk’ section. Income statement volatility risk We measure most of the assets and liabilities in our banking book balance sheet at amortised cost. We sometimes manage their risk profile by using derivatives. As all derivatives are accounted for at fair value, the mismatch in their accounting treatment can lead to volatility in our Income Statement. This happens even if the derivative is an economic hedge of the asset or liability. NII and EVE sensitivities (audited) The calculations for NII and EVE sensitivities to interest rate moves involve many assumptions, including expected customer behaviour (such as early repayment of loans) and the projected evolution and repricing of our balance sheet. These assumptions are a key part of our overall control framework, so we update and review them regularly. Our NII and EVE sensitivities include the interest rate risk from all our banking book positions. Our banking book positions generate almost all our reported net interest income. Net Interest Income (NII) sensitivity – NII sensitivity is an income-based measure we use to forecast the changes to interest income and interest expense in different scenarios. It gives us a combined impact on net interest income over a given period – usually 12 or 36 months. – We calculate NII sensitivity as the change in NII for a defined set of instantaneous parallel and non-parallel shifts in the yield curve. EVE sensitivity – We calculate EVE sensitivity as the change in the net present value of all the interest rate sensitive items in the banking book balance sheet for a defined set of instantaneous parallel and non-parallel shifts in the yield curve. The limitations of sensitivities We use sensitivities to measure the impact of standard, instantaneous, parallel shifts in relevant yield curves. The advantage of using standard parallel shifts is they generally give us a constant measure of the size of our market risk exposure, with a simple and consistent stress. We also run non-parallel stress tests, to calculate the impact of some plausible non-parallel scenarios, and over various time periods for income stresses, usually one or three years. Value at Risk (VaR) (audited) VaR – VaR indicates the losses that we might suffer because of unfavourable changes in the markets under normal (non-stressed) market conditions. We run a historical simulation using historical daily price moves to find how much we might lose, normally at a 99% confidence level. The limitations of VaR VaR is a useful and important market standard measure of risk, but it does have some limitations. These include: – VaR assumes what happened in the past is a reliable way to predict what will happen in the future. This may not always be the case – VaR is based on positions at the end of the business day so it doesn’t include intra-day positions – VaR does not predict how big the loss could be on the 1 % of trading days that it is greater than the VaR – Using a time horizon of one day means VaR does not tell us everything about exposures that we cannot liquidate or hedge within a day, or products with infrequent pricing. Back-testing – comparing VaR estimates with reality To check that the way we estimate VaR is reasonable, we back-test our VaR by comparing it against both actual and hypothetical profits and losses, using a one- day time horizon. Back-testing allows us to identify exceptions – times when the predictions were out of line with what happened. We can then look for trends in these exceptions, which can help us decide whether we need to recalibrate our VaR model. Risk mitigation (audited) We typically hedge the interest rate risk of the securities we hold for liquidity and investment purposes with interest rate swaps. We retain spread exposures, and these are the key drivers of the VaR and stress tests we use to assess the risk of the portfolio. We mitigate Income Statement volatility mainly through hedge accounting. We monitor any hedge accounting ineffectiveness that might lead to Income Statement volatility with a VaR measure and trigger, reported monthly. For our accounting policies for derivatives and hedge accounting, see Note 1 to the Consolidated Financial Statements. We hedge our foreign currency funding positions back to sterling, so our foreign exchange positions tend to be residual exposures that remain after hedging. These exposures could be, for example, to ‘spot’ foreign exchange rates or to cross currency basis. We monitor foreign exchange risk against absolute net exposures and VaR-based limits and triggers. For more on this, see ‘Funding strategy‘ and ‘Term issuance’ in the ‘Liquidity risk’ section. Risk monitoring and reporting (audited) We monitor our non-traded market risks using NII and EVE sensitivities, VaR and stress tests. We report them against limits and triggers to senior management daily and to ALCO and ERCC each month. The VaR we report captures all key sources of volatility (including interest rate and spread risks) to fully reflect potential volatility.

Liquidity Risk

Liquidity Risk	12 Months Ended
	Dec. 31, 2023
Disclosure Of Liquidity Risk Exposure [Abstract]
Liquidity Risk	Liquidity risk Overview Liquidity risk is the risk that we do not have sufficient liquid financial resources available to meet our obligations when they fall due, or we can only secure such resources at excessive cost. In this section, we describe our sources and uses of liquidity and how we manage liquidity risk. We also analyse our key liquidity metrics, including our LCRs and our eligible liquidity pools. We then explain our funding strategy and structure and we analyse our wholesale funding. Finally, we analyse how we have encumbered some of our assets to support our funding activities. Key metrics LCR of 162% ( 2022 : 163% ) NSFR of 138% ( 2022 : 137% ) Wholesale funding with maturity <1 year £ 11.9 bn ( 2022 : £ 11.0 bn) LCR eligible liquidity pool of £ 50.9 bn ( 2022 : £49.0bn ) OUR KEY LIQUIDITY RISKS (audited) Through our Liquidity Risk Appetite (LRA) framework, we manage our funding or structural contingent and market liquidity risks wherever they arise. This can be in retail and corporate deposit outflows, wholesale secured and unsecured liquidity outflows and off-balance sheet activities. Other risks our framework covers include funding concentrations, intra-day cash flows, intra-group commitments and support, franchise retention and cross currency risk. Our main sources of liquidity Customer deposits finance most of our customer lending. Although these funds are mostly callable, in practice they give us a stable and predictable core of funding. This is due to the nature of retail accounts and the breadth of our retail customer relationships. We have a strong wholesale funding investor base, diversified across product types and geographies. Through the wholesale markets, we have active relationships in many sectors including banks, other financial institutions, corporates, pensions and investment funds. We access the wholesale funding markets through the issuance of capital, senior unsecured debt, covered bonds, structured notes and short-term funding. We also access these markets through securitisations of certain assets of Santander UK plc and our operating subsidiaries. For more on our programmes, see Notes 14 , 26 and 27 in the Consolidated Financial Statements. We generate funding on the strength of our own balance sheet, our own profitability and our own network of investors. In addition, we have access to UK Government funding schemes. We comply with rules set by the PRA, other regulators, and Banco Santander standards. While we manage, consolidate and monitor liquidity risk centrally, we also manage and monitor it in the business area it comes from. Our main uses of liquidity Our main uses of liquidity are to fund our lending in Retail and Business Banking, Consumer Finance and Corporate & Commercial Banking, to pay interest and dividends, and to repay debt. Our ability to pay dividends depends on various factors. These include our regulatory capital needs, the level of our distributable reserves, and our financial performance. We also use liquidity to pay for business combinations. LIQUIDITY RISK MANAGEMENT Introduction We manage liquidity risk on a consolidated basis in our CFO division, which is our centralised function for managing funding, liquidity and capital. We created our governance, oversight and control frameworks, and our LRA, on the same consolidated basis. We also monitor and manage liquidity risk for the Santander UK plc group and SFS separately. Under this model, and the PRA’s liquidity rules, Santander UK plc and its subsidiary Cater Allen Limited form the RFB Domestic Liquidity Sub-group (the RFB DoLSub), which allows them to collectively meet regulatory requirements to manage liquidity risk. Each member of the RFB DoLSub will support the other by transferring surplus liquidity in times of stress. We continue to transfer liquidity risks from the securities Santander UK Group Holdings plc issues, or the contracts it executes, into our subsidiaries largely through back-to-back transactions. We fund any mismatches, if needed, by ordinary share dividends from subsidiaries. Risk appetite Separate LRAs are in place for Santander UK plc group and SFS. These are appropriate to their individual business models and consistent with the strategy of Santander UK Group Holdings plc. Our LRA is based on the principles of liquidity management we use to manage our balance sheet. It also supports our need to meet or exceed regulatory rules. In line with our liquidity management principles, we avoid an over-reliance on funding from a single product, customer or counterparty. We also maintain enough unencumbered customer assets to support current and future funding and collateral requirements and maintain enough capacity to monetise liquid assets and other counterbalancing capacity on a timely basis. Our LRA is proposed to the Risk division and the Board, which is then approved under advice from the Board Risk Committee. Our LRA, in the context of our overall Risk Appetite, is reviewed and approved by the Board each year, or more often if needed. Risk measurement We use a number of metrics to manage liquidity risk. These include metrics that show the difference between cash and collateral inflows and outflows in different periods. They also include structural metrics, such as our level of encumbered assets. Ongoing business management Within our framework of prudent funding and liquidity management, we manage our activities to our liquidity risk appetite. We have clear responsibilities for short- term funding, medium-term funding, encumbrance, collateral and liquid asset management. This ensures we manage liquidity risks as part of our daily operations, strategy and planning. Our liquidity management framework is split between short-term and strategic activities. Our short-term activities focus on intra-day collateral management and maintaining liquid assets to cover unexpected demands on cash in a stress, such as large and unexpected deposit withdrawals by customers and loss of wholesale funding. Our strategic activities focus on ensuring we are not over reliant on any one source for funding and that we avoid excessive concentrations in the maturity of our funding. We regularly test the liquidity of our eligible liquidity pool, in line with PRA rules and Basel guidelines. We do this by realising some of the assets by repurchase or outright sale to the market. We make sure that over any 12-month period we realise a significant part of our eligible liquidity pool. As well as our eligible liquidity pool, we always hold a portfolio of unencumbered liquid assets. Our LRA and PRA requirements determine the size and composition of this portfolio. These assets give us a source of contingent liquidity, as we can realise some of them in a stress to create liquidity by repurchase or outright sale to the market. Stress testing Our liquidity stress testing framework is central to our LRA measurement and monitoring. To fit with our Risk Appetite, the liquidity outflows that come from these stress tests must be fully covered with high-quality liquid assets, other liquid assets and appropriate management actions. Our Risk division runs a range of stress tests. Our LRA stress test consists of three tests that cover idiosyncratic, market-wide and combined scenarios. Our other tests consider scenarios such as a global economic slowdown that results in reduced confidence in banks, a slowdown in a major economy or a decline in access to liquidity. These are considered on both an acute and protracted basis. We also run severe combined stress tests which look at both a deep and prolonged UK recession that results in a reduction in wholesale funding availability and an idiosyncratic shock that would lead to retail and commercial outflows. We run climate change stresses, these include severe physical risks which result in a reduction in retail deposits, increased use of corporate lending facilities and an increase in mortgage defaults and a scenario where there is disorderly transition to net zero, resulting in supply shocks and data transparency concerns. We also conduct sensitivity analysis and reverse stress testing for instant liquidity shocks by each key liquidity risk. We do this to understand the impacts they would have on our LRA and our regulatory liquidity metrics. We monitor our LCR and our Net Stable Funding Ratio (NSFR) to ensure we continue to meet the requirements. Risk mitigation (audited) The Board aims to make our balance sheet resilient at all times and for it to be perceived as such by stakeholders. This preserves our short and long-term viability. The Board recognises that as we are involved in maturity transformation, we cannot hold enough liquidity to cover all possible stress scenarios. The Board requires us to hold enough liquidity to make sure we will survive three plausible but severe stress scenarios (our LRA stress test, described above). We do this by maintaining a prudent balance sheet structure and approved liquid resources. Recovery and Resolution framework The CFO is the accountable SMF for recovery and resolution and the related work is managed by the CFO division. They are overseen by the Board Audit Committee and the Board. We review and refresh our recovery plan each year. It sets out the risks, the indicators we use to monitor those risks, and the actions that are available to mitigate capital, liquidity or combined stress event. We are confident that we have sufficient credible and executable options to respond to a wide range of stresses, be they market-wide or idiosyncratic, in a timely and effective manner. Recovery indicators are both qualitative and quantitative and we have embedded them into our risk frameworks. We monitor recovery capacity, headroom to recovery triggers and recovery indicators regularly. If needed, we would invoke recovery early to mitigate the effects of a stress and restore our financial position and balance sheet strength. Our resolution capabilities are underpinned by comprehensive governance, testing and assurance arrangements, which seek to ensure that our resolution readiness is maintained and enhanced on an ongoing basis. In October 2023, we submitted our second resolvability self-assessment report to the PRA. This builds on the first self-assessment report submitted in October 2021, as summarised in our June 2022 resolvability public disclosure. The next resolvability public disclosures by the Bank of England and Santander UK are due in June 2024. Risk monitoring and reporting (audited) We monitor liquidity risk daily, weekly and monthly. We do this through different committees and levels of management, including ALCO and the BRC. LIQUIDITY RISK REVIEW Liquidity Coverage Ratio This table shows our LCR at 31 December 2023 and 31 December 2022 . 2023 2022 LCR £bn £bn Eligible liquidity pool (liquidity value) (1) 50.4 48.9 Net stress outflows (31.1) (30.0) Surplus 19.3 18.9 Eligible liquidity pool as a percentage of anticipated net cash flows 162 % 163 % (1) The liquidity value is calculated as applying an applicable haircut to the carrying value. LCR eligible liquidity pool This table shows the carrying value of our eligible liquidity pool assets at 31 December 2023 and 31 December 2022 . It also shows the weighted average carrying value in the year. Carrying value Weighted average carrying value in the year 2023 2022 2023 2022 Level 1 Level 2 Total Level 1 Level 2 Total Total Total £bn £bn £bn £bn £bn £bn £bn £bn Cash and balances at central banks 38.4 — 38.4 44.5 — 44.5 41.0 45.5 Government bonds 9.0 0.3 9.3 3.2 — 3.2 7.1 4.1 Supranational bonds and multilateral development banks 0.3 — 0.3 0.3 — 0.3 0.1 0.1 Covered bonds 1.2 1.0 2.2 0.1 0.9 1.0 1.7 0.9 Asset-backed securities — 0.7 0.7 — — — 0.4 0.1 48.9 2.0 50.9 48.1 0.9 49.0 50.3 50.7 Term duration in the LCR eligible liquidity pool is hedged with swaps to offset mark to market movements from interest rate changes. Currency analysis This table shows the carrying value of our eligible liquidity pool by major currencies at 31 December 2023 and 31 December 2022 . The composition of the pool is consistent with the currency profile of our net liquidity outflows. US Dollar Euro Sterling Other Total £bn £bn £bn £bn £bn 2023 2.4 1.1 46.6 0.8 50.9 2022 0.8 1.3 46.9 — 49.0 Net Stable Funding Ratio (NSFR) 2023 2022 % % NSFR 138 137 2023 compared to 2022 We remain in a strong liquidity position. We hold sufficient liquid resources and have adequate governance and controls in place to manage the liquidity risks arising from our business and strategy. At 31 December 2023 and 31 December 2022 , the LCR and NSFR significantly exceeded regulatory requirements. FUNDING RISK MANAGEMENT Funding strategy Our funding strategy continues to be based on maintaining a conservatively structured balance sheet and diverse sources of funding to meet the needs of our business strategy and plans. The CFO Division maintains a funding plan that complies with the LRA and regulatory liquidity and capital requirements. Most of our funding comes from customer deposits. We source the rest from a mix of secured and unsecured funding in the wholesale markets. Overall, this means that we do not rely too heavily on wholesale funds. We manage funding requirements by targeting a specific Liquidity Coverage Ratio, we ensure maturities are prefunded and capital/Minimum Requirements for Eligible Liabilities (MREL) requirements are prioritised. We also have checks and controls to limit our asset encumbrance from our secured funding operations. As part of maintaining a diverse funding base, we raise funding in a number of currencies, including EUR and USD, and convert it into sterling through currency swaps to fund our commercial assets which are largely sterling denominated. Our base of stable retail and corporate deposits is a key funding source for us. We leverage our large and diverse customer base to offer products that give us a long-term sustainable source of funding. We do this by focusing on building long-term relationships. At 31 December 2023, 86% of our total core retail customer liabilities were covered by the Financial Services Compensation Scheme (the FSCS). Behavioural maturities The contractual maturity of our balance sheet assets and liabilities highlights the maturity transformation that underpins the role of banks to lend long term, but to fund themselves mainly with shorter-term liabilities, like customer deposits. We do this by diversifying our funding operations across a wide customer base, both in numbers and by type of depositor. In practice, the behavioural profiles of many liabilities show more stability and longer maturity than their contractual maturity. This is especially true of many retail and corporate deposits that, while they may be repayable on demand or at short notice, have shown good stability even in times of stress. We model behaviour profiles using our experience of customer behaviour. We use this data to determine the funds transfer pricing rates at which we reward and charge our business units for sources and uses of funds. We apply this rate until a customer changes to a different product or service offered by us or by one of our competitors. We continue to maintain the quality of our retail, commercial and wholesale deposits. We aim to deepen our customer relationships across all customer segments. We do this to lengthen the contractual and behavioural profile of our liability base. Deposit funding We mainly fund our Retail and Business Banking, Consumer Finance and Corporate & Commercial Banking activities by customer deposits. We fund the rest through wholesale markets. Composition of wholesale funding We are active in the wholesale markets and we have direct access to both money market and long-term investors through our funding programmes. This makes our wholesale funding well diversified by product, maturity, geography and currency. This includes currencies available across a range of channels from money markets, repo markets, senior unsecured, secured, medium-term and capital. Santander UK plc is our main operating company issuer of senior unsecured debt, structured notes, short-term funding and covered bonds. Santander UK Group Holdings plc is the issuer of capital and MREL/Total Loss Absorbing Capacity (TLAC) eligible senior unsecured debt. In line with the UK CRR and the Bank of England Statement of Policy on MREL, resolution entities that are G-SIBs or are part of a G-SIB are required to hold a minimum amount of loss absorbing and recapitalisation capacity on an ongoing basis. The minimum requirement is the higher of (i) two times the sum of Pillar 1 and Pillar 2A; (ii) 18% of RWAs; (iii) two times the minimum leverage ratio requirement; or (iv) 6.75% of leverage exposures. Santander UK plc is subject to internal MREL as it meets the requirements of a material subsidiary of our ultimate parent Banco Santander SA. We also access the wholesale markets through securitisations of certain assets of our operating subsidiaries. We also have access to UK Government funding schemes. Eligible collateral for these schemes includes all collateral that is eligible in the Bank of England’s Discount Window Facility. We ensure that enough collateral is placed and available at the Discount Window. Issuance model and resolution Banco Santander is a multiple point of entry resolution group. This means that should it fail, it would be split up into parts. Healthy parts might be sold or be kept as a residual group without their distressed sister companies. The resolution or recapitalisation of the distressed parts might be effected via ‘bail in’ of bonds that had been issued to the market by a regional intermediate holding company. Santander UK is a single point of entry resolution group. This means that resolution would work downwards from the group’s holding company i.e. Santander UK Group Holdings plc. Losses in subsidiaries would first be transferred up to Santander UK Group Holdings plc. If the holding company is bankrupt as a result, the group is deemed to be failing or likely to fail, it will be put into resolution. The ‘bail in’ tool is applied to the holding company, with the equity being written off and bonds written off or converted into equity as needed to recapitalise the group. Those bondholders would become the new owners, and the group would stay together. Santander UK Group Holdings plc is the immediate holding company of Santander UK plc but does not guarantee its debts or other obligations. This structure is a Bank of England recommended configuration which aims to ensure the activities of the operating company are not disrupted as the Santander UK group goes through resolution, thereby maintaining continuity of services for customers. FUNDING RISK REVIEW Our funding strategy continues to be based on maintaining a conservatively structured balance sheet and diverse sources of funding to meet the needs of our business strategy and plans. The CFO Division maintains a funding plan that complies with our LRA and regulatory liquidity and capital requirements. Reconciliation of wholesale funding to the balance sheet (audited) This table reconciles our wholesale funding to our balance sheet at 31 December 2023 and 31 December 2022 . Balance sheet line item Funding analysis Deposits by banks (1) Repurchas e agreement s - non trading Financial liabilities designated at fair value Debt securities in issue Subordinated liabilities Other equity instruments and non- controlling interests (2) 2023 £bn £bn £bn £bn £bn £bn £bn Deposits by banks 1.1 1.1 — — — — — Certificates of deposit and commercial paper 4.3 — — — 4.3 — — Senior unsecured – public benchmark 12.9 — — — 12.9 — — – privately placed 0.8 — — 0.6 0.2 — — Covered bonds 14.8 — — — 14.8 — — Securitisation and structured issuance 2.7 — — — 2.7 — — TFSME 17.0 17.0 — — — — — Subordinated liabilities and equity 4.4 — — — — 2.2 2.2 Total wholesale funding 58.0 18.1 — 0.6 34.9 2.2 2.2 Repos 8.4 — 8.4 — — — — Foreign exchange and hedge accounting 1.1 — — — 0.9 0.2 — Other 2.6 2.3 — 0.3 — — — Balance sheet total 70.1 20.4 8.4 0.9 35.8 2.4 2.2 2022 Deposits by banks 0.5 0.5 — — — — — Certificates of deposit and commercial paper 4.7 — — — 4.7 — — Senior unsecured – public benchmark 14.4 — — — 14.4 — — – privately placed 0.6 — — 0.4 0.2 — — Covered bonds 14.9 — — — 14.9 — — Securitisation and structured issuance 1.0 — — — 1.0 — — TFSME 25.0 25.0 — — — — — Subordinated liabilities and equity 4.1 — — — — 1.9 2.2 Total wholesale funding 65.2 25.5 — 0.4 35.2 1.9 2.2 Repos 8.0 — 8.0 — — — — Foreign exchange and hedge accounting 1.6 — — — 1.2 0.4 — Other 3.4 3.0 — 0.4 — — — Balance sheet total 78.2 28.5 8.0 0.8 36.4 2.3 2.2 (1) Consists of Perpetual Capital Securities (net of issuance costs) . See Note 33 to the Consolidated Financial Statements. (2) Other consists of items in the course of transmission and other deposits. See Note 24 to the Consolidated Financial Statements. Maturity profile of wholesale funding (audited) This table shows our main sources of wholesale funding. It does not include securities finance agreements. The table is based on exchange rates at issue and scheduled repayments and call dates. It does not reflect the final contractual maturity of the funding. For details of the maturities of financial liabilities and off-balance sheet commitments, see Note 39 to the Consolidated Financial Statements . ≤ 1 month >1 and ≤ 3 months >3 and ≤ 6 months >6 and ≤ 9 months >9 and ≤ 12 months Sub-total ≤ 1 year >1 and ≤ 2 years >2 and ≤ 5 years >5 years Total 2023 £bn £bn £bn £bn £bn £bn £bn £bn £bn £bn Santander UK Group Holdings plc (1) Senior unsecured – public benchmark — 1.6 — — — 1.6 2.5 6.8 0.5 11.4 – privately placed — — — — — — — 0.1 — 0.1 Subordinated liabilities and equity (incl. AT1) — — 0.5 — — 0.5 0.8 1.5 0.9 3.7 — 1.6 0.5 — — 2.1 3.3 8.4 1.4 15.2 Santander UK plc Deposits by banks 0.3 0.8 — — — 1.1 — — — 1.1 Certificates of deposit and commercial paper 1.0 3.3 — — — 4.3 — — — 4.3 Senior unsecured – public benchmark — 0.6 0.2 — — 0.8 0.4 — 0.3 1.5 – privately placed — — — 0.1 — 0.1 0.1 0.2 0.3 0.7 Covered bonds 0.1 1.0 0.9 0.4 1.0 3.4 1.1 9.2 1.1 14.8 Securitisation & structured issuance (2) — — — — 0.1 0.1 — 2.1 — 2.2 TFSME — — — — — — 17.0 — — 17.0 Subordinated liabilities — — — — — — — — 0.7 0.7 1.4 5.7 1.1 0.5 1.1 9.8 18.6 11.5 2.4 42.3 Other group entities Securitisation & structured issuance (3) — — — — — — 0.5 — — 0.5 31 December 2023 1.4 7.3 1.6 0.5 1.1 11.9 22.4 19.9 3.8 58.0 Of which: – Secured 0.1 1.0 0.9 0.4 1.1 3.5 18.6 11.3 1.1 34.5 – Unsecured 1.3 6.3 0.7 0.1 — 8.4 3.8 8.6 2.7 23.5 2022 Total at 31 December 2022 2.6 5.2 0.5 1.5 1.2 11.0 6.6 42.5 5.1 65.2 Of which: – Secured 0.1 1.0 0.2 0.9 — 2.2 3.5 34.0 1.2 40.9 – Unsecured 2.5 4.2 0.3 0.6 1.2 8.8 3.1 8.5 3.9 24.3 (1) 96% of senior unsecured debt issued from Santander UK Group Holdings plc has been downstreamed to Santander UK plc as ‘secondary non-preferential debt’ in line with the guidelines from the Bank of England for Internal MREL. (2) Includes funding from mortgage-backed securitisation vehicles where Santander UK plc is the asset originator. (3) Includes funding from asset-backed securitisation vehicles where entities other than Santander UK plc are the asset originator. 2023 compared to 2022 O ur overall funding strategy remains to develop and sustain a diversified funding base. We also need to fulfil regulatory requirements as well as support our credit ratings. We have stable and diversified wholesale funding programmes. We repaid £8.0bn of TFSME in 2023 as planned, with £17.0bn outstanding. At 31 December 2023 , 79% (2022: 83% ) of wholesale funding had a maturity of greater than one year, with an overall residual duration of 35 months (2022: 37 months). Currency composition of wholesale funds (audited) This table shows our wholesale funding by major currency at 31 December 2023 and 31 December 2022 . 2023 2022 Sterling US Dollar Euro Other Sterling US Dollar Euro Other % % % % % % % % Santander UK Group Holdings plc Senior unsecured – public benchmark 24 59 16 1 18 58 24 — – privately placed — — — 100 — — 100 Subordinated liabilities and equity (incl. AT1) 88 12 — — 75 25 — — 40 47 13 — 28 51 20 1 Santander UK plc Deposits by banks 1 97 2 — 29 71 — — Certificates of deposit and commercial paper 29 70 — 1 56 42 2 — Senior unsecured – public benchmark 21 56 23 — 18 62 20 — – privately placed 98 — 2 — 95 — 5 — Covered bonds 54 5 39 2 43 12 45 — Securitisation & structured issuance 100 — — — 100 — — — TFSME 100 — — — 100 — — — Subordinated liabilities 76 24 — — 48 52 — — 71 14 15 — 74 12 14 — Other group entities Securitisation & structured issuance 1.00 — — — — — — — Total 63 22 14 1 63 21 16 — Term issuance (audited) In 2023 , our external term issuance (sterling equivalent) was: Sterling US Dollar Euro Other 2023 2022 £bn £bn £bn £bn £bn £bn Santander UK Group Holdings plc Senior unsecured – public benchmark 0.4 1.1 — — 1.5 3.9 Subordinated debt and equity (inc. AT1) 1.1 — — — 1.1 0.8 1.5 1.1 — — 2.6 4.7 Santander UK plc Securitisations and other secured funding 1.5 — — — 1.5 0.6 Covered bonds 1.5 — — 0.3 1.8 4.0 Senior unsecured – privately placed 0.3 — — — 0.3 0.1 3.3 — — 0.3 3.6 4.7 Other group entities Securitisations 0.5 — — — 0.5 — Total gross issuances 5.3 1.1 — 0.3 6.7 9.4 In 2023 we issued c£5.6bn medium-term funding across a range of currencies, including c£1.5bn of MREL issuance and c£4.1bn of other secured issuance from Santander UK plc . We also issued £1.1bn of Tier 2 securities which were bought by Banco Santander . Loan to deposit ratio This table shows our customer loans, customer deposits and loan to deposit ratio (LDR) at 31 December 2023 and 31 December 2022 , and the adjustments to reconcile the data to the balance sheet. 2023 2022 Customer loans Customer deposits LDR (2) Customer loans Customer deposits LDR (2) £bn £bn % £bn £bn % Total customer loans and deposits (1) 206.7 193.6 107 % 219.7 196.5 112 % Adjust for fair value loans, impairment loss allowances, accrued interest and other 4.5 1.5 4.1 0.8 Statutory loans and advances to customers and deposits by customers 211.2 195.1 108 % 223.8 197.3 113 % (1) The customer loans and customer deposits numbers agree to the customer balances in the Balance sheet review section of the Financial review. (2) Customer loans (Loans and advances to customers) divided by Customer deposits (Deposits by customers) The LDR reduced as a result of active balance sheet management. 2023 compared to 2022 LDR reduced to 108% in 2023 with lower customer lending and deposits after pricing actions to optimise the customer balance sheet. Encumbrance We encumber an asset if we pledge or transfer it as collateral against a liability. This means it is no longer available to secure funding, meet our collateral needs or be sold to reduce funding needs. Being able to pledge or transfer assets as collateral is a key part of a bank’s operations. The main ways we encumber assets are that we: enter into securitisation, covered bonds, and repurchase agreements to access medium and long-term funding; enter into short-term funding transactions (including repurchase agreements and stock borrowing) as part of our liquidity management; pledge collateral as part of participating in payment and settlement systems; and post collateral as part of derivatives activity. We control levels of encumbrance by setting a minimum level of unencumbered assets after we factor in our funding plans, whether we can use our assets for our future collateral needs, the impact of a stress and our current encumbrance level. Assets classified as readily available for encumbrance include cash and securities in our eligible liquidity pool. They also include other unencumbered assets that give us a source of contingent liquidity. We do not rely on these extra unencumbered assets in our LRA, but we might use them in a stress. We can create liquidity by using them as collateral for secured funding or through outright sale. This includes excess collateral already in a secured funding structure and collateral pre- positioned at central banks that is available for use in secured funding. All other loans and advances are classified as not readily available for encumbrance, however, they may still be suitable for use in secured funding structures. Encumbrance of customer loans and advances We issued securitised products to a diverse investor base through our prime mortgage-backed and other asset-backed funding programmes. We raised funding with mortgage-backed notes, both issued to third parties and retained – the latter being central bank eligible collateral for funding purposes in other Bank of England facilities. We also have a covered bond programme, under which we issue securities to investors secured by a pool of residential mortgages. For more on these programmes, see Notes 14 and 26 to the Consolidated Financial Statements . On-balance sheet encumbered and unencumbered assets (audited) Encumbered with counterparties other than central banks Assets positioned at central banks (3) Covered bonds Securitis- ations Other Total 2023 £m £m £m £m £m Cash and balances at central banks (1)(2) — — 1,480 1,480 847 Financial assets at FVTPL: – Derivative financial instruments — — — — — – Other financial assets at FVTPL — — — — — Financial assets at amortised cost: – Loans and advances to customers 21,880 5,208 55 27,143 58,489 – Loans and advances to banks — — 254 254 — – Repurchase agreements – non trading — — — — — – Other financial assets at amortised cost — — 14 14 — Financial assets at FVOCI — — 5,254 5,254 — Interests in other entities — — — — — Intangible assets — — — — — Property, plant and equipment — — — — — Current tax assets — — — — — Retirement benefit assets — — — — — Other assets — — — — — Total assets 21,880 5,208 7,057 34,145 59,336 2022 £m £m £m £m £m Cash and balances at central banks (1)(2) — — 1,330 1,330 911 Financial assets at FVTPL: – Derivative financial instruments — — — — — – Other financial assets at FVTPL — — — — — Financial assets at amortised cost: – Loans and advances to customers 21,304 2,851 46 24,201 68,535 – Loans and advances to banks — — 163 163 — – Repurchase agreements – non trading — — — — — – Other financial assets at amortised cost — — 35 35 — Financial assets at FVOCI — — 4,441 4,441 — Interests in other entities — — — — — Intangible assets — — — — — Property, plant and equipment — — — — — Current tax assets — — — — — Retirement benefit assets — — — — — Other assets — — — — — Total assets 21,304 2,851 6,015 30,170 69,446 (1) Encumbered cash and balances at central banks include minimum cash balances we have to hold at central banks for regulatory purposes. (2) Readily realisable cash and balances at central banks are amounts held at central banks as part of our liquidity management activities. (3) Comprises pre-positioned assets and encumbered assets.

Capital Risk

Capital Risk	12 Months Ended
	Dec. 31, 2023
Disclosure Of Capital Risk Exposure [Abstract]
Capital Risk	Capital risk Overview Capital risk is the risk that we do not have an adequate amount or quality of capital to meet our business objectives, regulatory requirements and market expectations. In this section, we set out how we are regulated. We explain how we manage capital on a standalone basis as a subsidiary in the Banco Santander group. We then analyse our capital resources and key capital ratios including our leverage and RWAs. Key metrics CET1 capital ratio of 15.2% ( 2022 : 15.2% ) Total qualifying regulatory capital of £ 14.8 bn ( 2022 : £14.5b n) UK leverage ratio (T1 capital) of 5.1% ( 2022 : 5.2% ) THE SCOPE OF OUR CAPITAL ADEQUACY Regulatory supervision For capital purposes, we are subject to prudential supervision by the PRA, as a UK banking group, and by the European Central Bank (ECB) as part of the Banco Santander group. The ECB supervises Banco Santander as part of the Single Supervisory Mechanism (SSM). Although we are part of the Banco Santander group, we do not have a guarantee from Banco Santander SA and we operate as a standalone subsidiary. As we are part of the UK sub-group regulated by the PRA, we have to meet the PRA capital requirements on a standalone basis. We also have to show the PRA that we can withstand capital stress tests without the support of our parent. Reinforcing our corporate governance framework, the PRA exercises oversight through its rules and regulations on the Board and senior management appointments. Santander UK Group Holdings plc is the holding company of Santander UK plc and is the head of the Santander UK group for regulatory capital and leverage purposes. Santander UK plc is the head of the ring-fenced bank sub-group and is subject to regulatory capital and leverage rules in relation to that sub-group. Our basis of consolidation for our capital disclosures is substantially the same as for our Consolidated Financial Statements. CAPITAL RISK MANAGEMENT The Board is responsible for capital management strategy and policy and ensuring that we monitor and control our capital within regulatory and internal limits. We manage our funding and maintain capital adequacy on a standalone basis. We operate within the capital risk framework and appetite approved by our Board. This reflects the environment we operate in, our strategy for each material risk and the potential impact of adverse scenarios or stresses on our capital. Management of capital requirements (audited) Our capital risk appetite aims to maintain capital levels appropriate to the level of stress applied, and the expected regulatory response. In: – An adverse economic stress, which we expect once in 20 years, the firm should remain profitable and exceed all regulatory capital minimums at all times. – A very severe economic stress, which we expect once in 100 years, and which has been designed to test any specific weaknesses of a firm’s business model, the firm should meet all regulatory capital minimums at all times. This is subject to using regulatory buffers designed to absorb losses in such a stress. Management of capital resources (audited) We use a mix of regulatory and EC ratios and limits, internal buffers and restrictions to manage our capital resources. We also take account of the costs of differing capital instruments and capital management techniques. We also use these to shape the best structure for our capital needs. We decide how to allocate our capital resources as part of our strategic planning process. We base this in part on the relative returns on capital using both EC and regulatory capital measures. We plan for severe stresses and we set out what action we would take if an extremely severe stress threatened our viability and solvency. This could include not paying dividends, selling assets, reducing our business and issuing more capital. Risk measurement We apply Banco Santander’s approach to capital measurement and risk management for CRD IV. Santander UK Group Holdings plc is classified as a significant subsidiary of Banco Santander SA. For more on the CRD IV risk measurement of our exposures, see Banco Santander’s Pillar 3 report. Key metrics The main metrics we use to measure capital risk are CET1 capital ratio , and total capital ratio and UK leverage ratio . We continue to be in excess of overall capital requirements, minimum leverage requirements and minimum requirements for own funds and eligible liabilities (MREL). Stress testing Each year we create a capital plan, as part of our ICAAP. We share our ICAAP with the PRA. The PRA then tells us how much capital (Pillar 2A), and of what quality, it thinks we should hold on top of our Pillar 1 requirements and buffer levels. We also develop a series of economic scenarios to stress test our capital needs and confirm that we have enough regulatory capital to meet our projected and stressed capital needs and to meet our obligations as they fall due. In 2022, we developed a Climate Internal Scenario Analysis (CISA) to help understand better the potential impact of climate change on our business portfolios and balance sheet. Since then, we have invested in a strategic solution to deliver capability to run long-term horizon multi-scenario assessments which will inform future strategic decisions and enhance risk management capabilities (CISA Development). The model capability will support in exploring scenarios which would reflect a range of climate outcomes, covering shorter and longer-term (30-year) horizons and reflect physical and transition risks. The CISA outputs will form the basis of our future ICAAP exercises for climate risk and will help us prioritise our actions for the next five years. We augment our regulatory minimum capital with internal buffers. We hold buffers to ensure we have enough time to take action against unexpected changes. Risk mitigation We designed our capital risk framework, policies and procedures to ensure that we operate within our Risk Appetite. We manage capital transferability between our subsidiaries in line with our business strategy, our risk and capital management policies, UK laws and regulations. There are no legal restrictions on us moving capital resources promptly, or repaying liabilities, between the Company and its subsidiaries except for distributions between Santander UK entities in the ring- fenced bank sub-group and Santander UK entities that are not members of the ring-fenced bank sub-group, where the PRA is required to assess the impact of proposed distribution prior to payment. For details on our Recovery framework in the event of a capital stress, see 'risk mitigation' in the ‘Liquidity risk’ section. At 31 December 2023 , Santander UK Group Holdings plc, Santander Financial Services plc and Santander Equity Investments Limited were party to a capital support deed entered into on 17 December 2021 and effective from 1 January 2022 (the Non-RFB Sub-Group Capital Support Deed). These parties were permitted by the PRA to form a core UK group as defined in the PRA Rulebook, a permission which expires on 31 December 2024. Exposures of Santander Financial Services plc, the regulated entity, to other members of the core UK group are exempt from large exposure limits that would otherwise apply and these exposures are risk-weighted at 0% . Where applicable this permission also provides for intra-group exposures to be excluded from the leverage exposure measure. The purpose of the Non-RFB Sub-Group Capital Support Deed is to facilitate the prompt transfer of available capital resources from, or repayment of liabilities by, the non-regulated parties to the regulated party in the event that the regulated party breached or was at risk of breaching its capital resources or risk concentrations requirements. Risk monitoring and reporting We monitor and report regularly against our capital plan. We do this to identify any change in our business performance that might affect our capital. Each month, we also review the economic assumptions we use to create and stress test our capital plan. We do this to identify any potential reduction in our capital. CAPITAL RISK REVIEW Meeting evolving capital requirements We target a CET1 management buffer of sufficient size to absorb volatility in CET1 deductions, capital supply and capital demand whilst remaining above the current and expected future regulatory CET1 requirement. Distribution restrictions would be expected to be applied if we were unable to meet both our minimum requirement, which consists of the Pillar 1 minimum plus Pillar 2A, the CRD IV buffers consisting of the Capital Conservation Buffer (CCB), the Countercyclical Capital Buffer (CCyB), and the Other Systemically Important Institutions Buffer (O-SII) at the level of the RFB group . Impact of IFRS 9 on regulatory capital Our ECL methodology takes account of forward-looking data and covers a range of possible economic outcomes, and so provision movements may result in increased pro-cyclicality of risk-based capital and leverage ratios. However, the impact is currently mitigated by our surplus of IRB model regulatory expected losses over provisions for exposures using the IRB approach. For such exposures (which include residential mortgages) the adverse impact on CET1 capital of provision increases from reserve movements is offset by the related reduction of the negative CET1 capital adjustment for regulatory expected loss amounts. Also, the UK CRR transitional rules for the capital impact of IFRS 9 mean that adverse CET1 effects from increases in ECL-based provisions from the level of such provisions at 1 January 2018 are partly reduced until the end of 2024. We reflect projections of ECL provisions in our capital position forecasting under base case and stress scenarios for ICAAP and capital management purposes. We also consider the dynamics of ECL in how we assess and manage capital risk. A period of economic instability, such as that seen in early 2020 due to the impacts of the Covid-19 pandemic, could significantly impact our results and our financial assets. It could also impact the amount of capital we have to hold. We take into account the volatility of ECL in our capital planning strategy. Bank of England stress testing The results of the latest Bank of England stress test were released on 12 July 2023. As a result of the exercise, the Bank of England did not require Santander UK to undertake any actions. Before management actions, the CET1 capital ratio low-point of 11.3% is well above the hurdle rate of 8.1%. Additionally, the UK leverage ratio low-point of 4.1% without strategic management actions and 4.5% with strategic management actions is above the hurdle rate of 3.5%. The Bank of England’s hurdle rate comprises the sum of minimum capital requirements (4.5% of RWA plus Pillar 2A for the CET1 ratio, and 3.25% of leverage exposure for the UK leverage ratio), applicable systemic buffers, and an adjustment to offset the pro-cyclical impacts of IFRS 9. Headroom of our CET1 capital ratio to our current MDA trigger level at 31 December 2023 At 31 December 2023 , the headroom of our CET1 capital ratio of 15.2% to our 7% AT1 permanent write down (PWD) securities trigger was 8.2% of total RWAs or £ 5.7 bn ( 2022 : 8.2% of total RWAs or £ 5.8 bn). Higher profit and a reduction in RWA exposure was partially offset by the dividends paid in 2023. The headroom of our CET1 capital ratio to our current maximum distributable amount (MDA) trigger level at 31 December 2023 was: Minimum % Pillar 1 4.5 Pillar 2A (1) 2.3 Capital conservation buffer 2.5 Countercyclical capital buffer 2.0 Current MDA trigger 11.3 Headroom 3.9 CET1 capital ratio 15.2 (1) Santander UK's Pillar 2A regulatory requirement reduced by 1.6pp at 31 December 2023 , This results in c.£2bn lower MREL requirements in 2024. Pillar 2A guidance is a point in time assessment. Significant headroom to minimum capital requirements and MDA We remain very strongly capitalised with significant headroom to minimum requirements and MDA trigger. The UK leverage ratio of 5.1% remained broadly stable and is well above regulatory requirements. Key capital ratios Santander UK Group Holdings plc 2023 2022 % % CET1 capital ratio 15.2 15.2 AT1 3.2 3.1 Tier 2 3.0 2.1 Total capital ratio 21.4 20.4 Total capital ratio increased to 21.4% ( 2022 : 20.4% ) as a result of higher total qualifying capital, lower RWA and Tier 2 issuances. The total subordination available to Santander UK plc senior unsecured bondholders was 21.5% ( 2022 : 20.4% ) of RWAs. Return on assets - profit after tax divided by average total assets was 0.55 % ( 2022 : 0.48 %). Summarised change in CET1 capital ratio Change CET1 Capital ratio pp % 1 January 2023 15.2 Profit +2.2pp Dividends on ordinary shares -1.1pp AT1 coupons -0.2pp Special dividend -1.0pp Pension -0.3pp Expected loss less provisions -0.1pp RWA growth and other +0.5pp 31 December 2023 15.2 2023 compared to 2022 The CET1 capital ratio remained stable at 15.2% . Higher profit and a reduction in RWA exposure was partially offset by the dividends paid in 2023. Regulatory capital resources (audited) This table shows our qualifying regulatory capital: 2023 2022 £m £m CET1 capital instruments and reserves: – Capital instruments 7,060 7,060 – Retained earnings 6,047 6,563 – Accumulated other reserves and non-controlling interests (337) (1,108) CET1 capital before regulatory adjustments 12,770 12,515 CET1 regulatory adjustments: – Additional value adjustments (unaudited) (15) (18) – Goodwill (net of tax) (1,129) (1,133) – Other intangibles (349) (351) – Fair value reserves related to gains or losses on cash flow hedges (1) 335 1,116 – Negative amounts resulting from the calculation of regulatory expected loss amounts (unaudited) (595) (517) – Gains or losses on liabilities valued at fair value resulting from changes in own credit standing (14) (27) – Defined benefit pension fund assets (520) (755) – NPE Backstop 0 (4) – Dividend accrual (3) (3) – IFRS 9 Transitional Adjustment (unaudited) 44 20 CET1 capital 10,524 10,843 AT1 capital instruments: – Capital instruments 2,196 2,196 AT1 capital 2,196 2,196 Tier 1 capital 12,720 13,039 Tier 2 capital instruments: – Capital instruments 2,193 2,111 – Amount of qualifying items subject to phase out from Tier 2 193 207 – Regulatory deductions for instruments issued by subsidiary undertakings or subject to CRDIV amortisation and repurchases (331) (857) Tier 2 capital 2,055 1,461 Total regulatory capital 14,775 14,500 (1) From H223, amount includes £1.3m for cashflow hedge reserves FVOCI. 2023 compared to 2022 We paid £1.5bn interim dividends (2022: £1.0bn), £750m (2022: £300m) of which was a special dividend. Movements in regulatory capital CET1 capital AT1 capital Tier 2 capital Total £m £m £m £m At 1 January 2023 10,843 2,196 1,461 14,500 – Retained earnings (516) — — (516) – Other reserves and non-controlling interests (1) 770 — — 770 – Additional value adjustments (unaudited) 3 — — 3 – Goodwill (net of tax) 4 — — 4 – Other intangibles 2 — — 2 – Fair value reserves related to gains and losses on cash flow hedges (1) (780) — — (780) – Negative amounts resulting from the calculation of regulatory expected loss amounts (unaudited) (78) — — (78) – Gains or losses on liabilities valued at fair value resulting from changes in own credit standing 13 — — 13 – Defined benefit pension fund assets 235 — — 235 – NPE Backstop 4 — — 4 – Capital instruments — — 82 82 – IFRS 9 Transitional Adjustment (unaudited) 24 — — 24 – Amount of qualifying items subject to phase out from Tier 2 — — (14) (14) - Deductions for instruments issued by subsidiary undertakings or subject to CRD IV amortisation — — 526 526 At 31 December 2023 10,524 2,196 2,055 14,775 (1) From H223, amount includes £1.3m for cashflow hedge reserves FVOCI. In line with the position of the Basel Committee views following the outbreak of the Covid-19 pandemic, the UK adopted revised IFRS 9 transitional adjustment rules which apply a higher level of transitional relief to capital following rises in IFRS 9 provisions. The original transitional adjustments consisted of a Static component, which was impacted on 1 January 2018 and a Dynamic component with changes in provisions for non-impaired assets made after 1 January 2018. A transitional factor was applied to the Dynamic component to determine the level of offset that was available over time (95% in 2018, 85% in 2019, 70% in 2020, 50% in 2021 and 25% in 2022). The revisions to the transitional adjustment are part of the ‘Quick fix' CRR amendments which have been in force from 27 June 2020. They have involved dividing the original Dynamic component into two parts – creating an ‘old’ component for provision changes from 1 January 2018 to 1 January 2020, and then a new Dynamic component for provision changes from 1 January 2020 and applying a revised higher transitional factor to this latter component, with an extended transitional period lasting until the end of 2024. CET1, AT1 and Tier 2 regulatory adjustments These are adjustments required by CRD IV. AT1 capital The £750m Fixed Rate Reset Perpetual AT1 Capital Securities (net of issuance costs), the £800m Perpetual Capital Securities and the £500m Perpetual Capital Securities we have issued since 2017 fully meet the CRD IV AT1 capital rules. Tier 2 capital These are fully CRD IV eligible Tier 2 instruments under CRD IV. The adjustments are: – Derivatives netting and potential future exposure: where a qualifying netting agreement is in place netting is allowed for leverage purposes. This is partially offset by including the Potential Future Exposure (PFE) we use to calculate EADs – Securities financing current exposure add-on: we include an add-on for securities financing transactions to show current exposure for leverage purposes – Removal of IFRS netting: where netting of assets and liabilities is allowed under IFRS, but not under the Basel rules, we remove it for leverage purposes – Removal of qualifying central banks claims: permitted under PRA Rulebook, but under CRD IV rules the exposure measure does not allow the removal of qualifying central bank deposits or claims – Commitments calculated in accordance with Basel Committee Leverage Framework: we add the gross value of off-balance sheet commitments for leverage purposes after we apply regulatory credit conversion factors – CET1 regulatory adjustments: where we have deducted assets from CET1, they can be deducted for leverage purposes. MREL recapitalisation At 2023 , we had outstanding £11.8 bn of MREL compliant senior unsecured bonds. Our forward-looking MREL recapitalisation plan assumes the Pillar 2A requirement remains at 4.13% and is calculated using RWA, leverage exposures and exchange rates at 31 December 2023 . Based on this set of assumptions, our MREL requirements are driven by our RWAs. Santander UK’s indicative MREL requirements including combined buffer requirements are currently circa £21bn from 31 December 2022. In addition to meeting our minimum requirement, we intend to have an MREL recapitalisation management buffer in excess of the value of Santander UK Group Holdings plc senior unsecured securities that are due to become MREL ineligible over the following six months, plus a buffer for foreign exchange movements. Risk-weighted assets The tables below are consistent with our regulatory filings for 31 December 2023 and 31 December 2022 . 2023 2022 RWAs by risk £bn £bn Credit risk 60.2 63.0 Counterparty risk 0.7 0.7 Market risk 0.4 0.3 Operational risk 7.8 7.2 69.1 71.2 2023 2022 RWAs by segment £bn £bn Retail and Business Banking 43.2 44.6 – Mortgages 32.8 35.0 – Everyday Banking 10.4 9.6 Consumer Finance 7.4 7.3 Corporate & Commercial Banking 13.6 14.0 Corporate Centre 4.9 5.3 69.1 71.2 Credit/ counterparty risk Market risk Operational risk Total Movements in RWAs by risk £bn £bn £bn £bn At 1 January 2023 63.7 0.3 7.2 71.2 Asset size (2.9) 0.1 0.6 (2.2) Asset quality 0.2 — — 0.2 Model updates 0.1 — — 0.1 Methodology and policy 0.3 — — 0.3 Other (0.5) — — (0.5) At 31 December 2023 60.9 0.4 7.8 69.1 2023 compared to 2022 RWAs decreased with lower mortgage lending and active balance sheet management. Regulatory leverage 2023 2022 £m £m Regulatory exposure 247,214 248,602 End-point Tier 1 capital (1) 12,533 12,863 UK leverage ratio 5.1 % 5.2 % BBLS lending excluded from leverage exposure (1,828) (2,564) (1) Includes deductions and AT1 adjustment permitted under the recommendation from the Financial Policy Committee on 25 July 2016. Under the PRA rules, we adjust our total assets per the Consolidated Balance Sheet to calculate our regulatory exposure for leverage purposes. We do this as follows: 2023 2022 £m £m Total assets per the Consolidated Balance Sheet 282,083 292,243 Derivatives netting and potential future exposure (252) (1,305) Securities financing current exposure add-on 778 371 Removal of IFRS netting 805 923 Removal of qualifying central bank claims (42,351) (49,199) Commitments calculated in accordance with Basel Committee Leverage Framework 7,275 6,971 CET1 regulatory adjustments (1,124) (1,402) 247,214 248,602 The adjustments are: – Derivatives netting and potential future exposure: where a qualifying netting agreement is in place netting is allowed for leverage purposes. This is partially offset by including the Potential Future Exposure (PFE) we use to calculate EADs – Securities financing current exposure add-on: we include an add-on for securities financing transactions to show current exposure for leverage purposes – Removal of IFRS netting: where netting of assets and liabilities is allowed under IFRS, but not under the Basel rules, we remove it for leverage purposes – Removal of qualifying central banks claims: permitted under the recommendation of the Financial Policy Committee (FPC) on 25 July 2016, but under CRD IV rules the exposure measure does not allow the removal of qualifying central bank deposits or claims – Commitments calculated in accordance with Basel Committee Leverage Framework: we add the gross value of off-balance sheet commitments for leverage purposes after we apply regulatory credit conversion factors – CET1 regulatory adjustments: where we have deducted assets from CET1, they can be deducted for leverage purposes. Distributable items Distributable items are equivalent to distributable profits under the UK Companies Act 2006. The distributable items of Santander UK Group Holdings plc under CRD IV at 31 December 2023 and 31 December 2022 , and movements in the period, were as follows: 2023 2022 £m £m At 1 January 4,307 4,262 Dividends approved: – AT1 Capital Securities (133) (143) – Tax on above item 25 27 – Ordinary shares (1,538) (1,013) Dividends receivable: – Investment in AT1 Capital Securities 123 133 – Tax on above item (23) (25) – Investment in ordinary shares of subsidiary 1,562 1,079 Other income statement items (Company) (8) (13) At period end 4,315 4,307

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2023
Disclosure Of Significant Accounting Policies [Abstract]
Accounting Policies	1. ACCOUNTING POLICIES These financial statements are prepared for Santander UK Group Holdings plc (the Company) and the Santander UK Group Holdings plc group (the Santander UK group) under the UK Companies Act 2006. The principal activity of the Santander UK group is the provision of a wide range of banking and financial services to personal, business and corporate customers. Santander UK Group Holdings plc is a public company, limited by shares and incorporated in England and Wales having a registered office at 2 Triton Square, Regent’s Place, London, NW1 3AN . It is a financial services holding company. Basis of preparation These financial statements incorporate the financial statements of the Company and entities it controls (its subsidiaries) made up to 31 December each year. The consolidated financial statements have been prepared on the going concern basis using the historical cost convention, except for financial assets and liabilities that have been measured at fair value. An assessment of the appropriateness of the adoption of the going concern basis of accounting is disclosed in the statement of going concern in the Directors’ report. Compliance with International Financial Reporting Standards (IFRS) The consolidated financial statements of the Santander UK group and the separate financial statements of the Company comply with UK-adopted International Accounting Standards (IAS). The financial statements are also prepared in accordance with IFRS as issued by the International Accounting Standards Board (IASB), including interpretations issued by the IFRS Interpretations Committee, as there are no applicable differences from IFRS as issued by the IASB for the periods presented. Disclosures required by IFRS 7 ‘Financial Instruments: Disclosure’ relating to the nature and extent of risks arising from financial instruments, and IAS 1 ‘Presentation of Financial Statements’ relating to objectives, policies and processes for managing capital, have been included in the Risk review section of this Annual Report. This information forms an integral part of these financial statements by this cross reference, is marked as audited, and is covered by the Independent auditors' report. Climate change Santander UK continues to develop its assessment of the potential impacts that climate change and the transition to a low carbon economy may have on the assets and liabilities recognised and presented in its financial statements. Santander UK is mindful of its responsibilities as a responsible lender and is focused on ways to meet the objectives of the Paris Agreement on climate change and to support the UK’s transition to a climate-resilient, net zero economy. Santander UK's current climate change strategy focuses on three main areas to achieve Banco Santander's ambition to reach net zero emissions by 2050: 1. Managing climate risks by integrating climate considerations into risk management frameworks, screening and stress testing our portfolio for climate related financial risks, and setting risk appetites to help steer our portfolio in line with the Paris Agreement, 2. Supporting our customers’ transition by developing products and services that promote a reduction in CO 2 emissions, and 3. Reducing emissions in our operations and supply chain by focusing on continuous improvement in our operations, and environmental and energy management systems in accordance with ISO14001 and 15001, promoting responsible procurement practices and employee engagement. Santander UK's current climate change strategy and its view of the risks associated with climate change and the transition to a low carbon economy are reflected in its critical judgements and accounting estimates, although climate change risk did not have a material impact at 31 December 2023 and 2022, consistent with management's assessment that climate change and the transition to a low carbon economy are not currently expected to have a meaningful impact on the viability of the Santander UK group in the medium term. At 31 December 2023 and 2022, management specifically considered the potential impact of climate change and the transition to a low carbon economy on: – Loans and advances to customers ( see Note 13 and the credit risk section of the Risk review). Some climate change risks arise due to the requirements of IFRS 9 and others relate to specific portfolios and sectors: – ECL calculations are based on multiple forward-looking economic scenarios developed by management covering a period of 5 years , during which timeframe climate change risks may crystallise; – For mortgages in Retail & Business Banking and commercial real estate lending in Corporate & Commercial Banking, the value of property collateral might be affected by physical impacts related to the frequency and scale of extreme weather events, such as flood and subsidence risk, or changing environmental performance standards for property. – For automotive loans in Consumer Finance, the residual value of automotive vehicles might be impacted by diesel obsolescence and the transition to electric vehicles. – For corporate lending in Corporate & Commercial Banking, certain sectors give rise to fossil fuel exposures, such as Oil & Gas, Mining & Extraction and Power Generation. – Goodwill impairment assessment (see Note 20). Estimates underpinning the determination of whether or not goodwill balances are impaired are partly based on forecast business performance beyond the time horizon for management's detailed plans. Future changes to Santander UK's climate change strategy may impact Santander UK's critical judgements and accounting estimates and result in material changes to financial results and the carrying values of certain assets and liabilities in future reporting periods. Future accounting developments At 31 December 2023 , for the Santander UK group, there were no significant new or revised standards and interpretations, and amendments thereto, which have been issued but which are not yet effective, or which have otherwise not been early adopted where permitted. Comparative information As required by US public company reporting requirements, these financial statements include two years of comparative information for the consolidated income statement, consolidated statement of comprehensive income, consolidated statement of changes in equity, consolidated statement of cash flows and related notes. Material accounting policy information The following material accounting policies have been applied in preparing these financial statements. For material accounting policies which involve the application of judgements or accounting estimates that are determined to be critical to the preparation of these financial statements see 'Critical judgements and accounting estimates'. Consolidation The consolidated financial statements incorporate the financial statements of the Company and entities (including structured entities) controlled by it and its subsidiaries. The acquisition method of accounting is used to account for the acquisition of subsidiaries which meet the definition of a business. Business combinations between entities under common control (i.e. fellow subsidiaries of Banco Santander SA, the ultimate parent) are outside the scope of IFRS 3 – ‘Business Combinations’, and there is no other guidance for such transactions under IFRS. The Santander UK group elects to account for business combinations between entities under common control at their book values in the acquired entity by including the acquired entity’s results from the date of the business combination and not restating comparatives. Reorganisations of entities within the Santander UK group are also accounted for at their book values. Credit protection entities established as part of significant risk transfer (SRT) transactions are not consolidated by the Santander UK group in cases where third party investors have the exposure, or rights, to all of the variability of returns from the performance of the entities. Revenue recognition a) Interest income and expense Interest and similar income and expense are recognised in the income statement using the effective interest rate method for: all financial instruments measured at amortised cost; debt instruments measured at FVOCI; and the effective part of any related accounting hedging instruments. Interest income is calculated by applying the effective interest rate to the gross carrying amount of financial assets, except for financial assets that have subsequently become credit-impaired (i.e. Stage 3), for which interest revenue is calculated by applying the effective interest rate to their amortised cost (i.e. net of the ECL provision). For more information on stage allocations of credit risk exposures, see ‘Significant increase in credit risk’ in the ‘Santander UK group level – credit risk management’ section of the Risk review. b) Fee and commission income and expense Fees and commissions that are not an integral part of the effective interest rate are recognised when the service is performed. Most fee and commission income is recognised at a point in time. Certain commitment, upfront and management fees are recognised over time but are not material. For retail and corporate products, fee and commission income consists principally of collection services fees, commission on foreign currencies, commission and other fees received from retailers for processing credit card transactions, fees received from other credit card issuers for providing cash advances for their customers through the Santander UK group’s branch and ATM networks, annual fees payable by credit card holders and fees for non-banking financial products. For insurance products, fee and commission income consists principally of commissions and profit share arising from the sale of building and contents insurance and life protection insurance. Commissions arising from the sale of buildings and contents insurance are recognised over the period of insurance cover, adjusted to take account of cancelled policies. Profit share income from the sale of buildings and contents insurance which is not subject to any adjustment is recognised when the profit share income is earned. Commissions and profit share arising from the sale of life protection insurance is subject to adjustment for cancellations of policies within 3 years from inception. Fee and commission income which forms an integral part of the effective interest rate of a financial instrument (for example certain loan commitment fees) is recognised as an adjustment to the effective interest rate and recorded in ‘Interest income’. c) Other operating income Other operating income includes all gains and losses from changes in the fair value of financial assets and liabilities held at fair value through profit or loss (comprising financial assets and liabilities held for trading, trading derivatives and other financial assets and liabilities at fair value through profit or loss), together with related interest income, expense, dividends, and changes in fair value of any derivatives managed in conjunction with these assets and liabilities. Other operating income also includes hedge ineffectiveness arising from fair value and cash flow hedging, income from operating lease assets, and profits and losses arising on the sales of property, plant and equipment and subsidiary undertakings. Defined benefit pension schemes (see 'Critical judgements and accounting estimates') A defined benefit scheme is a pension scheme that guarantees an amount of pension benefit to be provided, usually as a function of one or more factors such as age, years of service or compensation. Pension costs are charged to ‘Administration expenses’, within the line item ‘Operating expenses before impairment losses, provisions and charges’ with the net interest on the defined benefit asset or liability included within ‘Net interest income’ in the income statement. The asset or liability recognised in respect of defined benefit pension schemes is the present value of the defined benefit obligation at the balance sheet date, less the fair value of scheme assets. The defined benefit obligation is calculated annually by independent actuaries using the projected unit credit method. The assets of the schemes are measured at their fair values at the balance sheet date. The present value of the defined benefit obligation is estimated by projecting forward the growth in current accrued pension benefits to reflect inflation and salary growth to the date of pension payment, then discounted to present value using the yield applicable to high-quality AA rated corporate bonds of the same currency and which have terms to maturity closest to the terms of the scheme liabilities, adjusted where necessary to match those terms. In determining the value of scheme liabilities, demographic and financial assumptions are made by management about life expectancy, inflation, discount rates, pension increases and earnings growth, based on past experience and future expectations. Financial assumptions are based on market conditions at the balance sheet date and can generally be derived objectively. Demographic assumptions require a greater degree of estimation and judgement to be applied to externally derived data. Any surplus or deficit of scheme assets over liabilities is recognised in the balance sheet as an asset (surplus) or liability (deficit). An asset is only recognised to the extent that the surplus can be recovered through reduced contributions in the future or through refunds from the scheme. Share-based payments The Santander UK group engages in cash-settled and equity-settled share-based payment transactions in respect of services received from certain of its employees. Shares of the Santander UK group’s parent, Banco Santander SA are purchased in the open market by the Santander UK group (for the Employee Sharesave scheme) or are purchased by Banco Santander SA or another Banco Santander subsidiary (including awards granted under the Long-Term Incentive Plan and the Deferred Shares Bonus Plan) to satisfy share options or awards as they vest. Options granted under the Employee Sharesave scheme and awards granted under the Transformation Incentive Plan are accounted for as cash-settled share- based payment transactions. Awards granted under the Long-Term Incentive Plan and Deferred Shares Bonus Plan are accounted for as equity-settled share- based payment transactions. The fair value of the options granted under the Employee Sharesave scheme is determined using an option pricing model, which takes into account the exercise price of the option, the current share price, the risk-free interest rate, the expected volatility of the Banco Santander SA share price over the life of the option and the dividend growth rate. The fair value of the awards granted for the Long-Term Incentive Plan was determined at the grant date using an option pricing model, which takes into account the share price at grant date, the risk-free interest rate, the expected volatility of the Banco Santander SA share price over the life of the award and the dividend growth rate. Goodwill and other intangible assets (for goodwill see 'Critical judgements and accounting estimates') Goodwill represents the excess of the cost of an acquisition, as well as the fair value of any interest previously held, over the fair value of the share of the identifiable net assets of the acquired subsidiary, or business at the date of acquisition. Goodwill on the acquisition of subsidiaries and businesses is included in intangible assets. Goodwill is tested for impairment annually, or more frequently when events or changes in circumstances dictate and carried at cost less accumulated impairment losses. Gains and losses on the disposal of an entity or business include the carrying amount of goodwill relating to the entity or business sold. Other intangible assets are recognised if they arise from contractual or other legal rights or if they are capable of being separated or divided from Santander UK and sold, transferred, licensed, rented or exchanged. The value of such intangible assets, where they are available for use, is amortised on a straight-line basis over their useful economic life of three to seven years and the assets are reviewed annually for impairment indicators and tested for impairment where indicators are present. Other intangible assets that are not yet available for use are tested for impairment annually or more frequently when events or changes in circumstances dictate. Software development costs are capitalised when they are direct costs associated with identifiable and unique software products that are expected to provide future economic benefits and the cost of those products can be measured reliably. These costs include payroll, materials, services and directly attributable overheads. Internally developed software meeting these criteria and externally purchased software are classified in intangible assets on the balance sheet and amortised on a straight-line basis over their useful life of three to seven years, unless the software is an integral part of the related computer hardware, in which case it is treated as property, plant and equipment as described below. Capitalisation of costs ceases when the software is capable of operating as intended. Costs of maintaining software are expensed as incurred. Property, plant and equipment Property, plant and equipment include owner-occupied properties (including leasehold properties), office fixtures and equipment and computer software. Property, plant and equipment also includes operating leases where the Santander UK group is the lessor and right-of-use assets where the Santander UK group is the lessee. Internally developed software meeting the criteria set out in ‘Goodwill and other intangible assets’ above and externally purchased software are classified in property, plant and equipment where the software is an integral part of the related computer hardware (for example, the operating system of a computer). Classes of property, plant and equipment are depreciated on a straight-line basis over their useful life, as follows: Owner-occupied properties Not exceeding 50 years Office fixtures and equipment 3 to 15 years Computer software 3 to 7 years Right-of-use assets Shorter of the lease term or the useful life of the underlying asset Operating lease assets - vehicles 1 to 4 years Depreciation is not charged on freehold land. Depreciation of operating lease assets where the Santander UK group is the lessor is described in 'Leases' below. Financial instruments (for impairment of debt instrument financial assets see 'Critical judgements and accounting estimates: Credit impairment losses') a) Initial recognition and measurement Financial assets and liabilities are initially recognised when the Santander UK group becomes a party to the contractual terms of the instrument. The Santander UK group determines the classification of its financial assets and liabilities at initial recognition and measures a financial asset or financial liability at its fair value plus or minus, in the case of a financial asset or financial liability not at FVTPL, transaction costs that are incremental and directly attributable to the acquisition or issue of the financial asset or financial liability. Transaction costs of financial assets and financial liabilities carried at FVTPL are expensed in profit or loss. Immediately after initial recognition, an expected credit loss (ECL) allowance is recognised for financial assets measured at amortised cost and investments in debt instruments measured at FVOCI. A regular way purchase or sale is a purchase or sale of a financial asset under a contract whose terms require delivery of the asset within the timeframe established generally by regulation or convention in the marketplace concerned. Regular way purchases and sales of financial assets measured at amortised cost are recognised on settlement date; all other regular way purchases and sales of financial assets are recognised on trade date. b) Financial assets and liabilities i) Classification and subsequent measurement The Santander UK group classifies its financial assets in the measurement categories of amortised cost, FVOCI and FVTPL. Financial assets and financial liabilities are classified as FVTPL where there is a requirement to do so or where they are otherwise designated at FVTPL on initial recognition. Financial assets and financial liabilities which are required to be held at FVTPL include: – Financial assets and financial liabilities held for trading. – Debt instruments that do not have solely payments of principal and interest (SPPI) characteristics. Otherwise, such instruments are measured at amortised cost or FVOCI, and – Equity instruments that have not been designated as held at FVOCI. Financial assets and financial liabilities are classified as held for trading if they are derivatives or if they are acquired or incurred principally for the purpose of selling or repurchasing in the near-term, or form part of a portfolio of financial instruments that are managed together and for which there is evidence of short-term profit taking. In certain circumstances, other financial assets and financial liabilities are designated at FVTPL where this results in more relevant information. This may arise because it significantly reduces a measurement inconsistency that would otherwise arise from measuring assets or liabilities or recognising the gains or losses on them on a different basis, where the assets and liabilities are managed and their performance evaluated on a fair value basis or, in the case of financial liabilities, where it contains one or more embedded derivatives which are not closely related to the host contract. The classification and measurement requirements for financial asset debt and equity instruments and financial liabilities are set out below. Financial assets: debt instruments Debt instruments are those instruments that meet the definition of a financial liability from the issuer’s perspective, such as loans and government and corporate bonds. Classification and subsequent measurement of debt instruments depend on the Santander UK group’s business model for managing the asset, and the cash flow characteristics of the asset. Business model The business model reflects how the Santander UK group manages the assets in order to generate cash flows and, specifically, whether the Santander UK group’s objective is solely to collect the contractual cash flows from the assets or is to collect both the contractual cash flows and cash flows arising from the sale of the assets. If neither of these is applicable, such as where the financial assets are held for trading purposes, then the financial assets are classified as part of an ‘other’ business model and measured at FVTPL. Factors considered in determining the business model for a group of assets include past experience on how the cash flows for these assets were collected, how the assets’ performance is evaluated and reported to key management personnel, and how risks are assessed and managed. SPPI Where the business model is to hold assets to collect contractual cash flows or to collect contractual cash flows and sell, the Santander UK group assesses whether the assets’ cash flows represent SPPI. In making this assessment, the Santander UK group considers whether the contractual cash flows are consistent with a basic lending arrangement (i.e. interest includes only consideration for the time value of money, credit risk, other basic lending risks and a profit margin that is consistent with a basic lending arrangement). Where the contractual terms introduce exposure to risk or volatility that is inconsistent with a basic lending arrangement, the related asset is classified and measured at FVTPL. Financial assets with embedded derivatives are considered in their entirety when determining whether their cash flows are SPPI. Based on these factors, the Santander UK group classifies its debt instruments into one of the following measurement categories: – Amortised cost – Financial assets that are held for collection of contractual cash flows where those cash flows represent SPPI, and that are not designated at FVTPL, are measured at amortised cost. The carrying amount of these assets is adjusted by any ECL recognised and measured as presented in Note 13 . Interest income from these financial assets is included in ‘Interest and similar income’ using the effective interest rate method. When estimates of future cash flows are revised, the carrying amount of the respective financial assets is adjusted to reflect the new estimate discounted using the original effective interest rate. Any changes are recognised in the income statement. – FVOCI – Financial assets that are held for collection of contractual cash flows and for selling the assets, where the assets’ cash flows represent SPPI, and that are not designated at FVTPL, are measured at FVOCI. Movements in the carrying amount are recognised in OCI, except for the recognition of impairment gains or losses, interest revenue and foreign exchange gains and losses which are recognised in profit or loss. When the financial asset is derecognised, the cumulative gain or loss previously recognised in OCI is reclassified from equity to profit or loss and recognised in ‘Other operating income’. Interest income from these financial assets is included in ‘Interest and similar income’ using the effective interest rate method. – FVTPL – Financial assets that do not meet the criteria for amortised cost or FVOCI are measured at FVTPL. A gain or loss on a debt instrument that is subsequently measured at FVTPL, including any debt instruments designated at fair value, is recognised in profit or loss and presented in the income statement in ‘Other operating income’ in the period in which it arises. The Santander UK group reclassifies financial assets when and only when its business model for managing those assets changes. The reclassification takes place from the start of the first reporting period following the change. Such changes are expected to be very infrequent. Financial assets: equity instruments Equity instruments are instruments that meet the definition of equity from the issuer’s perspective, being instruments that do not contain a contractual obligation to pay cash and that evidence a residual interest in the issuer’s net assets. All equity investments are subsequently measured at FVTPL; management may elect, at initial recognition, to irrevocably designate an equity investment at FVOCI but has not currently done so. When this election is used, fair value gains and losses are recognised in OCI and are not subsequently reclassified to profit or loss, including on disposal. ECLs (and reversal of ECLs) are not reported separately from other changes in fair value. Dividends, when representing a return on such investments, continue to be recognised in profit or loss as other income when the right to receive payments is established. Gains and losses on equity investments at FVTPL are included in ‘Other operating income’ in the income statement. Financial liabilities Financial liabilities, which include deposits by banks, deposits by customers, debt securities in issue and subordinated liabilities, are classified as subsequently measured at amortised cost, except for: – Financial liabilities at FVTPL (see Note 22 ): this classification is applied to derivatives and other financial liabilities designated as such at initial recognition. Gains or losses on financial liabilities designated at FVTPL are presented partially in other comprehensive income (the amount of change in the fair value of the financial liability that is attributable to changes in the credit risk of that liability) and partially in profit or loss (the remaining amount of change in the fair value of the liability) – Financial liabilities arising from the transfer of financial assets which did not qualify for derecognition, whereby a financial liability is recognised for the consideration received for the transfer. In subsequent periods, the Santander UK group recognises any expense incurred on the financial liability, and – Financial guarantee contracts and loan commitments. Preference shares which carry a contractual obligation to transfer economic benefits are classified as financial liabilities and are presented in subordinated liabilities. The coupon on these preference shares is recognised in the income statement as interest expense on an amortised cost basis using the effective interest method. Contracts involving the receipt of cash on which customers receive an index-linked return are accounted for as equity index-linked deposits. The principal products are Capital Guaranteed/Protected Products which give the customers a limited participation in the upside growth of an equity index. In the event the index falls in price, a cash principal element is guaranteed/protected. The equity index-linked deposits contain embedded derivatives. These embedded derivatives, in combination with the principal cash deposit element, are designed to replicate the investment performance profile tailored to the return agreed in the contracts with customers. The cash principal element is accounted for as deposits by customers at amortised cost. The embedded derivatives are separated from the host instrument and are separately accounted for as derivatives. Sale and repurchase agreements (including stock borrowing and lending) Securities sold subject to a commitment to repurchase them at a predetermined price (repos) under which substantially all the risks and rewards of ownership are retained by the Santander UK group remain on the balance sheet and a liability is recorded in respect of the consideration received. Securities purchased under commitments to resell (reverse repos) are not recognised on the balance sheet and the consideration paid is recorded as an asset. The difference between the sale and repurchase price is treated as trading income in the income statement, except where the repo is not treated as part of the trading book, in which case the difference is recorded in interest income or expense. Securities lending and borrowing transactions are generally secured, with collateral in the form of securities or cash advanced or received. Securities borrowed are not reflected on the balance sheet. Collateral in the form of cash received or advanced is recorded as a deposit or a loan. Collateral in the form of securities is not recognised. Day One profit adjustments The fair value of a financial instrument on initial recognition is generally its transaction price (that is, the fair value of the consideration given or received). However, sometimes the fair value will be based on other observable current market transactions in the same instrument, without modification or repackaging, or on a valuation technique whose variables include only data from observable markets, such as interest rate yield curves, option volatilities and currency rates. When such evidence exists, the Santander UK group recognises a trading gain or loss at inception (Day One gain or loss), being the difference between the transaction price and the fair value. When significant unobservable parameters are used, the entire Day One gain or loss is deferred and is recognised in the income statement over the life of the transaction until the transaction matures, is closed out, the valuation inputs become observable, or an offsetting transaction is entered into. ii) Impairment of debt instrument financial assets The Santander UK group assesses on a forward-looking basis the ECL associated with its debt instrument assets carried at amortised cost and FVOCI and with the exposure arising from financial guarantee contracts and loan commitments. The Santander UK group recognises a loss allowance for such losses at each reporting date. The measurement of ECL reflects: – An unbiased and probability-weighted amount that is determined by evaluating a range of possible outcomes. – The time value of money, and – Reasonable and supportable information that is available without undue cost or effort at the reporting date about past events, current conditions and forecasts of future economic conditions. Grouping of instruments for losses measured on a collective basis We typically group instruments and assess them for impairment collectively where they share risk characteristics (as described in the Credit risk section of the Risk review) using one or more statistical models. Wh

Segments

Segments	12 Months Ended
	Dec. 31, 2023
Disclosure of operating segments [abstract]
Segments	2. SEGMENTS Santander UK’s principal activity is financial services, mainly in the UK. The business is managed and reported on the basis of four segments, which are strategic business units that offer different products and services, have different customers and require different technology and marketing strategies. Geographical information is not provided, as substantially all of Santander UK’s activities are in the UK. Retail & Business Banking (formerly Retail Banking) consists of two business units, Mortgages and Everyday Banking. Mortgages provides prime UK mortgage lending to owner occupiers and buy-to-let landlords with small portfolios. Everyday Banking provides banking services and unsecured lending to individuals and small businesses as well alongside wealth management for high-net-worth clients. – Consumer Finance provides prime auto consumer financing for individuals, businesses, and automotive distribution networks. – Corporate & Commercial Banking provides banking products and services to SMEs, mid-sized and larger corporates, typically with annual turnovers of between £2m and £500m as well as to Local Authorities and Housing Associations. – Corporate Centre provides treasury services for asset and liability management of our balance sheet. Retail & Business Banking delivers products through our omni-channel presence comprising branches, ATMs, telephony, digital and intermediary channels. Consumer Finance business is primarily introduced by car dealerships acting as our intermediary along with a small amount of new business introduced via digital channels. Corporate and Commercial Banking expertise is provided by relationship managers, product specialists and through digital and telephony channels, and cover clients' needs both in the UK and overseas. In addition, Corporate and Investment Banking (CIB) provided services to corporate clients with an annual turnover of £500m and above. Santander UK transferred a significant part of the CIB business to the London branch of Banco Santander SA under a part VII banking business transfer scheme which completed on 11 October 2021. The residual parts of the business were wound down or transferred to other segments. The segmental data is prepared on a statutory basis of accounting, in line with the accounting policies set out in Note 1 . Transactions between segments are on normal commercial terms and conditions. Internal charges and internal UK transfer pricing adjustments are reflected in the results of each segment, and eliminate on consolidation. Revenue sharing agreements are used to allocate external customer revenues to a segment on a reasonable basis. Funds are ordinarily reallocated between segments, resulting in funding cost transfers disclosed in operating income. Interest charged for these funds is based on Santander UK’s cost of wholesale funding. Interest income and interest expense have not been reported separately. The majority of segment revenues are interest income in nature and net interest income is relied on primarily to assess segment performance and to make decisions on the allocation of segment resources. Results by segment 3 For the year ended 31 December Retail & Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 2023 £m £m £m £m £m Net interest income/(expense) 3,740 156 841 (70) 4,667 Non-interest income 177 192 135 5 509 Total operating income/(expense) 3,917 348 976 (65) 5,176 Operating expenses before credit impairment charges, provisions and charges (1,816) (141) (351) (177) (2,485) Credit impairment charges (150) (15) (40) (1) (206) Provisions for other liabilities and charges (233) (18) (15) (70) (336) Total operating credit impairment charges, provisions and charges (383) (33) (55) (71) (542) Profit/(loss) from continuing operations before tax 1,718 174 570 (313) 2,149 Revenue from external customers 3,670 663 712 131 5,176 Inter-segment revenue/(expense) 247 (315) 264 (196) — Total operating income/(expense) 3,917 348 976 (65) 5,176 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 493 — 49 — 542 – Insurance, protection and investments 47 — — — 47 – Credit cards 94 — — — 94 – Non-banking and other fees (2) 3 25 79 11 118 Total fee and commission income 637 25 128 11 801 Fee and commission expense (463) (6) (11) (25) (505) Net fee and commission income/(expense) 174 19 117 (14) 296 Customer loans 182,267 5,228 17,939 1,256 206,690 Customer deposits 158,329 — 24,066 11,168 193,563 Average number of full-time equivalent staff 16,330 816 2,376 184 19,706 (1) The disaggregation of fees and commission income as shown above is not included in reports provided to the chief operating decision maker but is provided to show the split by reportable segments. (2) Non-banking and other fees include mortgages (except mortgage account fees), consumer finance, commitment commission, asset finance, invoice finance and trade finance. (3) Total assets and total liabilities are no longer included in reports provided to the chief operating decision maker. Retail & Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 2022 £m £m £m £m £m Net interest income 3,689 180 580 23 4,472 Non-interest income/(expense) 197 195 146 (4) 534 Total operating income 3,886 375 726 19 5,006 Operating expenses before credit impairment charges, provisions and charges (1,683) (144) (342) (201) (2,370) Credit impairment charges (263) (27) (31) — (321) Provisions for other liabilities and charges (395) (6) (8) (12) (421) Total operating credit impairment charges, provisions and charges (658) (33) (39) (12) (742) Profit/(loss) from continuing operations before tax 1,545 198 345 (194) 1,894 Revenue/(expense) from external customers 4,153 513 732 (392) 5,006 Inter-segment (expense)/revenue (267) (138) (6) 411 — Total operating income 3,886 375 726 19 5,006 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 502 — 60 — 562 – Insurance, protection and investments 78 — — — 78 – Credit cards 95 — — — 95 – Non-banking and other fees (2) 2 20 77 2 101 Total fee and commission income 677 20 137 2 836 Fee and commission expense (483) (5) (18) (6) (512) Net fee and commission income/(expense) 194 15 119 (4) 324 31 December 2022 Customer loans 194,661 5,384 18,518 1,141 219,704 Customer deposits 161,748 — 24,798 9,930 196,476 Average number of full-time equivalent staff 15,212 531 2,336 194 18,273 Retail & Business Banking Consumer Finance Corporate & Commercial Banking Corporate & Investment Banking Corporate Centre Total 2021 £m £m £m £m £m £m Net interest income/(expense) 3,374 233 397 — (7) 3,997 Non-interest income 201 178 112 — 56 547 Total operating income 3,575 411 509 — 49 4,544 Operating expenses before credit impairment write-backs, provisions and charges (1,703) (163) (365) — (309) (2,540) Credit impairment write-backs 98 33 90 — 12 233 Provisions for other liabilities and charges (187) 4 (34) — (162) (379) Total operating credit impairment (charges)/write-backs, provisions and charges (89) 37 56 — (150) (146) Profit/(loss) from continuing operations before tax 1,783 285 200 — (410) 1,858 Revenue/(expense) from external customers 4,061 489 619 — (625) 4,544 Inter-segment (expense)/revenue (486) (78) (110) — 674 — Total operating income 3,575 411 509 — 49 4,544 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 428 — 50 — — 478 – Insurance, protection and investments 67 — — — — 67 – Credit card fees 73 — — — — 73 – Non-banking and other fees (2) 2 10 62 — 2 76 Total fee and commission income 570 10 112 — 2 694 Fee and commission expense (384) — (22) — (8) (414) Net fee and commission income/(expense) 186 10 90 — (6) 280 Customer loans 185,608 4,984 19,282 — 742 210,616 Customer deposits 156,991 — 26,466 — 8,719 192,176 Average number of full-time equivalent staff 16,149 670 2,281 528 216 19,844 (1) The disaggregation of fees and commission income as shown above is not included in reports provided to the chief operating decision maker but is provided to show the split by reportable segments. (2) Non-banking and other fees include mortgages (except mortgage account fees), consumer finance, commitment commission, asset finance, invoice finance and trade finance. (3) Total assets and total liabilities are no longer included in reports provided to the chief operating decision maker. The table below shows the relationships between Customer assets and Loans and advances to customers as presented in the Consolidated Balance Sheet. Customer assets exclude Joint ventures, as they carry low credit risk and therefore have an immaterial ECL, and Other items, mainly accrued interest that we have not yet charged to the customer's account, and cash collateral. It also shows the relationship between customer liabilities (see above) and Deposits by customers as presented in the Consolidated Balance Sheet. Assets Liabilities 2023 2022 2023 2022 £m £m £m £m Customer balances (gross) 206,690 219,704 193,563 196,476 Loan loss allowance (916) (933) — — Customer balances (net) 205,774 218,771 193,563 196,476 Intercompany balances 4,488 4,165 958 1,153 Accrued interest 747 647 834 237 Other items 213 257 (206) (553) Loans and advances to customers / Deposits by customers 211,222 223,840 195,149 197,313

Net Interest Income

Net Interest Income	12 Months Ended
	Dec. 31, 2023
Analysis of income and expense [abstract]
Net Interest Income	3. NET INTEREST INCOME Group 2023 2022 2021 £m £m £m Interest and similar income: Loans and advances to customers 8,888 5,854 4,685 Loans and advances to banks 1,865 651 54 Reverse repurchase agreements – non-trading 625 149 35 Other 475 168 56 Total interest and similar income (1) 11,853 6,822 4,830 Interest expense and similar charges: Deposits by customers (3,283) (827) (331) Deposits by banks (1,167) (496) (23) Repurchase agreements – non-trading (538) (120) (3) Debt securities in issue (2,024) (795) (372) Subordinated liabilities (169) (108) (92) Other (5) (4) (12) Total interest expense and similar charges (2) (7,186) (2,350) (833) Net interest income 4,667 4,472 3,997 (1) Includes £230m ( 2022 : £87m , 2021 : £22m ) of interest income on financial assets at FVOCI. (2) Includes £707m ( 2022 : £6m , 2021 : £317m ) of interest expense on the effective part of derivatives hedging debt issuances and £3m ( 2022 : £3m , 2021 : £3m ) of interest expense on lease liabilities.

Net Fee and Commission Income

Net Fee and Commission Income	12 Months Ended
	Dec. 31, 2023
Fee and commission income (expense) [abstract]
Net Fee and Commission Income	4. NET FEE AND COMMISSION INCOME Group 2023 2022 2021 £m £m £m Fee and commission income: Current account and debit card fees 542 562 478 Insurance, protection and investments 47 78 67 Credit cards 94 95 73 Non-banking and other fees (1) 118 101 76 Total fee and commission income 801 836 694 Total fee and commission expense (505) (512) (414) Net fee and commission income 296 324 280 (1) Non-banking and other fees include mortgages (except mortgage account fees), consumer finance, commitment commission, asset finance, invoice finance and trade finance.

Other Operating Income

Other Operating Income	12 Months Ended
	Dec. 31, 2023
Net Trading And Other Income [Abstract]
Other Operating Income	5. OTHER OPERATING INCOME Group 2023 2022 2021 £m £m £m Net (losses) on financial instruments designated at fair value through profit or loss (1) (33) (74) (68) Net gains on financial instruments mandatorily at fair value through profit or loss (2) 42 84 50 Hedge ineffectiveness 18 28 8 Net profit on sale of financial assets at fair value through other comprehensive income — — 6 Income from operating lease assets 118 129 136 Other 68 43 135 213 210 267 (1) Net (losses) on financial instruments designated at fair value through profit or loss include losses of £24m on deposits ( 2022 : £35m gains, 2021 £18m losses), losses of £32m on debt securities ( 2022 : £31m gains, 2021 : £nil ). (2) Net gains on financial instruments mandatorily at fair value through profit or loss include gains of £5m on debt securities ( 2022 : £13m gains, 2021 : £10m losses). Net gains on financial instruments mandatorily at FVTPL includes fair value losses of £12m ( 2022 : gains of £14m , 2021 : losses of £15m ) on embedded derivatives bifurcated from certain equity index-linked deposits, as described in the derivatives accounting policy in Note 1 . The embedded derivatives are economically hedged, the results of which are also included in this line item and amounted to gains of £12m ( 2022 : losses of £14m , 2021 : gains of £15m ). As a result, the net fair value movements recognised on the equity index-linked deposits and the related economic hedges were net gains of £nil ( 2022 : £nil , 2021 : £nil ). Group 2023 2022 2021 £m £m £m Exchange rate differences in the consolidated income statement on items not at fair value through profit and loss 1,215 (2,147) 215 These are principally offset by related releases from the cash flow hedge reserve (1,231) 2,130 (357) In 2023 , the Santander UK group repurchased certain debt securities and subordinated liabilities as part of ongoing liability management exercises. For more, see Note 27 . In 2022, Other includes £7m of losses on the sale of property under our transformation programme. In 2021, Other includes £73m of property gains from the sale of our London head office and branch properties.

Operating Expenses Before Credi

Operating Expenses Before Credit Impairment Charges, Provisions and Charges	12 Months Ended
	Dec. 31, 2023
Expenses by nature [abstract]
Operating Expenses Before Credit Impairment Charges, Provisions and Charges	6. OPERATING EXPENSES BEFORE CREDIT IMPAIRMENT CHARGES, PROVISIONS AND CHARGES For the year ended 31 December Group 2023 2022 2021 £m £m £m Staff costs: Wages and salaries 854 761 759 Performance-related payments 164 173 184 Social security costs 116 112 113 Pensions costs: – defined contribution plans 71 60 65 – defined benefit plans 13 28 38 Other share-based payments 4 1 1 Other personnel costs 42 44 42 1,264 1,179 1,202 Other administration expenses 931 894 831 Depreciation, amortisation and impairment 290 297 507 2,485 2,370 2,540 Staff costs Performance-related payments’ include bonuses paid in cash and share awards granted under the arrangements described in Note 36 . Included in this are equity- settled share-based payments, none of which related to option-based schemes. These are disclosed in the table below as ‘Shares awards’. Performance-related payments above include amounts related to deferred performance awards as follows: Costs recognised in 2023 Costs expected to be recognised in 2024 or later Arising from awards in current year Arising from awards in prior year Total Arising from awards in current year Arising from awards in prior year Total £m £m £m £m £m £m Cash 3 4 7 5 7 12 Shares 2 5 7 4 7 11 5 9 14 9 14 23 The following table shows the amount of bonus awarded to employees for the performance year 2023 . In the case of deferred cash and shares awards, the final amount paid to an employee is influenced by forfeiture provisions and any performance conditions to which the awards are subject. The deferred shares award amount is based on the fair value of the awards at the date of grant. Expenses charged in the year Expenses deferred to future periods Total 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m Cash award – not deferred 142 148 — — 142 148 – deferred 7 8 12 14 19 22 Shares award – not deferred 8 9 — — 8 9 – deferred 7 8 11 14 18 22 Total discretionary bonus 164 173 23 28 187 201 Other share-based payments’ consist of options granted under the Employee Sharesave scheme which comprise the Santander UK group’s cash-settled share- based payments. For more, see Note 36 . The average number of full-time equivalent staff was 19,706 ( 2022 : 18,273 , 2021 : 19,844 ) . Depreciation, amortisation and impairment In 2023 , depreciation, amortisation and impairment included depreciation of £64m ( 2022 : £73m , 2021 : £81m ) on operating lease assets (where the Santander UK group is the lessor) with a carrying amount of £488m at 31 December 2023 ( 2022 : £577m , 2021 : £595m ). It also included depreciation of £30m ( 2022 : £19m , 2021 : £20m ) on right-of-use assets with a carrying amount of £93m at 31 December 2023 ( 2022 : £115m , 2021 : £119m ) . Other administration expenses includes £19m ( 2022 : £21m , 2021 : £23m ) related to short-term leases. In 2023 , depreciation, amortisation and impairment included an impairment charge of £25m ( 2022 : £10m , 2021 : £88m ) associated with branch and head office site closures as part of the transformation programme. For more, see Note 21 .

Audit and Other Services

Audit and Other Services	12 Months Ended
	Dec. 31, 2023
Audit And Other Services [Abstract]
Audit and Other Services	7. AUDIT AND OTHER SERVICES Group 2023 2022 2021 £m £m £m Audit fees: Fees payable to the Company’s auditor and its associates for the audit of the Santander UK group’s annual accounts 15.0 12.8 12.1 Fees payable to the Company’s auditor and its associates for other services to the Santander UK group: – Audit of the Santander UK group’s subsidiaries 0.7 0.8 1.2 Total audit fees (1) 15.7 13.6 13.3 Non-audit fees: Audit-related assurance services 2.3 1.9 1.7 Other assurance services 0.8 0.8 0.5 Other non-audit services 0.2 0.2 0.2 Total non-audit fees 3.3 2.9 2.4 (1) 2023 audit fees included £0.7m ( 2022 : £0.6m , 2021 : £1.2m ) which related to the prior year. Audit fees payable for the statutory audit of Santander UK Group Holdings plc were £0.6m ( 2022 : £0.6m , 2021 : £0.5m ). Audit-related assurance services mainly comprised services performed in connection with review of the financial information of the Company and reporting to the Company's UK regulators. Other assurance services mainly comprised services performed in support of various debt issuance programmes. Of the total non-audit fees, £1.7m ( 2022 : £1.5m , 2021 : £1.2m ) accords with the definition of 'Audit Fees' per US Securities and Exchange Commission (SEC) guidance, £1.6m ( 2022 : £1.4m , 2021 : £1.2m ) accords with the definition of 'Audit related fees' per that guidance and £37,000 ( 2022 : £nil , 2021 : £nil ) accords with the definition of 'All other fees' per that guidance. In 2023 , the Company’s auditors earned no fees ( 2022 : £nil , 2021 : £27,000 fees) payable by entities outside the Santander UK group for the review of the financial position of corporate and other borrowers. In 2023 , the Company's auditors earned £1.6m ( 2022 : £1.6m , 2021 : £1.4m ), in relation to incremental work undertaken in support of the audit of Banco Santander SA.

Credit Impairment Charges and P

Credit Impairment Charges and Provisions	12 Months Ended
	Dec. 31, 2023
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Credit Impairment Charges and Provisions	8. CREDIT IMPAIRMENT CHARGES AND PROVISIONS For the year ended 31 December Group 2023 2022 2021 £m £m £m Credit impairment charges/(write-backs): Loans and advances to customers 192 249 (186) Recoveries of loans and advances, net of collection costs 10 36 (17) Off-balance sheet credit exposures (See Note 29) 4 36 (30) 206 321 (233) Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 29) 335 424 388 Releases for residual value and voluntary termination 1 (3) (9) 336 421 379 542 742 146 In 2023 , 2022 and 2021 there were no material credit impairment charges on loans and advances to banks, non-trading reverse repurchase agreements, other financial assets at amortised cost and financial assets at FVOCI.

Taxation

Taxation	12 Months Ended
	Dec. 31, 2023
Major components of tax expense (income) [abstract]
Taxation	9. TAXATION Group 2023 2022 2021 £m £m £m Current tax: UK corporation tax on profit for the year 474 524 400 Adjustments in respect of prior years (23) (88) (30) Total current tax 451 436 370 Deferred tax: Charge/(credit) for the year 109 (30) 101 Adjustments in respect of prior years (7) 65 14 Total deferred tax 102 35 115 Tax on profit from continuing operations 553 471 485 The standard rate of UK corporation tax was 28% for banking entities and 24% for non-banking entities ( 2022 : 27% for banking entities and 19% for non-banking entities; 2021 : 27% for banking entities and 19% for non-banking entities) following the introduction of a surcharge on banking companies in 2016. Taxation for other jurisdictions is calculated at the rates prevailing in the relevant jurisdictions. The Santander UK group’s effective tax rate for 2023 was 25.7% ( 2022 : 24.9% , 2021 : 26.1% ). The tax on profit from continuing operations before tax differs from the theoretical amount that would arise using the basic corporation tax rate as follows: For the year ended 31 December Group 2023 2022 2021 £m £m £m Profit from continuing operations before tax 2,149 1,894 1,858 Tax calculated at a tax rate of 23.5% (2022:19%, 2021: 19%) 505 360 353 Bank surcharge on profits 84 123 106 Non-deductible preference dividends paid 9 9 9 Non-deductible UK Bank Levy 10 13 14 Non-deductible conduct remediation, fines and penalties 13 48 6 Other non-deductible costs and non-taxable income (5) 20 33 Effect of change in tax rate on deferred tax provision 2 (28) 8 Tax relief on dividends in respect of other equity instruments (35) (40) (40) Adjustment to prior year provisions (30) (34) (4) Tax on profit from continuing operations 553 471 485 On 20 June 2023, Finance (No.2) Act 2023 was substantively enacted in the UK to implement the OECD Pillar Two model rules and which introduces a global minimum effective tax rate of 15% with effect from 1 January 2024. Santander UK will therefore fall within the scope of these rules from 2024. However, since this legislation does not apply to earlier periods, Santander UK has no related current tax exposure in 2023. Santander UK has also applied the exception to recognising and disclosing information about deferred tax assets and liabilities related to Pillar Two income taxes, as provided in the amendments to IAS 12 issued in May 2023. Santander UK continues to assess its exposure to the Pillar Two legislation for when it comes into effect. This assessment currently indicates that there should be no impact on the UK activities but that an additional top up tax will apply to its operations in Jersey and the Isle of Man where both the statutory rate and effective tax rates are expected to be 10% for 2024. The effect on the Santander UK tax charge for 2024 is not expected to be material. Current tax assets and liabilities Movements in current tax assets and liabilities during the year were as follows: Group 2023 2022 £m £m Assets 484 351 At 1 January 484 351 Income statement charge (including discontinued operations) (451) (436) Other comprehensive income (charge)/credit (70) 159 Corporate income tax received 539 397 Other movements 5 13 507 484 Assets 507 484 At 31 December 507 484 The amount of corporation income tax paid differs from the tax charge for the period as a result of the timing of payments due to the tax authorities, the effects of movements in deferred tax, adjustments to prior period current tax provisions and current tax recognised directly in other comprehensive income. Santander UK proactively engages and cooperates with relevant tax authorities in their oversight of the company's tax matters. The accounting policy for recognising provisions for any tax risks identified is described in Note 1 . It is not expected that there will be any material movement in such provisions within the next 12 months. The Santander UK group has applied the UK’s Code of Practice on Taxation for Banks following its adoption in 2010. For more information, see our Taxation Strategy on our website aboutsantander.co.uk. Deferred tax The table below shows the deferred tax balances including the movement in the deferred tax account during the year. Deferred tax balances are presented in the balance sheet after offsetting assets and liabilities where the Santander UK group has the legal right to offset and intends to settle on a net basis. Group Fair value of financial instruments Pension remeasurement Cash flow hedges Fair value reserve Tax losses carried forward Accelerated tax depreciation Other temporary differences Total £m £m £m £m £m £m £m £m At 1 January 2023 27 (290) 305 (2) — 35 (105) (30) Income statement (charge)/credit (35) (63) — — — (17) 13 (102) Transfers/reclassifications — 2 (2) — — — — — Credited/(charged) to other comprehensive income — 167 (232) 5 — — 4 (56) At 31 December 2023 (8) (184) 71 3 — 18 (88) (188) At 1 January 2022 (123) (508) (7) (12) 8 68 1 (573) Income statement credit/(charge) 150 (49) — — (7) (33) (96) (35) Transfers/reclassifications — — 3 (1) (1) — (1) — Credited/(charged) to other comprehensive income — 267 309 11 — — (9) 578 At 31 December 2022 27 (290) 305 (2) — 35 (105) (30) The deferred tax assets and liabilities above have been recognised in the Santander UK group on the basis that sufficient future taxable profits are forecast within the foreseeable future, in excess of the profits arising from the reversal of existing taxable temporary differences, to allow for the utilisation of the assets as they reverse. Based on the conditions at the balance sheet date, management determined that a reasonably possible change in any of the key assumptions underlying the estimated future taxable profits in the Santander UK group’s three-year plan (described in Note 20 ) would not cause a reduction in the deferred tax assets recognised. There are £nil unrecognised deferred tax assets on capital losses carried forward ( 2022 : £ nil ).

Dividends on Ordinary Shares

Dividends on Ordinary Shares	12 Months Ended
	Dec. 31, 2023
Dividends On Ordinary Shares [Abstract]
Dividends on Ordinary Shares	10. DIVIDENDS ON ORDINARY SHARES Dividends on ordinary shares declared and paid in the year were as follows: Group Group 2023 2022 2021 2023 2022 2021 Pence per share Pence per share Pence per share £m £m £m In respect of current year – first interim 5.86 5.62 4.05 414 397 286 – second interim 15.92 8.73 15.01 1,124 616 1,060 21.78 14.35 19.06 1,538 1,013 1,346 In 2023 an interim dividend of £1,538m ( 2022 : £1,013m , 2021 : £1,346m ) was paid on the Company's ordinary shares in issue. In 2023, £750m ( 2022 : £300m ) of the dividend was a special dividend. These were paid following review and approval by the Board in line with our dividend policy.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2023
Disclosure of nature and extent of risks arising from financial instruments [abstract]
Derivative Financial Instruments	11. DERIVATIVE FINANCIAL INSTRUMENTS a) Use of derivatives Santander UK undertakes derivative activities primarily to provide customers with risk management solutions and to manage and hedge its own risks. These derivative activities do not give rise to significant open positions in portfolios of derivatives. Any residual position is managed to ensure that it remains within acceptable risk levels, with matching transactions used to achieve this where necessary. When entering into derivatives, Santander UK employs the same credit risk management procedures to assess and approve potential credit exposures that are used for traditional lending. b) Analysis of derivatives The table below includes the notional amounts of transactions outstanding at the balance sheet date; they do not represent actual exposures. Group 2023 2022 Fair value Fair value Notional amount Assets Liabilities Notional amount Assets Liabilities £m £m £m £m £m £m Derivatives held for trading: Exchange rate contracts 13,536 92 241 14,769 320 299 Interest rate contracts 28,806 398 626 31,599 473 792 Equity and credit contracts 810 143 25 954 142 25 Total derivatives held for trading 43,152 633 892 47,322 935 1,116 Derivatives held for hedging Designated as fair value hedges: Exchange rate contracts 1,145 29 2 538 12 4 Interest rate contracts 107,753 1,276 843 77,885 1,776 411 108,898 1,305 845 78,423 1,788 415 Designated as cash flow hedges: Exchange rate contracts 21,618 1,008 290 26,035 1,717 186 Interest rate contracts 51,881 554 911 25,971 164 1,463 Equity derivative contracts 59 19 — 51 8 1 73,558 1,581 1,201 52,057 1,889 1,650 Total derivatives held for hedging 182,456 2,886 2,046 130,480 3,677 2,065 Derivative netting (1) — (2,047) (2,047) — (2,173) (2,173) Total derivatives 225,608 1,472 891 177,802 2,439 1,008 (1) Derivative netting excludes the effect of cash collateral, which is offset against the gross derivative position. The amount of cash collateral received that had been offset against the gross derivative assets was £472m ( 2022 : £1,368m ) and the amount of cash collateral paid that had been offset against the gross derivative liabilities was £12m ( 2022 : £70m ). At 31 December 2023 , the fair value of derivative assets included amounts due from Banco Santander group entities of £802m ( 2022 : £1,346m ) and the fair value of derivative liabilities included amounts due to Banco Santander group entities of £298m ( 2022 : £246m ). For information about the impact of netting arrangements on derivative assets and liabilities in the table above, see Note 40 . The table below analyses the notional and fair values of derivatives by trading and settlement method. Notional Traded over the counter Asset Liability Settled by central counterparties Not settled by central counterparties Total Traded over the counter Traded over the counter 2023 £m £m £m £m £m Exchange rate contracts — 36,299 36,299 1,129 533 Interest rate contracts 174,460 13,980 188,440 181 333 Equity and credit contracts — 869 869 162 25 174,460 51,148 225,608 1,472 891 2022 Exchange rate contracts — 41,342 41,342 2,049 489 Interest rate contracts 124,638 10,817 135,455 240 493 Equity and credit contracts — 1,005 1,005 150 26 124,638 53,164 177,802 2,439 1,008 c) Analysis of derivatives designated as hedges Santander UK applies hedge accounting on both a fair value and cash flow basis depending on the nature of the underlying exposure. We establish the hedge ratio by matching the notional of the derivative with the underlying position being hedged. Only the designated risk is hedged and therefore other risks, such as credit risk are managed but not hedged. For interest rate hedges, the designated hedged risk is determined with reference to the underlying benchmark rate. Fair value hedges Portfolio hedges of interest rate risk Santander UK holds portfolios of fixed rate assets and liabilities which expose it to changes in fair value due to movements in market interest rates. We manage these exposures by entering into interest rate swaps. Each portfolio contains assets or liabilities that are similar in nature and share the risk exposure that is designated as being hedged. The interest rate risk component is the change in fair value of fixed rate instruments for changes in the designated benchmark rate. Such changes are usually the largest component of the overall change in fair value. Separate hedges are maintained for each underlying currency. Effectiveness is assessed by comparing changes in the fair value of the hedged item attributable to changes in the designated benchmark interest rate, with changes in the fair value of the interest rate swaps. Micro hedges of interest rate risk and foreign currency risk Santander UK accesses international markets to obtain funding, to issue fixed rate debt or to invest in fixed rate debt of other issuers as part of maintaining a portfolio of HQLA (High Quality Liquid Assets) in its functional currency and other currencies. We are therefore exposed to changes in fair value due to changes in market interest rates and/or foreign exchange rates, principally in USD and EUR, which we mitigate through the use of receive fixed/pay floating rate interest rate swaps and/or receive fixed/pay floating rate cross currency swaps. The interest rate risk component is the change in fair value of the fixed rate debt due to changes in the benchmark rate. The foreign exchange component is the change in the fair value of the fixed rate debt issuance due to changes in foreign exchange rates prevailing from the time of execution. Effectiveness is assessed by using linear regression techniques to compare changes in the fair value of the debt caused by changes in the benchmark interest rate and foreign exchange rates, with changes in the fair value of the interest rate swaps and/or cross currency swaps. Cash flow hedges Hedges of interest rate risk Santander UK manages its exposure to the variability in cash flows of floating rate assets and liabilities attributable to movements in market interest rates by entering into interest rate swaps. The interest rate risk component is determined with reference to the underlying benchmark rate attributable to the floating rates asset or liability. Designated benchmark rates referenced are currently SONIA or BoE base rate. Effectiveness is assessed by comparing changes in the fair value of the interest rate swap with changes in the fair value of the hedged item attributable to the hedged risk, applying a hypothetical derivative method using linear regression techniques. Hedges of foreign currency risk As Santander UK obtains funding in international markets, we assume significant foreign currency risk exposure, mainly in USD and EUR. In addition, Santander UK also holds debt securities for liquidity purposes which assumes foreign currency exposure, principally in JPY and CHF. Santander UK manages the exposures to the variability in cash flows of foreign currency denominated assets and liabilities to movements in foreign exchange rates by entering into either foreign exchange contracts (spot, forward and swaps) or cross currency swaps. These instruments are entered into to match the cash flow profile and maturity of the estimated interest and principal repayments of the hedged item. The foreign currency risk component is the change in cash flows of the foreign currency debt arising from changes in the relevant foreign currency forward exchange rate. Such changes constitute a significant component of the overall changes in cash flows of the instrument. Effectiveness is assessed by comparing changes in the fair value of the foreign exchange contracts (spot, forward and swaps) or cross currency swaps with changes in the fair value of the hedged debt attributable to the hedged risk applying a hypothetical derivative method using linear regression techniques. Equity risk on cash settled share-based transactions Santander Equity Investments Limited (SEIL) offers employees the chance to buy shares in Banco Santander SA at a discount under Sharesave, or other incentive schemes. This exposes Santander UK to equity price risk. The equity risk is managed by purchasing share options which allow Santander UK to buy shares at a fixed price. These instruments are entered into to match the amount of employee share options expected to be exercised. The equity price risk is the change in cash flows arising from the change in share price over time. Santander UK established the hedge ratio by matching the notional of the derivative with the notional of the employee share options being hedged. Effectiveness is assessed using the Dollar Offset method by comparing the actual changes in the intrinsic value of the hedging instruments and the actual changes in the intrinsic value of the hedged item which have resulted from the actual movements in the Banco Santander share price. Possible sources of hedge ineffectiveness For both fair value and cash flow hedges, hedge ineffectiveness can arise from hedging derivatives with a non-zero fair value at the date of initial designation. In addition, for: Fair value hedges Hedge ineffectiveness can also arise due to differences in discounting between the hedged item and the hedging instrument as cash collateralised swaps discount using Overnight Indexed Swaps discount curves not applied to the hedged item; and where counterparty credit risk impacts the fair value of the derivative but not the hedged item. For portfolio hedges of interest rate risk, it can also arise due to differences in the expected and actual volume of prepayments. Cash flow hedges Hedge ineffectiveness can also arise due to differences in the timing of cash flows between the hedged item and the hedging instrument. For micro hedges of interest rate risk, it can also arise due to differences in the basis of cash flows between the hedged item and the hedging instrument. For hedges of equity risk on cash settled share-based transactions, it can also arise due to changes in the expected number of Sharesave options to be exercised. Maturity profile and average price/rate of hedging instruments The following table sets out the maturity profile and average price/rate of the hedging instruments used in the Santander UK group’s hedging strategies: Group 2023 Hedging Instruments ≤1 month >1 and ≤3 months >3 and ≤12 months >1 and ≤5 years >5 years Total Fair value hedges: Interest rate risk Interest rate contracts - Nominal amount (£m) 3,612 7,141 32,241 60,803 3,008 106,805 Average fixed interest rate - GBP 2.38 % 3.19 % 3.42 % 3.89 % 3.99 % Average fixed interest rate - EUR 1.14 % 0.18 % 0.45 % 0.21 % 3.92 % Average fixed interest rate - USD 2.60 % 2.46 % 4.23 % 1.36 % 4.91 % Interest rate/FX risk Exchange rate contracts - Nominal amount (£m) — 18 — 1,041 86 1,145 Interest rate contracts - Nominal amount (£m) — 18 — 844 86 948 Average GBP - EUR exchange rate — 1.11 — 1.16 1.15 Average GBP - USD exchange rate — — — 1.32 — Average fixed interest rate - EUR — — — 2.77 % 3.48 % Average fixed interest rate - USD — — — 4.83 % — Cash flow hedges: Interest rate risk Interest rate contracts - Nominal amount (£m) 911 3,083 13,671 27,715 1,219 46,599 Average fixed interest rate - GBP 5.06 % 3.05 % 5.38 % 3.84 % 3.45 % FX risk Exchange rate contracts - Nominal amount (£m) 927 3,238 2,692 9,447 588 16,892 Interest rate contracts - Nominal amount (£m) — 2,199 — — 942 3,141 Average GBP - JPY exchange rate 154.14 153.95 167.85 — — Average GBP - CHF exchange rate 1.09 1.09 1.09 1.12 1.12 Average GBP - EUR exchange rate — 1.20 1.17 1.18 — Average GBP - USD exchange rate — 1.39 — 1.28 1.39 Equity risk Equity derivative contracts - Nominal amount (£m) — — 7 50 2 59 Interest rate/FX risk Exchange rate contracts - Nominal amount (£m) 87 785 500 2,896 458 4,726 Interest rate contracts - Nominal amount (£m) — — — 1,975 166 2,141 Average GBP - EUR exchange rate 1.18 — 1.25 1.20 1.19 Average GBP - USD exchange rate — 1.66 — 1.38 1.54 Average fixed interest rate - GBP 2.57 % 2.54 % 2.96 % 2.42 % 4.81 % 2022 Fair value hedges: Interest rate risk Interest rate contracts - Nominal amount (£m) 2,210 4,468 21,678 45,451 3,808 77,615 Average fixed interest rate - GBP 2.58 % 0.88 % 0.56 % 2.07 % 3.78 % Average fixed interest rate - EUR 1.77 % 1.60 % 0.77 % 0.28 % 3.09 % Average fixed interest rate - USD 1.35 % 3.47 % 3.51 % 2.00 % 4.92 % Interest rate/FX risk Exchange rate contracts - Nominal amount (£m) — — 66 465 7 538 Interest rate contracts - Nominal amount (£m) — — — 263 7 270 Average GBP - EUR exchange rate — — 1.20 1.16 1.10 Average GBP - USD exchange rate — — — 1.19 — Average fixed interest rate - EUR — — 3.42 % 2.06 % — Average fixed interest rate - USD — — — 4.63 % — Cash flow hedges: Interest rate risk Interest rate contracts - Nominal amount (£m) 1,042 2,191 1,940 13,060 1,076 19,309 Average fixed interest rate - GBP 1.77 % 2.29 % 1.98 % 2.35 % 1.84 % FX risk Exchange rate contracts - Nominal amount (£m) 2,301 3,135 2,381 10,606 1,163 19,586 Interest rate contracts - Nominal amount (£m) 415 — — 2,325 997 3,737 Average GBP - JPY exchange rate — 157.45 160.04 — — Average GBP - CHF exchange rate — 1.13 — — — Average GBP - EUR exchange rate — — 1.12 1.18 1.17 Average GBP - USD exchange rate 1.22 1.25 1.17 1.31 1.39 Equity risk Equity derivative contracts - Nominal amount (£m) — — 6 43 2 51 Interest rate/FX risk Exchange rate contracts - Nominal amount (£m) — — 1,173 4,626 650 6,449 Interest rate contracts - Nominal amount (£m) — — 585 2,132 208 2,925 Average GBP - EUR exchange rate — — 1.19 1.21 1.20 Average GBP - USD exchange rate — — 1.60 1.50 1.54 Average fixed interest rate - GBP — — 3.27 % 2.58 % 4.59 % Net gains or losses arising from fair value and cash flow hedges included in other operating income Group 2023 2022 2021 £m £m £m Fair value hedging: (Losses)/gains on hedging instruments (1,878) 2,371 846 Gains/(losses) on hedged items attributable to hedged risks 1,893 (2,307) (804) Fair value hedging ineffectiveness 15 64 42 Cash flow hedging ineffectiveness 3 (36) (34) 18 28 8 Hedge ineffectiveness can be analysed by risk category as follows: Group 2023 2022 2021 Change in FV of hedging instruments Change in FV of hedged items Recognised in income statement Change in FV of hedging instruments Change in FV of hedged items Recognised in income statement Change in FV of hedging instruments Change in FV of hedged items Recognised in income statement Fair value hedges: £m £m £m £m £m £m £m £m £m Interest rate risk (1,864) 1,874 10 2,382 (2,324) 58 868 (838) 30 Interest rate/FX risk (14) 19 5 (11) 17 6 (22) 34 12 (1,878) 1,893 15 2,371 (2,307) 64 846 (804) 42 Group Hedging Instruments Recognised in income statement Reclassified from reserves to income Income statement line item affected by reclassification Change in FV Recognised in OCI Cash flow hedges: £m £m £m £m 2023 Interest rate risk Net interest income 449 (447) 2 (464) FX risk Net interest income/other operating income (375) 377 2 (392) Equity risk Operating expenses 20 (20) — 13 Interest rate/FX risk Net interest income/other operating income (238) 237 (1) (388) (144) 147 3 (1,231) 2022 Interest rate risk Net interest income (1,150) 1,150 — (96) FX risk Net interest income/other operating income 1,602 (1,602) — 1,691 Equity risk Operating expenses 2 (2) — 2 Interest rate/FX risk Net interest income/other operating income (54) 18 (36) 533 400 (436) (36) 2,130 2021 Interest rate risk Net interest income (312) 306 (6) 70 FX risk Net interest income/other operating income (54) 54 — (158) Equity risk Operating expenses (1) 1 — 2 Interest rate/FX risk Net interest income/other operating income (542) 514 (28) (273) (909) 875 (34) (359) In 2023 , cash flow hedge accounting of £nil ( 2022 : £10m ) had to cease due to the hedged cash flows no longer being expected to occur. The following table provides a reconciliation by risk category of components of equity and analysis of OCI items (before tax) resulting from hedge accounting. Group 2023 2022 £m £m Balance at 1 January (1,561) 133 Effective portion of changes in fair value: – Interest rate risk 447 (1,150) – Foreign currency risk (377) 1,602 – Equity risk 20 2 – Interest rate/foreign currency risk (237) (18) (147) 436 Income statement transfers: – Interest rate risk 464 96 – Foreign currency risk 392 (1,691) – Equity risk (13) (2) – Interest rate/foreign currency risk 388 (533) 1,231 (2,130) Balance at 31 December (477) (1,561) Hedged exposures Santander UK hedges its exposures to various risks, including interest rate risk and foreign currency risk, as set out in the following table. Group 2023 2022 Accumulated amount of FV hedge adjustments Change in value to calculate hedge ineffectiveness Accumulated amount of FV hedge adjustments Change in value to calculate hedge ineffectiveness Carrying value Hedged item Portfolio hedge of interest rate risks Of which Discontinued hedges Carrying value Hedged item Portfolio hedge of interest rate risks Of which Discontinued hedges £m £m £m £m £m £m £m £m £m £m Fair value hedges Interest rate risk: Loans and advances to customers 73,270 — (622) (435) 1,969 60,783 — (2,637) (651) (2,708) Other financial assets at amortised cost 152 1 (8) (8) 5 156 — (12) 2 (14) Reverse repurchase agreements – non trading 6,186 — — — 4 4,045 — (5) (1) — Other financial assets at FVOCI 2,013 (113) — (131) 82 2,325 (200) — 35 (227) Deposits by customers (15,052) — (10) — (15) (1,394) — 5 — 5 Debt securities in issue (5,065) 162 (75) (114) (170) (5,210) 355 (95) (172) 566 Subordinated liabilities (522) (27) (1) (42) (1) (250) (27) (6) (62) 54 Interest rate/FX risk: Other financial assets at FVOCI 989 4 — — 12 237 (21) — 1 (9) Debt securities in issue (214) (14) — (24) 8 (290) (18) — (37) 27 Subordinated liabilities — — — — (1) 1 1 — 1 (1) 61,757 13 (716) (754) 1,893 60,403 90 (2,750) (884) (2,307) Group 2023 2022 Change in value to calculate hedge ineffectiveness Cash flow hedge reserve Balances on cash flow hedge reserve for discontinued hedges Change in value to calculate hedge ineffectiveness Cash flow hedge reserve Balances on cash flow hedge reserve for discontinued hedges Hedged item balance sheet line item £m £m £m £m £m £m Cash flow hedges: Interest rate risk: Loans and advances to customers (163) (455) 1 925 (999) (1) Cash and balances at central banks (283) 100 (76) 233 (274) (106) Deposits by banks (1) (1) — (8) 7 — FX risk: Other financial assets at FVOCI (253) 1 — — (6) — Not applicable – highly probable forecast transactions 88 1 — (349) 2 — Deposits by customers (21) — — (74) — — Debt securities in issue 605 (9) — (1,142) (19) (2) Repurchase agreements - non trading (42) — — (37) — — Equity risk: Other liabilities (20) 10 — (2) 3 — Interest rate/FX risk: Debt securities in issue/loans and advances to customers 194 (114) — 55 (244) (3) Subordinated liabilities/loans and advances to customers 43 (10) 52 (37) (31) 77 147 (477) (23) (436) (1,561) (35)

Other Financial Assets at Fair

Other Financial Assets at Fair Value Through Profit or Loss	12 Months Ended
	Dec. 31, 2023
Financial assets at fair value through profit or loss [abstract]
Other Financial Assets at Fair Value Through Profit or Loss	12. OTHER FINANCIAL ASSETS AT FAIR VALUE THROUGH PROFIT OR LOSS Group 2023 2022 £m £m Loans and advances to customers: Loans to housing associations 8 4 Other loans 347 335 355 339 Debt securities 168 16 Other debt instruments 49 69 Equity securities 30 10 602 434 In 2023 , Santander UK revalued a portfolio of unlisted equity securities held at fair value through profit or loss in Santander Equity Investments Limited (SEIL) ahead of the sale of part of the portfolio, resulting in a gain of £46m . For the Santander UK group, other financial assets at FVTPL comprised £317m ( 2022 : £312m ) of financial assets designated at FVTPL and £285m ( 2022 : £122m ) of financial assets mandatorily held at FVTPL. Loans and advances to customers principally represent other loans, being a portfolio of roll-up mortgages and deferred consideration . These are managed, and have their performance evaluated, on a fair value basis in accordance with a documented investment strategy, and information about them is provided on that basis to management. Since 2009, the Santander UK group’s policy has been not to designate similar new loans at FVTPL. The net loss in the year attributable to changes in credit risk for loans and advances at FVTPL was £nil ( 2022 : £1m , 2021 : £nil ). The cumulative net loss attributable to changes in credit risk for loans and advances at FVTPL at 31 December 2023 was £3m ( 2022 : £3m , 2021 : £2m ).

Loans and Advances to Customers

Loans and Advances to Customers	12 Months Ended
	Dec. 31, 2023
Net Loans And Advances To Customers [Abstract]
Loans and Advances to Customers	13. LOANS AND ADVANCES TO CUSTOMERS Group 2023 2022 £m £m Loans secured on residential properties 176,495 188,282 Corporate loans 18,454 19,057 Finance leases 4,530 4,645 Other unsecured loans 7,232 7,742 Accrued interest and other adjustments 960 904 Amounts due from fellow Banco Santander subsidiaries and joint ventures 4,488 4,165 Loans and advances to customers 212,159 224,795 Credit impairment loss allowances on loans and advances to customers (916) (933) Residual value and voluntary termination provisions on finance leases (21) (22) Net loans and advances to customers 211,222 223,840 For movements in expected credit losses, see the 'Movement in total exposures and the corresponding ECL' table in the Santander UK group level - Credit risk review section of the Risk review. Finance lease and hire purchase contract receivables may be analysed as follows: Group 2023 2022 Gross investment Unearned finance income Net investment Gross investment Unearned finance income Net investment £m £m £m £m £m £m No later than one year 1,502 (216) 1,286 1,493 (182) 1,311 Later than one year and not later than two years 1,426 (208) 1,218 1,367 (168) 1,199 Later than two years and not later than three years 1,331 (194) 1,137 1,190 (147) 1,043 Later than three years and not later than four years 882 (129) 753 1,044 (129) 915 Later than four years and not later than five years 99 (14) 85 143 (18) 125 Later than five years 60 (9) 51 59 (7) 52 5,300 (770) 4,530 5,296 (651) 4,645 The Santander UK group enters into finance leasing arrangements primarily for the financing of motor vehicles and a range of assets for its corporate customers. Included in the carrying value of net investment in finance leases and hire purchase contracts is £1,830m ( 2022 : £1,761m ) of unguaranteed RV at the end of the current lease terms, which is expected to be recovered through re-payment, re-financing or sale. Contingent rent income of nil ( 2022 : £nil , 2021 : £nil ) was earned in the year, which was classified in ‘Interest and similar income’. Finance income on the net investment in finance leases was £266m ( 2022 : £230m , 2021 : £243m ). Finance lease receivable balances are secured over the asset leased. The Santander UK group is not permitted to sell or repledge the asset in the absence of default by the lessee. The Directors consider that the carrying amount of the finance lease receivables approximates to their fair value. Included within loans and advances to customers are advances assigned to bankruptcy remote structured entities and Abbey Covered Bonds LLP. These loans provide security to issues of covered bonds and mortgage-backed or other asset-backed securities issued by the Santander UK group. For more, see Note 14 . At 31 December 2023 and 2022 , the Santander UK group had contracted with lessees for the following future undiscounted minimum lease payments receivable under operating leases. Group 2023 2022 £m £m No later than one year 29 31 Later than one year and not later than two years 26 28 Later than two years and not later than three years 19 23 Later than three years and not later than four years 14 13 Later than four years and not later than five years 7 11 Later than five years 19 22 114 128

Securitisations and Covered Bon

Securitisations and Covered Bonds	12 Months Ended
	Dec. 31, 2023
Disclosure Of Securitisations And Covered Bonds [Abstract]
Securitisations and Covered Bonds	14. SECURITISATIONS AND COVERED BONDS The information in this Note relates to securitisations and covered bonds for consolidated structured entities, used to obtain funding or collateral. It excludes structured entities relating to credit protection transactions. The Santander UK group uses structured entities to securitise some of the mortgage and other loans to customers that it originates. The Santander UK group also issues covered bonds, which are guaranteed by, and secured against, a pool of the Santander UK group’s mortgage loans transferred to Abbey Covered Bonds LLP. The Santander UK group issues mortgage-backed securities, other asset-backed securities and covered bonds mainly in order to obtain diverse, low-cost funding, but also to use as collateral for raising funds via third party bilateral secured funding transactions or for liquidity purposes in the future. The Santander UK group has successfully used bilateral secured transactions as an additional form of medium-term funding; this has allowed the Santander UK group to further diversify its medium-term funding investor base. Loans and advances to customers include portfolios of residential mortgage loans, and receivables derived from credit agreements with retail customers for the purchases of financed vehicles, which are subject to non-recourse finance arrangements. These loans and receivables have been purchased by, or assigned to, structured entities or Abbey Covered Bonds LLP, and have been funded primarily through the issue of mortgage-backed securities, other asset-backed securities or covered bonds. No gain or loss has been recognised as a result of these sales. The structured entities and Abbey Covered Bonds LLP are consolidated as subsidiary undertakings. The Company and its subsidiaries do not own directly, or indirectly, any of the share capital of any of the structured entities. a) Securitisations i) Master trust structures The Santander UK group makes use of master trust structures, whereby a pool of residential mortgage loans is assigned to a trust company by the asset originator. A funding entity acquires a beneficial interest in the pool of assets held by the trust company with funds borrowed from qualifying structured entities, which at the same time issue asset-backed securities to third-party investors or the Santander UK group. Santander UK plc and its subsidiaries receive payments from the securitisation companies in respect of fees for administering the loans, and payment of deferred consideration for the sale of the loans. Santander UK plc and its subsidiaries have no right or obligation to repurchase any securitised loan, except if certain representations and warranties given by Santander UK plc or its subsidiaries at the time of transfer are breached and, in certain cases, if there is a product switch or further advance, if a securitised loan is in arrears for over two months or if a securitised loan does not comply with regulatory requirements. ii) Other securitisation structures The Santander UK group also makes use of auto loan securitisations, whereby a pool of auto loans originated by a member of the Santander UK group is sold to a special purpose vehicle by the asset originator. The special purpose vehicle funds the purchase of the auto loans by issuing asset-backed securities to third- party investors. A proportion of the securities are also retained by members of the Santander UK group. Members of the Santander UK group also receive payments from the special purpose vehicle in respect of fees for administering the auto loans, and payment of deferred consideration for the sale of the auto loans. The seller has no right or obligation to repurchase any securitised loan, except if certain representations and warranties given by the seller at the time of transfer are breached and, in certain cases, if there has been a subsequent variation in the terms of the underlying auto loan not permitted under the sale agreement. b) Covered bonds Santander UK plc also issues covered bonds, which are its direct, unsecured and unconditional obligation. The covered bonds benefit from a guarantee from Abbey Covered Bonds LLP. Santander UK plc makes a term advance to Abbey Covered Bonds LLP equal to the sterling proceeds of each issue of covered bonds. Abbey Covered Bonds LLP uses the proceeds of the term advance to purchase portfolios of residential mortgage loans and their security from Santander UK plc. Under the terms of the guarantee, Abbey Covered Bonds LLP has agreed to pay an amount equal to the guaranteed amounts when the same shall become due for payment, but which would otherwise be unpaid by Santander UK plc. c) Analysis of securitisations and covered bonds The Santander UK group’s principal securitisation programmes and covered bond programme, together with the balances of the advances subject to securitisation (or for the covered bond programme assigned) and the carrying value of the notes in issue at 31 December 2023 and 2022 are listed below. Gross assets External notes in issue Notes issued to Santander UK plc/subsidiaries as collateral 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m Mortgage-backed master trust structures: – Holmes 3,242 1,646 2,119 790 300 176 – Fosse 2,048 2,028 100 100 1,382 1,365 5,290 3,674 2,219 890 1,682 1,541 Other asset-backed securitisation structures: – Motor — 6 — 7 — — – Repton 757 — 550 — — — 757 6 550 7 — — Total securitisation programmes 6,047 3,680 2,769 897 1,682 1,541 Covered bond programme: – Euro 35bn Global Covered Bond Programme 21,880 21,304 15,000 15,205 — — Total securitisation and covered bond programmes 27,927 24,984 17,769 16,102 1,682 1,541 The following table sets out the internal and external issuances and redemptions in 2023 and 2022 for each securitisation and covered bond programme. Internal issuances External issuances Internal redemptions External redemptions 2023 2022 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m £m £m Mortgage-backed master trust structures: – Holmes 241 — 1,500 600 121 100 186 200 – Fosse — — — — — — — 200 Other asset-backed securitisation structures: – Motor — — — — — — 7 33 – Repton — — 550 — — — — — Covered bond programme: – Euro 35bn Global Covered Bond Programme 1,100 — 1,844 4,200 16 100 1,897 1,700 1,341 — 3,894 4,800 137 200 2,090 2,133 During 2023 , the remaining asset-backed notes from the Motor securitisation structure were redeemed. In 2023 Repton 2023-1 Limited borrowed £550m through an asset-backed variable funding note facility. Repayment of this will begin in 2025 . Holmes Funding Ltd has a beneficial interest of £2,396m ( 2022 : £796m ) in the residential mortgage loans held by Holmes Trustees Ltd. The remaining share of the beneficial interest in residential mortgage loans held by Holmes Trustees Ltd belongs to Santander UK plc. Fosse Funding (No.1) Ltd has a beneficial interest of £1,393m ( 2022 : £1,465m ) in the residential mortgage loans held by Fosse Trustee (UK) Ltd. The remaining share of the beneficial interest in residential mortgage loans held by Fosse Trustee (UK) Ltd belongs to Santander UK plc. The Holmes securitisation companies have cash deposits of £80m ( 2022 : £112m ), which have been accumulated to finance the redemption of a number of securities issued by the Holmes securitisation companies. The share of Holmes Funding Ltd in the trust assets is therefore reduced by this amount. The Fosse securitisation companies have cash deposits of £108m ( 2022 : £108m ), which have been accumulated to finance the redemption of a number of securities issued by Fosse securitisation companies. The share of Fosse Funding (No.1) Ltd’s beneficial interest in the assets held by Fosse Trustee (UK) Ltd is therefore reduced by this amount.

Transfers of Financial Assets N

Transfers of Financial Assets Not Qualifying for Derecognition	12 Months Ended
	Dec. 31, 2023
Disclosure of transferred financial assets that are not derecognised in their entirety [abstract]
Transfers of Financial Assets Not Qualifying for Derecognition	15. TRANSFERS OF FINANCIAL ASSETS NOT QUALIFYING FOR DERECOGNITION The Santander UK group enters into transactions in the normal course of business by which it transfers recognised financial assets directly to third parties or to structured entities. These transfers may give rise to the full or partial derecognition of those financial assets. Transferred financial assets that do not qualify for derecognition consist of (i) securities held by counterparties as collateral under repurchase agreements, (ii) securities lent under securities lending agreements, and (iii) loans that have been securitised under arrangements by which the Santander UK group retains a continuing involvement in such transferred assets. As a result of these sale and repurchase and securities lending transactions, the Santander UK group is unable to use, sell or pledge the transferred assets for the duration of the transaction. The Santander UK group remains exposed to interest rate risk and credit risk on these pledged instruments. The counterparty’s recourse is not limited to the transferred assets. The Santander UK group securitisation transfers do not qualify for derecognition. The Santander UK group remains exposed to credit risks arising from the mortgage loans or credit agreements and has retained control of the transferred assets. Circumstances in which the Santander UK group has continuing involvement in the transferred assets may include retention of servicing rights over the transferred assets (the servicing fee in respect of which is dependent on the amount or timing of the cash flows collected from, or the non-performance of, the transferred assets), entering into a derivative transaction with the securitisation vehicle, retaining an interest in the securitisation vehicle or providing a cash reserve fund. Where the Santander UK group has continuing involvement, it continues to recognise the transferred assets to the extent of its continuing involvement and recognises an associated liability. The net carrying amount of the transferred assets and associated liabilities reflects the rights and obligations that the Santander UK group has retained. The following table analyses the carrying amount of financial assets that did not qualify for derecognition and their associated financial liabilities: Group 2023 2022 Assets Liabilities Assets Liabilities Nature of transaction £m £m £m £m Sale and repurchase agreements 14 (14) 120 (128) Securities lending agreements 3,136 (2,735) 2,871 (2,509) Securitisations (See Notes 14 and 26) 6,047 (2,769) 3,680 (897) 9,197 (5,518) 6,671 (3,534)

Reverse Repurchase Agreements -

Reverse Repurchase Agreements - Non Trading	12 Months Ended
	Dec. 31, 2023
Disclosure Of Reserve Repurchase Agreements Non-Trading [Abstract]
Reverse Repurchase Agreements - Non Trading	16. REVERSE REPURCHASE AGREEMENTS – NON-TRADING Group 2023 2022 £m £m Agreements with banks 2,397 885 Agreements with customers 10,071 6,463 12,468 7,348

Other Financial Assets at Amort

Other Financial Assets at Amortised Cost	12 Months Ended
	Dec. 31, 2023
Financial assets at fair value through profit or loss [abstract]
Other Financial Assets at Amortised Cost	17. OTHER FINANCIAL ASSETS AT AMORTISED COST Group 2023 2022 £m £m Asset backed securities — — Debt securities 152 156 152 156 A significant portion of the debt securities are held in our eligible liquidity pool and consist mainly of government bonds and covered bonds. Detailed disclosures can be found in the 'Liquidity risk' section of the Risk review.

Financial Assets at Fair Value

Financial Assets at Fair Value Through Other Comprehensive Income	12 Months Ended
	Dec. 31, 2023
Financial assets at fair value through other comprehensive income [abstract]
Financial Assets at Fair Value Through Other Comprehensive Income	18. FINANCIAL ASSETS AT FAIR VALUE THROUGH OTHER COMPREHENSIVE INCOME Group 2023 2022 £m £m Debt securities 8,481 6,024 8,481 6,024 A significant portion of the debt securities are held in our eligible liquidity pool and consist mainly of government bonds and covered bonds. Detailed disclosures can be found in the 'Liquidity risk' section of the Risk review.

Interests in Other Entities

Interests in Other Entities	12 Months Ended
	Dec. 31, 2023
Investments accounted for using equity method [abstract]
Interests in Other Entities	19. INTERESTS IN OTHER ENTITIES Group 2023 2022 £m £m Joint Ventures 245 252 245 252 The Santander UK group consists of a parent company, Santander UK Group Holdings plc, incorporated and domiciled in the UK and a number of subsidiaries and joint ventures held directly and indirectly by it. Details of subsidiaries and joint ventures are set out in the Shareholder Information section and form an integral part of these financial statements. Details of subsidiaries benefitting from an audit exemption according to section 479A of the Companies Act 2006 are also set out in the Shareholder Information section and form an integral part of these financial statements. a) Interests in subsidiaries The Company holds directly or indirectly 100% of the issued ordinary share capital of its principal subsidiaries. All companies operate principally in their country of incorporation or registration. SFS has branch offices in Jersey and the Isle of Man. Interests in consolidated structured entities Structured entities are formed by Santander UK to accomplish specific and well-defined objectives. Santander UK consolidated these structured entities when the substance of the relationship indicates control, as described in Note 1 . In addition to the structured entities disclosed in Note 14 which are used for securitisation and covered bond programmes, the only other structured entities consolidated by Santander UK are described below. All the external assets and liabilities in these entities are included in the financial statements and in relevant Notes. Other than as set out below, no significant judgements were required with respect to control or significant influence. Motor Securities 2018-1 Designated Activity Company (Motor 2018) Motor 2018 is a credit protection entity, and a Designated Activity Company limited by shares, incorporated in Ireland. It issued a series of credit linked notes varying in seniority which referenced a portfolio of Santander UK group auto loans. Concurrently, this entity sold credit protection to SCUK in respect of the referenced loans and, in return for a fee, was liable to make protection payments to SCUK upon the occurrence of a credit event in relation to any of the referenced loans. Motor 2018 is consolidated as Santander UK held a variable interest by retaining the junior tranche of notes issued by the entity. The outstanding notes were redeemed and the transaction terminated in 2023 . b) Interests in joint ventures Santander UK does not have any individually material interests in joint ventures. In 2023 , Santander UK’s share in the profit after tax of its joint ventures was £43m ( 2022 : £36m ) before elimination of transactions between Santander UK and the joint ventures. At 31 December 2023 , the carrying amount of Santander UK’s interest was £245m ( 2022 : £252m ). At 31 December 2023 and 2022 , the joint ventures had no commitments and contingent liabilities. c) Interests in unconsolidated structured entities Structured entities sponsored by the Santander UK group Santander UK has interests in structured entities which it sponsors but does not control. Santander UK considers itself a sponsor of a structured entity when it facilitates the establishment of the structured entity. Other than as set out below, no significant judgements were required with respect to control or significant influence. The structured entities sponsored but not consolidated by Santander UK are as follows: i) Santander (UK) Common Investment Fund (the Fund) The Fund is a common investment fund that was established to hold the assets of the Santander (UK) Group Pension Scheme. The Fund is not consolidated by Santander UK, but its assets of £8,551m ( 2022 : £8,646m ) are accounted for as part of the defined benefit assets and obligations recognised on Santander UK’s balance sheet. For more on the Fund, see Note 30 . As the Fund holds the assets of the pension scheme, it is outside the scope of IFRS 10. Santander UK’s maximum exposure to loss is the carrying amount of the assets held. ii) Credit protection entities Santander UK has established four ( 2022 : four ) unconsolidated credit protection entities, which are Designated Activity Companies limited by shares, incorporated in Ireland. Each entity has issued a series of credit linked notes varying in seniority which reference portfolios of Santander UK group loans. Concurrently, these entities sell credit protection to Santander UK in respect of the referenced loans and, in return for a fee, are liable to make protection payments to Santander UK upon the occurrence of a credit event in relation to any of the referenced loans. Santander UK has no holdings in senior credit linked notes ( 2022 : £180m ). Junior credit linked notes, which amounted to £185m ( 2022 : £465m ), are all held by third party investors and suffer the first losses incurred in the referenced portfolios. Funds raised by the sale of the credit linked notes are deposited with Santander UK as collateral for the credit protection. The senior credit linked notes, along with the deposits and associated guarantees, are presented on a net basis, to reflect a legal right of set-off between the principal amounts of senior notes and the cash deposits. Deposits and associated guarantees in respect of the junior credit linked notes are included in ‘Deposits by customers’ (see Note 23 ). The entities are not consolidated by Santander UK because the third-party investors have the exposure, or rights, to all of the variability of returns from the performance of the entities. No assets are transferred to, or income received from, these entities. Since the credit linked notes (including those held by Santander UK) are fully cash collateralised, Santander UK’s maximum exposure to loss is equal to any unamortised fees paid to the entities in connection with the credit protection outlined above. Structured entities not sponsored by the Santander UK group Santander UK also has interests in structured entities which it does not sponsor or control. These consist of holdings of mortgage and other asset backed securities issued by entities that were established and/or sponsored by other unrelated financial institutions. These securities comprise the asset backed securities included in Note 17 . Management has concluded that the Santander UK group has no control or significant influence over these entities and that the carrying value of the interests held in these entities represents the maximum exposure to loss.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2023
Disclosure of detailed information about intangible assets [abstract]
Intangible Assets	20. INTANGIBLE ASSETS a) Goodwill Group Cost Accumulated impairment Carrying amount £m £m £m At 31 December 2022 and 1 January 2023 and 31 December 2023 1,285 (86) 1,199 Impairment of goodwill In 2023 and 2022 , no impairment of goodwill was recognised. Goodwill is tested for impairment annually, or more frequently, if reviews identify an impairment indicator or when events or changes in circumstances dictate. Goodwill is tested for impairment annually at 31 December, with a review for impairment indicators at 30 June. The annual review identified that the risks of ongoing global conflicts, places increasing uncertainty on the UK economic trajectory, and its potential impact on the carrying value of goodwill as impairment indicators for all cash-generating units (CGUs). As a result, management updated the impairment test at 31 December 2023 for all CGUs. Basis of the recoverable amount The recoverable amount of all CGUs was determined based on its value in use (VIU) methodology at each testing date. For each CGU, the VIU is calculated by discounting management’s cash flow projections for the CGU. The cash flow projections also take account of increased internal capital allocations needed to achieve internal and regulatory capital targets including the leverage ratio. The key assumptions used in the VIU calculation for each CGU are set out below. The Retail & Business Banking segment consists of the Private Banking CGU and the rest of Retail & Business Banking, known as the Personal Financial Services CGU. Carrying amount of Goodwill by CGU and key assumptions in the VIU calculation Goodwill Discount rate Growth rate beyond initial cash flow projections 2023 2022 2023 2022 2023 2022 CGU £m £m % % % % Personal Financial Services 1,169 1,169 16.7 16.6 1.6 1.6 Private Banking 30 30 14.6 15.3 1.6 1.6 1,199 1,199 The CGUs do not carry on their balance sheets any other intangible assets with indefinite useful lives. Management’s judgement in estimating the cash flows of a CGU The cash flow projections for the purpose of impairment testing for each CGU are derived from the latest 3-year plan presented to the Board. The Board challenges and endorses management’s planning assumptions in light of internal capital allocations needed to support Santander UK’s strategy, current market conditions and the macroeconomic outlook. For the goodwill impairment tests conducted at 31 December 2023 , the determination of the carrying amount of the Personal Financial Services CGU was based on an allocation of regulatory capital and management’s cash flow projections until the end of 2026. The assumptions included in the cash flow projections reflect an allocation to the cost of capital to support future growth, as well as the expected impact of recent events in the UK economic environment on the financial outlook within which the CGUs operate. The cash flow projections are supported by Santander UK’s base case economic scenario. For more on the base case economic scenario, including our forecasting approach and the assumptions in place at 31 December 2023 , see the Credit risk – Santander UK group level section of the Risk review. The cash flow projections take into account the likely impact of recent changes to the BoE Bank Rate, inflation and also consider the impact of future climate change. Cash flow projections for the purpose of impairment testing do not take account of any adverse outcomes arising from contingent liabilities (see Note 31 ), whose existence will be confirmed by uncertain future events or where any obligation is not probable or otherwise cannot be measured reliably, nor do they take account of the benefits arising from Santander UK’s transformation plans that had not yet been implemented or committed at 31 December 2023 . Discount rate The rate used to discount the cash flows is based on the cost of equity assigned to each CGU, which is derived using a capital asset pricing model (CAPM) and calculated on a post-tax basis. The CAPM depends on a number of inputs reflecting financial and economic variables, including the risk-free rate and a premium to reflect the inherent risk of the business being evaluated. These variables are based on the market’s assessment of the economic variables and management’s judgement. The inputs to the CAPM are observable on a post-tax basis. In determining the discount rate, management has identified the cost of equity associated with market participants that closely resemble our CGUs and adjusted them for tax to arrive at the pre-tax equivalent rate. The Private Banking CGU has a different discount rate compared to the Personal Financial Services CGU because different market participants closely resemble each CGU. Growth rate beyond initial cash flow projections The growth rate for periods beyond the initial cash flow projections is used to extrapolate the cash flows in perpetuity because of the long-term perspective of CGUs. In line with the accounting requirements, management uses the UK Government’s official estimate of UK long-term average GDP growth rate, as this is lower than management's estimate of the long-term average growth rate of the business. The estimated UK long-term average GDP growth rate has regard to the long-term impact of inherent uncertainties, such as Brexit, climate change and higher living costs, driven by high inflation and rising interest rates. Goodwill arising on the acquisition of Personal Financial Services and Private Banking The VIU of each CGU remains higher than the carrying value of the related goodwill. The VIU review at 31 December 2023 did not indicate the need for an impairment in the Company’s goodwill balances. Management considered the level of headroom and the uncertainty relating to the respective estimates of the VIU for those CGUs but determined that there was a sufficient basis to conclude that no impairment was required. Sensitivities of key assumptions in calculating the value in use At 31 December 2023 and 31 December 2022 , the VIU of the Personal Financial Services CGU was sensitive to reasonably possible changes in the key assumptions supporting the recoverable amount. The table below presents a summary of the key assumptions underlying the most sensitive inputs to the model for the Personal Financial Services CGU, the key risks associated with each and details of a reasonably possible change in assumptions, such as a decrease in mortgage new business. The sensitivity analysis presented below has been prepared on the basis that a change in each key assumption would not have a consequential impact on other assumptions used in the impairment review. However, due to the interrelationships between some of the assumptions, a change in one of the assumptions might impact one or more of the other assumptions and could result in a larger or smaller overall impact. Reasonably possible changes in key assumptions CGU Input Key assumptions Associated risks Reasonably possible change Personal Financial Services Cash flow projections – BoE Bank Rate – UK house price growth – UK mortgage loan market growth – UK unemployment rate – Position in the market – Regulatory capital levels. – Uncertain market outlook – Higher interest rate environment impact on customer affordability – Customer remediation and regulatory action outcomes – Uncertain regulatory capital requirements. – Cash flow projections decrease by 10% ( 2022 : 5% ) . Discount rate – Discount rate used is a reasonable estimate of a suitable market rate for the profile of the business. – Market rates of interest rise. – Discount rate increases by 100 basis points ( 2022 : 100 basis points ) . GDP growth rate – High oil / gas prices – Elevated wage growth – Weak productivity – Large government debt burden – Fragile business and consumer confidence – Inflation and interest rates stay higher for longer, hitting the disposable income of our customers – Affects the profitability of our customers – Limits the scope for tax cuts, hitting the disposable income of our customers – Affects business and consumer spending decisions of our customers – GDP Growth rate decreases by 10% ( 2022 : 10% ) At 31 December 2023 and 31 December 2022 , a reasonably possible change in the key assumptions in relation to the VIU calculation for the goodwill balance in the Personal Financial Services CGU would have resulted in a reduction in headroom as follows. Reduction in headroom 2023 2022 CGU Reasonably possible change £m £m Personal Financial Services Cash flow projections decrease by 10% ( 2022 : 5% ) (818) (538) Discount rate increases by 100 basis points ( 2022 : 100 basis points ) (663) (887) GDP Growth rate decreases by 10% ( 2022 : 10% ) (19) (31) Sensitivity of Value in use changes to current assumptions to achieve nil headroom Although there was no impairment of goodwill relating to the Personal Financial Services CGU or the Private Banking CGU at 31 December 2023 , the test for the Personal Financial Services CGU remains sensitive to some of the assumptions used, as described above. In addition, the changes in assumptions detailed below for the discount rate and cash flow projections would eliminate the current headroom. As a result, there is a risk of impairment in the future should business performance or economic factors diverge from forecasts. In 2023 , there was a decrease in headroom arising from a decline in cash flow forecasts, this is partially offset by a decrease to RWAs which has led to a reduction in the required CET1 capital requirement. The sensitivity analysis presented below has been prepared on the basis that a change in each key assumption would not have a consequential impact on other assumptions used in the impairment review. However, due to the interrelationships between some of the assumptions, a change in one of the assumptions might impact one or more of the other assumptions and could result in a larger or smaller overall impact. 2023 Carrying value Value in use Headroom Increase in discount rate Decrease in GDP growth rate Decrease in cash flows CGU £m £m £m bps % % Personal Financial Services 7,513 8,178 665 101 4 8 2022 Personal Financial Services 8,860 10,752 1,892 239 13 18 b) Other intangibles Group Cost Accumulated amortisation / impairment Carrying amount £m £m £m At 1 January 2023 1,272 (921) 351 Additions 114 — 114 Disposals (36) 36 — Charge — (116) (116) At 31 December 2023 1,350 (1,001) 349 At 1 January 2022 1,346 (1,004) 342 Additions 112 — 112 Disposals (186) 186 — Charge — (100) (100) Impairment — (3) (3) At 31 December 2022 1,272 (921) 351 Other intangibles which consist of computer software, include computer software under development of £157m ( 2022 : £149m ), of which £35m is internally generated ( 2022 : £33m ). The impairment charge of £nil ( 2022 : £3m ) relates to computer software no longer expected to yield future economic benefits as it has become obsolete.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2023
Property, plant and equipment [abstract]
Property, Plant and Equipment	21. PROPERTY, PLANT AND EQUIPMENT Group Property Office fixtures and equipment Computer software Operating lease assets Right-of-use assets Total (1) £m £m £m £m £m £m Cost: At 1 January 2023 893 831 79 722 272 2,797 Additions 89 88 1 85 31 294 Reclassification (to)/from assets held for sale 8 — — — — 8 Disposals (66) (29) (5) (172) (35) (307) At 31 December 2023 924 890 75 635 268 2,792 Accumulated depreciation: At 1 January 2023 271 625 73 145 157 1,271 Charge for the period 17 63 1 64 30 175 Impairment during the period — — — — (11) (11) Disposals (61) (26) (5) (62) (1) (155) At 31 December 2023 227 662 69 147 175 1,280 Carrying amount 697 228 6 488 93 1,512 Cost: At 1 January 2022 981 1,056 437 755 258 3,487 Additions 62 87 4 185 39 377 Reclassification to assets held for sale (98) (13) — — — (111) Disposals (52) (299) (362) (218) (25) (956) At 31 December 2022 893 831 79 722 272 2,797 Accumulated depreciation: At 1 January 2022 335 863 435 160 139 1,932 Charge for the year 18 69 1 73 19 180 Impairment during the year 8 2 — — — 10 Reclassification to assets held for sale (49) (13) — — — (62) Disposals (41) (296) (363) (88) (1) (789) At 31 December 2022 271 625 73 145 157 1,271 Carrying amount 622 206 6 577 115 1,526 Property includes investment properties of £17m ( 2022 : £17m ) and assets under construction of £nil ( 2022 : £204m ). In September 2023, we completed the construction of a new head office in Milton Keynes. In 2023 , right-of-use assets were impaired as a result of our multi-year transformation project. The impairment relates to leasehold properties within the scope of our branch network restructuring programme and head office sites which are either closing or consolidating.

Other Financial Liabilities at

Other Financial Liabilities at Fair Value Through Profit or Loss	12 Months Ended
	Dec. 31, 2023
Disclosure of financial liabilities [abstract]
Other Financial Liabilities at Fair Value Through Profit or Loss	22. OTHER FINANCIAL LIABILITIES AT FAIR VALUE THROUGH PROFIT OR LOSS Group 2023 2022 £m £m Structured Notes Programmes 369 375 Structured deposits 426 321 Zero Amortising Guaranteed Notes 104 107 899 803 For the Santander UK group all ( 2022 : all) of the other financial liabilities at FVTPL were designated as such. Gains and losses arising from changes in the credit spread of securities issued by the Santander UK group reverse over the contractual life of the debt, provided that the debt is not repaid at a premium or a discount. The net loss during the year attributable to changes in the Santander UK group’s own credit risk on the above securities was £21m ( 2022 : £25m gain, 2021 : £12m loss). The cumulative net loss attributable to changes in the Santander UK group’s own credit risk on the above securities at 31 December 2023 was £6m ( 2022 : £15m gain, 2021 : £10m loss). At 31 December 2023 , the amount that would be required to be contractually paid at maturity of the securities above was £97m ( 2022 : £138m ) higher than the carrying value.

Deposits by Customers

Deposits by Customers	12 Months Ended
	Dec. 31, 2023
Deposits from customers [abstract]
Deposits by Customers	23. DEPOSITS BY CUSTOMERS Group 2023 2022 £m £m Demand and time deposits (1) 194,191 196,160 Amounts due to fellow Banco Santander subsidiaries and joint ventures 958 1,153 195,149 197,313 (1) Includes capital amount guaranteed / protected equity index-linked deposits of £304m ( 2022 : £408m ).

Deposits by Banks

Deposits by Banks	12 Months Ended
	Dec. 31, 2023
Disclosure Of Deposits From Banks [Abstract]
Deposits by Banks	24. DEPOSITS BY BANKS Group 2023 2022 £m £m Items in the course of transmission 732 701 Deposits held as collateral 888 1,758 Other deposits (1) 18,737 26,084 20,357 28,543 (1) Includes drawdown from the TFSME of £17.0bn ( 2022 : £25.0bn ).

Repurchase Agreements - Non Tra

Repurchase Agreements - Non Trading	12 Months Ended
	Dec. 31, 2023
Disclosure Of Repurchase Agreements 1 [Abstract]
Repurchase Agreements - Non Trading	25. REPURCHASE AGREEMENTS – NON TRADING Group 2023 2022 £m £m Agreements with banks 551 50 Agreements with customers 7,860 7,932 8,411 7,982

Debt Securities in Issue

Debt Securities in Issue	12 Months Ended
	Dec. 31, 2023
Debt Securities In Issue [Abstract]
Debt Securities in Issue	26. DEBT SECURITIES IN ISSUE Group 2023 2022 £m £m Medium-term notes: – US $30bn Euro Medium Term Note Programme 744 739 – Euro 30bn Euro Medium Term Note Programme 5,619 6,435 – US SEC-registered Debt Programme - Santander UK Group Holdings plc 6,130 7,083 - US SEC-registered Debt Programme - Santander UK plc 1,031 1,276 Medium-term notes 13,524 15,533 Euro 35bn Global Covered Bond Programme 15,000 15,205 US $20bn Commercial Paper Programmes 2,761 1,851 Certificates of deposit 1,530 2,874 Credit linked notes 194 60 Securitisation programmes 2,769 897 35,778 36,420 The funding from the Euro 30bn Euro Medium Term Note Programme and the US SEC-registered Debt Programme in the name of Santander UK Group Holdings plc has mainly been downstreamed to our operating company Santander UK plc.

Subordinated Liabilities

Subordinated Liabilities	12 Months Ended
	Dec. 31, 2023
Subordinated liabilities [abstract]
Subordinated Liabilities	27. SUBORDINATED LIABILITIES Group 2023 2022 £m £m £325m Sterling preference shares 343 344 Undated subordinated liabilities 205 219 Dated subordinated liabilities 1,838 1,769 2,386 2,332 In 2023 , certain subordinated liabilities were repurchased as part of ongoing liability management exercises, resulting in a profit of £4m ( 2022 : a loss of £5m ). The above securities will, in the event of the winding up of the issuer, be subordinated to the claims of depositors and all other creditors of the issuer, other than creditors whose claims rank equally with, or are junior to, the claims of the holders of the subordinated liabilities. The subordination amongst each of the subordinated liabilities upon a winding up of the issuer is specified in their respective terms and conditions. In 2023 and 2022 , the Santander UK group had no defaults of principal, interest or other breaches with respect to its subordinated liabilities. No repayment or purchase by the issuer of the subordinated liabilities may be made prior to their stated maturity without the consent of the PRA. Each of the subordinated liabilities issued by Santander UK Group Holdings plc has been downstreamed to Santander UK plc by means of Santander UK plc issuing equivalent subordinated liabilities to Santander UK Group Holdings plc. Undated subordinated liabilities Group 2023 2022 First call date £m £m 10.0625% Exchangeable capital securities n/a 205 205 7.125% 30 Year Step-up perpetual callable subordinated notes 2030 — 14 205 219 In common with other debt securities issued by Santander UK group companies and notwithstanding the issuer’s first call dates in the table above, in the event of certain tax changes affecting the treatment of payments of interest on subordinated liabilities in the UK, the 7.125% 30 Year Step-up perpetual callable subordinated notes are redeemable at any time, and the 10.0625% Exchangeable capital securities are redeemable on any interest payment date – each in whole at the option of Santander UK, at their principal amount together with any accrued interest. The 10.0625% Exchangeable capital securities are exchangeable into fully paid 10.375% non-cumulative non-redeemable sterling preference shares of £1 each, at the option of Santander UK, on the business day immediately following any interest payment date. Dated subordinated liabilities Group 2023 2022 Maturity £m £m 5% Subordinated notes 2023 — 591 4.75% Subordinated notes 2025 326 608 7.95% Subordinated notes 2029 193 207 6.50% Subordinated notes 2030 1 22 5.875% Subordinated notes 2031 7 7 5.625% Subordinated notes 2045 222 334 7.869% Subordinated notes 2033 321 — 8.296% Subordinated notes 2033 768 — 1,838 1,769 The dated subordinated liabilities are redeemable in whole at the option of Santander UK in the event of certain tax changes affecting the treatment of payments of interest on the subordinated liabilities in the UK, at their principal amount together with any accrued interest.

Other Liabilities

Other Liabilities	12 Months Ended
	Dec. 31, 2023
Subclassifications of assets, liabilities and equities [abstract]
Other Liabilities	28. OTHER LIABILITIES Group 2023 2022 £m £m Lease liabilities 114 129 Other 2,387 2,472 2,501 2,601

Provisions

Provisions	12 Months Ended
	Dec. 31, 2023
Disclosure of other provisions [abstract]
Provisions	29. PROVISIONS Group Customer remediation Litigation and other regulatory Bank Levy Property ECL on undrawn facilities and guarantees Restructuring Other Total £m £m £m £m £m £m £m £m At 1 January 2023 90 136 4 47 74 22 7 380 Additional provisions (See Note 8) 45 28 46 16 4 56 168 363 Provisions released (See Note 8) (8) — (8) (6) — — (1) (23) Utilisation and other (21) (32) (95) (10) — (46) (167) (371) Recharge (1) — — 20 — — — — 20 Reclassification from provisions to other assets — — 36 — — — — 36 At 31 December 2023 106 132 3 47 78 32 7 405 Recharge in respect of the UK Bank Levy paid on behalf of other UK entities in the Banco Santander group Provisions expected to be settled within no more than 12 months after 31 December 2023 were £220m ( 2022 : £130m ). a) Customer remediation Net provisions of £37m were recognised in 2023 for customer remediations. An additional provision of £45m was recognised in 2023 for customer remediation exercises relating to our mortgage book. £30m of this relates to the proposed refund of interest inconsistently charged on mortgage products for customers in Financial Support, and £10m relates to the proposed refund of early repayment charges paid by a specific group of customers who historically switched mortgage products. The provisions remain subject to change as additional data becomes available and remediation boundaries are finalised. b) Litigation and other regulatory Litigation and other regulatory provisions principally comprised amounts in respect of litigation and other regulatory charges, operational loss and operational risk provisions, and related expenses. A number of uncertainties exist with respect to these provisions given the uncertainties inherent in litigation and other regulatory matters, that affect the amount and timing of any potential outflows with respect to which provisions have been established. These provisions are reviewed at least quarterly. In 2023 there were charges of £12m for legal provisions and £16m for regulatory fees and other issues. The balance also included an amount in respect of our best estimate of liability relating to a legal dispute regarding allocation of responsibility for a specific PPI portfolio of complaints, further described in Note 31 . No further information on the best estimate is provided on the basis that it would be seriously prejudicial. c) Bank Levy In 2023 , a rate of 0.05% ( 2022 : 0.05% ) was charged on long term chargeable equity and liabilities and 0.10% on short-term chargeable liabilities ( 2022 : 0.10% ). d) Property Property provisions include leasehold vacant property provisions, dilapidation provisions for leased properties within the scope of IFRS 16 and decommissioning and disposal costs relating to vacant freehold properties. Leasehold vacant property provisions are made by reference to an estimate of any expected sub-let income, compared to the head rent, and the possibility of disposing of Santander UK’s interest in the lease, taking into account conditions in the property market. Property provisions included £4m of transformation charges in 2023. These charges consist of costs relating to leasehold head office closures, along with decommissioning costs relating to freehold head office sites which are either closing or consolidating. e) ECL on undrawn facilities and guarantees Provisions include expected credit losses relating to guarantees given to third parties and undrawn loan commitments. f) Restructuring Restructuring provisions relate to severance costs associated with transformation and organisational changes. The provision includes a charge of £51m as part of our multi-year transformation programme to improve future returns, focused on simplifying, digitising and automating the bank. g) Other Other provisions include provisions that do not fit into any of the other categories, such as fraud losses and some categories of operational losses. In 2023 , other provisions included charges for operational risk provisions of £163m , including fraud losses of £136m .

Retirement Benefit Plans

Retirement Benefit Plans	12 Months Ended
	Dec. 31, 2023
Disclosure of net defined benefit liability (asset) [abstract]
Retirement Benefit Plans	30. RETIREMENT BENEFIT PLANS The amounts recognised in the balance sheet were as follows: Group 2023 2022 £m £m Assets/(liabilities) Funded defined benefit pension scheme - surplus 723 1,051 Funded defined benefit pension scheme - deficit (41) — Unfunded pension and post-retirement medical benefits (25) (25) Total net assets 657 1,026 a) Defined contribution pension plans The majority of employees are members of a defined contribution Master Trust, LifeSight. This is the plan into which eligible employees are enrolled automatically. The assets of LifeSight are held in separate trustee-administered funds. Funds arising from Additional Voluntary Contributions (AVCs) are largely held within the main defined benefit scheme operated by the Santander UK group. An expense of £71m ( 2022 : £60m ) was recognised for defined contribution plans in the period and is included in staff costs within operating expenses (see Note 6 ). b) Defined benefit pension schemes The Santander UK group operates a number of defined benefit pension schemes. The main scheme is the Santander (UK) Group Pension Scheme (the Scheme). It comprises seven legally segregated sections. The Scheme covers 7% ( 2022 : 10% ) of the Santander UK group’s current employees and is a funded defined benefit scheme which is closed to new members. Members accrue final salary benefits for each year of service in the Scheme, according to a salary definition which varies across the sections. The corporate trustee of the Scheme is Santander (UK) Group Pension Scheme Trustees Limited (the Trustee), a private limited company incorporated in 1996 and a wholly owned subsidiary of Santander UK Group Holdings plc. The principal duty of the Trustee is to act in the best interests of the members of the Scheme. The Trustee board comprises six ( 2022 : six ) Directors selected by Santander UK Group Holdings plc, plus four ( 2022 : four ) member-nominated Directors selected from eligible members who apply for the role. The assets of the funded schemes including the Scheme are held independently of the Santander UK group’s assets in separate trustee administered funds. Investment strategy across the sections of the Scheme remains under regular review. Responsibility for investment decisions, policy and strategy rests with the Trustee of the Scheme who is required under the Pensions Act 2004 to prepare a statement of investment principles. The defined benefit pension schemes expose the Santander UK group to risks such as investment risk, interest rate risk, longevity risk and inflation risk. The Santander UK group does not hold any insurance policies over the defined benefit pension schemes and has not entered into any significant transactions with them. For IAS 19, an accounting valuation of the assets and liabilities of the defined benefits schemes is prepared at each balance sheet date. For funding purposes, formal actuarial valuations are carried out on at least a triennial basis. Both valuations are carried out by independent professionally qualified actuaries. The Scheme Trustee is responsible for the funding actuarial valuations and in doing so considers, or relies in part on, a report of a third-party expert. The latest triennial funding valuation for the Scheme at 31 March 2022 was finalised in November 2022, with an overall scheme deficit of £183m . The next scheduled triennial funding valuation will be at 31 March 2025. Any funding surpluses can be recovered by Santander UK plc from the Scheme through refunds as the Scheme is run off over time or could be used to pay for the cost of benefits which are accruing. The main differences between the assumptions used for assessing the defined benefit liabilities for the funding valuation and those used for IAS 19 are that the financial and demographic assumptions used for the funding valuation are generally more prudent than those used for the IAS 19 valuation. The total amount charged to the income statement was as follows: Group 2023 2022 2021 £m £m £m Net interest income (54) (31) (5) Current service cost 13 30 38 Past service and GMP costs 1 — — Past service curtailment costs — — 5 Administration costs 7 9 8 (33) 8 46 The amounts recognised in other comprehensive income were as follows: Group 2023 2022 2021 £m £m £m Return on plan assets (excluding amounts included in net interest expense) 352 5,531 (452) Actuarial (gains) arising from changes in demographic assumptions (51) (122) (17) Actuarial losses/(gains) arising from experience adjustments 91 481 (19) Actuarial losses/(gains) arising from changes in financial assumptions 206 (5,167) (775) Pension remeasurement 598 723 (1,263) Movements in the present value of defined benefit scheme obligations were as follows: Group 2023 2022 £m £m At 1 January (7,937) (12,884) Current service cost paid by Santander UK plc (13) (29) Current service cost paid by other subsidiaries — (1) Interest cost (379) (241) Employer salary sacrifice contributions (1) (3) Past service cost (1) — Remeasurement due to actuarial movements arising from: – Changes in demographic assumptions 51 122 – Experience adjustments (91) (481) – Changes in financial assumptions (206) 5,167 Benefits paid 372 413 Derecognition of pension scheme liabilities arising from the wind up of the offshore scheme 4 — At 31 December (8,201) (7,937) Movements in the fair value of the schemes’ assets were as follows: Group 2023 2022 £m £m At 1 January 8,963 14,420 Interest income 433 272 Contributions paid by employer and scheme members 197 224 Administration costs paid (7) (9) Return on plan assets (excluding amounts included in net interest expense) (352) (5,531) Benefits paid (372) (413) Derecognition of pension scheme assets arising from the wind up of the offshore scheme (4) — At 31 December 8,858 8,963 The composition and fair value of the schemes’ assets by category was: Group Quoted prices in active markets Prices not quoted in active markets Total Valuation 2023 £m % £m % £m % technique Overseas equities — — 980 11 980 11 A,C Corporate bonds 2,284 26 242 3 2,526 29 A,C Government fixed interest bonds 1,618 18 — — 1,618 18 A Government index-linked bonds 4,422 50 — — 4,422 50 A Property — — 1,080 12 1,080 12 B Derivatives — — (2) — (2) — A Cash — — 586 7 586 7 A Repurchase agreements (1) — — (3,062) (35) (3,062) (35) A Infrastructure — — 408 5 408 5 B,C Annuities — — 293 3 293 3 D Longevity swap — — (16) — (16) — D Other — — 25 — 25 — C 8,324 94 534 6 8,858 100 2022 Overseas equities — — 1,172 13 1,172 13 A,C Corporate bonds 1,991 22 244 3 2,235 25 A,C Government fixed interest bonds 1,138 13 — — 1,138 13 A Government index-linked bonds 5,525 62 — — 5,525 62 A Property — — 1,202 13 1,202 13 B Derivatives — — (78) (1) (78) (1) A Cash — — 1,340 15 1,340 15 A Repurchase agreements (1) — — (4,312) (48) (4,312) (48) A Infrastructure — — 426 5 426 5 B,C Annuities — — 298 3 298 3 D Longevity swap — — (12) — (12) — D Other — — 29 — 29 — C 8,654 97 309 3 8,963 100 (1) Sale and repurchase agreements net of purchase and resale agreements. Valuation techniques The main methods for measuring the fair value of the Scheme’s assets at 31 December 2023 and 2022 are set out below. A. The asset valuation is provided by the asset manager. The valuation is based on observable market data, and where relevant is typically based on bid price values, or the single price if only one price is available. B. The underlying asset valuations are prepared by an independent expert, adjusted for any cash movements where necessary since the latest valuation. C. Assets are valued by reference to the latest manager statements provided by the managers, adjusted for any cash movements since the latest valuation. D. Assets relating to insured liabilities are valued by the actuaries based on our year-end accounting assumptions. The ‘Other’ category includes hedge fund investments. A number of insurance transactions have been entered into that have been included in the asset valuation under annuities and Longevity swap. The transactions were as follows: – In May 2020 a pensioner buy-in was entered into by the Trustee. This transaction insured 100% of the SMA section pensioner liabilities and 50% of the SPI section pensioner liabilities based on membership in the Scheme at 31 December 2018. – In March 2021, the Trustee entered into a longevity swap. Approximately 85% of pensioner liabilities were covered by the longevity swap at inception, excluding pensioners in the SMA and SPI sections. – In 2022, a pensioner buy-in was entered into by the Trustee covering pensioners in the SMA and SPI sections who were uninsured at 30 June 2021. – In July 2022, the Trustee entered into a second longevity swap, extending the insurance over uninsured pensioners in the same membership groups covered by the first swap transacted in March 2021, based on membership in the Scheme at 31 December 2021. At 31 December 2023, as highlighted above, the Scheme was invested in certain assets whose values are not based on market observable data, such as the investments in unquoted equities and bonds, as well as property, infrastructure and hedge funds. The valuation of these assets relies on unobservable data as these assets do not have a readily available quoted price in an active market. A large proportion of the property is directly held and valued using a bespoke valuation method taking both the nature of the properties and the tenancy schedules as inputs to derive the fair value. Where there is a time lag between the net asset value and the balance sheet date, management adjusts the value of the assets for any cash movements. Due diligence has been conducted to ensure the values obtained in respect of these assets are appropriate and represent fair value. Given the nature of these investments, we are unable to prepare sensitivities on how their values could vary as market conditions or other variables change. A strategy is in place to manage interest rate and inflation risk relating to the liabilities. The Scheme also hedges a proportion of its foreign exchange exposure to manage currency risk. At 31 December 2023 the currency forwards had a notional value of £859m ( 2022 : £985m ). There have been no significant changes to the asset allocation over 2023 . The Santander UK group’s pension schemes did not directly hold any equity securities of the Company or any of its related parties at 31 December 2023 and 2022 . The Santander UK group’s pension scheme assets do not include any property or other assets that are occupied or used by the Santander UK group. Funding In November 2022, in compliance with the Pensions Act 2004, the Trustee and the Santander UK group agreed to a new recovery plan in respect of the Scheme and a schedule of contributions following the finalisation of the 31 March 2022 actuarial valuation. The funding target for this actuarial valuation is for the Scheme to have sufficient assets to make payments to members in respect of the accrued benefits as and when they fall due. In accordance with the terms of the Trustee agreement in place at the time, the Santander UK group contributed £194m in 2023 ( 2022 : £218m ) to the Scheme, of which £164m ( 2022 : £178m ) was in respect of agreed deficit repair contributions. The agreed schedule of the Santander UK group’s contributions to the Scheme covers the period up to 31 March 2026 , and comprises contingent contributions which become due if the funding position of any section falls behind the agreed plan . The Santander UK group also meets Scheme administration expenses. The funding valuation is used to judge the amount of cash contributions the Santander UK group needs to put into the pension scheme. It will always be different to the IAS 19 accounting position, which is an accounting rule concerning employee benefits and shown on the balance sheet of our financial statements. Actuarial assumptions The principal actuarial assumptions used for the Scheme were: Group 2023 2022 2021 % % % To determine benefit obligations (1) : – Discount rate for scheme liabilities 4.6 4.9 1.9 – General price inflation 3.0 3.1 3.4 – General salary increase 1.0 1.0 1.0 – Expected rate of pension increase 3.0 3.0 3.2 Years Years Years Longevity at 60 for current pensioners, on the valuation date: – Males 27.0 27.4 27.5 – Females 29.8 30.1 30.1 Longevity at 60 for future pensioners currently aged 40, on the valuation date: – Males 28.6 28.9 29.0 – Females 31.3 31.6 31.6 (1) The discount rate and inflation related assumptions set out in the table above reflect the assumptions calculated based on the Scheme’s duration and cash flow profile as a whole. The actual assumptions used were determined for each section independently based on each section’s duration and cash flow profile. The majority of the liability movement in 2023 was due to the reduction in credit spreads over the year. Discount rate for scheme liabilities The rate used to discount the retirement benefit obligation for accounting purposes is based on the annual yield at the balance sheet date of high-quality corporate bonds on that date. There are only a limited number of higher quality Sterling-denominated corporate bonds, particularly those that are longer-dated. Therefore, in order to set a suitable discount rate, we need to construct a corporate bond yield curve. The model which we use to construct the curve uses corporate bond data but excludes convertible bonds, asset-backed bonds and government related bonds. The curve is then constructed from this data by extrapolating the spot rates from 30 years to 50 years by holding the spread above nominal gilt spot rates constant. From 50 years onwards, it is assumed that spot rates remain constant. When considering an appropriate assumption, we project forward the expected cash flows of each section of the Scheme and adopt a single equivalent cash flow weighted discount rate for each section, subject to management judgement. General price inflation Consistent with our discount rate methodology, we set the inflation assumption using the expected cash flows for each section of the Scheme, fitting them to an inflation curve to give a weighted average inflation assumption. We then deduct an inflation risk premium to reflect the compensation holders of fixed rate instruments expect to receive for taking on the inflation risk. This premium is subject to a cap, to better reflect management’s view of inflation expectations. General salary increase From 1 March 2015, a cap on pensionable pay increases of 1% each year was applied to staff in the Scheme. Expected rate of pension increase The pension increase assumption methodology uses a stochastic model, which is calibrated to consider both the observed historical volatility term structure and derivative pricing. The model allows for the likelihood that high or low inflation in one year, feeds into inflation remaining high or low in the next year. Mortality assumptions The mortality assumptions are based on an independent analysis of the Scheme’s actual mortality experience, carried out as part of the triennial actuarial valuation, together with recent evidence from the Continuous Mortality Investigation. An allowance is then made for expected future improvements to life expectancy based on the Continuous Mortality Investigation Tables. Following this review the S3 Medium all pensioner mortality table was adopted with appropriate adjustments to reflect the actual mortality experience. At 31 December 2023 the assumption for future improvements was updated and the CMI 2022 projection model was adopted, with model parameters selected having had regard to the Scheme’s membership profile with an initial addition to improvements of 0.25% per annum, together with a long-term rate of future improvements to life expectancy of 1.25% for male and female members. In 2022, the methodology for setting the demographic assumptions was changed to better represent current expectations, following a review carried out by the Trustee as part of the 2022 triennial valuation. These reviews resulted in changes in the assumptions for family statistics, early retirement and the withdrawal assumption, which were retained at 31 December 2023. Actuarial assumption sensitivities The sensitivity analyses below have been determined based on reasonably possible changes of the respective assumptions occurring at the end of the reporting period, while holding all other assumptions constant. Group (Decrease)/increase 2023 2022 Assumption Change in pension obligation at period end from £m £m Discount rate 50 bps increase (507) (501) General price inflation 50 bps increase 385 374 Mortality Each additional year of longevity assumed 223 203 The 50 bps sensitivity to the inflation assumption includes the corresponding impact of changes in future pension increase assumptions before and after retirement. The sensitivity analysis presented above may not be representative of the actual change in the defined benefit obligation as it is unlikely that the changes in assumptions would occur in isolation of one another as some of the assumptions may be correlated. Furthermore, in presenting the sensitivity analysis, the present value of the defined benefit obligation has been calculated using the projected unit credit method at the end of the reporting period, which is the same method used to calculate the defined benefit obligation recognised in the balance sheet. There were no changes in the methods and assumptions used in preparing the sensitivity analyses from prior years. The benefits expected to be paid in each of the next five years, and in the aggregate for the five years thereafter are: Year ending 31 December £m 2024 455 2025 389 2026 404 2027 428 2028 444 Five years ending 2033 2,398 The average duration of the defined benefit obligation at 31 December 2023 was 13.8 years ( 2022 : 14.2 years ). Emerging risks The focus in 2023 shifted to the risks arising from the Scheme’s private market assets, rising interest rates and cybersecurity risk. The Santander UK group collaborated with the Trustee to identify and monitor such risks to ensure they are adequately managed. The Trustee has engaged an independent cybersecurity advisor to review the cybersecurity arrangements of its most critical suppliers and provide recommendations on potential improvements. The Trustee has established the Sustainability Committee which is responsible for overseeing the Scheme’s policies, regulatory obligations and priorities in respect of climate change and wider Environmental, Social and Governance (ESG) related matters. This includes the monitoring of climate change related risks and opportunities, scenario analysis and monitoring of investments from an ESG perspective. The Santander UK group's employee pension funds recognise the magnitude of the challenges that climate and energy transition pose to governments, companies and civil society. They are also aware of their impact on the ability to comply with their fiduciary duty providing long-term risk-adjusted returns to their members. They have committed to a target of net zero by 2050, showing their full support for the Santander UK group's vision, commitment to sustainability and climate change.

Contingent Liabilities and Comm

Contingent Liabilities and Commitments	12 Months Ended
	Dec. 31, 2023
Disclosure of contingent liabilities [abstract]
Contingent Liabilities and Commitments	31. CONTINGENT LIABILITIES AND COMMITMENTS Group 2023 2022 £m £m Guarantees given to third parties 452 448 Formal standby facilities, credit lines and other commitments 30,987 31,410 31,439 31,858 At 31 December 2023 , the Santander UK group had credit impairment loss provisions relating to guarantees given to third parties and undrawn loan commitments. See Note 29 for more details. Where the items set out below can be reliably estimated, they are disclosed in the table above. Guarantees given to third parties Guarantees given to third parties consist primarily of letters of credit, bonds and guarantees granted as part of normal product facilities which are offered to customers. Formal standby facilities, credit lines and other commitments Standby facilities, credit lines and other commitments are also granted as part of normal product facilities which are offered to customers. Retail facilities comprise undrawn facilities granted on flexible mortgages, bank overdrafts and credit cards. On flexible mortgages, the credit limit is set at the point of granting the loan through property value and affordability assessments. Ongoing assessments are made to ensure that credit limits remain appropriate considering any change in the security value or the customer’s financial circumstances. For unsecured overdraft facilities and credit cards, the facilities are granted based on new business risk assessment and are reviewed more frequently based on internal, as well as external data. Corporate facilities can comprise standby and revolving facilities which are subject to ongoing compliance with covenants and may require the provision of agreed security. FSCS The FSCS is the UK’s independent statutory compensation fund for customers of authorised financial services firms and pays compensation if a firm is unable to pay certain claims against it. The FSCS is funded by levies on the industry and recoveries and borrowings where appropriate. Loan representations and warranties In connection with the securitisations and covered bond transactions described in Note 14 , the Santander UK group entities selling the relevant loans into the applicable securitisation or covered bond portfolios make representations and warranties with respect to such loans, in each case as of the date of the sale of the loans into the applicable portfolio. These representations and warranties cover, among other things, the ownership of the loan by the relevant Santander UK group entity, absence of a material breach or default by the relevant borrower under the loan, the loan’s compliance with applicable laws and absence of material disputes with respect to the relevant borrower, asset and loan. The specific representations and warranties made by Santander UK group companies which act as sellers of loans in these securitisations and covered bond transactions depend in each case on the nature of the transaction and the requirements of the transaction structure. In the event that there is a material breach of the representations and warranties given by Santander UK plc as seller of loans under the residential mortgage- backed securitisations or the covered bond programmes included in Note 14 , or if such representations and warranties prove to be materially untrue at the date when they were given (being the sale date of the relevant mortgage loans), Santander UK plc may be required to repurchase the affected mortgage loans (generally at their outstanding principal balance plus accrued interest). These securitisations and covered bond programmes are collateralised by prime residential mortgage loans. Santander UK plc is principally a retail prime lender and has no appetite or product offering for any type of sub-prime business. Similarly, under the auto loan securitisations in Note 14 , in the event that there is a breach or inaccuracy in respect of a representation or warranty relating to the loans, the relevant Santander UK group entity who sold the auto loans into the securitisation portfolio will be required to repurchase such loans from the structure (also at their outstanding principal balance plus accrued interest). In addition to breaches of representation and warranties, under the auto loan securitisations, the seller may also have a repurchase obligation if certain portfolio limits are breached (which include, amongst other things, limits as to the size of a loan given to an individual customer, LTV ratio, average term to maturity and average seasoning). In the case of a repurchase of a loan from the relevant securitisation or covered bond programmes, the Santander UK group may bear any subsequent credit loss on such loan. The Santander UK group manages and monitors its securitisation and covered bond activities closely to minimise potential claims. Other legal actions and regulatory matters Santander UK engages in discussion, and co-operates, with the FCA, PRA, CMA and other regulators and government agencies in various jurisdictions in their supervision and review of Santander UK including reviews exercised under statutory powers, regarding its interaction with past and present customers, both as part of general thematic work and in relation to specific products, services and activities. During the ordinary course of business, Santander UK is also subject to complaints and threatened legal proceedings brought by or on behalf of current or former employees, customers, investors or other third parties, in addition to legal and regulatory reviews, challenges and tax or enforcement investigations or proceedings by relevant regulators or government agencies in various jurisdictions. All such matters are assessed periodically to determine the likelihood of Santander UK incurring a liability. In those instances where it is concluded that it is not yet probable that a quantifiable payment will be made, for example because the facts are unclear or further time is required to fully assess the merits of the case or to reasonably quantify the expected payment, no provision is made. In addition, where it is not currently practicable to estimate the possible financial effect of these matters, no provision is made. Payment Protection Insurance AXA France IARD and AXA France Vie (former GE Capital Corporation Group entities (GE Capital), known as Financial Insurance Company Ltd (FICL) and Financial Assurance Company Ltd (FACL), acquired by AXA SA in 2015) (together, AXA France) have brought a claim for £552m (plus interest) against (i) Santander Cards UK Limited (former GE Capital entity known as GE Capital Bank Limited (GECB), which was acquired by Banco Santander SA in 2008 and subsequently transferred to Santander UK plc); and (ii) Santander Insurance Services UK Limited (a Banco Santander SA subsidiary) (together the Santander Entities). The claim relates to the allocation of liability for compensation and associated costs in respect of a large number of PPI policies distributed by GECB pre-2005, which were underwritten by FICL and FACL. AXA France reduced their claim from £670m (plus interest) to £552m (plus interest) in their Re-Re- Amended Particulars of Claim dated 29 June 2023. The Santander Entities strongly refute the claim. Trial has been fixed for six weeks, beginning on 3 March 2025. There are ongoing factual issues to be resolved which may have legal consequences including in relation to liability. These issues create uncertainties which mean that it is difficult to reliably predict the outcome or the timing of the resolution of the matter. The litigation and other regulatory provision in Note 29 includes our best estimate of the Santander Entities’ liability to the specific portfolio. Further information has not been provided on the basis that it would be seriously prejudicial to the Santander Entities’ interests in connection with the dispute. In addition, and in relation to PPI more generally, the PPI provision includes an amount relating to legal claims challenging the FCA’s industry guidance on the treatment of Plevin / recurring non-disclosure assessments. This provision is based on current stock levels, future projected claims, and average redress. There remains a risk that volumes received in future may be higher than forecast. The provision in Note 29 includes our best estimate of Santander UK’s liability for the specific issue. The actual cost of customer compensation could differ from the amount provided. It is not currently practicable to provide an estimate of the risk and amount of any further financial impact. German dividend tax arbitrage transactions In June 2018 the Cologne Criminal Prosecution Office and the German Federal Tax Office commenced an investigation in relation to the historical involvement of Santander UK plc, Santander Financial Services plc and Cater Allen International Limited (all subsidiaries of Santander UK Group Holdings plc) in German dividend tax arbitrage transactions (known as cum/ex transactions). These transactions allegedly exploited a loophole of a specific German settlement mechanism through short-selling and complex derivative structuring which resulted in the German government either refunding withholding tax where such tax had not been paid or refunding it more than once. The German authorities are investigating numerous institutions and individuals in connection with alleged transactions and practices which may be found to be illegal under German law. During 2023 we continued to cooperate with the German authorities and, with the assistance of external experts, to progress an internal investigation into the matters in question. From Santander UK plc’s perspective, t he investigation is focused principally on the period 2009-2011 and remains on-going. There remain factual issues to be resolved which may have legal consequences including potentially material financial penalties. These issues create uncertainties which mean that it is difficult to predict the resolution of the matter including timing or the significance of the possible impact. These uncertainties mean it is not currently practicable to make a reliable assessment of the size of any related potential liability. Any potential losses, claims or expenses suffered or incurred by Santander Financial Services plc in respect of these matters have been fully indemnified by Santander UK plc, as part of the ring-fencing transfer scheme between Santander UK plc, Santander Financial Services plc and Banco Santander SA. SCUK - Motor Finance Broker Commissions Following the FCA’s Motor Market review in 2019 which resulted in a change in rules in January 2021, Santander Consumer (UK) plc (SCUK) has received a number of county court claims and complaints in respect of its historical use of discretionary commission arrangements (DCAs) prior to the 2021 rule changes. In the context of the complaints made to the Financial Ombudsman Service relating to such commission arrangements, the FCA announced on 11 January 2024 that it intends to use its powers under s166 of the Financial Services and Markets Act 2000 to review the historical use of DCAs between lenders and credit brokers (the “FCA Review”) and whether redress should be payable. In line with the FCA's announcement, we have paused the response to customer complaints until at least 20 November 2024. A claim has been issued against SCUK, Santander UK plc and others in the Competition Appeal Tribunal (CAT), alleging that SCUK’s historical commission arrangements in respect of used car financing operated in breach of the Competition Act 1998. While it is possible that certain charges may be incurred in relation to existing or future county court claims, Financial Ombudsman Service (FOS) complaints and the CAT proceedings, it is not considered that a legal or constructive obligation has been incurred in relation to these matters that would require a provision to be recognised at this stage. The resolution of such matters is not possible to predict with any certainty and there remain significant inherent uncertainties regarding the existence, scope and timing of any possible outflow which make it impracticable to disclose the extent of any potential financial impact. Other On 2 November 2015, Visa Europe Ltd agreed to sell 100% of its share capital to Visa Inc. The deal closed on 21 June 2016. As a member and shareholder of Visa Europe Ltd, Santander UK received upfront consideration made up of cash and convertible preferred stock. Conversion of the preferred stock into Class A Common Stock of Visa Inc. depends on the outcome of litigation against Visa involving UK & Ireland multilateral interchange fees (UK&I MIFs). Following ring- fencing, all Visa stock is now held by Santander Equity Investments Limited (SEIL), outside the ring-fenced bank. In valuing the preferred stock, SEIL makes adjustments for illiquidity and the potential for changes in the conversion rate due to litigation costs. In addition, Santander UK plc and certain other UK&I banks have agreed to indemnify Visa Inc. in the event that the preferred stock is insufficient to meet the costs of this litigation. Visa Inc. has recourse to this indemnity once more than €1bn of losses relating to UK&I MIFs have arisen or once the total value of the preferred stock issued to UK&I banks on closing has been reduced to nil . Santander UK plc's liability under this indemnity is capped at €39.85m . At this stage, it is unclear whether the litigation will give rise to more than €1bn of losses relating to UK&I MIFs which means it is not practicable to predict the resolution of the matter including the timing or the significance of the possible impact. As part of the sale of subsidiaries, businesses and other entities, and as is normal in such circumstances, entities within the Santander UK group have given warranties and/or indemnities to the purchasers. Obligations under stock borrowing and lending agreements Obligations under stock borrowing and lending agreements represent contractual commitments to return stock borrowed. These obligations are offset by a contractual right to receive stock under other contractual agreements. See Note 35 . Other off-balance sheet commitments The Santander UK group has commitments to lend at fixed interest rates which expose us to interest rate risk. For more, see the Risk review. Liquidity support arrangements Under the PRA’s liquidity rules, Santander UK plc and its subsidiary Cater Allen Limited form the RFB Domestic Liquidity Sub-group (the RFB DoLSub), which allows the entities to collectively meet regulatory requirements for the purpose of managing liquidity risk. Each member of the RFB DoLSub will support the other by transferring surplus liquidity in times of stress.

Share Capital

Share Capital	12 Months Ended
	Dec. 31, 2023
Disclosure of classes of share capital [abstract]
Share Capital	32. SHARE CAPITAL Group Ordinary shares of £1 each Issued and fully paid share capital No. £m At 31 December 2022, 1 January 2023 and 31 December 2023 7,060,000,000 7,060

Other Equity Instruments

Other Equity Instruments	12 Months Ended
	Dec. 31, 2023
Disclosure of classes of share capital [abstract]
Other Equity Instruments	33. OTHER EQUITY INSTRUMENTS Group Interest rate 2023 2022 % Next call date £m £m AT1 securities: - £500m Fixed Rate Reset Perpetual AT1 Capital Securities 6.75 June 2024 496 496 - £500m Fixed Rate Reset Perpetual AT1 Capital Securities 6.30 March 2025 500 500 - £450m Fixed Rate Reset Perpetual AT1 Capital Securities 4.25 March 2026 450 450 - £750m Fixed Rate Reset Perpetual AT1 Capital Securities 6.50 June 2027 750 750 2,196 2,196 AT1 securities The AT1 securities are perpetual and pay a quarterly distribution. At each distribution payment date, the Company can decide whether to pay the distribution, which is non-cumulative, in whole or in part. The distribution rate resets every five years . The securities will be automatically written down and the investors will lose their entire investment in the securities should the CET1 capital ratio of the Santander UK prudential consolidation group fall below 7% . All AT1 securities are redeemable at the option of the Company, and only with the consent of the PRA. The £450m 4.25% Fixed Rate Reset Perpetual AT1 Capital Securities, the £500m 6.30% Fixed Rate Reset Perpetual AT1 Capital Securities and the £750m 6.50% Fixed Rate Reset Perpetual AT1 Capital Securities were fully subscribed by the Company's immediate parent company, Banco Santander SA.

Notes to Cash Flows

Notes to Cash Flows	12 Months Ended
	Dec. 31, 2023
Cash Flows Explanatory Notes [Abstract]
Notes to Cash Flows	34. NOTES TO CASH FLOWS Changes in liabilities arising from financing activities The table below shows the changes in liabilities arising from financing activities. The changes in equity arising from financing activities are set out in the Consolidated Statement of Changes in Equity. Group Balance sheet line item Debt securities in issue Subordinated liabilities Other equity instruments Lease liabilities Dividends paid Total 2023 £m £m £m £m £m £m At 1 January 36,420 2,332 2,196 129 — 41,077 Proceeds from issue of debt securities 5,347 — — — — 5,347 Repayment of debt securities (5,438) — — — — (5,438) Proceeds from issue of subordinated liabilities — 1,050 — — — 1,050 Repayment of subordinated liabilities — (971) — — — (971) Principal elements of lease payments — — — (48) — (48) Dividends paid — — — — (1,671) (1,671) Liability-related other changes (159) 25 — 33 — (101) Non-cash changes: – Unrealised foreign exchange (750) (54) — — — (804) – Other changes 358 4 — — 1,671 2,033 At 31 December 35,778 2,386 2,196 114 — 40,474 2022 At 1 January 31,580 2,228 2,191 134 — 36,133 Proceeds from issue of debt securities 8,667 — — — — 8,667 Repayment of debt securities (4,482) — — — — (4,482) Repayment of subordinated liabilities — (40) — — — (40) Issue of other equity instruments — — 750 — — 750 Repurchase of other equity instruments — — (750) — — (750) Principal elements of lease payments — — — (26) — (26) Dividends paid — — — — (1,173) (1,173) Liability-related other changes (1,282) 2 5 21 — (1,254) Non-cash changes: – Unrealised foreign exchange 1,893 190 — — — 2,083 – Other changes 44 (47) — — 1,173 1,169 At 31 December 36,420 2,332 2,196 129 — 41,077 2021 At 1 January 43,679 2,556 2,241 100 — 48,576 Proceeds from issue of debt securities 2,847 — — — — 2,847 Repayment of debt securities (13,724) — — — — (13,724) Repayment of subordinated liabilities — (4) — — — (4) Issue of other equity instruments — — 450 — — 450 Repurchase of other equity instruments — — (500) — — (500) Principal elements of lease payments — — — (25) — (25) Dividends paid — — — — (1,506) (1,506) Liability-related other changes (473) (4) — 59 — (418) Non-cash changes: – Unrealised foreign exchange (930) 14 — — — (916) – Other changes 181 (334) — — 1,506 1,353 At 31 December 31,580 2,228 2,191 134 — 36,133 Footnotes to the cash flow statement Net cash flows from operating activities includes interest received of £11,627m ( 2022 : £6,618m , 2021 : £4,873m ), interest paid of £6,496m ( 2022 : £2,107m , 2021 : £1,085m ) and dividends received of £nil ( 2022 : £nil , 2021 : £nil ). Total cash outflow for leases was £50m ( 2022 : £28m , 2021 : £28m ). Other matters In 2022, the non-controlling interests were redeemed. In 2021, there was a disposal of non-controlling interests of £181m .

Assets Charged as Security for

Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets	12 Months Ended
	Dec. 31, 2023
Disclosure Of Assets Pledged As Security [Abstract]
Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets	35. ASSETS CHARGED AS SECURITY FOR LIABILITIES AND COLLATERAL ACCEPTED AS SECURITY FOR ASSETS The following transactions are conducted under terms that are usual and customary to collateralised transactions including, where relevant, standard securities lending and repurchase agreements. a) Assets charged as security for liabilities The financial assets below are analysed between those assets accounted for on-balance sheet and off-balance sheet. Group 2023 2022 £m £m On-balance sheet: Cash and balances at central banks 1,480 1,330 Loans and advances to banks 254 163 Loans and advances to customers - securitisations and covered bonds (See Note 14) 27,088 24,155 Loans and advances to customers - other 20,703 32,011 Other financial assets at amortised cost 14 35 Financial assets at fair value through other comprehensive income 5,253 4,441 Total on-balance sheet 54,792 62,135 Total off-balance sheet 10,184 9,184 Santander UK provides assets as collateral in the following areas of the business. Sale and repurchase agreements Santander UK also enters into sale and repurchase agreements and similar transactions of debt securities. Upon entering into such transactions, Santander UK provides collateral in excess of the borrowed amount. The carrying amount of assets that were so provided at 31 December 2023 was £13,291m ( 2022 : £11,553m ), of which £909m ( 2022 : £900m ) was classified in ‘Loans and advances to customers – securitisations and covered bonds’ in the table above. Securitisations and covered bonds As described in Note 14 , Santander UK plc and certain of its subsidiaries issue securitisations and covered bonds. At 31 December 2023 , there were £27,927m ( 2022 : £24,984m ) of gross assets in these secured programmes and £839m ( 2022 : £829m ) of these related to internally retained issuances that were available for use as collateral for liquidity purposes in the future. At 31 December 2023 , £2,928m ( 2022 : £1,725m ) of notes issued under securitisation and covered bond programmes had been retained internally, a proportion of which had been used as collateral via third party bilateral secured funding transactions, which totalled £1,500m at 31 December 2023 ( 2022 : £500m ), or for use as collateral for liquidity purposes in the future. Stock borrowing and lending agreements Asset balances under stock borrowing and lending agreements represent stock lent by Santander UK. These balances amounted to £23,713m at 31 December 2023 ( 2022 : £34,963m ) and are offset by contractual commitments to return stock borrowed or cash received. Derivatives business In addition to the arrangements described above, collateral is also provided in the normal course of derivative business to counterparties. At 31 December 2023 £1,793m ( 2022 : £1,548m ) of such collateral in the form of cash had been provided by Santander UK and is included in the table. b) Collateral accepted as security for assets The collateral held as security for assets, analysed between those liabilities accounted for on balance sheet and off-balance sheet, was: Group 2023 2022 £m £m On-balance sheet: Deposits by banks 888 1,758 Total on-balance sheet 888 1,758 Total off-balance sheet 15,652 10,395 Purchase and resale agreements Santander UK also enters into purchase and resale agreements and similar transactions of debt securities. Upon entering into such transactions, Santander UK receives collateral in excess of the loan amount. The level of collateral held is monitored daily and if required, further calls are made to ensure the market values of collateral remains at least equal to the loan balance. The subsidiaries are permitted to sell or repledge the collateral held in the absence of default. At 31 December 2023 , the fair value of such collateral received was £12,983m ( 2022 : £8,628m ). Of the collateral received, almost all was sold or repledged. The subsidiaries have an obligation to return collateral that they have sold or pledged. Stock borrowing and lending agreements Obligations representing contractual commitments to return stock borrowed by Santander UK amounted to £2,669m at 31 December 2023 ( 2022 : £1,767m ) and are offset by a contractual right to receive stock lent. Derivatives business In addition to the arrangements described, collateral is also received from counterparties in the normal course of derivative business. At 31 December 2023 , £888m ( 2022 : £1,758m ) of such collateral in the form of cash had been received by Santander UK and is included in the table. Lending activities In addition to the collateral held as security for assets, Santander UK may obtain a charge over a customer’s property in connection with its lending activities. Details of these arrangements are set out in the ‘Credit risk’ section of the Risk review.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2023
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Share-Based Compensation	36. SHARE-BASED COMPENSATION The Santander UK group operates share schemes and arrangements for eligible employees. The main current schemes are the Sharesave Schemes, the Deferred Shares Bonus Plan, the Partnership Shares scheme and the Transformation Incentive Plan. All the share options and awards relate to shares in Banco Santander SA. The amount charged to the income statement in respect of share-based payment transactions is set out in Note 6 . At 31 December 2023 , the carrying amount of liabilities arising from share-based payment transactions, excluding any cash element was £14.7m ( 2022 : £6.6m ), of which £1.1m had vested at 31 December 2023 ( 2022 : £0.1m ). a) Sharesave Schemes The Santander UK group launched its sixteenth HM Revenue & Customs approved Sharesave invitation under Banco Santander SA sponsorship in September 2023 . Sharesave invitations have been offered since 2008 under broadly similar terms. Under the Sharesave Scheme’s HMRC-approved savings limits, eligible employees may enter into contracts to save between £5 and £500 per month. For all schemes, at the end of a fixed term of three or five years after the grant date, the employees can use these savings to buy shares in Banco Santander SA at a discount, calculated in accordance with the rules of the scheme. The option price is calculated as the average middle market quoted price of Banco Santander SA shares over the first three dealing days prior to invitation and discounted by up to 20% . This year a 10% discount was applied. The vesting of awards under the scheme depends on continued employment with the Banco Santander group. Participants in the scheme have six months from the date of vesting to exercise the option. The table below summarises movements in the number of options, and changes in weighted average exercise price over the same period. 2023 2022 Number of options Weighted average exercise price Number of options Weighted average exercise price ‘000 £ ‘000 £ Outstanding at 1 January 29,988 2.00 25,993 2.25 Granted 7,175 2.78 13,068 1.89 Exercised (5,980) 1.70 (242) 1.69 Forfeited/expired (4,044) 2.53 (8,831) 2.59 Outstanding at 31 December 27,139 2.19 29,988 2.00 Exercisable at 31 December 868 1.84 3,439 3.22 The weighted average share price at the date the options were exercised was £3.22 ( 2022 : £2.34 ). The following table summarises the range of exercise prices and weighted average remaining contractual life of the options at 31 December 2023 and 2022 . 2023 2022 Weighted average remaining contractual life Weighted average exercise price Weighted average remaining contractual life Weighted average exercise price Range of exercise prices Years £ Years £ £1 to £2 3 1.84 3 1.79 £2 to £3 3 2.65 2 2.56 £3 to £4 0 3.46 1 3.46 £4 to £5 0 — 0 4.02 The fair value of each option at the date of grant is estimated using an analytical model that also reflects the correlation between EUR and GBP. This model uses assumptions on the share price, the EUR/GBP FX rate, the EUR/GBP risk-free interest rate, dividend yields, the expected volatilities of both the underlying shares and EUR/GBP for the expected lives of options granted. The weighted average grant-date fair value of options granted during the year was £0.33 ( 2022 : £0.23 ). b) Deferred shares bonus plan Deferred bonus awards are designed to align employee performance with shareholder value and encourage increased retention of senior employees. Those employees who are designated as Material Risk Takers receive part of their annual bonus as a deferred award comprising 50% in shares and 50% in cash. Either 40% (for any variable pay award of less than £500,000 ) or 60% (for any variable pay award greater than £500,000 ) is deferred over a four -, five - or seven - year period from the anniversary of the initial award. Deferred bonus awards in shares or share options are subject to an additional one -year retention period from the point of delivery. Any deferred awards are dependent on continued employment and subject to Santander UK's discretion, and the vesting of deferred bonus awards is subject to potential performance adjustment. c) Partnership Shares scheme A Partnership Shares scheme is operated for eligible employees under the Share Incentive Plan (SIP) umbrella. Participants can choose to invest up to £1,800 per tax year (or no more than 10% of an employee’s salary for the tax year) from pre-tax salary to buy Banco Santander SA shares. Shares are held in trust for the participants. There are no vesting conditions attached to these shares, and no restrictions as to when the shares can be removed from the trust. However, if a participant chooses to sell the shares before the end of five years , they will be liable for the taxable benefit received when the shares are taken out of the trust. The shares can be released from trust after five years free of income tax and national insurance contributions. 3,937,473 shares were outstanding at 31 December 2023 ( 2022 : 3,974,698 shares). d) Transformation Incentive Plan This one-off long-term incentive plan was designed to recognise the achievement of financial targets and an enhanced customer experience, whilst maintaining appropriate conduct controls and risk management, over the course of our transformation period. Awards under the plan were granted in 2021 , 2022 and 2023 with performance assessed over the period 1 January 2021 to 31 December 2023 . Awards for Material Risk Takers were granted half in cash and half in share based awards (linked to the Banco Santander SA share price), and will vest in accordance with regulatory requirements. The total value of share-based awards granted in 2023 was £1.3m ( 2022 : £1m ) and the liability arising from share-based payment transactions, excluding any cash element was £3.8m ( 2022 : £1.8m ).

Transactions with Directors and

Transactions with Directors and Other Key Management Personnel	12 Months Ended
	Dec. 31, 2023
Disclosure Of Remuneration Of Directors And Other Key Management Personnel [Abstract]
Transactions with Directors and Other Key Management Personnel	37. TRANSACTIONS WITH DIRECTORS AND OTHER KEY MANAGEMENT PERSONNEL The Directors of Santander UK Group Holdings plc did not receive any remuneration in respect of their services to the Company. The remuneration disclosures in these financial statements reflect their remuneration in respect of the Santander UK plc group. a) Remuneration of Directors and Other Key Management Personnel The remuneration of the Directors and Other Key Management Personnel (KMP) of the Santander UK group is set out in aggregate below. 2023 2022 2021 Directors’ remuneration £ £ £ Salaries and fees 4,008,772 4,037,116 3,828,333 Performance-related payments 1,002,607 3,701,569 3,431,294 Other fixed remuneration (pension and other allowances & non-cash benefits) 222,538 906,201 806,103 Expenses — 13,004 3,705 Total remuneration 5,233,917 8,657,890 8,069,435 2023 2022 2021 Directors' and Other Key Management Personnel compensation £ £ £ Short-term employee benefits 13,235,757 15,641,669 18,831,380 Post-employment benefits 611,769 740,333 913,842 Compensation for loss of office (1) — 1,540,400 — Total compensation 13,847,526 17,922,402 19,745,222 (1) Compensation for loss of office was not paid to Directors or KMPs in 2023 ( 2022 : three KMPs, £1,540,400 ; 2021 : nil ). In 2023 , the remuneration, excluding pension contributions, of the highest paid Director, was £2,640,491 ( 2022 : £3,510,441 , 2021 : £3,740,810 ) of which £1,002,607 ( 2022 : £1,900,506 , 2021 : £1,864,320 ) was performance related. In 2023 , the accrued defined benefit pension relating to the highest paid director was £nil ( 2022 : £nil , 2021 : £22,119 per annum for a different individual). b) Retirement benefits Defined benefit pension schemes are provided to certain employees. See Note 30 for details of the schemes and the related costs and obligations. No director has a deferred pension benefit accruing under a defined benefit scheme. Ex-gratia pensions paid to former Directors of Santander UK plc in 2023 , which have been provided for previously, amounted to £327,462 ( 2022 : £379,945 ; 2021 : £370,668 ). Since the Company became part of the Banco Santander group, the Board has not awarded any new ex-gratia pensions. c) Transactions with Directors, Other Key Management Personnel and each of their connected persons Directors, Other KMP (defined as the Executive Committee of Santander UK plc who served during the year) and their connected persons have undertaken the following transactions with the Santander UK group in the ordinary course of business. 2023 2022 No. £000 No. £000 Secured loans, unsecured loans and overdrafts At 1 January 6 647 4 27 Net movements — 244 2 620 At 31 December 6 891 6 647 Deposit, bank and instant access accounts and investments At 1 January 16 2,995 16 6,427 Net movements (3) (1,819) — (3,432) At 31 December 13 1,176 16 2,995 In 2023 and 2022 , no Director held any interest in the shares of any company in the Santander UK group and no Director exercised or was granted any rights to subscribe for shares in any company in the Santander UK group. In addition, in 2023 and 2022 , no Directors exercised share options over shares in Banco Santander SA, the ultimate parent company of the Company. Secured loans, unsecured loans and overdrafts are made to Directors, Other KMP and their connected persons, in the ordinary course of business, with terms prevailing for comparable transactions and on the same terms and conditions as applicable to other employees in the Santander UK group. Such loans do not involve more than the normal risk of collectability or present any unfavourable features. Amounts deposited by Directors, Other KMP and their connected persons earn interest at the same rates as those offered to the market or on the same terms and conditions applicable to other employees in the Santander UK group. Deposits, bank and instant access accounts and investments are entered into by Directors, Other KMP and their connected persons on normal market terms and conditions, or on the same terms and conditions as applicable to other employees in Santander UK group. In 2023 , loans were made to one Directors ( 2022 : four Directors), with a principal amount of £312,846 outstanding at 31 December 2023 ( 2022 : £332,426 ). In 2023 , loans were made to five Other KMP ( 2022 : two ), with a principal amount of £578,568 outstanding at 31 December 2023 ( 2022 : £314,667 ). In 2023 and 2022 , there were no other transactions, arrangements or agreements with Santander UK in which Directors, Other KMP or their connected persons had a material interest. In addition, in 2023 and 2022 , no Director had a material interest in any contract of significance with Santander UK other than a service contract or appointment letter, as appropriate.

Related Party Disclosures

Related Party Disclosures	12 Months Ended
	Dec. 31, 2023
Disclosure of transactions between related parties [abstract]
Related Party Disclosures	38. RELATED PARTY DISCLOSURES a) Parent undertaking and controlling party The Company’s immediate and ultimate parent and controlling party is Banco Santander SA , a company incorporated in Spain. The smallest and largest groups into which the Santander UK group’s results are included are the group accounts of Banco Santander SA , copies of which may be obtained from Shareholder Relations, 2 Triton Square, Regent’s Place, London NW1 3AN. b) Transactions with related parties Transactions with related parties during the year and balances outstanding at the year-end: Group Interest, fees and other income received Interest, fees and other expenses paid Amounts owed by related parties Amounts owed to related parties 2023 2022 2021 2023 2022 2021 2023 2022 2023 2022 £m £m £m £m £m £m £m £m £m £m Ultimate parent (12) (863) (210) 475 47 34 903 1,423 (2,250) (1,732) Fellow subsidiaries (28) (60) (47) 194 171 151 26 31 (251) (278) Joint ventures (183) (77) (34) 55 17 4 4,486 4,151 (781) (973) (223) (1,000) (291) 724 235 189 5,415 5,605 (3,282) (2,983) For more on this, see ‘Balances with other Banco Santander group members’ in the Risk review, Note 13. Loans and advances to customers, Note 23. Deposits by customers and Note 33. Other Equity Instruments. In addition, transactions with pension schemes operated by the Santander UK group are described in Note 30 . The above transactions were made in the ordinary course of business, on substantially the same terms as for comparable transactions with third party counterparties, and within limits acceptable to the PRA. Such transactions do not involve more than the normal risk of collectability or present any unfavourable features. In 2021, SCUK sold its entire 50% shareholding in PSA Finance UK Limited to PSA Financial Services Spain EFC SA, a joint venture between Santander Consumer Finance SA, a fellow subsidiary of Banco Santander SA, and Banque PSA Finance SA. In 2021 , a significant part of the CIB business of Santander UK was transferred to the London branch of Banco Santander SA by way of a Part VII banking business transfer scheme. For more details, see Note 42. In 2021, we sold our then head office site in Triton Square, London to Santander UK Investments Ltd, a wholly owned subsidiary of our ultimate parent. Santander UK occupies space within the building and paid fees of £9m ( 2022 : £6m ) under an occupational licence arrangement. In November 2022, Santander (UK) Group Pension Scheme Trustees Limited entered into an unsecured committed liquidity facility with Santander UK plc for £600m with a maturity date of 31 December 2024. This facility provides an alternate source of short-term liquidity for day-to-day operational needs. At the balance sheet date, no drawings had been made from this facility and the entire facility remained undrawn.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2023
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Abstract]
Financial Instruments	39. FINANCIAL INSTRUMENTS a) Fair value measurement and hierarchy (i) Fair value measurement The fair value of financial instruments is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date in the principal, or in its absence, the most advantageous market to which Santander UK has access at that date. The fair value of a liability reflects its non-performance risk. Financial instruments valued using observable market prices If a quoted market price in an active market is available for an instrument, the fair value is calculated as the current bid price multiplied by the number of units of the instrument held. Financial instruments valued using a valuation technique In the absence of a quoted market price in an active market, management uses internal models to make its best estimate of the price that the market would set for that financial instrument. In order to make these estimations, various techniques are employed, including extrapolation from observable market data and observation of similar financial instruments with similar characteristics. Wherever possible, valuation parameters for each product are based on prices directly observable in active markets or that can be derived from directly observable market prices. Chosen valuation techniques incorporate all the factors that market participants would take into account in pricing transactions. Santander UK manages certain groups of financial assets and liabilities on the basis of its net exposure to either market risks or credit risk. As a result, it has elected to use the exception under IFRS 13 which permits the fair value measurement of a group of financial assets and financial liabilities on the basis of the price that would be received to sell a net long position for a particular risk exposure or paid to transfer a net short position for a particular risk exposure in an orderly transaction between market participants at the measurement date under current market conditions. (ii) Fair value hierarchy Santander UK applies the following fair value hierarchy that prioritises the inputs to valuation techniques used in measuring fair value. The hierarchy establishes three categories for valuing financial instruments, giving the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The three categories are: quoted prices in active markets (Level 1), internal models based on observable market data (Level 2) and internal models based on other than observable market data (Level 3). If the inputs used to measure an asset or a liability fall to different levels within the hierarchy, the classification of the entire asset or liability will be based on the lowest level input that is significant to the overall fair value measurement of the asset or liability. Santander UK categorises assets and liabilities measured at fair value within the fair value hierarchy based on the inputs to the valuation techniques as follows: Level 1 Unadjusted quoted prices for identical assets or liabilities in an active market that Santander UK can access at the measurement date. Active markets are assessed by reference to average daily trading volumes in absolute terms and, where applicable, by reference to market capitalisation for the instrument. Level 2 Quoted prices in inactive markets, quoted prices for similar assets or liabilities, recent market transactions, inputs other than quoted market prices for the asset or liability that are observable either directly or indirectly for substantially the full term, and inputs to valuation techniques that are derived principally from or corroborated by observable market data through correlation or other statistical means for substantially the full term of the asset or liability. Level 3 Significant inputs to the pricing or valuation techniques are unobservable. These unobservable inputs reflect the assumptions that market participants would use when pricing assets or liabilities and are considered significant to the overall valuation. Changes in the observability of significant valuation inputs during the reporting period may result in a transfer of assets and liabilities within the fair value hierarchy. The Santander UK group recognises transfers between levels of the fair value hierarchy when there is a significant change in either its principal market or the level of observability of the inputs to the valuation techniques at the end of the reporting period. b) Valuation techniques The main valuation techniques employed in internal models to measure the fair value of the financial instruments at 31 December 2023 and 2022 are set out below. In substantially all cases, the principal inputs into these models are derived from observable market data. Santander UK did not make any material changes to the valuation techniques and internal models it used in 2023 , 2022 and 2021 . A In the valuation of financial instruments requiring static hedging (for example interest rate, currency derivatives and property derivatives) and in the valuation of loans and advances and deposits, the ‘present value’ method is used. Expected future cash flows are discounted using the interest rate curves of the applicable currencies or forward house price index levels, as well as credit spreads. The interest rate curves are generally observable market data and reference yield curves derived from quoted interest rates in appropriate time bandings, which match the timings of the cash flows and maturities of the instruments. B In the valuation of equity financial instruments requiring dynamic hedging (principally equity securities, options and other structured instruments), proprietary local volatility and stochastic volatility models are used. These types of models are widely accepted in the financial services industry. Observable market inputs used in these models include the bid-offer spread, foreign currency exchange rates, volatility and correlation between indices. In limited circumstances, other inputs may be used in these models that are based on unobservable market data, such as the Halifax’s UK HPI volatility, HPI forward growth, HPI spot rate, mortality , mean reversion and contingent litigation risk. C In the valuation of financial instruments exposed to interest rate risk that require either static or dynamic hedging (such as interest rate futures, caps and floors, and options), the present value method (futures), Black’s model (caps/floors) and the Hull/White and Markov functional models (Bermudan options) are used. These types of models are widely accepted in the financial services industry. The significant inputs used in these models are observable market data, including appropriate interest rate curves, volatilities, correlations and exchange rates. In limited circumstances, other inputs may be used in these models that are based on unobservable market data, such as HPI volatility, HPI forward growth, HPI spot rate and mortality. D In the valuation of linear instruments such as credit risk and fixed-income derivatives, credit risk is measured using dynamic models similar to those used in the measurement of interest rate risk. In the case of non-linear instruments, if the portfolio is exposed to credit risk such as credit derivatives, the probability of default is determined using the credit default spread market. The main inputs used to determine the underlying cost of credit of credit derivatives are quoted credit risk premiums and the correlation between the quoted credit derivatives of various issuers. The fair values of the financial instruments arising from Santander UK’s internal models take into account, among other things, contract terms and observable market data, which include such factors as bid-offer spread, interest rates, credit risk, exchange rates, the quoted market price of equity securities, volatility and prepayments. In all cases, when it is not possible to derive a valuation for a particular feature of an instrument, management uses judgement to determine the fair value of the particular feature. In exercising this judgement, a variety of tools are used including proxy observable data, historical data and extrapolation techniques. Extrapolation techniques take into account behavioural characteristics of equity markets that have been observed over time, and for which there is a strong case to support an expectation of a continuing trend in the future. Estimates are calibrated to observable market prices when they become available. Santander UK believes its valuation methods are appropriate and consistent with other market participants. Nevertheless, the use of different valuation methods or assumptions, including imprecision in estimating unobservable market inputs, to determine the fair value of certain financial instruments could result in different estimates of fair value at the reporting date and the amount of gain or loss recorded for a particular instrument. Most of the valuation models are not significantly subjective, because they can be tested and, if necessary, recalibrated by the internal calculation of and subsequent comparison to market prices of actively traded securities, where available. c) Control framework Fair values are subject to a control framework designed to ensure that they are either determined or validated by a function independent of the risk-taker. To this end, ultimate responsibility for the determination of fair values lies with the Risk Department. For all financial instruments where fair values are determined by reference to externally quoted prices or observable pricing inputs to models, independent price determination or verification is utilised. In inactive markets, direct observation of a traded price may not be possible. In these circumstances, Santander UK will source alternative market information to validate the financial instrument’s fair value, with greater weight given to information that is considered to be more relevant and reliable. The factors that are considered in this regard include: – The extent to which prices may be expected to represent genuine traded or tradeable prices – The degree of similarity between financial instruments – The degree of consistency between different sources – The process followed by the pricing provider to derive the data – The elapsed time between the date to which the market data relates and the balance sheet date – The manner in which the data was sourced. The source of pricing data is considered as part of the process that determines the classification of the level of a financial instrument. Consideration is given to the quality of the information available that provides the current mark-to-model valuation and estimates of how different these valuations could be on an actual trade, taking into consideration how active the market is. For spot assets that cannot be sold due to illiquidity, forward estimates are discounted to estimate a realisable value over time. Adjustments for illiquid positions are regularly reviewed to reflect changing market conditions. For fair values determined using a valuation model, the control framework may include as applicable, independent development and / or validation of: (i) the logic within the models; (ii) the inputs to those models; and (iii) any adjustments required outside the models. Internal valuation models are validated independently within the Risk Department. A validation report is produced for each model-derived valuation that assesses the mathematical assumptions behind the model, the implementation of the model and its integration within the trading system. d) Fair values of financial instruments carried at amortised cost The following tables analyse the fair value of the financial instruments carried at amortised cost at 31 December 2023 and 2022 , including their levels in the fair value hierarchy - Level 1, Level 2 and Level 3. Cash and balances at central banks, which consist of demand deposits with the Bank of England, together with cash in tills and ATMs, have been excluded from the table as the carrying amount is deemed an appropriate approximation of fair value. Group 2023 2022 Fair value Fair Carrying Fair value Fair Carrying Level 1 Level 2 Level 3 value value Level 1 Level 2 Level 3 value value £m £m £m £m £m £m £m £m £m £m Assets Loans and advances to customers — — 209,641 209,641 211,222 — — 216,451 216,451 223,840 Loans and advances to banks — 1,216 — 1,216 1,216 — 1,105 — 1,105 1,105 Reverse repurchase agreements - non trading — 12,470 — 12,470 12,468 — 7,341 — 7,341 7,348 Other financial assets at amortised cost 144 — — 144 152 144 — — 144 156 144 13,686 209,641 223,471 225,058 144 8,446 216,451 225,041 232,449 Liabilities Deposits by customers — 76 194,831 194,907 195,149 — 52 197,228 197,280 197,313 Deposits by banks — 20,371 37 20,408 20,357 — 27,997 54 28,051 28,543 Repurchase agreements - non trading — 8,413 — 8,413 8,411 — 7,982 — 7,982 7,982 Debt securities in issue 11,511 22,710 1,154 35,375 35,778 4,988 28,685 1,582 35,255 36,420 Subordinated liabilities 871 1,669 209 2,749 2,386 19 2,268 224 2,511 2,332 12,382 53,239 196,231 261,852 262,081 5,007 66,984 199,088 271,079 272,590 The carrying value above of any financial assets and liabilities that are designated as hedged items in a portfolio (or macro) fair value hedge relationship excludes gains and losses attributable to the hedged risk, as this is included as a separate line item on the balance sheet. Valuation methodology for financial instruments carried at amortised cost The valuation approach to specific categories of financial instruments is described below. Assets: Loans and advances to customers The approach to estimating the fair value of loans and advances to customers has been determined by discounting expected cash flows to reflect either current market rates or credit spreads relevant to the specific industry of the borrower. The determination of their fair values is an area of considerable estimation and uncertainty as there is no observable market and values are significantly affected by customer behaviour. i) Advances secured on residential property The fair value of the mortgage portfolio is calculated by discounting contractual cash flows by different spreads for each LTV Band, after taking account of expected customer prepayment rates. The spread is based on new business interest rates derived from publicly available competitor market information. ii) Corporate loans The determination of the fair values of performing loans is calculated by discounting the contractual cash flows and also deducting other costs relating to expected credit losses, cost of capital, credit risk capital, operational risk capital, cost of funding and operating costs. iii) Other loans These consist of unsecured personal loans, credit cards, overdrafts and consumer (auto) finance. The weighted average lives of these portfolios are typically short and relate to relatively new business. For unsecured personal loans and consumer (auto) finance loans, a small surplus or deficit has been recognised based on the differential between existing portfolio margins and the current contractual interest rates. Loans and advances to banks These comprise secured loans, short-term placements with banks including collateral and unsettled financial transactions. The secured loans have been valued based on a discounted spread for the term of the loans using valuation technique A as described above. The carrying amount of the other items is deemed a reasonable approximation of their fair value, as the transactions are very short-term in duration. Reverse repurchase agreements - non-trading The fair value of the reverse repurchase agreements - non trading has been estimated using valuation technique A as described above, using a spread appropriate to the underlying collateral. Other financial assets at amortised cost These consist of asset backed securities and debt securities. The asset backed securities can be complex products and in some instances are valued with the assistance of an independent, specialist valuation firm. These fair values are determined using industry-standard valuation techniques, including discounted cash flow models. The inputs to these models used in these valuation techniques include quotes from market makers, prices of similar assets, adjustments for differences in credit spreads, and additional quantitative and qualitative research. The debt security investments consist of a portfolio of government debt securities. The fair value of this portfolio has been determined using quoted market prices. Liabilities: Deposits by customers The majority of deposit liabilities are payable on demand and therefore can be deemed short-term in nature with the fair value equal to the carrying value. Certain of the deposit liabilities are at a fixed rate until maturity. The deficit/surplus of fair value over carrying value of these liabilities has been estimated by reference to the market rates available at the balance sheet date for similar deposit liabilities of similar maturities. The fair value of such deposit liabilities has been estimated using valuation technique A as described above. Deposits by banks The fair value of deposits by banks, including repos, has been estimated using valuation technique A as described above, discounted at the appropriate credit spread. Repurchase agreements - non trading The fair value of the repurchase agreements - non trading has been estimated using valuation technique A as described above, discounted at a spread appropriate to the underlying collateral. Debt securities in issue and subordinated liabilities Where reliable prices are available, the fair value of debt securities in issue and subordinated liabilities has been calculated using quoted market prices. Where reliable prices are not available, internal models have been used to determine fair values, which take into account, among other things, contract terms and observable market data, which include such factors as interest rates, credit risk and exchange rates. In all cases, when it is not possible to derive a valuation for a particular feature of an instrument, management uses judgement to determine the fair value of the particular feature. In exercising this judgement, a variety of tools are used including proxy observable data. e) Fair values of financial instruments measured at fair value The following tables summarise the fair values of the financial assets and liabilities accounted for at fair value at 31 December 2023 and 31 December 2022 , analysed by their levels in the fair value hierarchy - Level 1, Level 2 and Level 3. Group 2023 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Valuation £m £m £m £m £m £m £m £m technique Assets Derivative financial instruments Exchange rate contracts — 1,129 — 1,129 — 2,049 — 2,049 A Interest rate contracts — 2,227 1 2,228 — 2,406 7 2,413 A & C Equity and credit contracts — 127 35 162 — 103 47 150 B & D Netting — (2,047) — (2,047) — (2,173) — (2,173) — 1,436 36 1,472 — 2,385 54 2,439 Other financial assets at FVTPL Loans and advances to customers — 309 46 355 — 294 45 339 A Debt securities — 168 49 217 — 13 72 85 A, B & D Equity securities — — 30 30 — — 10 10 B — 477 125 602 — 307 127 434 Financial assets at FVOCI Debt securities 8,293 188 — 8,481 5,996 28 — 6,024 D 8,293 188 — 8,481 5,996 28 — 6,024 Total assets at fair value 8,293 2,101 161 10,555 5,996 2,720 181 8,897 Liabilities Derivative financial instruments Exchange rate contracts — 533 — 533 — 489 — 489 A Interest rate contracts — 2,379 1 2,380 — 2,662 4 2,666 A & C Equity and credit contracts — 16 9 25 — 18 8 26 B & D Netting — (2,047) — (2,047) — (2,173) — (2,173) — 881 10 891 — 996 12 1,008 Other financial liabilities at FVTPL Debt securities in issue — 369 — 369 — 372 3 375 A Structured deposits — 426 — 426 — 321 — 321 A Zero Amortising Guaranteed Notes — 104 — 104 — 107 — 107 D — 899 — 899 — 800 3 803 Total liabilities at fair value — 1,780 10 1,790 — 1,796 15 1,811 Transfers between levels of the fair value hierarchy In 2023 there were £22m ( 2022 : no significant) transfers of financial instruments between levels of the fair value hierarchy. f) Fair value adjustments The internal models incorporate assumptions that Santander UK believes would be made by a market participant to establish fair value. Fair value adjustments are adopted when Santander UK considers that there are additional factors that would be considered by a market participant that are not incorporated in the valuation model. Santander UK classifies fair value adjustments as either ‘risk-related’ or ‘model-related’. The fair value adjustments form part of the portfolio fair value and are included in the balance sheet values of the product types to which they have been applied. The fair value adjustments are set out in the following table: Group 2023 2022 £m £m Risk-related: - Bid-offer and trade specific adjustments (6) (12) - Uncertainty 29 27 - Credit risk adjustment (2) (1) - Funding fair value adjustment 1 1 22 15 Day One profit (1) (1) 21 14 Risk-related adjustments Risk-related adjustments are driven, in part, by the magnitude of Santander UK’s market or credit risk exposure, and by external market factors, such as the size of market spreads. (i) Bid-offer and trade specific adjustments Portfolios are marked at bid or offer, as appropriate. Valuation models will typically generate mid-market values. The bid-offer adjustment reflects the cost that would be incurred if substantially all residual net portfolio market risks were closed using available hedging instruments or by disposing of or unwinding the position. For debt securities, the bid-offer spread is based on a market price at an individual security level. For other products, the major risk types are identified. For each risk type, the net portfolio risks are first classified into buckets, and then a bid-offer spread is applied to each risk bucket based upon the market bid-offer spread for the relevant hedging instrument. (ii) Uncertainty Certain model inputs may be less readily determinable from market data, and/or the choice of model itself may be more subjective. In these circumstances, a range of possible values exists that the financial instrument or market parameter may assume, and an adjustment may be needed to reflect the likelihood that in estimating the fair value of the financial instrument, market participants would adopt more conservative values for uncertain parameters and/or model assumptions than those used in the valuation model. (iii) Credit risk adjustment Credit risk adjustments comprise credit and debit valuation adjustments. The credit valuation adjustment (CVA) is an adjustment to the valuation of OTC derivative contracts to reflect within fair value the possibility that the counterparty may default, and Santander UK may not receive the full market value of the transactions. The debit valuation adjustment (DVA) is an adjustment to the valuation of the OTC derivative contracts to reflect within the fair value the possibility that Santander UK may default, and that Santander UK may not pay full market value of the transactions. Santander UK calculates a separate CVA and DVA for each Santander UK legal entity, and within each entity for each counterparty to which the entity has exposure. Santander UK calculates the CVA by applying the probability of default of the counterparty to the expected positive exposure to the counterparty, and multiplying the result by the loss expected in the event of default i.e. LGD. Conversely, Santander UK calculates the DVA by applying the PD of the Santander UK group, to the expected positive exposure of the counterparty to Santander UK and multiplying the result by the LGD. Both calculations are performed over the life of the potential exposure. For most products Santander UK uses a simulation methodology to calculate the expected positive exposure to a counterparty. This incorporates a range of potential exposures across the portfolio of transactions with the counterparty over the life of the portfolio. The simulation methodology includes credit mitigants such as counterparty netting agreements and collateral agreements with the counterparty. (iv) Funding fair value adjustment (FFVA) The FFVA is an adjustment to the valuation of OTC derivative positions to include the net cost of funding uncollateralised derivative positions. This is calculated by applying a suitable funding cost to the expected future funding exposure of any uncollateralised component of the OTC derivative portfolio. Model-related adjustments Models used for portfolio valuation purposes may be based upon a simplifying set of assumptions that do not capture all material market characteristics. Additionally, markets evolve, and models that were adequate in the past may require development to capture all material market characteristics in current market conditions. In these circumstances, model limitation adjustments are adopted. As model development progresses, model limitations are addressed within the core revaluation models and a model limitation adjustment is no longer needed. Day One profit adjustments Day One profit adjustments are adopted where the fair value estimated by a valuation model is based on one or more significant unobservable inputs. Day One profit adjustments are calculated and reported on a portfolio basis. The timing of recognition of deferred Day One profit and loss is determined individually. It is deferred until either the instrument’s fair value can be determined using market observable inputs or is realised through settlement. The financial instrument is subsequently measured at fair value, adjusted for the deferred Day One profit and loss. Subsequent changes in fair value are recognised immediately in the Income Statement without immediate reversal of deferred Day One profits and losses. g) Internal models based on information other than market data (Level 3) The table below provides an analysis of financial instruments valued using internal models based on information other than market data together with further details on the valuation techniques used for each type of instrument. Each instrument is initially valued at transaction price: Group Balance sheet value Fair value movements recognised in profit/(loss) 2023 2022 2023 2022 2021 Balance sheet line item Category Financial instrument product type £m £m £m £m £m 1. Derivative assets Equity and credit contracts Reversionary property interests 35 30 12 (8) — 2. FVTPL assets Loans and advances to customers Roll-up mortgage portfolio 24 28 (2) (18) (5) 3. FVTPL assets Loans and advances to customers Other loans 22 17 4 (4) (2) 4. FVTPL assets Debt securities Reversionary property securities 49 70 (3) — 5 5. FVTPL assets Equity securities Unlisted equity shares 30 10 27 (10) 1 160 155 38 (40) (1) Other Level 3 assets 1 26 7 17 (6) Other Level 3 liabilities (10) (15) (1) 2 6 Total net assets 151 166 Total income/(expense) 44 (21) (1) Valuation techniques 1. Derivative assets – Equity and credit contracts These are valued using a probability weighted set of HPI forward prices, which are assumed to be a reasonable representation of the increase in value of the Santander UK group’s reversionary interest portfolio underlying the derivatives. The probability used reflects the likelihood of the homeowner vacating the property and is calculated from mortality rates and acceleration rates which are a function of age and gender, obtained from the relevant mortality tables. Indexing is felt to be appropriate due to the size and geographical dispersion of the reversionary interest portfolio. These are determined using HPI Spot Rates adjusted to reflect estimated forward growth. Non-seasonally adjusted (NSA) national and regional HPI are used in the valuation model to avoid any subjective judgement in the adjustment process, which is made by Markit, which publishes the Halifax House Price Index. The inputs used to determine the value of the reversionary property derivatives are HPI spot, HPI forward growth and mortality rates. The principal pricing parameter is HPI forward growth. 2. FVTPL assets – Loans and advances to customers – roll-up mortgage portfolio These represent roll-up mortgages (sometimes referred to as lifetime mortgages), which are an equity release scheme under which a property owner takes out a loan secured against their home. The owner does not have to make any interest payments during their lifetime in which case the fixed interest payments are rolled up into the mortgage. The loan or mortgage (capital and rolled-up interest) is repaid upon the owner’s vacation of the property and the value of the loan is only repaid from the value of the property. This is known as a ‘no negative equity guarantee’. Santander UK suffers a loss if the sale proceeds from the property are insufficient to repay the loan, as it is unable to pursue the homeowner’s estate or beneficiaries for the shortfall. The value of the mortgage ‘rolls up’ or accretes until the owner vacates the property. In order to value the roll-up mortgages, Santander UK uses a probability- weighted set of European option prices (puts) determined using the Black-Scholes model, in which the ‘no negative equity guarantee’ are valued as short put options. The probability weighting applied is calculated from mortality rates and acceleration rates as a function of age and gender, taken from mortality tables. The inputs used to determine the value of these instruments are HPI spot, HPI forward growth, HPI volatility, mortality rates and repayment rates. The principal pricing parameter is HPI forward growth. The HPI forward growth rate used is unobservable and is the same as used in the valuation of Instrument 1 above. The other parameters do not have a significant effect on the value of the instruments. 3. FVTPL assets – Loans and advances to customers – other loans These relate to loans to transport and education companies. The fair value of these loans is estimated using the ‘present value’ model based on a credit curve derived from current market spreads. Loan specific credit data is unobservable, so a proxy population is applied based on industry sector and credit rating. 4. FVTPL assets – Debt securities These consist of reversionary property securities and are an equity release scheme, where the property owner receives an upfront lump sum in return for paying a fixed percentage of the sales proceeds of the property when the owner vacates the property. These reversionary property securities are valued using a probability- weighted set of HPI forward prices which are assumed to be a reasonable representation of the increase in value of Santander UK’s reversionary interest portfolio underlying the derivatives. The probability weighting used reflects the probability of the homeowner vacating the property through death or moving into care and is calculated from mortality rates and acceleration factors which are a function of age and gender, obtained from the relevant mortality table. The inputs used to determine the value of these instruments are HPI spot, HPI forward growth and mortality rates. The principal pricing parameter is HPI forward growth. Discussion of the HPI spot rate, HPI forward growth rate and mortality rates for this financial instrument is the same as Instrument 1 above. An adjustment is also made to reflect the specific property risk. Specific property risk is from the difference between the specific properties in the portfolio, and the average price as expressed in the regionally weighted house price index. 5. FVTPL assets - Equity securities These consist of unquoted equity investments in companies providing infrastructure services to the financial services industry. Observable market inputs to valuation models used include equity prices and foreign currency exchange rates. The significant unobservable input is contingent litigation costs and related expenses in respect of convertible preferred stock in Visa Inc, as described in Note 31 . This is estimated by reference to best estimates received from third party legal counsel. Reconciliation of fair value measurement in Level 3 of the fair value hierarchy The following table sets out the movements in Level 3 financial instruments in 2023 : Group Assets Liabilities Derivatives Other financial assets at FVTPL Financial assets at FVOCI Total Derivatives Other financial liabilities at FVTPL Total £m £m £m £m

Offsetting Financial Assets and

Offsetting Financial Assets and Liabilities	12 Months Ended
	Dec. 31, 2023
Disclosure of offsetting of financial liabilities [abstract]
Offsetting Financial Assets and Liabilities	40. OFFSETTING FINANCIAL ASSETS AND LIABILITIES The following table shows the impact of netting arrangements on: – All financial assets and liabilities that are reported net on the balance sheet – All derivative financial instruments and repurchase agreements and other similar secured lending and borrowing agreements that are subject to enforceable master netting arrangements or similar agreements, but do not qualify for balance sheet netting. The table identifies the amounts that have been offset in the balance sheet and also those amounts that are covered by enforceable netting arrangements (offsetting arrangements and financial collateral) but do not qualify for netting under the requirements described above. For derivative contracts, the ‘Financial instruments’ column identifies financial assets and liabilities that are subject to set off under netting agreements, such as the ISDA Master Agreement or derivative exchange or clearing counterparty agreements, whereby all outstanding transactions with the same counterparty can be offset and close-out netting applied across all outstanding transactions covered by the agreements if an event of default or other predetermined events occur. Financial collateral refers to cash and non-cash collateral obtained, typically daily or weekly, to cover the net exposure between counterparties by enabling the collateral to be realised in an event of default or if other predetermined events occur. For repurchase and reverse repurchase agreements and other similar secured lending and borrowing, the ‘Financial instruments’ column identifies financial assets and liabilities that are subject to set off under netting agreements, such as global master repurchase agreements and global master securities lending agreements, whereby all outstanding transactions with the same counterparty can be offset and close-out netting applied across all outstanding transactions covered by the agreements if an event of default or other predetermined events occur. Financial collateral typically comprises highly liquid securities which are legally transferred and can be liquidated if a counterparty defaults. Santander UK engages in a variety of counterparty credit mitigation strategies in addition to netting and collateral arrangements. Therefore, the net amounts presented in the tables below do not purport to represent Santander UK’s actual credit exposure. Group Amounts subject to enforceable netting arrangements Effects of offsetting on balance sheet Related amounts not offset Assets not subject to enforceable netting arrangements (2) Gross amounts Amounts offset Net amounts on balance sheet Financial instruments Financial collateral (1) Net amount Balance sheet total (3) 2023 £m £m £m £m £m £m £m £m Assets Derivative financial assets 3,469 (2,047) 1,422 (479) (823) 120 50 1,472 Reverse repurchase, securities borrowing & similar agreements: - Amortised cost 15,625 (3,157) 12,468 (118) (12,350) — — 12,468 Loans and advances to customers and banks (4) 5,565 (805) 4,760 — (180) 4,580 207,678 212,438 24,659 (6,009) 18,650 (597) (13,353) 4,700 207,728 226,378 Liabilities Derivative financial liabilities 2,911 (2,047) 864 (479) (226) 159 27 891 Repurchase, securities lending & similar agreements: - Amortised cost 11,568 (3,157) 8,411 (118) (8,293) — — 8,411 Deposits by customers and banks (4) 2,370 (805) 1,565 — — 1,565 213,941 215,506 16,849 (6,009) 10,840 (597) (8,519) 1,724 213,968 224,808 2022 Assets Derivative financial assets 4,557 (2,173) 2,384 (526) (1,720) 138 55 2,439 Reverse repurchase, securities borrowing & similar agreements: - Amortised cost 8,826 (1,478) 7,348 (9) (7,339) — — 7,348 Loans and advances to customers and banks (4) 5,144 (908) 4,236 — — 4,236 220,709 224,945 18,527 (4,559) 13,968 (535) (9,059) 4,374 220,764 234,732 Liabilities Derivative financial liabilities 3,142 (2,173) 969 (526) (158) 285 39 1,008 Repurchase, securities lending & similar agreements: - Amortised cost 9,460 (1,478) 7,982 (9) (7,973) — — 7,982 Deposits by customers and banks (4) 3,265 (908) 2,357 — — 2,357 223,499 225,856 15,867 (4,559) 11,308 (535) (8,131) 2,642 223,538 234,846 (1) Financial collateral is reflected at its fair value but has been limited to the net balance sheet exposure so as not to include any over-collateralisation. (2) This column includes contractual rights of set-off that are subject to uncertainty under the laws of the relevant jurisdiction. (3) The balance sheet total is the sum of ‘Net amounts reported on the balance sheet’ that are subject to enforceable netting arrangements and ‘Amounts not subject to enforceable netting arrangements’. (4) The amounts offset within loans and advances to customers/banks or deposits by customers/banks relate to offset mortgages which are classified as either and that are subject to netting.

Interest Rate Benchmark Reform

Interest Rate Benchmark Reform	12 Months Ended
	Dec. 31, 2023
Interest Rate Benchmark Reform [Abstract]
Interest Rate Benchmark Reform	41. INTEREST RATE BENCHMARK REFORM Santander UK continues to work with customers and counterparties to transition any remaining agreements referencing 3-month synthetic LIBOR before that setting ends on 31 March 2024. At 31 December 2023 , these represent an insignificant element of Santander UK’s exposures and there are no remaining exposures which reference other LIBOR settings. The following tables show the notional amounts of assets, liabilities and off-balance sheet commitments at 31 December 2023 and 31 December 2022 affected by IBOR reform that have yet to transition to an alternative benchmark interest rate. Group GBP LIBOR USD LIBOR Total 2023 £m £m £m Assets Financial assets at amortised cost 6 — 6 6 — 6 2022 Assets Derivatives — 1,665 1,665 Financial assets at amortised cost 76 245 321 76 1,910 1,986 Liabilities Derivatives 66 1,846 1,912 Financial liabilities at amortised cost — 2,491 2,491 66 4,337 4,403 Off-balance sheet commitments given 2 — 2

Discontinued Operations and Ass

Discontinued Operations and Assets Held for Sale	12 Months Ended
	Dec. 31, 2023
Discontinued Operations and Assets and Liabilities Held for Sale [Abstract]
Discontinued Operations and Assets Held for Sale	42. DISCONTINUED OPERATIONS AND ASSETS HELD FOR SALE Discontinued operations Transfer of the CIB Business Santander UK plc transferred a significant part of its CIB business to the London branch of Banco Santander SA under a Part VII banking business transfer scheme, which completed on 11 October 2021. The residual parts of the CIB business were wound down or transferred to other segments. For the periods prior to its sale, the CIB business met the requirements for presentation as discontinued operations. The financial performance and cash flow information relating to the discontinued operations were as follows: For the year ended 31 December 2023 2022 2021 £m £m £m Net interest income — — 33 Net fee and commission income — — 34 Other operating income — — 2 Total operating income — — 69 Operating expenses before credit impairment (charges)/write-backs, provisions and charges — — (32) Credit impairment (charges)/write-backs — — 11 Provisions for other liabilities and charges — — (4) Total operating credit impairment (charges)/write-backs, provisions and charges — — 7 Profit from discontinued operations before tax — — 44 Tax on profit from discontinued operations — — (12) Profit from discontinued operations after tax — — 32 There were no gains or losses recognised on the measurement to fair value less costs to sell or on the disposal of the asset groups constituting the discontinued operations. In 2023 , the net cash flows attributable to the operating activities in respect of discontinued operations were £nil outflow ( 2022 : £nil ou tflow, 2021 : £3,612m outflow). There were no investing or financing activities in respect of discontinued operations. Assets held for sale Sale of property Management considered the sale of part of Santander House (Milton Keynes) under a proposed transaction with the developer for the construction of Unity Place and Buckingham House (Bletchley), to be highly probable at the balance sheet date. As such, the Santander UK group classified these properties, which are included in the Corporate Centre segment and carried at their sales prices, as held for sale. The sale is expected to complete in 2024 with no gain or loss. At 31 December 2023 , assets held for sale comprised: 2023 2022 £m £m Assets Property, plant and equipment 13 49 Total assets held for sale 13 49

Events After the Balance Sheet

Events After the Balance Sheet Date	12 Months Ended
	Dec. 31, 2023
Disclosure of non-adjusting events after reporting period [abstract]
Events After the Balance Sheet Date	43. EVENTS AFTER THE BALANCE SHEET DATE There have been no significant events between 31 December 2023 and the date of approval of these financial statements which would require a change to or additional disclosure in the financial statements.

Accounting Policies - Parent

Accounting Policies - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure Of Significant Accounting Policies [Line Items]
Accounting Policies	1. ACCOUNTING POLICIES These financial statements are prepared for Santander UK Group Holdings plc (the Company) and the Santander UK Group Holdings plc group (the Santander UK group) under the UK Companies Act 2006. The principal activity of the Santander UK group is the provision of a wide range of banking and financial services to personal, business and corporate customers. Santander UK Group Holdings plc is a public company, limited by shares and incorporated in England and Wales having a registered office at 2 Triton Square, Regent’s Place, London, NW1 3AN . It is a financial services holding company. Basis of preparation These financial statements incorporate the financial statements of the Company and entities it controls (its subsidiaries) made up to 31 December each year. The consolidated financial statements have been prepared on the going concern basis using the historical cost convention, except for financial assets and liabilities that have been measured at fair value. An assessment of the appropriateness of the adoption of the going concern basis of accounting is disclosed in the statement of going concern in the Directors’ report. Compliance with International Financial Reporting Standards (IFRS) The consolidated financial statements of the Santander UK group and the separate financial statements of the Company comply with UK-adopted International Accounting Standards (IAS). The financial statements are also prepared in accordance with IFRS as issued by the International Accounting Standards Board (IASB), including interpretations issued by the IFRS Interpretations Committee, as there are no applicable differences from IFRS as issued by the IASB for the periods presented. Disclosures required by IFRS 7 ‘Financial Instruments: Disclosure’ relating to the nature and extent of risks arising from financial instruments, and IAS 1 ‘Presentation of Financial Statements’ relating to objectives, policies and processes for managing capital, have been included in the Risk review section of this Annual Report. This information forms an integral part of these financial statements by this cross reference, is marked as audited, and is covered by the Independent auditors' report. Climate change Santander UK continues to develop its assessment of the potential impacts that climate change and the transition to a low carbon economy may have on the assets and liabilities recognised and presented in its financial statements. Santander UK is mindful of its responsibilities as a responsible lender and is focused on ways to meet the objectives of the Paris Agreement on climate change and to support the UK’s transition to a climate-resilient, net zero economy. Santander UK's current climate change strategy focuses on three main areas to achieve Banco Santander's ambition to reach net zero emissions by 2050: 1. Managing climate risks by integrating climate considerations into risk management frameworks, screening and stress testing our portfolio for climate related financial risks, and setting risk appetites to help steer our portfolio in line with the Paris Agreement, 2. Supporting our customers’ transition by developing products and services that promote a reduction in CO 2 emissions, and 3. Reducing emissions in our operations and supply chain by focusing on continuous improvement in our operations, and environmental and energy management systems in accordance with ISO14001 and 15001, promoting responsible procurement practices and employee engagement. Santander UK's current climate change strategy and its view of the risks associated with climate change and the transition to a low carbon economy are reflected in its critical judgements and accounting estimates, although climate change risk did not have a material impact at 31 December 2023 and 2022, consistent with management's assessment that climate change and the transition to a low carbon economy are not currently expected to have a meaningful impact on the viability of the Santander UK group in the medium term. At 31 December 2023 and 2022, management specifically considered the potential impact of climate change and the transition to a low carbon economy on: – Loans and advances to customers ( see Note 13 and the credit risk section of the Risk review). Some climate change risks arise due to the requirements of IFRS 9 and others relate to specific portfolios and sectors: – ECL calculations are based on multiple forward-looking economic scenarios developed by management covering a period of 5 years , during which timeframe climate change risks may crystallise; – For mortgages in Retail & Business Banking and commercial real estate lending in Corporate & Commercial Banking, the value of property collateral might be affected by physical impacts related to the frequency and scale of extreme weather events, such as flood and subsidence risk, or changing environmental performance standards for property. – For automotive loans in Consumer Finance, the residual value of automotive vehicles might be impacted by diesel obsolescence and the transition to electric vehicles. – For corporate lending in Corporate & Commercial Banking, certain sectors give rise to fossil fuel exposures, such as Oil & Gas, Mining & Extraction and Power Generation. – Goodwill impairment assessment (see Note 20). Estimates underpinning the determination of whether or not goodwill balances are impaired are partly based on forecast business performance beyond the time horizon for management's detailed plans. Future changes to Santander UK's climate change strategy may impact Santander UK's critical judgements and accounting estimates and result in material changes to financial results and the carrying values of certain assets and liabilities in future reporting periods. Future accounting developments At 31 December 2023 , for the Santander UK group, there were no significant new or revised standards and interpretations, and amendments thereto, which have been issued but which are not yet effective, or which have otherwise not been early adopted where permitted. Comparative information As required by US public company reporting requirements, these financial statements include two years of comparative information for the consolidated income statement, consolidated statement of comprehensive income, consolidated statement of changes in equity, consolidated statement of cash flows and related notes. Material accounting policy information The following material accounting policies have been applied in preparing these financial statements. For material accounting policies which involve the application of judgements or accounting estimates that are determined to be critical to the preparation of these financial statements see 'Critical judgements and accounting estimates'. Consolidation The consolidated financial statements incorporate the financial statements of the Company and entities (including structured entities) controlled by it and its subsidiaries. The acquisition method of accounting is used to account for the acquisition of subsidiaries which meet the definition of a business. Business combinations between entities under common control (i.e. fellow subsidiaries of Banco Santander SA, the ultimate parent) are outside the scope of IFRS 3 – ‘Business Combinations’, and there is no other guidance for such transactions under IFRS. The Santander UK group elects to account for business combinations between entities under common control at their book values in the acquired entity by including the acquired entity’s results from the date of the business combination and not restating comparatives. Reorganisations of entities within the Santander UK group are also accounted for at their book values. Credit protection entities established as part of significant risk transfer (SRT) transactions are not consolidated by the Santander UK group in cases where third party investors have the exposure, or rights, to all of the variability of returns from the performance of the entities. Revenue recognition a) Interest income and expense Interest and similar income and expense are recognised in the income statement using the effective interest rate method for: all financial instruments measured at amortised cost; debt instruments measured at FVOCI; and the effective part of any related accounting hedging instruments. Interest income is calculated by applying the effective interest rate to the gross carrying amount of financial assets, except for financial assets that have subsequently become credit-impaired (i.e. Stage 3), for which interest revenue is calculated by applying the effective interest rate to their amortised cost (i.e. net of the ECL provision). For more information on stage allocations of credit risk exposures, see ‘Significant increase in credit risk’ in the ‘Santander UK group level – credit risk management’ section of the Risk review. b) Fee and commission income and expense Fees and commissions that are not an integral part of the effective interest rate are recognised when the service is performed. Most fee and commission income is recognised at a point in time. Certain commitment, upfront and management fees are recognised over time but are not material. For retail and corporate products, fee and commission income consists principally of collection services fees, commission on foreign currencies, commission and other fees received from retailers for processing credit card transactions, fees received from other credit card issuers for providing cash advances for their customers through the Santander UK group’s branch and ATM networks, annual fees payable by credit card holders and fees for non-banking financial products. For insurance products, fee and commission income consists principally of commissions and profit share arising from the sale of building and contents insurance and life protection insurance. Commissions arising from the sale of buildings and contents insurance are recognised over the period of insurance cover, adjusted to take account of cancelled policies. Profit share income from the sale of buildings and contents insurance which is not subject to any adjustment is recognised when the profit share income is earned. Commissions and profit share arising from the sale of life protection insurance is subject to adjustment for cancellations of policies within 3 years from inception. Fee and commission income which forms an integral part of the effective interest rate of a financial instrument (for example certain loan commitment fees) is recognised as an adjustment to the effective interest rate and recorded in ‘Interest income’. c) Other operating income Other operating income includes all gains and losses from changes in the fair value of financial assets and liabilities held at fair value through profit or loss (comprising financial assets and liabilities held for trading, trading derivatives and other financial assets and liabilities at fair value through profit or loss), together with related interest income, expense, dividends, and changes in fair value of any derivatives managed in conjunction with these assets and liabilities. Other operating income also includes hedge ineffectiveness arising from fair value and cash flow hedging, income from operating lease assets, and profits and losses arising on the sales of property, plant and equipment and subsidiary undertakings. Defined benefit pension schemes (see 'Critical judgements and accounting estimates') A defined benefit scheme is a pension scheme that guarantees an amount of pension benefit to be provided, usually as a function of one or more factors such as age, years of service or compensation. Pension costs are charged to ‘Administration expenses’, within the line item ‘Operating expenses before impairment losses, provisions and charges’ with the net interest on the defined benefit asset or liability included within ‘Net interest income’ in the income statement. The asset or liability recognised in respect of defined benefit pension schemes is the present value of the defined benefit obligation at the balance sheet date, less the fair value of scheme assets. The defined benefit obligation is calculated annually by independent actuaries using the projected unit credit method. The assets of the schemes are measured at their fair values at the balance sheet date. The present value of the defined benefit obligation is estimated by projecting forward the growth in current accrued pension benefits to reflect inflation and salary growth to the date of pension payment, then discounted to present value using the yield applicable to high-quality AA rated corporate bonds of the same currency and which have terms to maturity closest to the terms of the scheme liabilities, adjusted where necessary to match those terms. In determining the value of scheme liabilities, demographic and financial assumptions are made by management about life expectancy, inflation, discount rates, pension increases and earnings growth, based on past experience and future expectations. Financial assumptions are based on market conditions at the balance sheet date and can generally be derived objectively. Demographic assumptions require a greater degree of estimation and judgement to be applied to externally derived data. Any surplus or deficit of scheme assets over liabilities is recognised in the balance sheet as an asset (surplus) or liability (deficit). An asset is only recognised to the extent that the surplus can be recovered through reduced contributions in the future or through refunds from the scheme. Share-based payments The Santander UK group engages in cash-settled and equity-settled share-based payment transactions in respect of services received from certain of its employees. Shares of the Santander UK group’s parent, Banco Santander SA are purchased in the open market by the Santander UK group (for the Employee Sharesave scheme) or are purchased by Banco Santander SA or another Banco Santander subsidiary (including awards granted under the Long-Term Incentive Plan and the Deferred Shares Bonus Plan) to satisfy share options or awards as they vest. Options granted under the Employee Sharesave scheme and awards granted under the Transformation Incentive Plan are accounted for as cash-settled share- based payment transactions. Awards granted under the Long-Term Incentive Plan and Deferred Shares Bonus Plan are accounted for as equity-settled share- based payment transactions. The fair value of the options granted under the Employee Sharesave scheme is determined using an option pricing model, which takes into account the exercise price of the option, the current share price, the risk-free interest rate, the expected volatility of the Banco Santander SA share price over the life of the option and the dividend growth rate. The fair value of the awards granted for the Long-Term Incentive Plan was determined at the grant date using an option pricing model, which takes into account the share price at grant date, the risk-free interest rate, the expected volatility of the Banco Santander SA share price over the life of the award and the dividend growth rate. Goodwill and other intangible assets (for goodwill see 'Critical judgements and accounting estimates') Goodwill represents the excess of the cost of an acquisition, as well as the fair value of any interest previously held, over the fair value of the share of the identifiable net assets of the acquired subsidiary, or business at the date of acquisition. Goodwill on the acquisition of subsidiaries and businesses is included in intangible assets. Goodwill is tested for impairment annually, or more frequently when events or changes in circumstances dictate and carried at cost less accumulated impairment losses. Gains and losses on the disposal of an entity or business include the carrying amount of goodwill relating to the entity or business sold. Other intangible assets are recognised if they arise from contractual or other legal rights or if they are capable of being separated or divided from Santander UK and sold, transferred, licensed, rented or exchanged. The value of such intangible assets, where they are available for use, is amortised on a straight-line basis over their useful economic life of three to seven years and the assets are reviewed annually for impairment indicators and tested for impairment where indicators are present. Other intangible assets that are not yet available for use are tested for impairment annually or more frequently when events or changes in circumstances dictate. Software development costs are capitalised when they are direct costs associated with identifiable and unique software products that are expected to provide future economic benefits and the cost of those products can be measured reliably. These costs include payroll, materials, services and directly attributable overheads. Internally developed software meeting these criteria and externally purchased software are classified in intangible assets on the balance sheet and amortised on a straight-line basis over their useful life of three to seven years, unless the software is an integral part of the related computer hardware, in which case it is treated as property, plant and equipment as described below. Capitalisation of costs ceases when the software is capable of operating as intended. Costs of maintaining software are expensed as incurred. Property, plant and equipment Property, plant and equipment include owner-occupied properties (including leasehold properties), office fixtures and equipment and computer software. Property, plant and equipment also includes operating leases where the Santander UK group is the lessor and right-of-use assets where the Santander UK group is the lessee. Internally developed software meeting the criteria set out in ‘Goodwill and other intangible assets’ above and externally purchased software are classified in property, plant and equipment where the software is an integral part of the related computer hardware (for example, the operating system of a computer). Classes of property, plant and equipment are depreciated on a straight-line basis over their useful life, as follows: Owner-occupied properties Not exceeding 50 years Office fixtures and equipment 3 to 15 years Computer software 3 to 7 years Right-of-use assets Shorter of the lease term or the useful life of the underlying asset Operating lease assets - vehicles 1 to 4 years Depreciation is not charged on freehold land. Depreciation of operating lease assets where the Santander UK group is the lessor is described in 'Leases' below. Financial instruments (for impairment of debt instrument financial assets see 'Critical judgements and accounting estimates: Credit impairment losses') a) Initial recognition and measurement Financial assets and liabilities are initially recognised when the Santander UK group becomes a party to the contractual terms of the instrument. The Santander UK group determines the classification of its financial assets and liabilities at initial recognition and measures a financial asset or financial liability at its fair value plus or minus, in the case of a financial asset or financial liability not at FVTPL, transaction costs that are incremental and directly attributable to the acquisition or issue of the financial asset or financial liability. Transaction costs of financial assets and financial liabilities carried at FVTPL are expensed in profit or loss. Immediately after initial recognition, an expected credit loss (ECL) allowance is recognised for financial assets measured at amortised cost and investments in debt instruments measured at FVOCI. A regular way purchase or sale is a purchase or sale of a financial asset under a contract whose terms require delivery of the asset within the timeframe established generally by regulation or convention in the marketplace concerned. Regular way purchases and sales of financial assets measured at amortised cost are recognised on settlement date; all other regular way purchases and sales of financial assets are recognised on trade date. b) Financial assets and liabilities i) Classification and subsequent measurement The Santander UK group classifies its financial assets in the measurement categories of amortised cost, FVOCI and FVTPL. Financial assets and financial liabilities are classified as FVTPL where there is a requirement to do so or where they are otherwise designated at FVTPL on initial recognition. Financial assets and financial liabilities which are required to be held at FVTPL include: – Financial assets and financial liabilities held for trading. – Debt instruments that do not have solely payments of principal and interest (SPPI) characteristics. Otherwise, such instruments are measured at amortised cost or FVOCI, and – Equity instruments that have not been designated as held at FVOCI. Financial assets and financial liabilities are classified as held for trading if they are derivatives or if they are acquired or incurred principally for the purpose of selling or repurchasing in the near-term, or form part of a portfolio of financial instruments that are managed together and for which there is evidence of short-term profit taking. In certain circumstances, other financial assets and financial liabilities are designated at FVTPL where this results in more relevant information. This may arise because it significantly reduces a measurement inconsistency that would otherwise arise from measuring assets or liabilities or recognising the gains or losses on them on a different basis, where the assets and liabilities are managed and their performance evaluated on a fair value basis or, in the case of financial liabilities, where it contains one or more embedded derivatives which are not closely related to the host contract. The classification and measurement requirements for financial asset debt and equity instruments and financial liabilities are set out below. Financial assets: debt instruments Debt instruments are those instruments that meet the definition of a financial liability from the issuer’s perspective, such as loans and government and corporate bonds. Classification and subsequent measurement of debt instruments depend on the Santander UK group’s business model for managing the asset, and the cash flow characteristics of the asset. Business model The business model reflects how the Santander UK group manages the assets in order to generate cash flows and, specifically, whether the Santander UK group’s objective is solely to collect the contractual cash flows from the assets or is to collect both the contractual cash flows and cash flows arising from the sale of the assets. If neither of these is applicable, such as where the financial assets are held for trading purposes, then the financial assets are classified as part of an ‘other’ business model and measured at FVTPL. Factors considered in determining the business model for a group of assets include past experience on how the cash flows for these assets were collected, how the assets’ performance is evaluated and reported to key management personnel, and how risks are assessed and managed. SPPI Where the business model is to hold assets to collect contractual cash flows or to collect contractual cash flows and sell, the Santander UK group assesses whether the assets’ cash flows represent SPPI. In making this assessment, the Santander UK group considers whether the contractual cash flows are consistent with a basic lending arrangement (i.e. interest includes only consideration for the time value of money, credit risk, other basic lending risks and a profit margin that is consistent with a basic lending arrangement). Where the contractual terms introduce exposure to risk or volatility that is inconsistent with a basic lending arrangement, the related asset is classified and measured at FVTPL. Financial assets with embedded derivatives are considered in their entirety when determining whether their cash flows are SPPI. Based on these factors, the Santander UK group classifies its debt instruments into one of the following measurement categories: – Amortised cost – Financial assets that are held for collection of contractual cash flows where those cash flows represent SPPI, and that are not designated at FVTPL, are measured at amortised cost. The carrying amount of these assets is adjusted by any ECL recognised and measured as presented in Note 13 . Interest income from these financial assets is included in ‘Interest and similar income’ using the effective interest rate method. When estimates of future cash flows are revised, the carrying amount of the respective financial assets is adjusted to reflect the new estimate discounted using the original effective interest rate. Any changes are recognised in the income statement. – FVOCI – Financial assets that are held for collection of contractual cash flows and for selling the assets, where the assets’ cash flows represent SPPI, and that are not designated at FVTPL, are measured at FVOCI. Movements in the carrying amount are recognised in OCI, except for the recognition of impairment gains or losses, interest revenue and foreign exchange gains and losses which are recognised in profit or loss. When the financial asset is derecognised, the cumulative gain or loss previously recognised in OCI is reclassified from equity to profit or loss and recognised in ‘Other operating income’. Interest income from these financial assets is included in ‘Interest and similar income’ using the effective interest rate method. – FVTPL – Financial assets that do not meet the criteria for amortised cost or FVOCI are measured at FVTPL. A gain or loss on a debt instrument that is subsequently measured at FVTPL, including any debt instruments designated at fair value, is recognised in profit or loss and presented in the income statement in ‘Other operating income’ in the period in which it arises. The Santander UK group reclassifies financial assets when and only when its business model for managing those assets changes. The reclassification takes place from the start of the first reporting period following the change. Such changes are expected to be very infrequent. Financial assets: equity instruments Equity instruments are instruments that meet the definition of equity from the issuer’s perspective, being instruments that do not contain a contractual obligation to pay cash and that evidence a residual interest in the issuer’s net assets. All equity investments are subsequently measured at FVTPL; management may elect, at initial recognition, to irrevocably designate an equity investment at FVOCI but has not currently done so. When this election is used, fair value gains and losses are recognised in OCI and are not subsequently reclassified to profit or loss, including on disposal. ECLs (and reversal of ECLs) are not reported separately from other changes in fair value. Dividends, when representing a return on such investments, continue to be recognised in profit or loss as other income when the right to receive payments is established. Gains and losses on equity investments at FVTPL are included in ‘Other operating income’ in the income statement. Financial liabilities Financial liabilities, which include deposits by banks, deposits by customers, debt securities in issue and subordinated liabilities, are classified as subsequently measured at amortised cost, except for: – Financial liabilities at FVTPL (see Note 22 ): this classification is applied to derivatives and other financial liabilities designated as such at initial recognition. Gains or losses on financial liabilities designated at FVTPL are presented partially in other comprehensive income (the amount of change in the fair value of the financial liability that is attributable to changes in the credit risk of that liability) and partially in profit or loss (the remaining amount of change in the fair value of the liability) – Financial liabilities arising from the transfer of financial assets which did not qualify for derecognition, whereby a financial liability is recognised for the consideration received for the transfer. In subsequent periods, the Santander UK group recognises any expense incurred on the financial liability, and – Financial guarantee contracts and loan commitments. Preference shares which carry a contractual obligation to transfer economic benefits are classified as financial liabilities and are presented in subordinated liabilities. The coupon on these preference shares is recognised in the income statement as interest expense on an amortised cost basis using the effective interest method. Contracts involving the receipt of cash on which customers receive an index-linked return are accounted for as equity index-linked deposits. The principal products are Capital Guaranteed/Protected Products which give the customers a limited participation in the upside growth of an equity index. In the event the index falls in price, a cash principal element is guaranteed/protected. The equity index-linked deposits contain embedded derivatives. These embedded derivatives, in combination with the principal cash deposit element, are designed to replicate the investment performance profile tailored to the return agreed in the contracts with customers. The cash principal element is accounted for as deposits by customers at amortised cost. The embedded derivatives are separated from the host instrument and are separately accounted for as derivatives. Sale and repurchase agreements (including stock borrowing and lending) Securities sold subject to a commitment to repurchase them at a predetermined price (repos) under which substantially all the risks and rewards of ownership are retained by the Santander UK group remain on the balance sheet and a liability is recorded in respect of the consideration received. Securities purchased under commitments to resell (reverse repos) are not recognised on the balance sheet and the consideration paid is recorded as an asset. The difference between the sale and repurchase price is treated as trading income in the income statement, except where the repo is not treated as part of the trading book, in which case the difference is recorded in interest income or expense. Securities lending and borrowing transactions are generally secured, with collateral in the form of securities or cash advanced or received. Securities borrowed are not reflected on the balance sheet. Collateral in the form of cash received or advanced is recorded as a deposit or a loan. Collateral in the form of securities is not recognised. Day One profit adjustments The fair value of a financial instrument on initial recognition is generally its transaction price (that is, the fair value of the consideration given or received). However, sometimes the fair value will be based on other observable current market transactions in the same instrument, without modification or repackaging, or on a valuation technique whose variables include only data from observable markets, such as interest rate yield curves, option volatilities and currency rates. When such evidence exists, the Santander UK group recognises a trading gain or loss at inception (Day One gain or loss), being the difference between the transaction price and the fair value. When significant unobservable parameters are used, the entire Day One gain or loss is deferred and is recognised in the income statement over the life of the transaction until the transaction matures, is closed out, the valuation inputs become observable, or an offsetting transaction is entered into. ii) Impairment of debt instrument financial assets The Santander UK group assesses on a forward-looking basis the ECL associated with its debt instrument assets carried at amortised cost and FVOCI and with the exposure arising from financial guarantee contracts and loan commitments. The Santander UK group recognises a loss allowance for such losses at each reporting date. The measurement of ECL reflects: – An unbiased and probability-weighted amount that is determined by evaluating a range of possible outcomes. – The time value of money, and – Reasonable and supportable information that is available without undue cost or effort at the reporting date about past events, current conditions and forecasts of future economic conditions. Grouping of instruments for losses measured on a collective basis We typically group instruments and assess them for impairment collectively where they share risk characteristics (as described in the Credit risk section of the Risk review) using one or more statistical models. Wh

Operating Expenses Before Cre_2

Operating Expenses Before Credit Impairment Charges, Provisions and Charges - Parent	12 Months Ended
	Dec. 31, 2023
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Operating Expenses Before Credit Impairment Charges, Provisions and Charges	6. OPERATING EXPENSES BEFORE CREDIT IMPAIRMENT CHARGES, PROVISIONS AND CHARGES For the year ended 31 December Group 2023 2022 2021 £m £m £m Staff costs: Wages and salaries 854 761 759 Performance-related payments 164 173 184 Social security costs 116 112 113 Pensions costs: – defined contribution plans 71 60 65 – defined benefit plans 13 28 38 Other share-based payments 4 1 1 Other personnel costs 42 44 42 1,264 1,179 1,202 Other administration expenses 931 894 831 Depreciation, amortisation and impairment 290 297 507 2,485 2,370 2,540 Staff costs Performance-related payments’ include bonuses paid in cash and share awards granted under the arrangements described in Note 36 . Included in this are equity- settled share-based payments, none of which related to option-based schemes. These are disclosed in the table below as ‘Shares awards’. Performance-related payments above include amounts related to deferred performance awards as follows: Costs recognised in 2023 Costs expected to be recognised in 2024 or later Arising from awards in current year Arising from awards in prior year Total Arising from awards in current year Arising from awards in prior year Total £m £m £m £m £m £m Cash 3 4 7 5 7 12 Shares 2 5 7 4 7 11 5 9 14 9 14 23 The following table shows the amount of bonus awarded to employees for the performance year 2023 . In the case of deferred cash and shares awards, the final amount paid to an employee is influenced by forfeiture provisions and any performance conditions to which the awards are subject. The deferred shares award amount is based on the fair value of the awards at the date of grant. Expenses charged in the year Expenses deferred to future periods Total 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m Cash award – not deferred 142 148 — — 142 148 – deferred 7 8 12 14 19 22 Shares award – not deferred 8 9 — — 8 9 – deferred 7 8 11 14 18 22 Total discretionary bonus 164 173 23 28 187 201 Other share-based payments’ consist of options granted under the Employee Sharesave scheme which comprise the Santander UK group’s cash-settled share- based payments. For more, see Note 36 . The average number of full-time equivalent staff was 19,706 ( 2022 : 18,273 , 2021 : 19,844 ) . Depreciation, amortisation and impairment In 2023 , depreciation, amortisation and impairment included depreciation of £64m ( 2022 : £73m , 2021 : £81m ) on operating lease assets (where the Santander UK group is the lessor) with a carrying amount of £488m at 31 December 2023 ( 2022 : £577m , 2021 : £595m ). It also included depreciation of £30m ( 2022 : £19m , 2021 : £20m ) on right-of-use assets with a carrying amount of £93m at 31 December 2023 ( 2022 : £115m , 2021 : £119m ) . Other administration expenses includes £19m ( 2022 : £21m , 2021 : £23m ) related to short-term leases. In 2023 , depreciation, amortisation and impairment included an impairment charge of £25m ( 2022 : £10m , 2021 : £88m ) associated with branch and head office site closures as part of the transformation programme. For more, see Note 21 .
Santander UK Group Holdings plc
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Operating Expenses Before Credit Impairment Charges, Provisions and Charges	44.2. OPERATING EXPENSES BEFORE CREDIT IMPAIRMENT CHARGES, PROVISIONS AND CHARGES These comprise wages and salaries of £7m ( 2022 : £6m ) recharged by the operating company, Santander UK plc. In 2023 and 2022 , the Company had no full- time staff as they are all employed by Santander UK plc.

Dividends on Ordinary Shares -

Dividends on Ordinary Shares - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure Of Dividends On Ordinary Shares [Line Items]
Dividends on Ordinary Shares	10. DIVIDENDS ON ORDINARY SHARES Dividends on ordinary shares declared and paid in the year were as follows: Group Group 2023 2022 2021 2023 2022 2021 Pence per share Pence per share Pence per share £m £m £m In respect of current year – first interim 5.86 5.62 4.05 414 397 286 – second interim 15.92 8.73 15.01 1,124 616 1,060 21.78 14.35 19.06 1,538 1,013 1,346 In 2023 an interim dividend of £1,538m ( 2022 : £1,013m , 2021 : £1,346m ) was paid on the Company's ordinary shares in issue. In 2023, £750m ( 2022 : £300m ) of the dividend was a special dividend. These were paid following review and approval by the Board in line with our dividend policy.
Santander UK Group Holdings plc
Disclosure Of Dividends On Ordinary Shares [Line Items]
Dividends on Ordinary Shares	44.3. DIVIDENDS ON ORDINARY SHARES Dividends on ordinary shares declared and paid during the year are set out in Note 10 to the Consolidated Financial Statements.

Other Financial Assets at Fai_2

Other Financial Assets at Fair Value Through Profit or Loss - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Other Financial Assets at Fair Value Through Profit or Loss	12. OTHER FINANCIAL ASSETS AT FAIR VALUE THROUGH PROFIT OR LOSS Group 2023 2022 £m £m Loans and advances to customers: Loans to housing associations 8 4 Other loans 347 335 355 339 Debt securities 168 16 Other debt instruments 49 69 Equity securities 30 10 602 434 In 2023 , Santander UK revalued a portfolio of unlisted equity securities held at fair value through profit or loss in Santander Equity Investments Limited (SEIL) ahead of the sale of part of the portfolio, resulting in a gain of £46m . For the Santander UK group, other financial assets at FVTPL comprised £317m ( 2022 : £312m ) of financial assets designated at FVTPL and £285m ( 2022 : £122m ) of financial assets mandatorily held at FVTPL. Loans and advances to customers principally represent other loans, being a portfolio of roll-up mortgages and deferred consideration . These are managed, and have their performance evaluated, on a fair value basis in accordance with a documented investment strategy, and information about them is provided on that basis to management. Since 2009, the Santander UK group’s policy has been not to designate similar new loans at FVTPL. The net loss in the year attributable to changes in credit risk for loans and advances at FVTPL was £nil ( 2022 : £1m , 2021 : £nil ). The cumulative net loss attributable to changes in credit risk for loans and advances at FVTPL at 31 December 2023 was £3m ( 2022 : £3m , 2021 : £2m ).
Santander UK Group Holdings plc
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Other Financial Assets at Fair Value Through Profit or Loss	44.4. OTHER FINANCIAL ASSETS AT FAIR VALUE THROUGH PROFIT OR LOSS 2023 2022 £m £m Debt securities 9,591 7,888 9,591 7,888 Other financial assets at FVTPL comprised £9,591m ( 2022 : £7,888m ) of financial assets mandatorily held at FVTPL. In 2023 , as part of MREL requirements, the Company issued £1,481m ( 2022 : £3,991m ) debt securities, which were subsequently downstreamed to Santander UK plc.

Loans and Advances to Banks - P

Loans and Advances to Banks - Parent	12 Months Ended
	Dec. 31, 2023
Santander UK Group Holdings plc
Net Loans And Advances To Banks [Line Items]
Loans and Advances to Banks	44.5. LOANS AND ADVANCES TO BANKS Loans and advances to banks comprise mainly amounts due from Santander UK group undertakings. The fair values of loans and advances to banks are equal to their carrying amounts. In 2023 and 2022 , there were no material expected credit losses. All of our senior debt issued out of Santander UK Group Holdings plc is downstreamed to our principal operating company Santander UK plc.

Other Financial Assets at Amo_2

Other Financial Assets at Amortised Cost - Parent	12 Months Ended
	Dec. 31, 2023
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Other Financial Assets at Amortised Cost	17. OTHER FINANCIAL ASSETS AT AMORTISED COST Group 2023 2022 £m £m Asset backed securities — — Debt securities 152 156 152 156 A significant portion of the debt securities are held in our eligible liquidity pool and consist mainly of government bonds and covered bonds. Detailed disclosures can be found in the 'Liquidity risk' section of the Risk review.
Santander UK Group Holdings plc
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Other Financial Assets at Amortised Cost	44.6. OTHER FINANCIAL ASSETS AT AMORTISED COST These consist of investments in subordinated notes and have a maturity of 10 years

Interests in Other Entities - P

Interests in Other Entities - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure of subsidiaries [line items]
Interests in Other Entities	19. INTERESTS IN OTHER ENTITIES Group 2023 2022 £m £m Joint Ventures 245 252 245 252 The Santander UK group consists of a parent company, Santander UK Group Holdings plc, incorporated and domiciled in the UK and a number of subsidiaries and joint ventures held directly and indirectly by it. Details of subsidiaries and joint ventures are set out in the Shareholder Information section and form an integral part of these financial statements. Details of subsidiaries benefitting from an audit exemption according to section 479A of the Companies Act 2006 are also set out in the Shareholder Information section and form an integral part of these financial statements. a) Interests in subsidiaries The Company holds directly or indirectly 100% of the issued ordinary share capital of its principal subsidiaries. All companies operate principally in their country of incorporation or registration. SFS has branch offices in Jersey and the Isle of Man. Interests in consolidated structured entities Structured entities are formed by Santander UK to accomplish specific and well-defined objectives. Santander UK consolidated these structured entities when the substance of the relationship indicates control, as described in Note 1 . In addition to the structured entities disclosed in Note 14 which are used for securitisation and covered bond programmes, the only other structured entities consolidated by Santander UK are described below. All the external assets and liabilities in these entities are included in the financial statements and in relevant Notes. Other than as set out below, no significant judgements were required with respect to control or significant influence. Motor Securities 2018-1 Designated Activity Company (Motor 2018) Motor 2018 is a credit protection entity, and a Designated Activity Company limited by shares, incorporated in Ireland. It issued a series of credit linked notes varying in seniority which referenced a portfolio of Santander UK group auto loans. Concurrently, this entity sold credit protection to SCUK in respect of the referenced loans and, in return for a fee, was liable to make protection payments to SCUK upon the occurrence of a credit event in relation to any of the referenced loans. Motor 2018 is consolidated as Santander UK held a variable interest by retaining the junior tranche of notes issued by the entity. The outstanding notes were redeemed and the transaction terminated in 2023 . b) Interests in joint ventures Santander UK does not have any individually material interests in joint ventures. In 2023 , Santander UK’s share in the profit after tax of its joint ventures was £43m ( 2022 : £36m ) before elimination of transactions between Santander UK and the joint ventures. At 31 December 2023 , the carrying amount of Santander UK’s interest was £245m ( 2022 : £252m ). At 31 December 2023 and 2022 , the joint ventures had no commitments and contingent liabilities. c) Interests in unconsolidated structured entities Structured entities sponsored by the Santander UK group Santander UK has interests in structured entities which it sponsors but does not control. Santander UK considers itself a sponsor of a structured entity when it facilitates the establishment of the structured entity. Other than as set out below, no significant judgements were required with respect to control or significant influence. The structured entities sponsored but not consolidated by Santander UK are as follows: i) Santander (UK) Common Investment Fund (the Fund) The Fund is a common investment fund that was established to hold the assets of the Santander (UK) Group Pension Scheme. The Fund is not consolidated by Santander UK, but its assets of £8,551m ( 2022 : £8,646m ) are accounted for as part of the defined benefit assets and obligations recognised on Santander UK’s balance sheet. For more on the Fund, see Note 30 . As the Fund holds the assets of the pension scheme, it is outside the scope of IFRS 10. Santander UK’s maximum exposure to loss is the carrying amount of the assets held. ii) Credit protection entities Santander UK has established four ( 2022 : four ) unconsolidated credit protection entities, which are Designated Activity Companies limited by shares, incorporated in Ireland. Each entity has issued a series of credit linked notes varying in seniority which reference portfolios of Santander UK group loans. Concurrently, these entities sell credit protection to Santander UK in respect of the referenced loans and, in return for a fee, are liable to make protection payments to Santander UK upon the occurrence of a credit event in relation to any of the referenced loans. Santander UK has no holdings in senior credit linked notes ( 2022 : £180m ). Junior credit linked notes, which amounted to £185m ( 2022 : £465m ), are all held by third party investors and suffer the first losses incurred in the referenced portfolios. Funds raised by the sale of the credit linked notes are deposited with Santander UK as collateral for the credit protection. The senior credit linked notes, along with the deposits and associated guarantees, are presented on a net basis, to reflect a legal right of set-off between the principal amounts of senior notes and the cash deposits. Deposits and associated guarantees in respect of the junior credit linked notes are included in ‘Deposits by customers’ (see Note 23 ). The entities are not consolidated by Santander UK because the third-party investors have the exposure, or rights, to all of the variability of returns from the performance of the entities. No assets are transferred to, or income received from, these entities. Since the credit linked notes (including those held by Santander UK) are fully cash collateralised, Santander UK’s maximum exposure to loss is equal to any unamortised fees paid to the entities in connection with the credit protection outlined above. Structured entities not sponsored by the Santander UK group Santander UK also has interests in structured entities which it does not sponsor or control. These consist of holdings of mortgage and other asset backed securities issued by entities that were established and/or sponsored by other unrelated financial institutions. These securities comprise the asset backed securities included in Note 17 . Management has concluded that the Santander UK group has no control or significant influence over these entities and that the carrying value of the interests held in these entities represents the maximum exposure to loss.
Santander UK Group Holdings plc
Disclosure of subsidiaries [line items]
Interests in Other Entities	44.7. INTERESTS IN OTHER ENTITIES 2023 2022 £m £m Interests in ordinary shares of subsidiaries 11,635 11,635 £500m Fixed Rate Reset Perpetual AT1 Capital Securities 495 495 £750m Fixed Rate Reset Perpetual AT1 Capital Securities 750 750 £500m Fixed Rate Reset Perpetual AT1 Capital Securities 210 210 £500m Fixed Rate Reset Perpetual AT1 Capital Securities 500 500 £450m Fixed Rate Reset Perpetual AT1 Capital Securities 50 50 13,640 13,640 Details of subsidiaries and joint ventures are set out in the Shareholder information section. For information on AT1 Capital Securities, see Note 33 to the Consolidated Financial Statements. The Company has no interests in joint ventures or associates. Interests in other entities mainly relate to investments in 100% of the ordinary share capital of Santander UK plc, Santander Financial Services plc and Santander Equity Investments Limited, as well as holdings of AT1 Capital Securities issued by Santander UK plc. Interests in subsidiaries are held at cost subject to impairment. The Company’s interests in subsidiaries were as follows: Cost Impairment Carrying amount £m £m £m At 31 December 2023 11,645 (10) 11,635 At 31 December 2022 11,645 (10) 11,635 Impairment testing Interests in other entities are tested for impairment annually at 31 December. Interests in other entities are otherwise tested for impairment if reviews identify an indicator of impairment or when events or changes in circumstances dictate. Impairment is required where the carrying value of an investment exceeds its recoverable amount. Basis of the recoverable amount The recoverable amount of all interests in other entities was determined based on a value in use (VIU) methodology at each testing date. For each investment, the VIU is calculated by discounting management’s cash flow projections for the investment. The cash flow projections also take account of increased internal capital allocations needed to achieve internal and regulatory capital targets including the leverage ratio. The key assumptions used in the VIU calculation for each investment are set out below. Carrying amount of investments and key assumptions in the VIU calculation Carrying amount of investment Discount rate Growth rate beyond initial cash flow projections 2023 2022 2023 2022 2023 2022 Investment £m £m % % % % Santander UK plc 11,268 11,268 16.7 16.9 1.6 1.6 Santander Financial Services plc 337 337 17.9 16.7 1.6 1.6 Other 30 30 11,635 11,635 Management’s judgement in estimating the cash flows of an investment The VIU calculation uses cash flow projections derived from the latest 3-year plan presented to the Board. For more details, see Note 20 to the Consolidated Financial Statements. Cash flow projections for the purpose of impairment testing do not take account of any adverse outcomes arising from contingent liabilities (see Note 31 to the Consolidated Financial Statements), whose existence will be confirmed by uncertain future events or where any obligation is not probable or otherwise cannot be measured reliably, nor do they take account of the benefits arising from Santander UK’s transformation plans that had not yet been implemented or committed at 31 December 2023 . Discount rate The rate used to discount the cash flows is based on the cost of equity assigned to each investment, which is derived using a CAPM. The CAPM depends on a number of inputs reflecting financial and economic variables, including the risk-free rate and a premium to reflect the inherent risk of the investment being evaluated. These variables are based on the market’s assessment of the economic variables and management’s judgement. In determining the discount rate, management have identified the cost of equity associated with market participants that closely resemble our investments and adjusted them for tax to arrive at the pre-tax equivalent rate. Growth rate beyond initial cash flow projections The growth rate for periods beyond the initial cash flow projections is used to extrapolate the cash flows in perpetuity because of the long-term perspective of the business. In line with the accounting requirements, management uses the UK Government’s official estimate of the UK long-term average GDP growth rate, as this is lower than management's estimate of the long-term average growth rate of the business. Investments in Santander UK plc and Santander Financial Services plc The VIU of each investment remains higher than the carrying value of the investment. The VIU review at 31 December 2023 did not indicate the need for an impairment in the Company’s investments in Santander UK plc and Santander Financial Services plc. Management considered the reduction in headroom and the uncertainty relating to the respective estimates of the VIU for those investments, but determined that there was a sufficient basis to conclude that no impairment was required. Sensitivities of key assumptions in calculating the VIU of the investment in Santander UK plc At 31 December 2023 and 2022 , the VIU was sensitive to reasonably possible changes in the key assumptions similar to those applied in determining the recoverable amount of goodwill recognised in the Santander UK plc group (see Note 20 to the Consolidated Financial Statements). At 31 December 2023 and 2022 , a reasonably possible change in the following key assumptions in relation to the VIU calculation for the Company’s investment in Santander UK plc would have resulted in a reduction in headroom, as shown in the table below. The sensitivity analysis presented below has been prepared on the basis that a change in each key assumption would not have a consequential impact on other assumptions used in the impairment review. However, due to the interrelationships between some of the assumptions, a change in one of the assumptions might impact one or more of the other assumptions and could result in a larger or smaller overall impact. Reduction in headroom 2023 2022 Subsidiary Reasonably possible change £m £m Santander UK plc Cash flow projections decrease by 10% ( 2022 : 5% ) (1,261) (773) Discount rate increases by 100 basis points ( 2022 : 100 basis points ) (1,026) (1,212) GDP growth rate decreases by 10 basis points ( 2022 : 10 basis points ) (24) (42) The decrease in cash flow projections in the table above includes the impact of holding back the required capital to support the growth of the business. Under current regulatory capital regulations as they apply to Santander UK plc, the calculation is not sensitive overall to the UK long-term average GDP growth rate assumption as the increased profit after tax generated by growth of the business is mostly offset by the need to retain more profit to meet increased regulatory capital requirements driven by the growth in assets. Sensitivity of VIU changes to current assumptions to achieve nil headroom Although there was no impairment of the Company's investment in Santander UK plc at 31 December 2023 and 2022 , the test remains sensitive to some of the assumptions used, as described above. In addition, the changes in assumptions detailed below for the discount rate and cash flow projections would eliminate the current headroom. As a result, there is a risk of impairment in the future should business performance or economic factors diverge from forecasts. The sensitivity analysis presented below has been prepared on the basis that a change in each key assumption would not have a consequential impact on other assumptions used in the impairment review. However, due to the interrelationships between some of the assumptions, a change in one of the assumptions might impact one or more of the other assumptions and could result in a larger or smaller overall impact. 2023 Carrying value Value in use Headroom Increase in post tax discount rate Decrease in cash flows Subsidiary £m £m £m bps % Santander UK plc 11,268 12,610 1,342 135 11 2022 Santander UK plc 11,268 15,461 4,193 450 27 Sensitivities of key assumptions in calculating the VIU of the investment in Santander Financial Services plc At 31 December 2023 and 2022 , the VIU was sensitive to reasonably possible changes in the key assumptions for the discount rate and cash flows similar to those applied in determining the recoverable amount of goodwill recognised in the Santander UK plc group (see Note 20 to the Consolidated Financial Statements). In line with the position for Santander UK plc, the VIU is not sensitive to the UK long-term average GDP growth rate assumption overall as the increased profit after tax generated by growth of the business is mostly offset by the need to retain more profit to meet increased regulatory capital requirements driven by the growth in assets. At 31 December 2023 and 2022 , a reasonably possible change in the following key assumptions in relation to the VIU calculation for the Company’s investment in Santander Financial Services plc would have resulted in a reduction in headroom, as shown in the table below. The sensitivity analysis presented below has been prepared on the basis that a change in each key assumption would not have a consequential impact on other assumptions used in the impairment review. However, due to the interrelationships between some of the assumptions, a change in one of the assumptions might impact one or more of the other assumptions and could result in a larger or smaller overall impact. Reduction in headroom 2023 2022 Subsidiary Reasonably possible change £m £m Santander Financial Services plc Cash flow projections decrease by 10% ( 2022 : 5% ) (50) (18) Discount rate increases by 100 basis points ( 2022 : 100 basis points ) (34) (29) The decrease in cash flow projections in the table above includes the impact of holding back the required capital to support the growth of the business. Sensitivity of VIU changes to current assumptions to achieve nil headroom Although there was no impairment of the Company's investment in Santander Financial Services plc at 31 December 2023 and 2022 , the test remains sensitive to some of the assumptions used, as described above. In addition, the changes in assumptions detailed below for the discount rate and cash flow projections would eliminate the current headroom. As a result, there is a risk of impairment in the future should business performance or economic factors diverge from forecasts. The sensitivity analysis presented below has been prepared on the basis that a change in each key assumption would not have a consequential impact on other assumptions used in the impairment review. However, due to the interrelationships between some of the assumptions, a change in one of the assumptions might impact one or more of the other assumptions and could result in a larger or smaller overall impact. 2023 Carrying value Value in use Headroom Increase in post tax discount rate Decrease in cash flows Subsidiary £m £m £m bps % Santander Financial Services plc 337 497 160 720 32 2022 Santander Financial Services plc 337 359 22 75 6

Other Financial Liabilities a_2

Other Financial Liabilities at Fair Value Through Profit or Loss - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other Financial Liabilities at Fair Value Through Profit or Loss	22. OTHER FINANCIAL LIABILITIES AT FAIR VALUE THROUGH PROFIT OR LOSS Group 2023 2022 £m £m Structured Notes Programmes 369 375 Structured deposits 426 321 Zero Amortising Guaranteed Notes 104 107 899 803 For the Santander UK group all ( 2022 : all) of the other financial liabilities at FVTPL were designated as such. Gains and losses arising from changes in the credit spread of securities issued by the Santander UK group reverse over the contractual life of the debt, provided that the debt is not repaid at a premium or a discount. The net loss during the year attributable to changes in the Santander UK group’s own credit risk on the above securities was £21m ( 2022 : £25m gain, 2021 : £12m loss). The cumulative net loss attributable to changes in the Santander UK group’s own credit risk on the above securities at 31 December 2023 was £6m ( 2022 : £15m gain, 2021 : £10m loss). At 31 December 2023 , the amount that would be required to be contractually paid at maturity of the securities above was £97m ( 2022 : £138m ) higher than the carrying value.
Santander UK Group Holdings plc
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other Financial Liabilities at Fair Value Through Profit or Loss	44.8. OTHER FINANCIAL LIABILITIES AT FAIR VALUE THROUGH PROFIT OR LOSS 2023 2022 £m £m Medium-term notes 9,591 7,888 9,591 7,888 Other financial liabilities at FVTPL comprised £9,591m ( 2022 : £7,888m ) of other financial liabilities designated at FVTPL. In 2023, as part of MREL requirements, the Company issued £1,481m ( 2022 : £3,991m ) of debt securities, which were then downstreamed to Santander UK plc. See Note 4. Gains and losses arising from changes in the credit spread of securities issued by the Santander UK group reverse over the contractual life of the debt, provided that the debt is not repaid at a premium or a discount. The cumulative net gain or loss at 31 December 2023, and net gain or loss for the year attributable to changes in the Santander UK group’s own credit risk on the above securities was £nil ( 2022 : £nil ) and has been included in profit and loss to offset credit risk on internal MREL assets held which are required to be recorded at FVTPL in accordance with IFRS 9. At 31 December 2023 , the amount that would be required to be contractually paid at maturity of the securities above was £197m higher ( 2022 : £755m higher) than the carrying value.

Deposits by Banks - Parent

Deposits by Banks - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure Of Deposits From Banks [Line Items]
Deposits by Banks	24. DEPOSITS BY BANKS Group 2023 2022 £m £m Items in the course of transmission 732 701 Deposits held as collateral 888 1,758 Other deposits (1) 18,737 26,084 20,357 28,543 (1) Includes drawdown from the TFSME of £17.0bn ( 2022 : £25.0bn ).
Santander UK Group Holdings plc
Disclosure Of Deposits From Banks [Line Items]
Deposits by Banks	44.9. DEPOSITS BY BANKS These consist of amounts due to subsidiaries under loan agreements and are repayable on demand.

Debt Securities in Issue - Pare

Debt Securities in Issue - Parent	12 Months Ended
	Dec. 31, 2023
Debt Securities In Issue [Line Items]
Debt Securities in Issue	26. DEBT SECURITIES IN ISSUE Group 2023 2022 £m £m Medium-term notes: – US $30bn Euro Medium Term Note Programme 744 739 – Euro 30bn Euro Medium Term Note Programme 5,619 6,435 – US SEC-registered Debt Programme - Santander UK Group Holdings plc 6,130 7,083 - US SEC-registered Debt Programme - Santander UK plc 1,031 1,276 Medium-term notes 13,524 15,533 Euro 35bn Global Covered Bond Programme 15,000 15,205 US $20bn Commercial Paper Programmes 2,761 1,851 Certificates of deposit 1,530 2,874 Credit linked notes 194 60 Securitisation programmes 2,769 897 35,778 36,420 The funding from the Euro 30bn Euro Medium Term Note Programme and the US SEC-registered Debt Programme in the name of Santander UK Group Holdings plc has mainly been downstreamed to our operating company Santander UK plc.
Santander UK Group Holdings plc
Debt Securities In Issue [Line Items]
Debt Securities in Issue	44.10. DEBT SECURITIES IN ISSUE The Company issues notes in the US from time to time pursuant to a shelf registration statement on Form F-3 filed with the SEC in 2021. 2023 2022 £m £m Medium-term notes: – Euro 30bn Euro Medium Term Note Programme 1,123 2,387 – US SEC-registered Debt Programme – Santander UK Group Holdings plc 788 2,511 1,911 4,898 The funding from the Euro 30bn Euro Medium Term Note Programme and the US SEC-registered Debt Programme in the name of Santander UK Group Holdings plc has predominantly been downstreamed to our operating company Santander UK plc. Debt securities in issue did not include any amounts due from Santander UK group undertakings.

Subordinated Liabilities - Pare

Subordinated Liabilities - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure Of Subordinated Liabilities [Line Items]
Subordinated Liabilities	27. SUBORDINATED LIABILITIES Group 2023 2022 £m £m £325m Sterling preference shares 343 344 Undated subordinated liabilities 205 219 Dated subordinated liabilities 1,838 1,769 2,386 2,332 In 2023 , certain subordinated liabilities were repurchased as part of ongoing liability management exercises, resulting in a profit of £4m ( 2022 : a loss of £5m ). The above securities will, in the event of the winding up of the issuer, be subordinated to the claims of depositors and all other creditors of the issuer, other than creditors whose claims rank equally with, or are junior to, the claims of the holders of the subordinated liabilities. The subordination amongst each of the subordinated liabilities upon a winding up of the issuer is specified in their respective terms and conditions. In 2023 and 2022 , the Santander UK group had no defaults of principal, interest or other breaches with respect to its subordinated liabilities. No repayment or purchase by the issuer of the subordinated liabilities may be made prior to their stated maturity without the consent of the PRA. Each of the subordinated liabilities issued by Santander UK Group Holdings plc has been downstreamed to Santander UK plc by means of Santander UK plc issuing equivalent subordinated liabilities to Santander UK Group Holdings plc. Undated subordinated liabilities Group 2023 2022 First call date £m £m 10.0625% Exchangeable capital securities n/a 205 205 7.125% 30 Year Step-up perpetual callable subordinated notes 2030 — 14 205 219 In common with other debt securities issued by Santander UK group companies and notwithstanding the issuer’s first call dates in the table above, in the event of certain tax changes affecting the treatment of payments of interest on subordinated liabilities in the UK, the 7.125% 30 Year Step-up perpetual callable subordinated notes are redeemable at any time, and the 10.0625% Exchangeable capital securities are redeemable on any interest payment date – each in whole at the option of Santander UK, at their principal amount together with any accrued interest. The 10.0625% Exchangeable capital securities are exchangeable into fully paid 10.375% non-cumulative non-redeemable sterling preference shares of £1 each, at the option of Santander UK, on the business day immediately following any interest payment date. Dated subordinated liabilities Group 2023 2022 Maturity £m £m 5% Subordinated notes 2023 — 591 4.75% Subordinated notes 2025 326 608 7.95% Subordinated notes 2029 193 207 6.50% Subordinated notes 2030 1 22 5.875% Subordinated notes 2031 7 7 5.625% Subordinated notes 2045 222 334 7.869% Subordinated notes 2033 321 — 8.296% Subordinated notes 2033 768 — 1,838 1,769 The dated subordinated liabilities are redeemable in whole at the option of Santander UK in the event of certain tax changes affecting the treatment of payments of interest on the subordinated liabilities in the UK, at their principal amount together with any accrued interest.
Santander UK Group Holdings plc
Disclosure Of Subordinated Liabilities [Line Items]
Subordinated Liabilities	44.11. SUBORDINATED LIABILITIES 2023 2022 Dated subordinated liabilities Maturity £m £m 4.75% Subordinated notes 2025 326 608 5.625% Subordinated notes 2045 222 334 8.296% Subordinated notes 2033 767 — 7.869% Subordinated notes 2033 318 — 1,633 942

Notes to Cash Flows - Parent

Notes to Cash Flows - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Notes to Cash Flows	34. NOTES TO CASH FLOWS Changes in liabilities arising from financing activities The table below shows the changes in liabilities arising from financing activities. The changes in equity arising from financing activities are set out in the Consolidated Statement of Changes in Equity. Group Balance sheet line item Debt securities in issue Subordinated liabilities Other equity instruments Lease liabilities Dividends paid Total 2023 £m £m £m £m £m £m At 1 January 36,420 2,332 2,196 129 — 41,077 Proceeds from issue of debt securities 5,347 — — — — 5,347 Repayment of debt securities (5,438) — — — — (5,438) Proceeds from issue of subordinated liabilities — 1,050 — — — 1,050 Repayment of subordinated liabilities — (971) — — — (971) Principal elements of lease payments — — — (48) — (48) Dividends paid — — — — (1,671) (1,671) Liability-related other changes (159) 25 — 33 — (101) Non-cash changes: – Unrealised foreign exchange (750) (54) — — — (804) – Other changes 358 4 — — 1,671 2,033 At 31 December 35,778 2,386 2,196 114 — 40,474 2022 At 1 January 31,580 2,228 2,191 134 — 36,133 Proceeds from issue of debt securities 8,667 — — — — 8,667 Repayment of debt securities (4,482) — — — — (4,482) Repayment of subordinated liabilities — (40) — — — (40) Issue of other equity instruments — — 750 — — 750 Repurchase of other equity instruments — — (750) — — (750) Principal elements of lease payments — — — (26) — (26) Dividends paid — — — — (1,173) (1,173) Liability-related other changes (1,282) 2 5 21 — (1,254) Non-cash changes: – Unrealised foreign exchange 1,893 190 — — — 2,083 – Other changes 44 (47) — — 1,173 1,169 At 31 December 36,420 2,332 2,196 129 — 41,077 2021 At 1 January 43,679 2,556 2,241 100 — 48,576 Proceeds from issue of debt securities 2,847 — — — — 2,847 Repayment of debt securities (13,724) — — — — (13,724) Repayment of subordinated liabilities — (4) — — — (4) Issue of other equity instruments — — 450 — — 450 Repurchase of other equity instruments — — (500) — — (500) Principal elements of lease payments — — — (25) — (25) Dividends paid — — — — (1,506) (1,506) Liability-related other changes (473) (4) — 59 — (418) Non-cash changes: – Unrealised foreign exchange (930) 14 — — — (916) – Other changes 181 (334) — — 1,506 1,353 At 31 December 31,580 2,228 2,191 134 — 36,133 Footnotes to the cash flow statement Net cash flows from operating activities includes interest received of £11,627m ( 2022 : £6,618m , 2021 : £4,873m ), interest paid of £6,496m ( 2022 : £2,107m , 2021 : £1,085m ) and dividends received of £nil ( 2022 : £nil , 2021 : £nil ). Total cash outflow for leases was £50m ( 2022 : £28m , 2021 : £28m ). Other matters In 2022, the non-controlling interests were redeemed. In 2021, there was a disposal of non-controlling interests of £181m .
Santander UK Group Holdings plc
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Notes to Cash Flows	44.12. NOTES TO CASH FLOWS Changes in liabilities arising from financing activities In addition to the changes in equity arising from financing activities, as set out in the Company Statement of Changes in Equity, the table below shows the changes in liabilities arising from financing activities. 2023 2022 Balance sheet line item Balance sheet line item Debt securities in issue Other liabilities at FVTPL (1) Subordinate d liabilities Other equity instruments Dividend s paid Total Debt securitie s in issue Other liabilities at FVTPL (1) Subordinated liabilities Other equity instruments Dividends paid Total £m £m £m £m £m £m £m £m £m £m £m £m At 1 January 4,898 7,888 942 2,196 — 15,924 6,013 4,190 838 2,191 — 13,232 Proceeds from issue of debt securities — 1,528 — — — 1,528 — 3,889 — — — 3,889 Repayment of debt securities (2,870) — — — — (2,870) (1,446) — — — — (1,446) Proceeds from issue of subordinated liabilities — — 1,050 — — 1,050 — — — — — — Repayment of subordinated liabilities — — (360) — — (360) — — — — — — Issue of other equity instruments — — — — — — — — — 750 — 750 Repurchase of other equity instruments — — — — — — — — — (750) — (750) Dividends paid — — — — (1,671) (1,671) — — — — (1,156) (1,156) Liability-related other changes (23) 558 30 — — 565 (14) (191) 1 5 — (199) Non-cash changes: – Unrealised foreign (99) (383) (32) — — (514) 339 — 103 — — 442 – Other changes 5 — 3 — 1,671 1,679 6 — — — 1,156 1,162 At 31 December 1,911 9,591 1,633 2,196 — 15,331 4,898 7,888 942 2,196 — 15,924 (1) Liability-related other changes for Other liabilities at FVTPL are not part of the changes in liability arising from financing activities. Footnotes to the cash flow statement Net cash flows from operating activities includes interest received of £197m ( 2022 : £202m ), interest paid of £130m ( 2022 : £159m ) and dividends received of £1,685m ( 2022 : £1,212m ).

Contingent Liabilities and Co_2

Contingent Liabilities and Commitments - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure of contingent liabilities [line items]
Contingent Liabilities and Commitments	31. CONTINGENT LIABILITIES AND COMMITMENTS Group 2023 2022 £m £m Guarantees given to third parties 452 448 Formal standby facilities, credit lines and other commitments 30,987 31,410 31,439 31,858 At 31 December 2023 , the Santander UK group had credit impairment loss provisions relating to guarantees given to third parties and undrawn loan commitments. See Note 29 for more details. Where the items set out below can be reliably estimated, they are disclosed in the table above. Guarantees given to third parties Guarantees given to third parties consist primarily of letters of credit, bonds and guarantees granted as part of normal product facilities which are offered to customers. Formal standby facilities, credit lines and other commitments Standby facilities, credit lines and other commitments are also granted as part of normal product facilities which are offered to customers. Retail facilities comprise undrawn facilities granted on flexible mortgages, bank overdrafts and credit cards. On flexible mortgages, the credit limit is set at the point of granting the loan through property value and affordability assessments. Ongoing assessments are made to ensure that credit limits remain appropriate considering any change in the security value or the customer’s financial circumstances. For unsecured overdraft facilities and credit cards, the facilities are granted based on new business risk assessment and are reviewed more frequently based on internal, as well as external data. Corporate facilities can comprise standby and revolving facilities which are subject to ongoing compliance with covenants and may require the provision of agreed security. FSCS The FSCS is the UK’s independent statutory compensation fund for customers of authorised financial services firms and pays compensation if a firm is unable to pay certain claims against it. The FSCS is funded by levies on the industry and recoveries and borrowings where appropriate. Loan representations and warranties In connection with the securitisations and covered bond transactions described in Note 14 , the Santander UK group entities selling the relevant loans into the applicable securitisation or covered bond portfolios make representations and warranties with respect to such loans, in each case as of the date of the sale of the loans into the applicable portfolio. These representations and warranties cover, among other things, the ownership of the loan by the relevant Santander UK group entity, absence of a material breach or default by the relevant borrower under the loan, the loan’s compliance with applicable laws and absence of material disputes with respect to the relevant borrower, asset and loan. The specific representations and warranties made by Santander UK group companies which act as sellers of loans in these securitisations and covered bond transactions depend in each case on the nature of the transaction and the requirements of the transaction structure. In the event that there is a material breach of the representations and warranties given by Santander UK plc as seller of loans under the residential mortgage- backed securitisations or the covered bond programmes included in Note 14 , or if such representations and warranties prove to be materially untrue at the date when they were given (being the sale date of the relevant mortgage loans), Santander UK plc may be required to repurchase the affected mortgage loans (generally at their outstanding principal balance plus accrued interest). These securitisations and covered bond programmes are collateralised by prime residential mortgage loans. Santander UK plc is principally a retail prime lender and has no appetite or product offering for any type of sub-prime business. Similarly, under the auto loan securitisations in Note 14 , in the event that there is a breach or inaccuracy in respect of a representation or warranty relating to the loans, the relevant Santander UK group entity who sold the auto loans into the securitisation portfolio will be required to repurchase such loans from the structure (also at their outstanding principal balance plus accrued interest). In addition to breaches of representation and warranties, under the auto loan securitisations, the seller may also have a repurchase obligation if certain portfolio limits are breached (which include, amongst other things, limits as to the size of a loan given to an individual customer, LTV ratio, average term to maturity and average seasoning). In the case of a repurchase of a loan from the relevant securitisation or covered bond programmes, the Santander UK group may bear any subsequent credit loss on such loan. The Santander UK group manages and monitors its securitisation and covered bond activities closely to minimise potential claims. Other legal actions and regulatory matters Santander UK engages in discussion, and co-operates, with the FCA, PRA, CMA and other regulators and government agencies in various jurisdictions in their supervision and review of Santander UK including reviews exercised under statutory powers, regarding its interaction with past and present customers, both as part of general thematic work and in relation to specific products, services and activities. During the ordinary course of business, Santander UK is also subject to complaints and threatened legal proceedings brought by or on behalf of current or former employees, customers, investors or other third parties, in addition to legal and regulatory reviews, challenges and tax or enforcement investigations or proceedings by relevant regulators or government agencies in various jurisdictions. All such matters are assessed periodically to determine the likelihood of Santander UK incurring a liability. In those instances where it is concluded that it is not yet probable that a quantifiable payment will be made, for example because the facts are unclear or further time is required to fully assess the merits of the case or to reasonably quantify the expected payment, no provision is made. In addition, where it is not currently practicable to estimate the possible financial effect of these matters, no provision is made. Payment Protection Insurance AXA France IARD and AXA France Vie (former GE Capital Corporation Group entities (GE Capital), known as Financial Insurance Company Ltd (FICL) and Financial Assurance Company Ltd (FACL), acquired by AXA SA in 2015) (together, AXA France) have brought a claim for £552m (plus interest) against (i) Santander Cards UK Limited (former GE Capital entity known as GE Capital Bank Limited (GECB), which was acquired by Banco Santander SA in 2008 and subsequently transferred to Santander UK plc); and (ii) Santander Insurance Services UK Limited (a Banco Santander SA subsidiary) (together the Santander Entities). The claim relates to the allocation of liability for compensation and associated costs in respect of a large number of PPI policies distributed by GECB pre-2005, which were underwritten by FICL and FACL. AXA France reduced their claim from £670m (plus interest) to £552m (plus interest) in their Re-Re- Amended Particulars of Claim dated 29 June 2023. The Santander Entities strongly refute the claim. Trial has been fixed for six weeks, beginning on 3 March 2025. There are ongoing factual issues to be resolved which may have legal consequences including in relation to liability. These issues create uncertainties which mean that it is difficult to reliably predict the outcome or the timing of the resolution of the matter. The litigation and other regulatory provision in Note 29 includes our best estimate of the Santander Entities’ liability to the specific portfolio. Further information has not been provided on the basis that it would be seriously prejudicial to the Santander Entities’ interests in connection with the dispute. In addition, and in relation to PPI more generally, the PPI provision includes an amount relating to legal claims challenging the FCA’s industry guidance on the treatment of Plevin / recurring non-disclosure assessments. This provision is based on current stock levels, future projected claims, and average redress. There remains a risk that volumes received in future may be higher than forecast. The provision in Note 29 includes our best estimate of Santander UK’s liability for the specific issue. The actual cost of customer compensation could differ from the amount provided. It is not currently practicable to provide an estimate of the risk and amount of any further financial impact. German dividend tax arbitrage transactions In June 2018 the Cologne Criminal Prosecution Office and the German Federal Tax Office commenced an investigation in relation to the historical involvement of Santander UK plc, Santander Financial Services plc and Cater Allen International Limited (all subsidiaries of Santander UK Group Holdings plc) in German dividend tax arbitrage transactions (known as cum/ex transactions). These transactions allegedly exploited a loophole of a specific German settlement mechanism through short-selling and complex derivative structuring which resulted in the German government either refunding withholding tax where such tax had not been paid or refunding it more than once. The German authorities are investigating numerous institutions and individuals in connection with alleged transactions and practices which may be found to be illegal under German law. During 2023 we continued to cooperate with the German authorities and, with the assistance of external experts, to progress an internal investigation into the matters in question. From Santander UK plc’s perspective, t he investigation is focused principally on the period 2009-2011 and remains on-going. There remain factual issues to be resolved which may have legal consequences including potentially material financial penalties. These issues create uncertainties which mean that it is difficult to predict the resolution of the matter including timing or the significance of the possible impact. These uncertainties mean it is not currently practicable to make a reliable assessment of the size of any related potential liability. Any potential losses, claims or expenses suffered or incurred by Santander Financial Services plc in respect of these matters have been fully indemnified by Santander UK plc, as part of the ring-fencing transfer scheme between Santander UK plc, Santander Financial Services plc and Banco Santander SA. SCUK - Motor Finance Broker Commissions Following the FCA’s Motor Market review in 2019 which resulted in a change in rules in January 2021, Santander Consumer (UK) plc (SCUK) has received a number of county court claims and complaints in respect of its historical use of discretionary commission arrangements (DCAs) prior to the 2021 rule changes. In the context of the complaints made to the Financial Ombudsman Service relating to such commission arrangements, the FCA announced on 11 January 2024 that it intends to use its powers under s166 of the Financial Services and Markets Act 2000 to review the historical use of DCAs between lenders and credit brokers (the “FCA Review”) and whether redress should be payable. In line with the FCA's announcement, we have paused the response to customer complaints until at least 20 November 2024. A claim has been issued against SCUK, Santander UK plc and others in the Competition Appeal Tribunal (CAT), alleging that SCUK’s historical commission arrangements in respect of used car financing operated in breach of the Competition Act 1998. While it is possible that certain charges may be incurred in relation to existing or future county court claims, Financial Ombudsman Service (FOS) complaints and the CAT proceedings, it is not considered that a legal or constructive obligation has been incurred in relation to these matters that would require a provision to be recognised at this stage. The resolution of such matters is not possible to predict with any certainty and there remain significant inherent uncertainties regarding the existence, scope and timing of any possible outflow which make it impracticable to disclose the extent of any potential financial impact. Other On 2 November 2015, Visa Europe Ltd agreed to sell 100% of its share capital to Visa Inc. The deal closed on 21 June 2016. As a member and shareholder of Visa Europe Ltd, Santander UK received upfront consideration made up of cash and convertible preferred stock. Conversion of the preferred stock into Class A Common Stock of Visa Inc. depends on the outcome of litigation against Visa involving UK & Ireland multilateral interchange fees (UK&I MIFs). Following ring- fencing, all Visa stock is now held by Santander Equity Investments Limited (SEIL), outside the ring-fenced bank. In valuing the preferred stock, SEIL makes adjustments for illiquidity and the potential for changes in the conversion rate due to litigation costs. In addition, Santander UK plc and certain other UK&I banks have agreed to indemnify Visa Inc. in the event that the preferred stock is insufficient to meet the costs of this litigation. Visa Inc. has recourse to this indemnity once more than €1bn of losses relating to UK&I MIFs have arisen or once the total value of the preferred stock issued to UK&I banks on closing has been reduced to nil . Santander UK plc's liability under this indemnity is capped at €39.85m . At this stage, it is unclear whether the litigation will give rise to more than €1bn of losses relating to UK&I MIFs which means it is not practicable to predict the resolution of the matter including the timing or the significance of the possible impact. As part of the sale of subsidiaries, businesses and other entities, and as is normal in such circumstances, entities within the Santander UK group have given warranties and/or indemnities to the purchasers. Obligations under stock borrowing and lending agreements Obligations under stock borrowing and lending agreements represent contractual commitments to return stock borrowed. These obligations are offset by a contractual right to receive stock under other contractual agreements. See Note 35 . Other off-balance sheet commitments The Santander UK group has commitments to lend at fixed interest rates which expose us to interest rate risk. For more, see the Risk review. Liquidity support arrangements Under the PRA’s liquidity rules, Santander UK plc and its subsidiary Cater Allen Limited form the RFB Domestic Liquidity Sub-group (the RFB DoLSub), which allows the entities to collectively meet regulatory requirements for the purpose of managing liquidity risk. Each member of the RFB DoLSub will support the other by transferring surplus liquidity in times of stress.
Santander UK Group Holdings plc
Disclosure of contingent liabilities [line items]
Contingent Liabilities and Commitments	44.13. CONTINGENT LIABILITIES AND COMMITMENTS Capital support arrangements At 31 December 2023 , Santander UK Group Holdings plc, Santander Financial Services plc and Santander Equity Investments Limited were party to a capital support deed entered into on 17 December 2021 and effective from 1 January 2022 (the Non-RFB Sub-Group Capital Support Deed). These parties were permitted by the PRA to form a core UK group as defined in the PRA Rulebook, a permission which expires on 31 December 2024. Exposures of Santander Financial Services plc, the regulated entity, to other members of the core UK group are exempt from large exposure limits that would otherwise apply and these exposures are risk-weighted at 0% . Where applicable this permission also provides for intra-group exposures to be excluded from the leverage exposure measure. The purpose of the Non-RFB Sub-Group Capital Support Deed is to facilitate the prompt transfer of available capital resources from, or repayment of liabilities by, the non-regulated parties to the regulated party in the event that the regulated party breached or was at risk of breaching its capital resources or risk concentrations requirements.

Share Capital - Parent

Share Capital - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure of classes of share capital [line items]
Share Capital	32. SHARE CAPITAL Group Ordinary shares of £1 each Issued and fully paid share capital No. £m At 31 December 2022, 1 January 2023 and 31 December 2023 7,060,000,000 7,060
Santander UK Group Holdings plc
Disclosure of classes of share capital [line items]
Share Capital	44.14. SHARE CAPITAL Details of the Company’s share capital are set out in Note 32 to the Consolidated Financial Statements.

Other Equity Instruments - Pare

Other Equity Instruments - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure Of Other Equity Instruments [Line Items]
Other Equity Instruments	33. OTHER EQUITY INSTRUMENTS Group Interest rate 2023 2022 % Next call date £m £m AT1 securities: - £500m Fixed Rate Reset Perpetual AT1 Capital Securities 6.75 June 2024 496 496 - £500m Fixed Rate Reset Perpetual AT1 Capital Securities 6.30 March 2025 500 500 - £450m Fixed Rate Reset Perpetual AT1 Capital Securities 4.25 March 2026 450 450 - £750m Fixed Rate Reset Perpetual AT1 Capital Securities 6.50 June 2027 750 750 2,196 2,196 AT1 securities The AT1 securities are perpetual and pay a quarterly distribution. At each distribution payment date, the Company can decide whether to pay the distribution, which is non-cumulative, in whole or in part. The distribution rate resets every five years . The securities will be automatically written down and the investors will lose their entire investment in the securities should the CET1 capital ratio of the Santander UK prudential consolidation group fall below 7% . All AT1 securities are redeemable at the option of the Company, and only with the consent of the PRA. The £450m 4.25% Fixed Rate Reset Perpetual AT1 Capital Securities, the £500m 6.30% Fixed Rate Reset Perpetual AT1 Capital Securities and the £750m 6.50% Fixed Rate Reset Perpetual AT1 Capital Securities were fully subscribed by the Company's immediate parent company, Banco Santander SA.
Santander UK Group Holdings plc
Disclosure Of Other Equity Instruments [Line Items]
Other Equity Instruments	44.15. OTHER EQUITY INSTRUMENTS Details of the Company’s other equity instruments are set out in Note 33 to the Consolidated Financial Statements.

Transactions with Directors a_2

Transactions with Directors and Other Key Management Personnel - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure Of Directors And Key Management Remuneration [Line Items]
Transactions with Directors and Other Key Management Personnel	37. TRANSACTIONS WITH DIRECTORS AND OTHER KEY MANAGEMENT PERSONNEL The Directors of Santander UK Group Holdings plc did not receive any remuneration in respect of their services to the Company. The remuneration disclosures in these financial statements reflect their remuneration in respect of the Santander UK plc group. a) Remuneration of Directors and Other Key Management Personnel The remuneration of the Directors and Other Key Management Personnel (KMP) of the Santander UK group is set out in aggregate below. 2023 2022 2021 Directors’ remuneration £ £ £ Salaries and fees 4,008,772 4,037,116 3,828,333 Performance-related payments 1,002,607 3,701,569 3,431,294 Other fixed remuneration (pension and other allowances & non-cash benefits) 222,538 906,201 806,103 Expenses — 13,004 3,705 Total remuneration 5,233,917 8,657,890 8,069,435 2023 2022 2021 Directors' and Other Key Management Personnel compensation £ £ £ Short-term employee benefits 13,235,757 15,641,669 18,831,380 Post-employment benefits 611,769 740,333 913,842 Compensation for loss of office (1) — 1,540,400 — Total compensation 13,847,526 17,922,402 19,745,222 (1) Compensation for loss of office was not paid to Directors or KMPs in 2023 ( 2022 : three KMPs, £1,540,400 ; 2021 : nil ). In 2023 , the remuneration, excluding pension contributions, of the highest paid Director, was £2,640,491 ( 2022 : £3,510,441 , 2021 : £3,740,810 ) of which £1,002,607 ( 2022 : £1,900,506 , 2021 : £1,864,320 ) was performance related. In 2023 , the accrued defined benefit pension relating to the highest paid director was £nil ( 2022 : £nil , 2021 : £22,119 per annum for a different individual). b) Retirement benefits Defined benefit pension schemes are provided to certain employees. See Note 30 for details of the schemes and the related costs and obligations. No director has a deferred pension benefit accruing under a defined benefit scheme. Ex-gratia pensions paid to former Directors of Santander UK plc in 2023 , which have been provided for previously, amounted to £327,462 ( 2022 : £379,945 ; 2021 : £370,668 ). Since the Company became part of the Banco Santander group, the Board has not awarded any new ex-gratia pensions. c) Transactions with Directors, Other Key Management Personnel and each of their connected persons Directors, Other KMP (defined as the Executive Committee of Santander UK plc who served during the year) and their connected persons have undertaken the following transactions with the Santander UK group in the ordinary course of business. 2023 2022 No. £000 No. £000 Secured loans, unsecured loans and overdrafts At 1 January 6 647 4 27 Net movements — 244 2 620 At 31 December 6 891 6 647 Deposit, bank and instant access accounts and investments At 1 January 16 2,995 16 6,427 Net movements (3) (1,819) — (3,432) At 31 December 13 1,176 16 2,995 In 2023 and 2022 , no Director held any interest in the shares of any company in the Santander UK group and no Director exercised or was granted any rights to subscribe for shares in any company in the Santander UK group. In addition, in 2023 and 2022 , no Directors exercised share options over shares in Banco Santander SA, the ultimate parent company of the Company. Secured loans, unsecured loans and overdrafts are made to Directors, Other KMP and their connected persons, in the ordinary course of business, with terms prevailing for comparable transactions and on the same terms and conditions as applicable to other employees in the Santander UK group. Such loans do not involve more than the normal risk of collectability or present any unfavourable features. Amounts deposited by Directors, Other KMP and their connected persons earn interest at the same rates as those offered to the market or on the same terms and conditions applicable to other employees in the Santander UK group. Deposits, bank and instant access accounts and investments are entered into by Directors, Other KMP and their connected persons on normal market terms and conditions, or on the same terms and conditions as applicable to other employees in Santander UK group. In 2023 , loans were made to one Directors ( 2022 : four Directors), with a principal amount of £312,846 outstanding at 31 December 2023 ( 2022 : £332,426 ). In 2023 , loans were made to five Other KMP ( 2022 : two ), with a principal amount of £578,568 outstanding at 31 December 2023 ( 2022 : £314,667 ). In 2023 and 2022 , there were no other transactions, arrangements or agreements with Santander UK in which Directors, Other KMP or their connected persons had a material interest. In addition, in 2023 and 2022 , no Director had a material interest in any contract of significance with Santander UK other than a service contract or appointment letter, as appropriate.
Santander UK Group Holdings plc
Disclosure Of Directors And Key Management Remuneration [Line Items]
Transactions with Directors and Other Key Management Personnel	44.16. TRANSACTIONS WITH DIRECTORS AND OTHER KEY MANAGEMENT PERSONNEL The Directors of Santander UK Group Holdings plc did not receive any remuneration in respect of their services to the Company. The remuneration disclosures in respect of the Santander UK group are set out in Note 37 to the Consolidated Financial Statements.

Related Party Transactions - Pa

Related Party Transactions - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure of transactions between related parties [line items]
Related Party Transactions	38. RELATED PARTY DISCLOSURES a) Parent undertaking and controlling party The Company’s immediate and ultimate parent and controlling party is Banco Santander SA , a company incorporated in Spain. The smallest and largest groups into which the Santander UK group’s results are included are the group accounts of Banco Santander SA , copies of which may be obtained from Shareholder Relations, 2 Triton Square, Regent’s Place, London NW1 3AN. b) Transactions with related parties Transactions with related parties during the year and balances outstanding at the year-end: Group Interest, fees and other income received Interest, fees and other expenses paid Amounts owed by related parties Amounts owed to related parties 2023 2022 2021 2023 2022 2021 2023 2022 2023 2022 £m £m £m £m £m £m £m £m £m £m Ultimate parent (12) (863) (210) 475 47 34 903 1,423 (2,250) (1,732) Fellow subsidiaries (28) (60) (47) 194 171 151 26 31 (251) (278) Joint ventures (183) (77) (34) 55 17 4 4,486 4,151 (781) (973) (223) (1,000) (291) 724 235 189 5,415 5,605 (3,282) (2,983) For more on this, see ‘Balances with other Banco Santander group members’ in the Risk review, Note 13. Loans and advances to customers, Note 23. Deposits by customers and Note 33. Other Equity Instruments. In addition, transactions with pension schemes operated by the Santander UK group are described in Note 30 . The above transactions were made in the ordinary course of business, on substantially the same terms as for comparable transactions with third party counterparties, and within limits acceptable to the PRA. Such transactions do not involve more than the normal risk of collectability or present any unfavourable features. In 2021, SCUK sold its entire 50% shareholding in PSA Finance UK Limited to PSA Financial Services Spain EFC SA, a joint venture between Santander Consumer Finance SA, a fellow subsidiary of Banco Santander SA, and Banque PSA Finance SA. In 2021 , a significant part of the CIB business of Santander UK was transferred to the London branch of Banco Santander SA by way of a Part VII banking business transfer scheme. For more details, see Note 42. In 2021, we sold our then head office site in Triton Square, London to Santander UK Investments Ltd, a wholly owned subsidiary of our ultimate parent. Santander UK occupies space within the building and paid fees of £9m ( 2022 : £6m ) under an occupational licence arrangement. In November 2022, Santander (UK) Group Pension Scheme Trustees Limited entered into an unsecured committed liquidity facility with Santander UK plc for £600m with a maturity date of 31 December 2024. This facility provides an alternate source of short-term liquidity for day-to-day operational needs. At the balance sheet date, no drawings had been made from this facility and the entire facility remained undrawn.
Santander UK Group Holdings plc
Disclosure of transactions between related parties [line items]
Related Party Transactions	44.17. RELATED PARTY TRANSACTIONS The Company’s transactions with related parties during the year and balances outstanding at the year-end: Interest, fees and other income received Interest, fees and other expenses paid Amounts owed by related parties Amounts owed to related parties 2023 2022 2021 2023 2022 2021 2023 2022 2023 2022 £m £m £m £m £m £m £m £m £m £m Ultimate parent — — — 36 — — — — (1,092) — Subsidiaries (990) (192) — 7 656 — 15,004 15,597 — (3) (990) (192) — 43 656 — 15,004 15,597 (1,092) (3) – Dividend income from subsidiaries of £1,685m ( 2022 : £1,212m , 2021 : £1,497m ), – Dividends on ordinary shares declared and paid during the year are set out in Note 10 to the Consolidated Financial Statements. – Loans and advances to banks include £1,772m due from Santander UK group undertakings, – Other financial assets at amortised cost, see Note 6, all of which are securities issued by Santander UK plc, – Other financial liabilities at fair value through profit or loss, see Note 8, all of which are securities subscribed for by Santander UK plc, – Deposits by banks, see Note 9, – Debt securities, see Note 10.

Events After the Balance Shee_2

Events After the Balance Sheet Date - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure of non-adjusting events after reporting period [line items]
Events After the Balance Sheet Date	43. EVENTS AFTER THE BALANCE SHEET DATE There have been no significant events between 31 December 2023 and the date of approval of these financial statements which would require a change to or additional disclosure in the financial statements.
Santander UK Group Holdings plc
Disclosure of non-adjusting events after reporting period [line items]
Events After the Balance Sheet Date	See Note 43 to the Consolidated Financial Statements.

Interest Rate Benchmark Reform

Interest Rate Benchmark Reform - Parent	12 Months Ended
	Dec. 31, 2023
Disclosure of expected impact of initial application of new standards or interpretations [line items]
Interest Rate Benchmark Reform	41. INTEREST RATE BENCHMARK REFORM Santander UK continues to work with customers and counterparties to transition any remaining agreements referencing 3-month synthetic LIBOR before that setting ends on 31 March 2024. At 31 December 2023 , these represent an insignificant element of Santander UK’s exposures and there are no remaining exposures which reference other LIBOR settings. The following tables show the notional amounts of assets, liabilities and off-balance sheet commitments at 31 December 2023 and 31 December 2022 affected by IBOR reform that have yet to transition to an alternative benchmark interest rate. Group GBP LIBOR USD LIBOR Total 2023 £m £m £m Assets Financial assets at amortised cost 6 — 6 6 — 6 2022 Assets Derivatives — 1,665 1,665 Financial assets at amortised cost 76 245 321 76 1,910 1,986 Liabilities Derivatives 66 1,846 1,912 Financial liabilities at amortised cost — 2,491 2,491 66 4,337 4,403 Off-balance sheet commitments given 2 — 2
Santander UK Group Holdings plc
Disclosure of expected impact of initial application of new standards or interpretations [line items]
Interest Rate Benchmark Reform	44.19. INTEREST RATE BENCHMARK REFORM At 31 December 2023 , the Company had no remaining exposures which reference LIBOR settings. At 31 December 2022 the company held, £2,491m of USD LIBOR-linked Financial liabilities at amortised cost that were affected by IBOR reform and have yet to transition to an alternative benchmark interest rate as provided internally to key management personnel. Further details of the significant interest rate benchmarks to which hedging relationships are exposed, the extent of risk exposure that is affected by IBOR reform, the effect of IBOR reform on interest rate risk management and how Santander UK's transition to alternative benchmark interest rates is being managed, are disclosed in Note 41 to the Consolidated Financial Statements.

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Significant Accounting Policies [Abstract]
Basis of preparation, future accounting developments and material accounting policy information	Basis of preparation These financial statements incorporate the financial statements of the Company and entities it controls (its subsidiaries) made up to 31 December each year. The consolidated financial statements have been prepared on the going concern basis using the historical cost convention, except for financial assets and liabilities that have been measured at fair value. An assessment of the appropriateness of the adoption of the going concern basis of accounting is disclosed in the statement of going concern in the Directors’ report. Compliance with International Financial Reporting Standards (IFRS) The consolidated financial statements of the Santander UK group and the separate financial statements of the Company comply with UK-adopted International Accounting Standards (IAS). The financial statements are also prepared in accordance with IFRS as issued by the International Accounting Standards Board (IASB), including interpretations issued by the IFRS Interpretations Committee, as there are no applicable differences from IFRS as issued by the IASB for the periods presented. Disclosures required by IFRS 7 ‘Financial Instruments: Disclosure’ relating to the nature and extent of risks arising from financial instruments, and IAS 1 ‘Presentation of Financial Statements’ relating to objectives, policies and processes for managing capital, have been included in the Risk review section of this Annual Report. This information forms an integral part of these financial statements by this cross reference, is marked as audited, and is covered by the Independent auditors' report. Climate change Santander UK continues to develop its assessment of the potential impacts that climate change and the transition to a low carbon economy may have on the assets and liabilities recognised and presented in its financial statements. Santander UK is mindful of its responsibilities as a responsible lender and is focused on ways to meet the objectives of the Paris Agreement on climate change and to support the UK’s transition to a climate-resilient, net zero economy. Santander UK's current climate change strategy focuses on three main areas to achieve Banco Santander's ambition to reach net zero emissions by 2050: 1. Managing climate risks by integrating climate considerations into risk management frameworks, screening and stress testing our portfolio for climate related financial risks, and setting risk appetites to help steer our portfolio in line with the Paris Agreement, 2. Supporting our customers’ transition by developing products and services that promote a reduction in CO 2 emissions, and 3. Reducing emissions in our operations and supply chain by focusing on continuous improvement in our operations, and environmental and energy management systems in accordance with ISO14001 and 15001, promoting responsible procurement practices and employee engagement. Santander UK's current climate change strategy and its view of the risks associated with climate change and the transition to a low carbon economy are reflected in its critical judgements and accounting estimates, although climate change risk did not have a material impact at 31 December 2023 and 2022, consistent with management's assessment that climate change and the transition to a low carbon economy are not currently expected to have a meaningful impact on the viability of the Santander UK group in the medium term. At 31 December 2023 and 2022, management specifically considered the potential impact of climate change and the transition to a low carbon economy on: – Loans and advances to customers ( see Note 13 and the credit risk section of the Risk review). Some climate change risks arise due to the requirements of IFRS 9 and others relate to specific portfolios and sectors: – ECL calculations are based on multiple forward-looking economic scenarios developed by management covering a period of 5 years , during which timeframe climate change risks may crystallise; – For mortgages in Retail & Business Banking and commercial real estate lending in Corporate & Commercial Banking, the value of property collateral might be affected by physical impacts related to the frequency and scale of extreme weather events, such as flood and subsidence risk, or changing environmental performance standards for property. – For automotive loans in Consumer Finance, the residual value of automotive vehicles might be impacted by diesel obsolescence and the transition to electric vehicles. – For corporate lending in Corporate & Commercial Banking, certain sectors give rise to fossil fuel exposures, such as Oil & Gas, Mining & Extraction and Power Generation. – Goodwill impairment assessment (see Note 20). Estimates underpinning the determination of whether or not goodwill balances are impaired are partly based on forecast business performance beyond the time horizon for management's detailed plans. Future changes to Santander UK's climate change strategy may impact Santander UK's critical judgements and accounting estimates and result in material changes to financial results and the carrying values of certain assets and liabilities in future reporting periods. Future accounting developments At 31 December 2023 , for the Santander UK group, there were no significant new or revised standards and interpretations, and amendments thereto, which have been issued but which are not yet effective, or which have otherwise not been early adopted where permitted. Comparative information As required by US public company reporting requirements, these financial statements include two years of comparative information for the consolidated income statement, consolidated statement of comprehensive income, consolidated statement of changes in equity, consolidated statement of cash flows and related notes. Material accounting policy information The following material accounting policies have been applied in preparing these financial statements. For material accounting policies which involve the application of judgements or accounting estimates that are determined to be critical to the preparation of these financial statements see 'Critical judgements and accounting estimates'. Compliance with International Financial Reporting Standards The Company’s financial statements comply with UK-adopted international accounting standards. The financial statements are also prepared in accordance with International Financial Reporting Standards (IFRSs) as issued by the International Accounting Standards Board (IASB), including interpretations issued by the IFRS Interpretations Committee, as there are no applicable differences from IFRSs as issued by the IASB for the periods presented. Climate change Management specifically also considered the potential impact of climate change and the transition to a low carbon economy on its Investment in Santander UK plc. Estimates underpinning the determination of whether or not the cost of the investment is impaired are partly based on forecast business performance beyond
Consolidation	Consolidation The consolidated financial statements incorporate the financial statements of the Company and entities (including structured entities) controlled by it and its subsidiaries. The acquisition method of accounting is used to account for the acquisition of subsidiaries which meet the definition of a business. Business combinations between entities under common control (i.e. fellow subsidiaries of Banco Santander SA, the ultimate parent) are outside the scope of IFRS 3 – ‘Business Combinations’, and there is no other guidance for such transactions under IFRS. The Santander UK group elects to account for business combinations between entities under common control at their book values in the acquired entity by including the acquired entity’s results from the date of the business combination and not restating comparatives. Reorganisations of entities within the Santander UK group are also accounted for at their book values. Credit protection entities established as part of significant risk transfer (SRT) transactions are not consolidated by the Santander UK group in cases where third party investors have the exposure, or rights, to all of the variability of returns from the performance of the entities.
Revenue recognition	Revenue recognition a) Interest income and expense Interest and similar income and expense are recognised in the income statement using the effective interest rate method for: all financial instruments measured at amortised cost; debt instruments measured at FVOCI; and the effective part of any related accounting hedging instruments. Interest income is calculated by applying the effective interest rate to the gross carrying amount of financial assets, except for financial assets that have subsequently become credit-impaired (i.e. Stage 3), for which interest revenue is calculated by applying the effective interest rate to their amortised cost (i.e. net of the ECL provision). For more information on stage allocations of credit risk exposures, see ‘Significant increase in credit risk’ in the ‘Santander UK group level – credit risk management’ section of the Risk review. b) Fee and commission income and expense Fees and commissions that are not an integral part of the effective interest rate are recognised when the service is performed. Most fee and commission income is recognised at a point in time. Certain commitment, upfront and management fees are recognised over time but are not material. For retail and corporate products, fee and commission income consists principally of collection services fees, commission on foreign currencies, commission and other fees received from retailers for processing credit card transactions, fees received from other credit card issuers for providing cash advances for their customers through the Santander UK group’s branch and ATM networks, annual fees payable by credit card holders and fees for non-banking financial products. For insurance products, fee and commission income consists principally of commissions and profit share arising from the sale of building and contents insurance and life protection insurance. Commissions arising from the sale of buildings and contents insurance are recognised over the period of insurance cover, adjusted to take account of cancelled policies. Profit share income from the sale of buildings and contents insurance which is not subject to any adjustment is recognised when the profit share income is earned. Commissions and profit share arising from the sale of life protection insurance is subject to adjustment for cancellations of policies within 3 years from inception. Fee and commission income which forms an integral part of the effective interest rate of a financial instrument (for example certain loan commitment fees) is recognised as an adjustment to the effective interest rate and recorded in ‘Interest income’. c) Other operating income Other operating income includes all gains and losses from changes in the fair value of financial assets and liabilities held at fair value through profit or loss (comprising financial assets and liabilities held for trading, trading derivatives and other financial assets and liabilities at fair value through profit or loss), together with related interest income, expense, dividends, and changes in fair value of any derivatives managed in conjunction with these assets and liabilities. Other operating income also includes hedge ineffectiveness arising from fair value and cash flow hedging, income from operating lease assets, and profits and losses arising on the sales of property, plant and equipment and subsidiary undertakings.
Defined benefit pension schemes	Defined benefit pension schemes (see 'Critical judgements and accounting estimates') A defined benefit scheme is a pension scheme that guarantees an amount of pension benefit to be provided, usually as a function of one or more factors such as age, years of service or compensation. Pension costs are charged to ‘Administration expenses’, within the line item ‘Operating expenses before impairment losses, provisions and charges’ with the net interest on the defined benefit asset or liability included within ‘Net interest income’ in the income statement. The asset or liability recognised in respect of defined benefit pension schemes is the present value of the defined benefit obligation at the balance sheet date, less the fair value of scheme assets. The defined benefit obligation is calculated annually by independent actuaries using the projected unit credit method. The assets of the schemes are measured at their fair values at the balance sheet date. The present value of the defined benefit obligation is estimated by projecting forward the growth in current accrued pension benefits to reflect inflation and salary growth to the date of pension payment, then discounted to present value using the yield applicable to high-quality AA rated corporate bonds of the same currency and which have terms to maturity closest to the terms of the scheme liabilities, adjusted where necessary to match those terms. In determining the value of scheme liabilities, demographic and financial assumptions are made by management about life expectancy, inflation, discount rates, pension increases and earnings growth, based on past experience and future expectations. Financial assumptions are based on market conditions at the balance sheet date and can generally be derived objectively. Demographic assumptions require a greater degree of estimation and judgement to be applied to externally derived data. Any surplus or deficit of scheme assets over liabilities is recognised in the balance sheet as an asset (surplus) or liability (deficit). An asset is only recognised to the extent that the surplus can be recovered through reduced contributions in the future or through refunds from the scheme.
Share-based payments	Share-based payments The Santander UK group engages in cash-settled and equity-settled share-based payment transactions in respect of services received from certain of its employees. Shares of the Santander UK group’s parent, Banco Santander SA are purchased in the open market by the Santander UK group (for the Employee Sharesave scheme) or are purchased by Banco Santander SA or another Banco Santander subsidiary (including awards granted under the Long-Term Incentive Plan and the Deferred Shares Bonus Plan) to satisfy share options or awards as they vest. Options granted under the Employee Sharesave scheme and awards granted under the Transformation Incentive Plan are accounted for as cash-settled share- based payment transactions. Awards granted under the Long-Term Incentive Plan and Deferred Shares Bonus Plan are accounted for as equity-settled share- based payment transactions. The fair value of the options granted under the Employee Sharesave scheme is determined using an option pricing model, which takes into account the exercise price of the option, the current share price, the risk-free interest rate, the expected volatility of the Banco Santander SA share price over the life of the option and the dividend growth rate. The fair value of the awards granted for the Long-Term Incentive Plan was determined at the grant date using an option pricing model, which takes into account the share price at grant date, the risk-free interest rate, the expected volatility of the Banco Santander SA share price over the life of the award and the dividend growth rate.
Goodwill and other intangible assets	Goodwill and other intangible assets (for goodwill see 'Critical judgements and accounting estimates') Goodwill represents the excess of the cost of an acquisition, as well as the fair value of any interest previously held, over the fair value of the share of the identifiable net assets of the acquired subsidiary, or business at the date of acquisition. Goodwill on the acquisition of subsidiaries and businesses is included in intangible assets. Goodwill is tested for impairment annually, or more frequently when events or changes in circumstances dictate and carried at cost less accumulated impairment losses. Gains and losses on the disposal of an entity or business include the carrying amount of goodwill relating to the entity or business sold. Other intangible assets are recognised if they arise from contractual or other legal rights or if they are capable of being separated or divided from Santander UK and sold, transferred, licensed, rented or exchanged. The value of such intangible assets, where they are available for use, is amortised on a straight-line basis over their useful economic life of three to seven years and the assets are reviewed annually for impairment indicators and tested for impairment where indicators are present. Other intangible assets that are not yet available for use are tested for impairment annually or more frequently when events or changes in circumstances dictate. Software development costs are capitalised when they are direct costs associated with identifiable and unique software products that are expected to provide future economic benefits and the cost of those products can be measured reliably. These costs include payroll, materials, services and directly attributable overheads. Internally developed software meeting these criteria and externally purchased software are classified in intangible assets on the balance sheet and amortised on a straight-line basis over their useful life of three to seven years, unless the software is an integral part of the related computer hardware, in which case it is treated as property, plant and equipment as described below. Capitalisation of costs ceases when the software is capable of operating as intended. Costs of maintaining software are expensed as incurred.
Property, plant and equipment	Property, plant and equipment Property, plant and equipment include owner-occupied properties (including leasehold properties), office fixtures and equipment and computer software. Property, plant and equipment also includes operating leases where the Santander UK group is the lessor and right-of-use assets where the Santander UK group is the lessee. Internally developed software meeting the criteria set out in ‘Goodwill and other intangible assets’ above and externally purchased software are classified in property, plant and equipment where the software is an integral part of the related computer hardware (for example, the operating system of a computer). Classes of property, plant and equipment are depreciated on a straight-line basis over their useful life, as follows: Owner-occupied properties Not exceeding 50 years Office fixtures and equipment 3 to 15 years Computer software 3 to 7 years Right-of-use assets Shorter of the lease term or the useful life of the underlying asset Operating lease assets - vehicles 1 to 4 years Depreciation is not charged on freehold land. Depreciation of operating lease assets where the Santander UK group is the lessor is described in 'Leases' below.
Financial instruments	Financial instruments (for impairment of debt instrument financial assets see 'Critical judgements and accounting estimates: Credit impairment losses') a) Initial recognition and measurement Financial assets and liabilities are initially recognised when the Santander UK group becomes a party to the contractual terms of the instrument. The Santander UK group determines the classification of its financial assets and liabilities at initial recognition and measures a financial asset or financial liability at its fair value plus or minus, in the case of a financial asset or financial liability not at FVTPL, transaction costs that are incremental and directly attributable to the acquisition or issue of the financial asset or financial liability. Transaction costs of financial assets and financial liabilities carried at FVTPL are expensed in profit or loss. Immediately after initial recognition, an expected credit loss (ECL) allowance is recognised for financial assets measured at amortised cost and investments in debt instruments measured at FVOCI. A regular way purchase or sale is a purchase or sale of a financial asset under a contract whose terms require delivery of the asset within the timeframe established generally by regulation or convention in the marketplace concerned. Regular way purchases and sales of financial assets measured at amortised cost are recognised on settlement date; all other regular way purchases and sales of financial assets are recognised on trade date. b) Financial assets and liabilities i) Classification and subsequent measurement The Santander UK group classifies its financial assets in the measurement categories of amortised cost, FVOCI and FVTPL. Financial assets and financial liabilities are classified as FVTPL where there is a requirement to do so or where they are otherwise designated at FVTPL on initial recognition. Financial assets and financial liabilities which are required to be held at FVTPL include: – Financial assets and financial liabilities held for trading. – Debt instruments that do not have solely payments of principal and interest (SPPI) characteristics. Otherwise, such instruments are measured at amortised cost or FVOCI, and – Equity instruments that have not been designated as held at FVOCI. Financial assets and financial liabilities are classified as held for trading if they are derivatives or if they are acquired or incurred principally for the purpose of selling or repurchasing in the near-term, or form part of a portfolio of financial instruments that are managed together and for which there is evidence of short-term profit taking. In certain circumstances, other financial assets and financial liabilities are designated at FVTPL where this results in more relevant information. This may arise because it significantly reduces a measurement inconsistency that would otherwise arise from measuring assets or liabilities or recognising the gains or losses on them on a different basis, where the assets and liabilities are managed and their performance evaluated on a fair value basis or, in the case of financial liabilities, where it contains one or more embedded derivatives which are not closely related to the host contract. The classification and measurement requirements for financial asset debt and equity instruments and financial liabilities are set out below. Financial assets: debt instruments Debt instruments are those instruments that meet the definition of a financial liability from the issuer’s perspective, such as loans and government and corporate bonds. Classification and subsequent measurement of debt instruments depend on the Santander UK group’s business model for managing the asset, and the cash flow characteristics of the asset. Business model The business model reflects how the Santander UK group manages the assets in order to generate cash flows and, specifically, whether the Santander UK group’s objective is solely to collect the contractual cash flows from the assets or is to collect both the contractual cash flows and cash flows arising from the sale of the assets. If neither of these is applicable, such as where the financial assets are held for trading purposes, then the financial assets are classified as part of an ‘other’ business model and measured at FVTPL. Factors considered in determining the business model for a group of assets include past experience on how the cash flows for these assets were collected, how the assets’ performance is evaluated and reported to key management personnel, and how risks are assessed and managed. SPPI Where the business model is to hold assets to collect contractual cash flows or to collect contractual cash flows and sell, the Santander UK group assesses whether the assets’ cash flows represent SPPI. In making this assessment, the Santander UK group considers whether the contractual cash flows are consistent with a basic lending arrangement (i.e. interest includes only consideration for the time value of money, credit risk, other basic lending risks and a profit margin that is consistent with a basic lending arrangement). Where the contractual terms introduce exposure to risk or volatility that is inconsistent with a basic lending arrangement, the related asset is classified and measured at FVTPL. Financial assets with embedded derivatives are considered in their entirety when determining whether their cash flows are SPPI. Based on these factors, the Santander UK group classifies its debt instruments into one of the following measurement categories: – Amortised cost – Financial assets that are held for collection of contractual cash flows where those cash flows represent SPPI, and that are not designated at FVTPL, are measured at amortised cost. The carrying amount of these assets is adjusted by any ECL recognised and measured as presented in Note 13 . Interest income from these financial assets is included in ‘Interest and similar income’ using the effective interest rate method. When estimates of future cash flows are revised, the carrying amount of the respective financial assets is adjusted to reflect the new estimate discounted using the original effective interest rate. Any changes are recognised in the income statement. – FVOCI – Financial assets that are held for collection of contractual cash flows and for selling the assets, where the assets’ cash flows represent SPPI, and that are not designated at FVTPL, are measured at FVOCI. Movements in the carrying amount are recognised in OCI, except for the recognition of impairment gains or losses, interest revenue and foreign exchange gains and losses which are recognised in profit or loss. When the financial asset is derecognised, the cumulative gain or loss previously recognised in OCI is reclassified from equity to profit or loss and recognised in ‘Other operating income’. Interest income from these financial assets is included in ‘Interest and similar income’ using the effective interest rate method. – FVTPL – Financial assets that do not meet the criteria for amortised cost or FVOCI are measured at FVTPL. A gain or loss on a debt instrument that is subsequently measured at FVTPL, including any debt instruments designated at fair value, is recognised in profit or loss and presented in the income statement in ‘Other operating income’ in the period in which it arises. The Santander UK group reclassifies financial assets when and only when its business model for managing those assets changes. The reclassification takes place from the start of the first reporting period following the change. Such changes are expected to be very infrequent. Financial assets: equity instruments Equity instruments are instruments that meet the definition of equity from the issuer’s perspective, being instruments that do not contain a contractual obligation to pay cash and that evidence a residual interest in the issuer’s net assets. All equity investments are subsequently measured at FVTPL; management may elect, at initial recognition, to irrevocably designate an equity investment at FVOCI but has not currently done so. When this election is used, fair value gains and losses are recognised in OCI and are not subsequently reclassified to profit or loss, including on disposal. ECLs (and reversal of ECLs) are not reported separately from other changes in fair value. Dividends, when representing a return on such investments, continue to be recognised in profit or loss as other income when the right to receive payments is established. Gains and losses on equity investments at FVTPL are included in ‘Other operating income’ in the income statement. Financial liabilities Financial liabilities, which include deposits by banks, deposits by customers, debt securities in issue and subordinated liabilities, are classified as subsequently measured at amortised cost, except for: – Financial liabilities at FVTPL (see Note 22 ): this classification is applied to derivatives and other financial liabilities designated as such at initial recognition. Gains or losses on financial liabilities designated at FVTPL are presented partially in other comprehensive income (the amount of change in the fair value of the financial liability that is attributable to changes in the credit risk of that liability) and partially in profit or loss (the remaining amount of change in the fair value of the liability) – Financial liabilities arising from the transfer of financial assets which did not qualify for derecognition, whereby a financial liability is recognised for the consideration received for the transfer. In subsequent periods, the Santander UK group recognises any expense incurred on the financial liability, and – Financial guarantee contracts and loan commitments. Preference shares which carry a contractual obligation to transfer economic benefits are classified as financial liabilities and are presented in subordinated liabilities. The coupon on these preference shares is recognised in the income statement as interest expense on an amortised cost basis using the effective interest method. Contracts involving the receipt of cash on which customers receive an index-linked return are accounted for as equity index-linked deposits. The principal products are Capital Guaranteed/Protected Products which give the customers a limited participation in the upside growth of an equity index. In the event the index falls in price, a cash principal element is guaranteed/protected. The equity index-linked deposits contain embedded derivatives. These embedded derivatives, in combination with the principal cash deposit element, are designed to replicate the investment performance profile tailored to the return agreed in the contracts with customers. The cash principal element is accounted for as deposits by customers at amortised cost. The embedded derivatives are separated from the host instrument and are separately accounted for as derivatives. Sale and repurchase agreements (including stock borrowing and lending) Securities sold subject to a commitment to repurchase them at a predetermined price (repos) under which substantially all the risks and rewards of ownership are retained by the Santander UK group remain on the balance sheet and a liability is recorded in respect of the consideration received. Securities purchased under commitments to resell (reverse repos) are not recognised on the balance sheet and the consideration paid is recorded as an asset. The difference between the sale and repurchase price is treated as trading income in the income statement, except where the repo is not treated as part of the trading book, in which case the difference is recorded in interest income or expense. Securities lending and borrowing transactions are generally secured, with collateral in the form of securities or cash advanced or received. Securities borrowed are not reflected on the balance sheet. Collateral in the form of cash received or advanced is recorded as a deposit or a loan. Collateral in the form of securities is not recognised. Day One profit adjustments The fair value of a financial instrument on initial recognition is generally its transaction price (that is, the fair value of the consideration given or received). However, sometimes the fair value will be based on other observable current market transactions in the same instrument, without modification or repackaging, or on a valuation technique whose variables include only data from observable markets, such as interest rate yield curves, option volatilities and currency rates. When such evidence exists, the Santander UK group recognises a trading gain or loss at inception (Day One gain or loss), being the difference between the transaction price and the fair value. When significant unobservable parameters are used, the entire Day One gain or loss is deferred and is recognised in the income statement over the life of the transaction until the transaction matures, is closed out, the valuation inputs become observable, or an offsetting transaction is entered into. ii) Impairment of debt instrument financial assets The Santander UK group assesses on a forward-looking basis the ECL associated with its debt instrument assets carried at amortised cost and FVOCI and with the exposure arising from financial guarantee contracts and loan commitments. The Santander UK group recognises a loss allowance for such losses at each reporting date. The measurement of ECL reflects: – An unbiased and probability-weighted amount that is determined by evaluating a range of possible outcomes. – The time value of money, and – Reasonable and supportable information that is available without undue cost or effort at the reporting date about past events, current conditions and forecasts of future economic conditions. Grouping of instruments for losses measured on a collective basis We typically group instruments and assess them for impairment collectively where they share risk characteristics (as described in the Credit risk section of the Risk review) using one or more statistical models. Where we have used internal capital or similar models as the basis for our ECL models, this typically results in a large number of relatively small homogenous groups which are determined by the permutations of the underlying characteristics in the statistical models. We calculate separate collective provisions for instruments in Stages 1, 2 and 3 where the instrument is not individually assessed, as described below. Individually assessed impairments (IAIs) We assess significant Stage 3 cases individually. We do this for Corporate & Commercial Banking cases, but not for Business Banking cases in Retail & Business Banking which we assess collectively. To calculate the estimated loss, we estimate the future cash flows under several scenarios each of which uses case-specific factors and circumstances. We then probability-weight the net present value of the cash flows under each scenario to arrive at a weighted average provision requirement. We update our assessment process every quarter and more frequently if there are changes in circumstances that might affect the scenarios, cash flows or probabilities we apply. For more on how ECL is calculated, see the Credit risk section of the Risk review. – Write-off For secured loans, a write-off is only made when all collection procedures have been exhausted and the security has been sold and/or a claim made on any mortgage indemnity guarantee or other insurance. In the corporate loan portfolio, there may be occasions where a write-off occurs for other reasons, such as following a consensual restructure or refinancing of the debt or where the debt is sold for strategic reasons into the secondary market at a value lower than its face value. There is no threshold based on past due status beyond which all secured loans are written off as there can be significant variations in the time needed to enforce possession and sale of the security, especially due to the different legal frameworks that apply in different regions of the UK. For unsecured loans, a write-off is only made when all internal avenues of collecting the debt have been exhausted. Where appropriate the debt is passed over to external collection agencies. A past due threshold is applied to unsecured debt where accounts that are 180 days past due are written off unless there is a dispute awaiting resolution. Contact is made with customers with the aim to achieve a realistic and sustainable repayment arrangement. Litigation and/or enforcement of security is usually carried out only when the steps described above have been undertaken without success. All write-offs are assessed / made on a case-by-case basis, taking account of the exposure at the date of write-off, after accounting for the value from any collateral or insurance held against the loan. The exception to this is in cases where fraud has occurred, where the exposure is written off once investigations have been completed and the probability of recovery is minimal. The time span between discovery and write-off will be short and may not result in an impairment loss allowance being raised. The write-off policy is regularly reviewed. Write-offs are charged against previously established loss allowances. – Recoveries Recoveries of credit impairment charges are not included in the impairment loss allowance but are taken to income and offset against credit impairment charges. Recoveries of credit impairment charges are classified in the income statement as ‘Credit impairment charges’. iii) Modifications of financial assets The treatment of a renegotiation or modification of the contractual cash flows of a financial asset normally depends upon whether the renegotiation or modification is due to financial difficulties of the borrower or for other commercial reasons. – Contractual modifications due to financial difficulties of the borrower: where the Santander UK group modifies the contractual conditions to enable the borrower to fulfil their payment obligations, the asset is not derecognised. The gross carrying amount of the financial asset is recalculated as the present value of the renegotiated/modified contractual cash flows that are discounted at the financial asset’s original EIR and any gain or loss arising from the modification is recognised in the income statement. – Contractual modifications for other commercial reasons: an assessment is performed to determine whether the terms of the new agreement are substantially different from the terms of the existing agreement, after considering changes in the cash flows arising from the modified terms and the overall instrument risk profile. Where terms are substantially different, such modifications are treated as a new transaction resulting in derecognition of the original financial asset, and the recognition of a ‘new’ financial asset with any difference between the carrying amount of the derecognised asset and the fair value of the new asset is recognised in the income statement as a gain or loss on derecognition. Where terms are not substantially different, the carrying value of the financial asset is adjusted to reflect the present value of modified cash flows discounted at the original EIR with any gain or loss arising from modification recognised immediately in the income statement. Any other contractual modifications, such as where a regulatory authority imposes a change in certain contractual terms or due to legal reasons, are assessed on a case-by-case basis to establish whether or not the financial asset should be derecognised. For IBOR reform see Note 41 . iv) Derecognition other than on a modification Financial assets are derecognised when the rights to receive cash flows have expired or the Santander UK group has transferred its contractual right to receive the cash flows from the assets and either: (1) substantially all the risks and rewards of ownership have been transferred; or (2) the Santander UK group has neither retained nor transferred substantially all of the risks and rewards but has transferred control. Financial liabilities are derecognised when extinguished, cancelled or expired. c) Financial guarantee contracts and loan commitments Financial guarantee contracts are contracts that require the issuer to make specified payments to reimburse the holder for a loss it incurs because a specified debtor fails to make payments when due, in accordance with the terms of a debt instrument. Such financial guarantees are given to banks, financial institutions and others on behalf of customers to secure loans, overdrafts and other banking facilities. Financial guarantee contracts are initially measured at fair value and subsequently measured at the higher of the amount of the loss allowance, and the premium received on initial recognition less income recognised in accordance with the principles of IFRS 15. Loan commitments are measured as the amount of the loss allowance (determined in accordance with IFRS 9 as described in Credit risk section of the Risk review). The Santander UK group has not provided any commitment to provide loans at a below-market interest rate, or that can be settled net in cash or by delivering or issuing another financial instrument. For financial guarantee contracts and loan commitments, the loss allowance is recognised as a provision and charged to credit impairment charges in the income statement. The loss allowance in respect of revolving facilities is classified in loans and advances to customers to the extent of any drawn balances. The loss allowance in respect of undrawn amounts is classified in provisions. When amounts are drawn, any related loss allowance is transferred from provisions to loans and advances to customers.
Derivative financial instruments (derivatives)	Derivative financial instruments (derivatives) Derivatives are contracts or agreements whose value is derived from one or more underlying indices or asset values inherent in the contract or agreement, which require no or little initial net investment and are settled at a future date. Transactions are undertaken in interest rate, cross currency, equity, residential property and other index-related swaps, forwards, caps, floors, swaptions, as well as credit default and total return swaps, equity index contracts and exchange traded interest rate futures, and equity index options. Derivatives are held for risk management purposes. Derivatives are classified as held for trading unless they are designated as being in a hedge accounting relationship. The Santander UK group chooses to designate certain derivatives as in a hedging relationship if they meet specific criteria, as further described in ‘Hedge accounting’ below. Derivatives are recognised initially (on the date on which a derivative contract is entered into), and are subsequently remeasured, at their fair value. Fair values of exchange-traded derivatives are obtained from quoted market prices. Fair values of over-the-counter derivatives are estimated using valuation techniques, including discounted cash flow and option pricing models. Certain derivatives may be embedded in hybrid contracts. If the hybrid contract contains a host that is a financial asset, then the Santander UK group assesses the entire contract as described in the financial asset section above for classification and measurement purposes. Otherwise, embedded derivatives are treated as separate derivatives when their economic characteristics and risks are not closely related to those of the host contract; the terms of the embedded derivative would meet the definition of a stand-alone derivative if they were contained in a separate contract; and the combined contract is not held for trading or designated at fair value. These embedded derivatives are measured at fair value with changes in fair value recognised in the income statement. Contracts containing embedded derivatives are not subsequently reassessed for separation unless either there has been a change in the terms of the contract which significantly modifies the cash flows (in which case the contract is reassessed at the time of modification) or the contract has been reclassified (in which case the contract is reassessed at the time of reclassification). All derivatives are carried as assets when their fair value is positive and as liabilities when their fair value is negative, except where netting is permitted. The method of recognising fair value gains and losses depends on whether derivatives are held for trading or are designated as hedging instruments and, if the latter, the nature of the risks being hedged. Gains and losses from changes in the fair value of derivatives held for trading are recognised in the income statement and included in Other operating income.
Offsetting financial assets and liabilities	Offsetting financial assets and liabilities Financial assets and liabilities including derivatives are offset and the net amount reported in the balance sheet when there is a legally enforceable right to set off the recognised amounts and there is an intention to settle on a net basis or realise the asset and settle the liability simultaneously. The Santander UK group is party to a number of arrangements, including master netting arrangements under industry standard agreements which facilitate netting of transactions in jurisdictions where netting agreements are recognised and have legal force. These netting arrangements do not generally result in an offset of balance sheet assets and liabilities for accounting purposes, as transactions are usually settled on a gross basis.
Hedge accounting	Hedge accounting The Santander UK group applies hedge accounting to represent, to the maximum possible extent permitted under accounting standards, the economic effects of its risk management strategies. Derivatives are used to hedge exposures to interest rates , exchange rates and equity prices . At the time a financial instrument is designated as a hedge (i.e. at the inception of the hedge), the Santander UK group formally documents the relationship between the hedging instrument(s) and hedged item(s), its risk management objective and strategy for undertaking the hedge. The documentation includes the identification of each hedging instrument and respective hedged item, the nature of the risk being hedged (including the benchmark interest rate being hedged in a hedge of interest rate risk) and how the hedging instrument’s effectiveness in offsetting the exposure to changes in the hedged item’s fair value attributable to the hedged risk is to be assessed. Accordingly, the Santander UK group formally assesses, both at the inception of the hedge and on an ongoing basis, whether the hedging derivatives have been and will be highly effective in offsetting changes in the fair value attributable to the hedged risk during the period that the hedge is designated. A hedge is normally regarded as highly effective if, at inception and throughout its life, the Santander UK group can expect, and actual results indicate, that changes in the fair value or cash flow of the hedged items are effectively offset by changes in the fair value or cash flow of the hedging instrument. If at any point it is concluded that it is no longer highly effective in achieving its documented objective, hedge accounting is discontinued. Where derivatives are held for risk management purposes, and when transactions meet the required criteria for documentation and hedge effectiveness, the derivatives may be designated as either: (i) hedges of the change in fair value of recognised assets or liabilities or firm commitments (fair value hedges); (ii) hedges of the variability in highly probable future cash flows attributable to a recognised asset or liability, or a forecast transaction (cash flow hedges); or (iii) a hedge of a net investment in a foreign operation (net investment hedges). The Santander UK group applies fair value and cash flow hedge accounting, but not hedging of a net investment in a foreign operation. a) Fair value hedge accounting Changes in the fair value of derivatives that are designated and qualify as fair value hedges are recorded in the income statement, together with the changes in the fair value of the hedged asset or liability that are attributable to the hedged risk. Where the hedged item is measured at amortised cost, the fair value changes due to the hedged risk adjust the carrying amount of the hedged asset or liability. Changes in the fair value of portfolio hedged items are presented separately in the consolidated balance sheet in macro hedge of interest rate risk and recognised in the income statement. If the hedge no longer meets the criteria for hedge accounting, changes in the fair value of the hedged item attributable to the hedged risk are no longer recognised in the income statement. For fair value hedges of interest rate risk, the cumulative adjustment that has been made to the carrying amount of the hedged item is amortised to the income statement using the effective interest method over the period to maturity. For portfolio hedged items, the cumulative adjustment is amortised to the income statement using the straight-line method over the period to maturity. b) Cash flow hedge accounting The effective portion of changes in the fair value of qualifying cash flow hedges is recognised in other comprehensive income in the cash flow hedging reserve. The gain or loss relating to the ineffective portion is recognised immediately in the income statement. Amounts accumulated in equity are reclassified to the income statement in the periods in which the hedged item affects profit or loss. When a hedging instrument expires or is sold, or when a hedge no longer meets the criteria for hedge accounting, any cumulative gain or loss existing in equity at that time remains in equity and is recognised in the income statement when the forecast transaction is ultimately recognised in the income statement. When a forecast transaction is no longer expected to occur, the cumulative gain or loss that was reported in equity is immediately transferred to the income statement. The Santander UK group is exposed to cash flow interest rate risk on its floating rate assets, foreign currency risk on its fixed rate debt issuances denominated in foreign currency and equity price risk arises from the Santander UK group operating the Employee Sharesave scheme. Cash flow hedging is used to hedge the variability in cash flows arising from these risks.
Securitisation transactions	Securitisation transactions The Santander UK group has entered into arrangements where undertakings have issued mortgage-backed and other asset-backed securities or have entered into funding arrangements with lenders in order to finance specific loans and advances to customers. The Santander UK group has also entered into synthetic securitisation arrangements, as part of significant risk transfer (SRT) transactions to reduce its risk-weighted assets, where undertakings have issued credit-linked notes, and in some cases deposited the funds raised as collateral, for credit protection in respect of specific loans and advances to customers. As the Santander UK group has retained substantially all the risks and rewards of the underlying assets, such financial instruments continue to be recognised on the balance sheet, and a liability recognised for the proceeds of the funding transaction, or in the case of SRT transactions, collateral deposited.
Impairment of non-financial assets	Impairment of non-financial assets At each balance sheet date, or more frequently when events or changes in circumstances dictate, property plant and equipment (including operating lease assets) and intangible assets (including goodwill) are assessed for indicators of impairment. If indications are present, these assets are subject to an impairment review. The impairment review comprises a comparison of the carrying value of the asset or cash generating unit with its recoverable amount: the higher of the asset’s or cash-generating unit’s fair value less costs to sell and its value in use. The cash-generating unit represents the lowest level at which non-financial assets, including goodwill, are monitored for internal management purposes and is not larger than an operating segment. The fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Value in use is calculated by discounting management’s expected future cash flows obtainable as a result of the asset’s continued use (after making allowance for increases in regulatory capital requirements), including those resulting from its ultimate disposal, at a market-based discount rate on a pre- tax basis. The recoverable amounts of goodwill have been based on value in use calculations. For conducting goodwill impairment reviews, cash generating units are the lowest level at which management monitors the return on investment on assets.
Leases (as lessor)	Leases (as lessor) Operating lease assets are recorded at cost and the difference between cost and residual value (RV) is depreciated over the life of the asset. Operating lease rental income and depreciation is recognised on a straight-line basis over the life of the asset. After initial recognition, residual values are reviewed regularly, and any changes are recognised prospectively through remaining depreciation charges. Amounts due from lessees under finance leases and hire purchase contracts are recorded as receivables at the amount of the Santander UK group’s net investment in the leases. Finance lease income is allocated to accounting periods to reflect a constant periodic rate of return on the Santander UK group’s net investment outstanding in respect of the leases and hire purchase contracts. A provision is recognised to reflect a reduction in any anticipated unguaranteed RV. A provision is also recognised for voluntary termination of the contract by the customer, where appropriate.
Income taxes, including deferred taxes	Income taxes, including deferred taxes The tax expense represents the sum of the income tax currently payable and deferred income tax. A current tax liability for the current or prior period is measured at the amount expected to be paid to the tax authorities. Where the amount of the final tax liability is uncertain or where a position is challenged by a taxation authority, the liability recognised is the most likely outcome. Where a most likely outcome cannot be determined, a weighted average basis is applied. Deferred tax is calculated at the tax rates that are expected to apply in the period when the liability is settled, or the asset is realised based on rates enacted or substantively enacted at the balance sheet date. Deferred tax is charged or credited in the income statement, except when it relates to items recognised in other comprehensive income or directly in equity, in which case the deferred tax is also recognised in other comprehensive income or directly in equity. Deferred and current tax assets and liabilities are only offset when they arise in the same tax reporting group and where there is both the legal right and the intention to settle on a net basis or to realise the asset and settle the liability simultaneously.
Cash and cash equivalents	Cash and cash equivalents For the purposes of the cash flow statement, cash and cash equivalents comprise balances with less than three months maturity from the date of acquisition, including cash and non-restricted balances with central banks, treasury bills and other eligible bills, loans and advances to banks, reverse repurchase agreements and short-term investments in securities. Balances with central banks represent amounts held at the Bank of England as part of the Santander UK group’s liquidity management activities. It includes certain minimum cash ratio deposits held for regulatory purposes and reserves collateralised accounts in respect of Santander UK’s participation in certain payments schemes which are required to be maintained with the Bank of England and are restricted balances.
Provisions and contingent liabilities	Provisions and contingent liabilities (see 'Critical judgements and accounting estimates') Provisions are recognised for present obligations arising as consequences of past events where it is more likely than not that a transfer of economic benefits will be necessary to settle the obligation, and it can be reliably estimated. Customer remediation provisions are made for the estimated cost of making redress payments with respect to the past sales of products, using conclusions such as the number of claims the number of those that will be upheld, the estimated average settlement per case and other related costs. Provision is made for the anticipated cost of restructuring, including redundancy costs, when an obligation exists. An obligation exists when the Santander UK group has a detailed formal plan for restructuring a business, has raised valid expectations in those affected by the restructuring, and has started to implement the plan or announce its main features. When a leasehold property ceases to be used in the business, provision is made where the unavoidable costs of the future obligations relating to the lease are expected to exceed anticipated rental income. The net costs are discounted using market rates of interest to reflect the long-term nature of the cash flows. Loan commitments are measured as the amount of the loss allowance, determined in line with IFRS 9 as set out in the Credit risk section of the Risk review. Contingent liabilities are possible obligations whose existence will be confirmed only by certain future events or present obligations where the transfer of economic benefit is uncertain or cannot be reliably measured. Contingent liabilities are not recognised but are disclosed unless they are remote.
Critical judgements and accounting estimates	Critical judgements and accounting estimates The preparation of Santander UK's consolidated financial statements in accordance with IFRS requires management to make judgements and assumptions in applying the accounting policies that affect the reported amounts of assets, liabilities, income and expenses. Due to the inherent uncertainty in making estimates, actual results reported in future periods may be based on amounts which differ from those estimates. Estimates, judgements and assumptions are continually evaluated and are based on historical experience and other factors, including expectations of future events that are believed to be reasonable under the circumstances. There has been no change in the inherent sensitivity of the areas of judgement in the period. Management have considered the impact of developments in principal risks and uncertainties, as set out in the Risk review, on critical judgements and accounting estimates. The significant judgements, apart from those involving estimation, made by management in applying Santander UK's accounting policies in these financial statements (key judgements) and the key sources of estimation uncertainty that may have a significant risk of causing a material adjustment to the carrying amount of assets and liabilities within the next financial year (key estimates), which together are considered critical to Santander UK's results and financial position, are as follows: a) Credit impairment charges The application of the ECL impairment methodology for calculating credit impairment allowances is highly susceptible to change from period to period. The methodology requires management to make judgmental assumptions in determining the estimates. Any significant difference between the estimated amounts and actual amounts could have a material impact on the future financial results and financial condition. The impact of the cost of living crisis has increased the uncertainty around ECL impairment calculations and has required management to make additional judgements and accounting estimates that affect the amount of assets and liabilities at the reporting date and the amount of income and expenses in the reporting period. The key additional judgements due to the impact of the cost of living crisis mainly reflect the increased uncertainty around forward-looking economic data and the need for additional judgemental adjustments. Key judgements – Determining an appropriate definition of default – Establishing the criteria for a significant increase in credit risk (SICR) and, for corporate borrowers, internal credit risk rating – Determining the need for any judgemental adjustments – Determining the need to assess corporate Stage 3 exposures individually Key estimates – Forward-looking multiple economic scenario assumptions – Probability weights assigned to multiple economic scenarios For more on each of these key judgements and estimates, see 'Critical judgements and accounting estimates applied in calculating ECL' in the ‘Credit risk – credit risk management’ section of the Risk review. Sensitivity of ECL allowance For detailed disclosures, see 'Sensitivity of ECL allowance' in the ‘Credit risk – credit risk management’ section of the Risk review. b) Provisions and contingent liabilities Key judgements – Determining whether a present obligation exists – Determining the likely outcome of future legal decisions Key estimates – Probability, timing, nature and amount of any outflows that may arise from past events Included in Litigation and other regulatory provisions in Note 29 are amounts in respect of management’s best estimates of liability relating to a legal dispute regarding allocation of responsibility for a specific PPI portfolio of complaints. Note 31 provides disclosure relating to ongoing factual issues and reviews that could impact the timing and amount of any outflows. Note 31 includes disclosure relating to an investigation in relation to the historical involvement of Santander UK plc, Santander Financial Services plc and Cater Allen International Limited (all subsidiaries of Santander UK Group Holdings plc) in German dividend tax arbitrage transactions. It also includes disclosure relating to the historical use of discretionary commission arrangements in Santander Consumer (UK) plc. These judgements are based on the specific facts available and often require specialist professional advice. There can be a wide range of possible outcomes and uncertainties, particularly in relation to legal actions, and regulatory and consumer credit matters. As a result, it is often not possible to make reliable estimates of the likelihood and amount of any potential outflows, or to calculate any resulting sensitivities. For more on these key judgements and estimates, see Notes 29 and 31 . c) Pensions The Santander UK group operates a number of defined benefit pension schemes as described in Note 30 and estimates their position as described in the accounting policy ‘Pensions and other post retirement benefits’. Key judgements – Setting the criteria for constructing the corporate bond yield curve used to determine the discount rate – Determining the methodology for setting the inflation assumption Key estimates – Discount rate applied to future cash flows – Rate of price inflation – Expected lifetime of the schemes' members – Valuation of pension fund assets whose values are not based on market observable data For more on each of these key judgements and estimates, see Note 30 . Sensitivity of defined benefit pension scheme estimates For detailed disclosures, see ‘Actuarial assumption sensitivities’ in Note 30 . The Scheme is invested in certain assets whose values are not based on market observable data, such as investments in private equity funds and property. Due diligence has been conducted to support the values obtained in respect of these assets are appropriate and represent fair value. Given the nature of these investments, we are unable to prepare sensitivities on how their values could vary as market conditions or other variables change. d) Goodwill The carrying amount of goodwill is based on the application of judgements including the basis of goodwill impairment calculation assumptions. Santander UK undertakes an annual assessment to evaluate whether the carrying amount of goodwill is impaired, carrying out this assessment more frequently if reviews identify indicators of impairment or when events or changes in circumstances dictate. Key judgements: – Determining the basis of goodwill impairment testing and the methodology for determining the carrying value of CGUs, including the need for planning assumptions and internal capital allocations Key estimates: – Forecast cash flows for cash generating units, including estimated allocations of regulatory capital – Growth rate beyond initial cash flow projections – Discount rates which factor in risk-free rates and applicable risk premiums All of these variables are subject to fluctuations in external market rates and economic conditions beyond management’s control Santander UK Group undertakes an annual assessment to evaluate whether the carrying amount of goodwill is impaired, carrying out this assessment more frequently if reviews identify indicators of impairment or when events or changes in circumstances dictate. The estimation of future cash flows and the level to which they are discounted is inherently uncertain and requires significant judgement and is subject to potential change over time. For more on each of these key judgements and estimates, see Note 20 . Sensitivity of goodwill For detailed disclosures, see ‘Sensitivities of key assumptions in calculating VIU’ in Note 20 .
Segmentation of business	The segmental data is prepared on a statutory basis of accounting, in line with the accounting policies set out in Note 1 . Transactions between segments are on normal commercial terms and conditions. Internal charges and internal UK transfer pricing adjustments are reflected in the results of each segment, and eliminate on consolidation. Revenue sharing agreements are used to allocate external customer revenues to a segment on a reasonable basis. Funds are ordinarily reallocated between segments, resulting in funding cost transfers disclosed in operating income. Interest charged for these funds is based on Santander UK’s cost of wholesale funding. Interest income and interest expense have not been reported separately. The majority of segment revenues are interest income in nature and net interest income is relied on primarily to assess segment performance and to make decisions on the allocation of segment resources.

Accounting Policies - Parent (P

Accounting Policies - Parent (Policies)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Significant Accounting Policies [Line Items]
Basis of preparation and accounting developments	Basis of preparation These financial statements incorporate the financial statements of the Company and entities it controls (its subsidiaries) made up to 31 December each year. The consolidated financial statements have been prepared on the going concern basis using the historical cost convention, except for financial assets and liabilities that have been measured at fair value. An assessment of the appropriateness of the adoption of the going concern basis of accounting is disclosed in the statement of going concern in the Directors’ report. Compliance with International Financial Reporting Standards (IFRS) The consolidated financial statements of the Santander UK group and the separate financial statements of the Company comply with UK-adopted International Accounting Standards (IAS). The financial statements are also prepared in accordance with IFRS as issued by the International Accounting Standards Board (IASB), including interpretations issued by the IFRS Interpretations Committee, as there are no applicable differences from IFRS as issued by the IASB for the periods presented. Disclosures required by IFRS 7 ‘Financial Instruments: Disclosure’ relating to the nature and extent of risks arising from financial instruments, and IAS 1 ‘Presentation of Financial Statements’ relating to objectives, policies and processes for managing capital, have been included in the Risk review section of this Annual Report. This information forms an integral part of these financial statements by this cross reference, is marked as audited, and is covered by the Independent auditors' report. Climate change Santander UK continues to develop its assessment of the potential impacts that climate change and the transition to a low carbon economy may have on the assets and liabilities recognised and presented in its financial statements. Santander UK is mindful of its responsibilities as a responsible lender and is focused on ways to meet the objectives of the Paris Agreement on climate change and to support the UK’s transition to a climate-resilient, net zero economy. Santander UK's current climate change strategy focuses on three main areas to achieve Banco Santander's ambition to reach net zero emissions by 2050: 1. Managing climate risks by integrating climate considerations into risk management frameworks, screening and stress testing our portfolio for climate related financial risks, and setting risk appetites to help steer our portfolio in line with the Paris Agreement, 2. Supporting our customers’ transition by developing products and services that promote a reduction in CO 2 emissions, and 3. Reducing emissions in our operations and supply chain by focusing on continuous improvement in our operations, and environmental and energy management systems in accordance with ISO14001 and 15001, promoting responsible procurement practices and employee engagement. Santander UK's current climate change strategy and its view of the risks associated with climate change and the transition to a low carbon economy are reflected in its critical judgements and accounting estimates, although climate change risk did not have a material impact at 31 December 2023 and 2022, consistent with management's assessment that climate change and the transition to a low carbon economy are not currently expected to have a meaningful impact on the viability of the Santander UK group in the medium term. At 31 December 2023 and 2022, management specifically considered the potential impact of climate change and the transition to a low carbon economy on: – Loans and advances to customers ( see Note 13 and the credit risk section of the Risk review). Some climate change risks arise due to the requirements of IFRS 9 and others relate to specific portfolios and sectors: – ECL calculations are based on multiple forward-looking economic scenarios developed by management covering a period of 5 years , during which timeframe climate change risks may crystallise; – For mortgages in Retail & Business Banking and commercial real estate lending in Corporate & Commercial Banking, the value of property collateral might be affected by physical impacts related to the frequency and scale of extreme weather events, such as flood and subsidence risk, or changing environmental performance standards for property. – For automotive loans in Consumer Finance, the residual value of automotive vehicles might be impacted by diesel obsolescence and the transition to electric vehicles. – For corporate lending in Corporate & Commercial Banking, certain sectors give rise to fossil fuel exposures, such as Oil & Gas, Mining & Extraction and Power Generation. – Goodwill impairment assessment (see Note 20). Estimates underpinning the determination of whether or not goodwill balances are impaired are partly based on forecast business performance beyond the time horizon for management's detailed plans. Future changes to Santander UK's climate change strategy may impact Santander UK's critical judgements and accounting estimates and result in material changes to financial results and the carrying values of certain assets and liabilities in future reporting periods. Future accounting developments At 31 December 2023 , for the Santander UK group, there were no significant new or revised standards and interpretations, and amendments thereto, which have been issued but which are not yet effective, or which have otherwise not been early adopted where permitted. Comparative information As required by US public company reporting requirements, these financial statements include two years of comparative information for the consolidated income statement, consolidated statement of comprehensive income, consolidated statement of changes in equity, consolidated statement of cash flows and related notes. Material accounting policy information The following material accounting policies have been applied in preparing these financial statements. For material accounting policies which involve the application of judgements or accounting estimates that are determined to be critical to the preparation of these financial statements see 'Critical judgements and accounting estimates'. Compliance with International Financial Reporting Standards The Company’s financial statements comply with UK-adopted international accounting standards. The financial statements are also prepared in accordance with International Financial Reporting Standards (IFRSs) as issued by the International Accounting Standards Board (IASB), including interpretations issued by the IFRS Interpretations Committee, as there are no applicable differences from IFRSs as issued by the IASB for the periods presented. Climate change Management specifically also considered the potential impact of climate change and the transition to a low carbon economy on its Investment in Santander UK plc. Estimates underpinning the determination of whether or not the cost of the investment is impaired are partly based on forecast business performance beyond
Critical judgements and accounting estimates	Critical judgements and accounting estimates The preparation of Santander UK's consolidated financial statements in accordance with IFRS requires management to make judgements and assumptions in applying the accounting policies that affect the reported amounts of assets, liabilities, income and expenses. Due to the inherent uncertainty in making estimates, actual results reported in future periods may be based on amounts which differ from those estimates. Estimates, judgements and assumptions are continually evaluated and are based on historical experience and other factors, including expectations of future events that are believed to be reasonable under the circumstances. There has been no change in the inherent sensitivity of the areas of judgement in the period. Management have considered the impact of developments in principal risks and uncertainties, as set out in the Risk review, on critical judgements and accounting estimates. The significant judgements, apart from those involving estimation, made by management in applying Santander UK's accounting policies in these financial statements (key judgements) and the key sources of estimation uncertainty that may have a significant risk of causing a material adjustment to the carrying amount of assets and liabilities within the next financial year (key estimates), which together are considered critical to Santander UK's results and financial position, are as follows: a) Credit impairment charges The application of the ECL impairment methodology for calculating credit impairment allowances is highly susceptible to change from period to period. The methodology requires management to make judgmental assumptions in determining the estimates. Any significant difference between the estimated amounts and actual amounts could have a material impact on the future financial results and financial condition. The impact of the cost of living crisis has increased the uncertainty around ECL impairment calculations and has required management to make additional judgements and accounting estimates that affect the amount of assets and liabilities at the reporting date and the amount of income and expenses in the reporting period. The key additional judgements due to the impact of the cost of living crisis mainly reflect the increased uncertainty around forward-looking economic data and the need for additional judgemental adjustments. Key judgements – Determining an appropriate definition of default – Establishing the criteria for a significant increase in credit risk (SICR) and, for corporate borrowers, internal credit risk rating – Determining the need for any judgemental adjustments – Determining the need to assess corporate Stage 3 exposures individually Key estimates – Forward-looking multiple economic scenario assumptions – Probability weights assigned to multiple economic scenarios For more on each of these key judgements and estimates, see 'Critical judgements and accounting estimates applied in calculating ECL' in the ‘Credit risk – credit risk management’ section of the Risk review. Sensitivity of ECL allowance For detailed disclosures, see 'Sensitivity of ECL allowance' in the ‘Credit risk – credit risk management’ section of the Risk review. b) Provisions and contingent liabilities Key judgements – Determining whether a present obligation exists – Determining the likely outcome of future legal decisions Key estimates – Probability, timing, nature and amount of any outflows that may arise from past events Included in Litigation and other regulatory provisions in Note 29 are amounts in respect of management’s best estimates of liability relating to a legal dispute regarding allocation of responsibility for a specific PPI portfolio of complaints. Note 31 provides disclosure relating to ongoing factual issues and reviews that could impact the timing and amount of any outflows. Note 31 includes disclosure relating to an investigation in relation to the historical involvement of Santander UK plc, Santander Financial Services plc and Cater Allen International Limited (all subsidiaries of Santander UK Group Holdings plc) in German dividend tax arbitrage transactions. It also includes disclosure relating to the historical use of discretionary commission arrangements in Santander Consumer (UK) plc. These judgements are based on the specific facts available and often require specialist professional advice. There can be a wide range of possible outcomes and uncertainties, particularly in relation to legal actions, and regulatory and consumer credit matters. As a result, it is often not possible to make reliable estimates of the likelihood and amount of any potential outflows, or to calculate any resulting sensitivities. For more on these key judgements and estimates, see Notes 29 and 31 . c) Pensions The Santander UK group operates a number of defined benefit pension schemes as described in Note 30 and estimates their position as described in the accounting policy ‘Pensions and other post retirement benefits’. Key judgements – Setting the criteria for constructing the corporate bond yield curve used to determine the discount rate – Determining the methodology for setting the inflation assumption Key estimates – Discount rate applied to future cash flows – Rate of price inflation – Expected lifetime of the schemes' members – Valuation of pension fund assets whose values are not based on market observable data For more on each of these key judgements and estimates, see Note 30 . Sensitivity of defined benefit pension scheme estimates For detailed disclosures, see ‘Actuarial assumption sensitivities’ in Note 30 . The Scheme is invested in certain assets whose values are not based on market observable data, such as investments in private equity funds and property. Due diligence has been conducted to support the values obtained in respect of these assets are appropriate and represent fair value. Given the nature of these investments, we are unable to prepare sensitivities on how their values could vary as market conditions or other variables change. d) Goodwill The carrying amount of goodwill is based on the application of judgements including the basis of goodwill impairment calculation assumptions. Santander UK undertakes an annual assessment to evaluate whether the carrying amount of goodwill is impaired, carrying out this assessment more frequently if reviews identify indicators of impairment or when events or changes in circumstances dictate. Key judgements: – Determining the basis of goodwill impairment testing and the methodology for determining the carrying value of CGUs, including the need for planning assumptions and internal capital allocations Key estimates: – Forecast cash flows for cash generating units, including estimated allocations of regulatory capital – Growth rate beyond initial cash flow projections – Discount rates which factor in risk-free rates and applicable risk premiums All of these variables are subject to fluctuations in external market rates and economic conditions beyond management’s control Santander UK Group undertakes an annual assessment to evaluate whether the carrying amount of goodwill is impaired, carrying out this assessment more frequently if reviews identify indicators of impairment or when events or changes in circumstances dictate. The estimation of future cash flows and the level to which they are discounted is inherently uncertain and requires significant judgement and is subject to potential change over time. For more on each of these key judgements and estimates, see Note 20 . Sensitivity of goodwill For detailed disclosures, see ‘Sensitivities of key assumptions in calculating VIU’ in Note 20 .
Santander UK Group Holdings plc
Disclosure Of Significant Accounting Policies [Line Items]
Critical judgements and accounting estimates	Critical judgements and accounting estimates The preparation of the financial statements requires management to make judgements and accounting estimates that affect the reported amount of assets and liabilities at the date of the financial statements and the reported amount of income and expenses during the reporting period. Management evaluates its judgements and accounting estimates, which are based on historical experience and on various other factors that are believed to be reasonable under the circumstances, on an ongoing basis. Actual results may differ from these accounting estimates under different assumptions or conditions. In preparing the financial statements, no significant judgements have been made in the process of applying the accounting policies, other than those involving estimations about interests in other entities. Interests in other entities - Investment in subsidiaries The carrying amount of investments in subsidiaries is based on the application of judgements including the basis of the cost of investment impairment calculation assumptions. Santander UK undertakes an annual assessment to evaluate whether the carrying amount of investments in subsidiaries is impaired, carrying out this assessment more frequently if reviews identify indicators of impairment or when events or changes in circumstances dictate. Key judgements: – Determining the basis of investment impairment testing methodology, including the need for planning assumptions and internal capital allocations Key estimates: – Forecast cash flows for investments, including estimated allocations of regulatory capital – Growth rate beyond initial cash flow projections – Discount rates which factor in risk-free rates and applicable risk premiums All of these variables are subject to fluctuations in external market rates and economic conditions beyond management’s control The estimation of future cash flows and the level to which they are discounted is inherently uncertain and requires significant judgement and is subject to potential change over time. For more on these assumptions, including changes in the assumptions that would trigger an impairment, see Note 7.

Credit Risk (Tables)

Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of credit risk exposure [abstract]
Disclosure of Exposures to Credit Risk by Segment	Exposures to credit risk arise in our business segments from: Retail and Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre In Mortgages: – Residential mortgages for customers with good credit quality (prime lending). – We provide these mostly for owner- occupiers, with buy-to-let mortgages for non-professional landlords. In Everyday Banking: – Unsecured lending to individuals, such as loans, credit cards and overdrafts. – Banking services to businesses with turnover up to £ 6.5 m per annum and simpler borrowing needs. We offer loans, credit cards and overdrafts. – Financing for cars, vans, motorbikes and leisure vehicles through Santander Consumer (UK) plc (SCUK). – Through our joint ventures, Hyundai Capital UK Ltd and Volvo Car Financial Services UK Limited, we provide retail point of sale customer finance and wholesale finance facilities (stock finance). – Loans, bank accounts, treasury services, invoice discounting, cash transmission, trade finance and asset finance. – We provide these to SMEs and mid- sized corporates with turnover up to £ 500 m per annum, Commercial Real Estate and Social Housing associations. – Asset and liability management of our balance sheet. – Exposures include financial institutions (derivatives and other treasury products), structured products, and sovereign and supranational assets chosen for diversification and liquidity. – Crown Dependencies - mainly residential mortgages to individuals in Jersey and the Isle of Man.
Disclosure of Type of Credit Risk Mitigation by Portfolio	The types of credit risk mitigation, including collateral, across each of our portfolios are: Portfolio Description Residential mortgages Collateral is in the form of a first legal charge over the property. Before we grant a mortgage, the property is valued either by a surveyor or using automated valuation methodologies where our confidence in the accuracy of this method is high. Unsecured lending There is no collateral or security tied to the loan that can be used to mitigate any potential loss if the customer does not pay us back. Business banking services Business banking lending is unsecured. When lending to incorporated businesses, we typically obtain personal guarantees from each director, but we do not treat these as collateral. We consider the UK Government guarantee supporting losses on amounts lent under its Coronavirus Loan Schemes as collateral with 100% for Bounce Back Loan Scheme (BBLS) and 80% for Coronavirus Business Interruption Loan Scheme (CBILS). The type of credit risk mitigation, including collateral, is: Portfolio Description Consumer (auto) finance Collateral is in the form of legal ownership of the vehicle for most loans, with the customer being the registered keeper. Only a very small proportion of business is underwritten as a personal loan. In these cases, there is no collateral or security tied to the loan. We use a leading vehicle valuation company to assess the LTV at the proposal stage to ensure the value of the vehicle is appropriate. The types of credit risk mitigation, including collateral, across each of our portfolios are as follows. In addition, from time to time, at a portfolio level we execute significant risk transfer transactions, which typically reduce RWAs. Portfolio Description SME and mid corporate Includes secured and unsecured lending. We can take mortgage debentures or a first charge on commercial property as collateral. Before agreeing the loan, we get an independent professional valuation of the property. Loan agreements typically allow us to obtain revaluations during the term of the loan. We can also take guarantees, but we do not treat them as collateral unless they are supported by a tangible asset charged to us. We also lend against assets (like vehicles and equipment) and invoices for some customers. We value assets before we lend. For invoices, we review the customers' ledgers regularly and lend against debtors who meet agreed criteria. Commercial Real Estate We take a first charge on commercial property as collateral. The loan is subject to criteria such as the property condition, age and location, tenant quality, lease terms and length, and the sponsor’s experience and creditworthiness. Before advancing the loan and where appropriate, a bank representative visits the property. We also get an independent professional valuation which typically includes a site visit. Loan agreements typically allow us to obtain revaluations during the term of the loan. Social Housing We take a first charge on portfolios of residential real estate owned and let by UK Housing Associations as collateral, in most cases. We revalue this every three to five years (in line with industry practice), using the standard methods for property used for Social Housing. The types of credit risk mitigation, including collateral, across each of our portfolios are as follows. In addition, from time to time, at a portfolio level we execute significant risk transfer transactions, which typically reduce RWAs. Portfolio Description Sovereign and Supranational In line with market practice, there is no collateral against these assets. Structured Products These are our High Quality Liquid Assets (HQLA) in our Eligible Liquidity Pool. They are mainly Asset Backed Securities (ABS) and covered bonds, which hold senior positions in the creditor hierarchy. Their credit rating reflects over-collateralisation in the structure and the assets that underpin their cash flows. Financial Institutions We use standard legal agreements to reduce credit risk via netting and collateralisation on derivatives, repos and reverse repos, and stock borrowing/lending. We also reduce risk by clearing trades through central counterparties (CCPs) where possible. Crown Dependencies We manage the risk on this portfolio in a similar way as for mortgages in Retail and Business Banking.
Disclosure of Types of Forbearance	The main types of forbearance we offer are: Action Description Term extension We can extend the loan term, making each monthly payment smaller. We may offer this if the customer is up to date with payments but shows signs of financial difficulties. We may also offer this if the loan is about to mature and refinancing is not possible on market terms. Interest-only Historical interest-only payments due to financial difficulties are classed as forborne. For corporate customers, interest-only concessions are considered on a case by case basis. Concessions are only granted if the nature of the financial difficulties is assessed to be temporary. Counterparties are expected to recover in full and resume making full capital and interest payments once they are in a stronger financial position. Other payment rescheduling, including capitalisation For retail customers, we may add the arrears to the mortgage balance (this is known as capitalisation) if they cannot afford to increase their monthly payment to pay off their arrears in a reasonable time but have been making their monthly payments, usually for at least six months. We can also capitalise property charges due to a landlord. We pay them for the customer to avoid the lease being forfeited. We may combine this help with term extensions and, in the past, interest-only concessions. In certain cases, we may offer interest rate concessions. For corporate customers, we may lower or stop their payments until they have time to recover. We may reschedule payments to better match the customer’s cash flow – for example if the business is seasonal - or provide a temporary increase in facilities to cover peak demand ahead of their trading improving. We might do this by arrears capitalisation or drawing from an overdraft. We may also offer to provide new facilities, interest rate concessions and interest roll-up. In rare cases, we agree to forgive or reduce part of the debt.
Disclosure of Other Ways to Manage Debt when Cutomer are in Financial Difficulty	Action Description Waiving or changing covenants If a borrower breaks a covenant, we can either waive it or change it, taking their latest and future financial position into account. We may also add a condition on the use of any surplus cash (after operating costs) to pay down their debt to us. Asking for more collateral or guarantees If a borrower has unencumbered assets, we may accept more collateral in return for revised financing terms. We may also take a guarantee from companies in the same group and/or major shareholders. We only do this where we believe the guarantor can meet their commitment. Asking for more equity Where a borrower can no longer pay the interest on their debt, we may accept fresh equity capital from new or existing investors to change the capital structure in return for better terms on the existing debt.
Disclosure of Key Metrics to Measure and Control Credit Risk	We use a number of key metrics to measure and control credit risk, as follows: Metric Description Expected Credit Loss (ECL) ECL tells us what credit risk is expected to cost us either over the next 12 months or over the lifetime of the exposure where there is evidence of a SICR since origination. We explain how we calculate ECL below. Stages 1, 2 and 3 We assess each facility’s credit risk profile to determine which stage to allocate them to, and we monitor where there is a SICR and transfers between the Stages including monitoring of coverage ratios for each stage. Stage 3 ratio The Stage 3 ratio is the sum of Stage 3 drawn and Stage 3 undrawn assets divided by the sum of total drawn assets and Stage 3 undrawn assets. The Stage 3 ratio is a key indicator used to monitor underlying asset performance. Expected Loss (EL) EL is based on the CRD IV regulatory capital rules and gives us another view of credit risk. It is the product of the probability of default, exposure at default and loss given default, and we include direct and indirect costs. We base it on our risk models and our assessment of each customer’s credit quality. The rest of our Risk review, impairments, losses and loss allowances refer to calculations in accordance with IFRS, unless we specifically say they relate to CRD IV. For our IFRS impairment accounting policy, see Note 1 to the Consolidated Financial Statements.
Disclosure of Key Differences between Regulatory EL and IFRS 9 ECL Models	There are differences between the regulatory EL and IFRS 9 ECL approaches. Although our IFRS 9 models use the existing Basel advanced IRB risk components, we make adjustments to ensure the outcome is in line with IFRS 9, i.e. the financial reporting standard we use, as follows. Basel advanced IRB EL IFRS 9 ECL Rating philosophy Mix of point-in-time, through-the-cycle or hybrid Point-in-time, forward-looking. Considers a range of economic scenarios Parameters calibration Contains regulatory floors and downturn calibration Unbiased estimate, based on conditions known at the balance sheet date Calculation timing Considers aggregation of possible default events in the next 12 months Considers monthly calculation of parameters, for all possible future default dates. First 12 months are used for Stage 1, full lifetime for Stages 2 and 3 Probability of Default (PD) PD in the next 12 months Includes forward-looking economic data and removes conservatism. PD in next 12 months for Stage 1, lifetime for Stages 2 and 3 Loss Given Default (LGD) Lifetime LGD for defaults in the next 12 months Modelled without regulatory floors and exclusion of indirect costs Exposure at Default (EAD) Exposure at the point of default if the customer defaults in the next 12 months Recognises ability for exposure to reduce from balance sheet date to default date SICR Does not include SICR concept Includes SICR concept Discounting applied At weighted average cost of capital to the default date At the effective interest rate (EIR) to the balance sheet date
Schedule of Macroeconomic Assumptions for Each Five Scenarios	Upside Base case Downside 1 Stubborn Inflation Downside 2 Weighted (4) % % % % % % GDP (1) 2022 (actual) 4.3 4.3 4.3 4.3 4.3 4.3 2023 0.6 0.5 0.5 0.5 0.3 0.5 2024 1.0 0.4 (0.1) (1.8) (3.3) (0.4) 2025 2.1 1.3 0.2 (0.9) (1.4) 0.6 2026 2.4 1.5 0.5 0.4 0.6 1.1 2027 2.4 1.4 0.3 0.7 2.2 1.4 2028 2.4 1.4 0.3 0.8 2.6 1.4 5-year average increase/decrease 2.1 1.2 0.3 (0.2) 0.1 N/A Peak/(trough) at (2)(3) — — (0.2) (2.8) (5.1) (1.1) Bank Rate (1) 2022 (actual) 3.50 3.50 3.50 3.50 3.50 3.50 2023 5.25 5.25 5.25 5.25 5.25 5.25 2024 4.25 4.50 5.25 6.50 3.75 4.88 2025 3.25 3.50 4.00 5.00 2.00 3.68 2026 2.75 3.25 3.25 3.75 2.00 3.18 2027 2.75 3.00 3.00 3.00 2.50 2.93 2028 2.75 3.00 3.00 3.00 2.50 2.93 5-year end period 2.75 3.00 3.00 3.00 2.50 N/A Peak/(trough) at 5.25 5.25 5.75 6.50 5.25 5.55 HPI (1) 2022 (actual) 5.0 5.0 5.0 5.0 5.0 5.0 2023 (1.7) (2.2) (4.7) (6.3) (7.8) (3.8) 2024 2.0 (1.0) (11.7) (18.8) (25.8) (7.8) 2025 6.5 2.5 3.4 3.6 3.6 3.3 2026 5.1 3.0 2.1 1.6 1.6 2.7 2027 4.0 3.0 3.0 1.6 1.6 2.7 2028 3.6 3.0 3.1 1.8 1.8 2.7 5-year average increase/decrease 4.3 2.0 (0.8) (3.3) (5.4) N/A Peak/(trough) at (2) (3.7) (6.5) (17.5) (25.5) (33.0) (13.8) Unemployment (1) 2022 (actual) 3.7 3.7 3.7 3.7 3.7 3.7 2023 4.3 4.3 4.3 4.3 4.4 4.3 2024 4.3 4.8 4.8 5.6 8.5 5.3 2025 3.7 4.4 4.9 5.9 8.0 5.1 2026 3.4 4.3 5.2 6.2 7.4 5.0 2027 3.0 4.3 5.4 6.1 6.8 4.9 2028 3.0 4.2 5.3 5.8 6.2 4.7 5-year end period 3.0 4.2 5.3 5.8 6.2 N/A Peak/(trough) at 4.5 4.8 5.5 6.2 8.5 5.5 (1) GDP is the calendar year annual growth rate, HPI is Q4 annual growth rate and all other data points are at 31 December in the year indicated. (2) GDP peak taken from GDP level at Q2-23 and HPI peak taken from HPI level at Q3-22. (3) Reported as Peak/(trough) from 2023 to align with other metrics. (4) The weighted peak to trough and 5 year peak calculations are based on the annual profiles shown. The table below sets out our macroeconomic assumptions and their evolution throughout the forecast period for each of the five scenarios at 31 December 2022 : Upside Base case Downside 1 Stubborn Inflation Downside 2 Weighted (5) % % % % % % GDP (1) 2021 (actual) 7.5 7.5 7.5 7.5 7.5 7.5 2022 4.4 4.4 4.3 4.2 3.7 4.3 2023 (1.0) (1.3) (1.9) (2.7) (6.4) (2.2) 2024 0.8 0.5 (0.3) (0.9) (0.7) — 2025 2.0 1.6 0.5 0.2 1.7 1.2 2026 2.0 1.5 0.4 0.6 1.5 1.2 5-year average increase/decrease 1.2 0.8 (0.2) (0.5) (0.6) 0.3 Cumulative growth/(fall) to peak/(trough) (2)(4) 6.0 3.8 (0.8) (2.2) (3.1) 1.3 Bank Rate (1) 2021 (actual) 0.25 0.25 0.25 0.25 0.25 0.25 2022 3.50 3.50 3.50 3.50 3.50 3.50 2023 3.75 4.00 3.50 6.00 3.75 4.29 2024 3.00 3.25 2.75 5.50 3.00 3.59 2025 2.50 2.75 2.50 3.50 2.75 2.85 2026 2.25 2.50 2.25 3.00 2.50 2.55 5-year end period 2.25 2.50 2.25 3.00 2.50 2.55 Peak/(trough) at (3) 3.75 4.00 3.50 6.00 4.00 4.31 HPI (1) 2021 (actual) 8.7 8.7 8.7 8.7 8.7 8.7 2022 7.6 7.0 7.6 7.6 7.6 7.3 2023 (8.8) (10.0) (10.0) (10.9) (15.8) (10.7) 2024 (4.3) — (6.7) (8.8) (14.3) (4.4) 2025 0.6 2.0 (3.1) (4.9) (4.1) (0.8) 2026 4.1 3.0 (0.2) (0.6) 4.7 2.0 5-year average increase/decrease (0.7) (0.6) (3.8) (4.7) (4.8) (2.3) Peak/(trough) at (3) (12.8) (11.2) (19.0) (23.1) (30.7) (16.8) Unemployment (1) 2021 (actual) 4.0 4.0 4.0 4.0 4.0 4.0 2022 3.7 3.8 3.7 3.7 4.4 3.8 2023 4.7 4.7 5.1 5.5 8.5 5.3 2024 4.5 5.1 5.4 5.9 8.0 5.6 2025 4.5 4.5 5.8 6.4 7.4 5.4 2026 4.4 4.3 6.1 6.6 6.8 5.3 5-year end period 4.2 4.3 6.1 6.4 6.2 5.2 Peak/(trough) at (3) 4.7 5.1 6.1 6.6 8.5 5.9 (1) GDP is the calendar year annual growth rate, HPI is Q4 annual growth rate and all other data points are at 31 December in the year indicated. (2) This is the cumulative growth for the 5-year period. (3) For GDP and house price growth it is the peak to trough change within the 5-year period; for the unemployment rate it is the peak; and for Bank Rate it is the peak or trough. (4) If we had calculated GDP on the peak/(trough) basis as adopted for 2023 our upside scenario would have been (1.5%); base case scenario (1.9%); downside 1 (2.7%); stubborn inflation (4.0%); downside 2 (8.8%). (5) The weighted peak to trough and 5-year peak calculations are based on the annual profiles shown.
Schedule of Scenario Weights Applied to Scenarios	The scenario weights we applied for 2023 and 2022 were: Upside Base case Downside 1 Stubborn Inflation Downside 2 Weighted Scenario weights % % % % % % 2023 10 50 10 20 10 100 2022 5 50 15 20 10 100 2023 compared to 2022 We continue to use both the entire historical GDP data set available for the Monte Carlo analysis to smooth out the large GDP data swings seen in the pandemic as well as the data set from 2009 onwards. The CAGRs are now returning to more 'normal' levels associated with our scenarios as the economy unwinds from the 2020 shock. For H223, the base case using the 2009 data set show that the base case sits around the 50th probability path and that the downside scenarios sit between the 60th to 80th probability paths suggesting that a lower weight than the base case remains appropriate. We also need to consider the UK economic and political environment when applying weights. Given the current cost of living crisis, we remain of the view that the risks to UK growth are still biased to the downside and include: further geopolitical events creating more challenges for economies both in the UK and abroad; the potential for further upside inflation surprises causing inflation to stay above target for longer, raising the cost of living and so reducing consumer demand; continuing weak investment reflecting the uncertain nature of the economic environment; and a continuing and significant mismatch between vacancies and skills along with a smaller labour force, which may bring disruption to any recovery in the latter years of the forecast. In 2023, we increased the weight on the Upside scenario by 5% with a corresponding decrease in our Downside 1 to rebalance the overall weighted ECL. It was also to reflect both the change in the fan chart parameters used to determine the Upside and Downside 1 scenarios and the fact that the economic growth outlook has improved slightly since the end of 2022.
Disclosure of Definition of Default by Segment	We define a financial instrument as in default (i.e. credit impaired) for the purpose of calculating ECL if it is more than three months past due, or if we have data that suggests the customer is unlikely to pay. The data we have on customers varies across our business segments. It typically includes where: Retail and Business Banking and Consumer Finance – They have been reported bankrupt or insolvent and are in arrears – Their loan term has ended, but they still owe us money more than three months later – They have had forbearance while in default and have failed to perform under the new arrangement terms, or have had multiple forbearance. Performing forborne accounts while not in default are reported in Stage 2 – We have suspended their fees and interest because they are in financial difficulties – We have repossessed the property. Corporate & Commercial Banking and Corporate Centre – They have had a winding up notice issued, or something happens that is likely to trigger insolvency – such as another lender calls in a loan – Something happens that makes them less likely to be able to pay us – such as they lose an important client or contract – They have regularly missed or delayed payments, even though they have not gone over the three-month limit for default – Their loan is unlikely to be refinanced or repaid in full on maturity – Their loan has an excessive LTV that is unlikely to be resolved, such as by a change in planning policy, pay-downs, or increase in market value – Loans restructured under financial difficulties, classified as forborne transactions, in last 12 months.
Disclosure of Quantitative Criteria to Identify When Exposure Has Increased Credit Risk	Retail and Business Banking Consumer Finance (2) Corporate & Commercial Banking Corporate Centre Mortgages Everyday Banking (1) Personal loans Credit cards Overdrafts 30 bps 30 bps 340 bps 260 bps 300 bps 30 bps Internal rating method (1) For larger business banking customers, we apply the same criteria that we use for Corporate & Commercial Banking. (2) Consumer Finance use the comparison of lifetime PDs to determine Stage allocation, unlike other products which first turn the lifetime PD into an average yearly PD (annualised) and then do the comparison.
Disclosure of Qualitative Criteria to Identify When Exposure Has Increased Credit Risk	We also use qualitative criteria to identify where an exposure has increased in credit risk, independent of changes in PD. The criteria for 2023 and 2022 were: Retail and Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Mortgages Everyday Banking (1) Personal loans Credit cards Overdrafts – In forbearance – Default in last 24m – 30 Days past due (DPD) in last 12m – Bankrupt – £100+ arrears – In Collections – Default in last 12m – £50+ arrears – In forbearance – Default in last 12m – In Collections – £100+ arrears – Behaviour score indicators – Fees suspended – Default in last 12m – Debit dormant >35 days – Any excess in month – In forbearance – Deceased or Insolvent – Court ‘Return of goods’ order or Police watchlist – Agreement terminated – Payment holiday – Cash Collection – In forbearance – Default in last 12m – Watchlist: proactive management – Default at proxy origination – Watchlist: proactive management (1) For larger business banking customers, we apply the same criteria that we use for Corporate & Commercial Banking.
Disclosure of ECL by Segment	Retail and Business Banking Mortgages Everyday Banking Consumer Finance CCB Corporate Centre Total Credit Cards Other 2023 £m £m £m £m £m £m £m Modelled ECL 134 123 123 62 240 — 682 Individually assessed 4 — — — 124 — 128 ECL before JAs 138 123 123 62 364 — 810 JAs (excluding Affordability and Cost of Living JAs) Long-term indeterminate arrears 16 — — — — — 16 12+ months in arrears 14 — — — — — 14 UPL loss floor — — 6 — — — 6 Model underestimation 36 — — — — — 36 Corporate single large exposure — — — — 23 — 23 Other 12 1 3 4 (31) — (11) Total JAs (excluding Affordability and Cost of Living JAs) 78 1 9 4 (8) — 84 Affordability and Cost of Living JAs Corporate lending to segments affected by supply chain pressures — — — — 24 — 24 Secured affordability 9 — — 4 — — 13 Unsecured affordability — 16 22 — — — 38 Mortgage refinancing risk 19 — — — — — 19 SME debt burden — — 6 — — — 6 Total Affordability and Cost of Living JAs 28 16 28 4 24 — 100 Total JAs 106 17 37 8 16 — 184 Total ECL 244 140 160 70 380 — 994 2022 £m £m £m £m £m £m £m Modelled ECL 134 112 93 65 194 — 598 Individually assessed — — — — 112 — 112 ECL before JAs 134 112 93 65 306 — 710 JAs (excluding Affordability and Cost of Living JAs) Long-term indeterminate arrears 13 — — — — — 13 12+ months in arrears 22 — — — — — 22 UPL loss floor — — 15 — — — 15 Model underestimation 36 2 19 — — — 57 Corporate single large exposure — — — — 23 — 23 Other 21 1 10 2 3 — 37 Total JAs (excluding Affordability and Cost of Living JAs) 92 3 44 2 26 — 167 Affordability and Cost of Living JAs Corporate lending to segments affected by supply chain pressures — — — — 61 — 61 Mortgage affordability 27 — — — — — 27 Retail Unsecured Affordability — 15 20 — — — 35 SME debt burden — — 7 — — — 7 Total Affordability and Cost of Living JAs 27 15 27 — 61 — 130 Total JAs 119 18 71 2 87 — 297 Total ECL 253 130 164 67 393 — 1,007
Disclosure of Base Expected Credit Losses to Probability Weighted Estimated Credit Losses	Upside Base case Downside 1 Stubborn Inflation Downside 2 Weighted 2023 £m £m £m £m £m £m Exposure 300,969 300,969 300,969 300,969 300,969 300,969 Retail and Business Banking 204,357 204,357 204,357 204,357 204,357 204,357 – Mortgages 183,568 183,568 183,568 183,568 183,568 183,568 – EDB - Credit Cards 13,116 13,116 13,116 13,116 13,116 13,116 – EDB - Other 7,673 7,673 7,673 7,673 7,673 7,673 Consumer Finance 5,228 5,228 5,228 5,228 5,228 5,228 CCB 27,277 27,277 27,277 27,277 27,277 27,277 Corporate Centre 64,107 64,107 64,107 64,107 64,107 64,107 ECL 834 898 993 1,179 1,412 994 Retail and Business Banking 420 467 538 692 891 544 – Mortgages 143 176 236 365 564 244 – EDB - Credit Cards 132 138 142 150 150 140 – EDB - Other 145 153 160 177 177 160 Consumer Finance 68 69 70 72 72 70 CCB 346 362 385 415 449 380 Corporate Centre — — — — — — % % % % % % Proportion of assets in Stage 2 6 6 6 7 12 8 Retail and Business Banking 6 7 7 8 15 9 – Mortgages 7 7 7 8 17 10 – EDB - Credit Cards 2 3 3 3 3 3 – EDB - Other 7 8 8 9 9 8 Consumer Finance 6 6 6 6 6 6 CCB 13 14 14 17 20 13 Corporate Centre — — — — — — % % % % % % Proportion of assets in Stage 3 1 1 1 1 1 1 Retail and Business Banking 1 1 1 1 1 1 – Mortgages 1 1 1 1 1 1 – EDB - Credit Cards — — — — — — – EDB - Other 2 2 2 2 2 2 Consumer Finance — — — — — — CCB 3 3 3 3 3 3 Corporate Centre — — — — — — Upside Base case Downside 1 Stubborn Inflation Downside 2 Weighted 2022 £m £m £m £m £m £m Exposure 312,830 312,830 312,830 312,830 312,830 312,830 Retail and Business Banking 216,383 216,383 216,383 216,383 216,383 216,383 – Mortgages 195,170 195,170 195,170 195,170 195,170 195,170 – EDB - Credit Cards 12,845 12,845 12,845 12,845 12,845 12,845 – EDB - Other 8,368 8,368 8,368 8,368 8,368 8,368 Consumer Finance 5,739 5,739 5,739 5,739 5,739 5,739 CCB 28,299 28,299 28,299 28,299 28,299 28,299 Corporate Centre 62,409 62,409 62,409 62,409 62,409 62,409 ECL 931 933 994 1,150 1,384 1,007 Retail and Business Banking 490 498 530 648 831 546 – Mortgages 215 219 245 325 502 253 – EDB - Credit Cards 122 123 127 140 142 130 – EDB - Other 153 156 158 183 187 163 Consumer Finance 65 66 65 68 69 67 CCB 376 369 399 434 484 394 Corporate Centre — — — — — — % % % % % % Proportion of assets in Stage 2 4 4 5 7 11 7 Retail and Business Banking 4 4 4 6 10 7 – Mortgages 4 4 4 6 11 7 – EDB - Credit Cards 2 2 2 3 3 3 – EDB - Other 7 7 7 8 9 8 Consumer Finance 6 6 6 6 6 6 CCB 8 9 9 14 18 12 Corporate Centre — — — — — — % % % % % % Proportion of assets in Stage 3 1 1 1 1 1 1 Retail and Business Banking 1 1 1 1 1 1 – Mortgages 1 1 1 1 1 1 – EDB - Credit Cards — — — — — — – EDB - Other 2 2 2 2 2 2 Consumer Finance 1 1 1 1 1 1 CCB 2 2 2 2 2 2 Corporate Centre — — — — — —
Schedule of Impact on Profit Before Tax of Applying an Immediate and Permanent House Price Increase or Decrease to Our Base Case Economic Scenario Explanatory	Increase/decrease in house prices +20% +10% -10% -20% Increase/(decrease) in profit before tax £m £m £m £m 2023 70 38 (54) (155) 2022 48 32 (61) (176)
Disclosure of Factors to Measure ECL	For accounts not in default at the reporting date, we estimate a monthly ECL for each exposure and for each month over the forecast period. The lifetime ECL is the sum of the monthly ECLs over the forecast period, while the 12-month ECL is limited to the first 12 months. We calculate each monthly ECL as the discounted value for the relevant forecast month of the product of the following factors: Factor Description Survival rate (SR) The probability that the exposure has not closed or defaulted since the reporting date. Probability of default (PD) The likelihood of a borrower defaulting in the following month, assuming it has not closed or defaulted since the reporting date. For each month in the forecast period, we estimate the monthly PD from a range of factors. These include the current risk grade for the exposure, which becomes less relevant further into the forecast period, as well as the expected evolution of the account risk with maturity and factors for changing economics. We support this with historical data analysis. Exposure at default (EAD) The amount we expect to be owed if a default event occurs. We determine EAD for each month of the forecast period by the expected payment profile, which varies by product. For amortising products, we base it on the borrower’s contractual repayments over the forecast period. We adjust this for any expected overpayments on Stage 1 accounts that the borrower may make and for any arrears we expect if the account was to default. For revolving products, or amortising products with an off-balance sheet element, we determine EAD using the balance at default and the contractual exposure limit. We vary these assumptions by product and base them on analysis of recent default data. Loss given default (LGD) Our expected loss if a default event were to occur. We express it as a percentage and calculate it based on factors that we have observed to affect the likelihood and/or value of any subsequent write-offs, which vary according to whether the product is secured or unsecured. If the product is secured, we take into account collateral values as well as the historical discounts to market/book values due to forced sales type.
Disclosure of Maximum and Net Exposure to Credit Risk	The tables below show the main differences between our maximum and net exposure to credit risk. They show the effects of collateral, netting, and risk transfer to mitigate our exposure. The tables only show the financial assets that credit risk affects and to which the impairment requirements in IFRS 9 are applied. For balance sheet assets, the maximum exposure to credit risk is the carrying value after impairment loss allowances. Off-balance sheet exposures are mortgage offers, guarantees, formal standby facilities, credit lines and other commitments. For off-balance sheet guarantees, the maximum exposure is the maximum amount that we would have to pay if the guarantees were called on. For formal standby facilities, credit lines and other commitments that are irrevocable over the life of the facility, the maximum exposure is the total amount of the commitment. Maximum exposure Balance sheet asset Off-balance sheet Collateral (1) Gross amounts Loss allowance Net amounts Gross amounts Loss allowance Net amounts Cash Non-cash Netting (2) Net exposure 2023 £bn £bn £bn £bn £bn £bn £bn £bn £bn £bn Cash and balances at central banks 40.5 — 40.5 — — — — — — 40.5 Financial assets at amortised cost: – Loans and advances to customers:⁽³⁾ – Retail Mortgages 176.5 (0.2) 176.3 8.3 — 8.3 — (179.1) — 5.5 – Corporate loans 18.5 (0.3) 18.2 8.9 — 8.9 (0.1) (15.3) — 11.7 – Finance leases 4.6 (0.1) 4.5 — — — — (4.5) — — – Accrued interest and other adjustments 0.9 — 0.9 — — — — — — 0.9 – Other unsecured loans 7.1 (0.3) 6.8 13.8 (0.1) 13.7 — — — 20.5 – Amounts due from fellow Banco Santander group subsidiaries and JVs 4.5 — 4.5 — — — — — — 4.5 Total loans and advances to customers 212.1 (0.9) 211.2 31.0 (0.1) 30.9 (0.1) (198.9) — 43.1 – Loans and advances to banks 1.2 — 1.2 0.5 — 0.5 — — — 1.7 – Reverse repurchase agreements – non trading 12.5 — 12.5 — — — — (12.4) (0.1) — – Other financial assets at amortised cost 0.2 — 0.2 — — — — — — 0.2 Total financial assets at amortised cost 226.0 (0.9) 225.1 31.5 (0.1) 31.4 (0.1) (211.3) (0.1) 45.0 Financial assets at fair value at FVOCI: – Debt securities 8.5 — 8.5 — — — — — — 8.5 Total financial assets at FVOCI 8.5 — 8.5 — — — — — — 8.5 Total 275.0 (0.9) 274.1 31.5 (0.1) 31.4 (0.1) (211.3) (0.1) 94.0 2022 Cash and balances at central banks 46.6 — 46.6 — — — — — — 46.6 Financial assets at amortised cost: – Loans and advances to customers: (3) – Retail Mortgages (4) 188.3 (0.3) 188.0 8.0 — 8.0 — (191.4) — 4.6 – Corporate loans 19.1 (0.3) 18.8 9.3 — 9.3 (0.1) (16.5) — 11.5 – Finance leases 4.6 (0.1) 4.5 0.4 — 0.4 — (4.8) — 0.1 – Accrued interest and other adjustments 0.9 — 0.9 — — — — — — 0.9 – Other unsecured loans 7.7 (0.2) 7.5 13.7 (0.1) 13.6 — — — 21.1 – Amounts due from fellow Banco Santander group subsidiaries and JVs 4.2 — 4.2 — — — — — — 4.2 Total loans and advances to customers 224.8 (0.9) 223.9 31.4 (0.1) 31.3 (0.1) (212.7) — 42.4 – Loans and advances to banks 1.1 — 1.1 0.4 — 0.4 — — — 1.5 – Reverse repurchase agreements – non trading 7.3 — 7.3 — — — — (7.3) — — – Other financial assets at amortised cost 0.2 — 0.2 — — — — — — 0.2 Total financial assets at amortised cost 233.4 (0.9) 232.5 31.8 (0.1) 31.7 (0.1) (220.0) — 44.1 Financial assets at FVOCI: – Debt securities 6.0 — 6.0 — — — — — — 6.0 Total financial assets at FVOCI 6.0 — 6.0 — — — — — — 6.0 Total 286.0 (0.9) 285.1 31.8 (0.1) 31.7 (0.1) (220.0) — 96.7 (1) The forms of collateral we take to reduce credit risk include: residential and commercial property; other physical assets, including motor vehicles; liquid securities, including those transferred under reverse repurchase agreements; cash, including cash used as collateral for derivative transactions; and receivables. Charges on residential property are most of the collateral we take. (2) We can reduce credit risk exposures by applying netting. We do this mainly for derivative and repurchase transactions with financial institutions. For derivatives and securities finance transactions, we use standard master netting agreements. For more on this, see ‘Credit risk mitigation’ in the ‘Credit risk - Credit risk management’ section. (3) Balances include interest we have charged to the customer’s account and accrued interest that we have not charged to the account yet. (4) The collateral value shown against advances secured on residential property is limited to the balance of each associated individual loan. It does not include the impact of over–collateralisation (where the collateral has a higher value than the loan balance) and includes collateral we would receive on draw down of certain off–balance sheet commitments.
Disclosure of Difference Between Maximum and Net Exposure to Credit Risk	The tables below show the main differences between our maximum and net exposure to credit risk on the financial assets that credit risk affects and to which the impairment requirements in IFRS 9 are not applied. Balance sheet asset gross amount Collateral (1) Netting (2) Net exposure Cash Non-cash 2023 £bn £bn £bn £bn £bn Financial assets at FVTPL: – Derivative financial instruments 1.5 (0.8) — (0.5) 0.2 – Other financial assets at FVTPL 0.6 — — — 0.6 Total 2.1 (0.8) — (0.5) 0.8 2022 Financial assets at FVTPL: – Derivative financial instruments 2.4 — (1.7) (0.5) 0.2 – Other financial assets at FVTPL 0.4 — — — 0.4 Total 2.8 — (1.7) (0.5) 0.6 (1) The forms of collateral we take to reduce credit risk include: liquid securities, including those transferred under reverse repurchase agreements; cash, including cash used as collateral for derivative transactions; and receivables. (2) We can reduce credit risk exposures by applying netting. We do this mainly for derivative and repurchase transactions with financial institutions. For derivatives and securities finance transactions, we use standard master netting agreements. They allow us to set off our credit risk exposure to a counterparty against our obligations to the counterparty in relation to transactions under the master netting agreement in the event of default. This gives us a lower net credit exposure. They may also reduce settlement exposure. For more on this, see ‘Credit risk mitigation’ in the ‘Credit risk – Credit risk management’ section.
Disclosure of Equivalent Credit Rating Grade used by Standard and Poors Ratings Services	In the final column of the table we show the approximate equivalent credit rating grade used by Standard & Poor’s Ratings Services (S&P). Santander UK risk grade PD range Mid Lower Upper S&P equivalent % % % 9 0.010 0.000 0.021 AAA to AA+ 8 0.032 0.021 0.066 AA to AA- 7 0.100 0.066 0.208 A+ to BBB 6 0.316 0.208 0.658 BBB- to BB 5 1.000 0.658 2.081 BB- 4 3.162 2.081 6.581 B+ to B 3 10.000 6.581 20.811 B- 2 31.623 20.811 99.999 CCC to C 1 (Default) 100.000 100.000 100.000 D
Disclosure of Credit Rating of Financial Assets Subject to Credit Risk	Santander UK risk grade Loss allowance Total 9 8 7 6 5 4 3 to 1 Other (1)(2) 2023 £bn £bn £bn £bn £bn £bn £bn £bn £bn £bn Exposures - On balance sheet Cash and balances at central banks 40.5 — — — — — — — — 40.5 – Stage 1 40.5 — — — — — — — — 40.5 Financial assets at amortised cost: – Loans and advances to customers (2) 5.3 34.7 85.6 49.3 14.7 8.4 5.5 8.6 (0.9) 211.2 – Stage 1 5.3 33.6 81.5 43.9 10.4 2.8 0.4 8.3 (0.1) 186.1 – Stage 2 — 1.1 4.1 5.4 4.3 5.5 2.4 0.1 (0.4) 22.5 – Stage 3 — — — — — 0.1 2.7 0.2 (0.4) 2.6 Of which mortgages: 5.2 33.1 81.0 42.0 6.7 3.8 3.4 1.3 (0.2) 176.3 – Stage 1 5.2 32.0 76.9 36.7 3.6 0.5 0.1 1.3 — 156.3 – Stage 2 — 1.1 4.1 5.3 3.1 3.2 1.4 — (0.1) 18.1 – Stage 3 — — — — — 0.1 1.9 — (0.1) 1.9 – Loans and advances to banks 0.1 0.2 — — — — — 0.9 — 1.2 – Stage 1 0.1 0.2 — — — — — 0.9 — 1.2 – Reverse repo agreements – non trading 9.6 1.6 0.7 0.6 — — — — — 12.5 – Stage 1 9.6 1.6 0.7 0.6 — — — — — 12.5 – Other financial assets at amortised cost 0.2 — — — — — — — — 0.2 – Stage 1 0.2 — — — — — — — — 0.2 Total financial assets at amortised cost 15.2 36.5 86.3 49.9 14.7 8.4 5.5 9.5 (0.9) 225.1 Financial assets at FVOCI: 4.2 3.9 0.2 — — — — 0.2 — 8.5 – Stage 1 4.2 3.9 0.2 — — — — 0.2 — 8.5 Total on balance sheet 59.9 40.4 86.5 49.9 14.7 8.4 5.5 9.7 (0.9) 274.1 Total off–balance sheet — 6.3 7.0 6.8 4.6 1.7 0.4 4.7 (0.1) 31.4 – Stage 1 — 6.3 6.9 6.7 4.4 1.2 0.1 4.7 — 30.3 – Stage 2 — — 0.1 0.1 0.2 0.5 0.2 — (0.1) 1.0 – Stage 3 — — — — — — 0.1 — — 0.1 Total exposures 59.9 46.7 93.5 56.7 19.3 10.1 5.9 14.4 (1.0) 305.5 Santander UK risk grade Total Coverage Ratio 9 8 7 6 5 4 3 to 1 Other (1)(2) 2023 £bn £bn £bn £bn £bn £bn £bn £bn £bn % ECL - On balance sheet Cash and balances at central banks — — — — — — — — — — – Stage 1 — — — — — — — — — — Financial assets at amortised cost: – Loans and advances to customers (2) — — — — 0.2 0.2 0.5 — 0.9 0.4 – Stage 1 — — — — 0.1 — — — 0.1 0.1 – Stage 2 — — — — 0.1 0.2 0.1 — 0.4 1.7 – Stage 3 — — — — — — 0.4 — 0.4 13.3 Of which mortgages: — — — — — 0.1 0.1 — 0.2 0.1 – Stage 1 — — — — — — — — — — – Stage 2 — — — — — 0.1 — — 0.1 0.5 – Stage 3 — — — — — — 0.1 — 0.1 5.0 – Loans and advances to banks — — — — — — — — — — – Stage 1 — — — — — — — — — — – Reverse repo agreements – non trading — — — — — — — — — — – Stage 1 — — — — — — — — — — – Other financial assets at amortised cost — — — — — — — — — — – Stage 1 — — — — — — — — — — Total financial assets at amortised cost — — — — 0.2 0.2 0.5 — 0.9 0.4 Financial assets at FVOCI: — — — — — — — — — — – Stage 1 — — — — — — — — — — Total on balance sheet — — — — 0.2 0.2 0.5 — 0.9 0.3 Total off–balance sheet — — — — — 0.1 — — 0.1 0.3 – Stage 1 — — — — — — — — — — – Stage 2 — — — — — 0.1 — — 0.1 9.1 – Stage 3 — — — — — — — — — — Total ECL — — — — 0.2 0.3 0.5 0.0 1.0 0.3 Santander UK risk grade Loss allowance 9 8 7 6 5 4 3 to 1 Other (1)(2) Total 2022 £bn £bn £bn £bn £bn £bn £bn £bn £bn £bn Exposures - On balance sheet Cash and balances at central banks 46.6 — — — — — — — — 46.6 – Stage 1 46.6 — — — — — — — — 46.6 Financial assets at amortised cost: – Loans and advances to customers⁽²⁾ 9.5 36.5 87.1 52.7 15.2 9.3 5.4 9.0 (0.9) 223.8 – Stage 1 9.5 36.2 85.4 48.4 11.1 4.0 0.5 8.6 (0.1) 203.6 – Stage 2 — 0.3 1.7 4.3 4.1 5.2 2.6 0.2 (0.5) 17.9 – Stage 3 — — — — — 0.1 2.3 0.2 (0.3) 2.3 Of which mortgages: 9.5 34.1 83.8 45.6 7.3 3.8 3.1 1.1 (0.3) 188.0 – Stage 1 9.5 33.8 82.1 41.6 4.2 0.5 0.1 1.1 — 172.9 – Stage 2 — 0.3 1.7 4.0 3.1 3.2 1.3 — (0.2) 13.4 – Stage 3 — — — — — 0.1 1.7 — (0.1) 1.7 – Loans and advances to banks 0.1 (0.1) — — — — — 1.1 — 1.1 – Stage 1 0.1 (0.1) — — — — — 1.1 — 1.1 – Reverse repo agreements – non trading 5.4 0.6 0.1 1.1 — — — 0.1 — 7.3 – Stage 1 5.4 0.6 0.1 1.1 — — — 0.1 — 7.3 – Other financial assets at amortised cost 0.2 — — — — — — — — 0.2 – Stage 1 0.2 — — — — — — — — 0.2 Total financial assets at amortised cost 15.2 37.0 87.2 53.8 15.2 9.3 5.4 10.2 (0.9) 232.4 Financial assets at FVOCI: 3.5 2.2 0.3 — — — — — — 6.0 – Stage 1 3.5 2.2 0.3 — — — — — — 6.0 Total on balance sheet 65.3 39.2 87.5 53.8 15.2 9.3 5.4 10.2 (0.9) 285.0 Total off–balance sheet 0.1 7.2 6.9 6.5 4.9 2.1 0.4 3.7 (0.1) 31.7 – Stage 1 0.1 7.2 6.8 6.4 4.7 1.7 0.2 3.7 — 30.8 – Stage 2 — — 0.1 0.1 0.2 0.4 0.1 — (0.1) 0.8 – Stage 3 — — — — — — 0.1 — — 0.1 Total exposures 65.4 46.4 94.4 60.3 20.1 11.4 5.8 13.9 (1.0) 316.7 Santander UK risk grade Coverage Ratio 9 8 7 6 5 4 3 to 1 Other (1)(2) Total 2022 £bn £bn £bn £bn £bn £bn £bn £bn £bn % ECL - On balance sheet Cash and balances at central banks — — — — — — — — — — – Stage 1 — — — — — — — — — — Financial assets at amortised cost: – Loans and advances to customers (2) — — — — 0.2 0.2 0.5 — 0.9 0.4 – Stage 1 — — — — 0.1 — — — 0.1 — – Stage 2 — — — — 0.1 0.2 0.2 — 0.5 2.8 – Stage 3 — — — — — — 0.3 — 0.3 13.0 Of which mortgages: — — — — 0.1 0.1 0.1 — 0.3 0.2 – Stage 1 — — — — — — — — — — – Stage 2 — — — — 0.1 0.1 — — 0.2 1.5 – Stage 3 — — — — — — 0.1 — 0.1 5.9 – Loans and advances to banks — — — — — — — — — — – Stage 1 — — — — — — — — — — – Reverse repo agreements – non trading — — — — — — — — — — – Stage 1 — — — — — — — — — — – Other financial assets at amortised cost — — — — — — — — — — – Stage 1 — — — — — — — — — — Total financial assets at amortised cost — — — — 0.2 0.2 0.5 — 0.9 0.4 Financial assets at FVOCI: — — — — — — — — — — – Stage 1 — — — — — — — — — — Total on balance sheet — — — — 0.2 0.2 0.5 — 0.9 0.3 Total off–balance sheet — — — — — — 0.1 — 0.1 0.3 – Stage 1 — — — — — — — — — — – Stage 2 — — — — — — 0.1 — 0.1 12.5 – Stage 3 — — — — — — — — — — Total ECL — — — — 0.2 0.2 0.6 — 1.0 0.3 (1) Includes Joint Ventures and Business Banking (including BBLs balances) as well as the Crown Dependencies portfolio . We use scorecards for these items, rather than rating models. Off-balance sheet exposures also include residential mortgage offers in the pipeline. (2) Includes interest we have charged to the customer’s account and accrued interest we have not charged to the account yet.
Disclosure of Credit Performance	Customer Loans 12 month Gross write-offs Loan Loss Allowance s Total Stage 1 Stage 2 Stage 3 (3) 2023 £bn £bn % £bn % £bn % £m £m Retail and Business Banking 182.3 160.8 88.3 19.2 10.5 2.3 1.27 141 501 – Mortgages 175.2 155.0 88.5 18.2 10.4 2.0 1.16 11 241 – EDB - Credit Cards 2.7 2.3 85.4 0.3 12.9 0.1 2.95 46 130 – EDB - Other (1) 4.4 3.5 80.9 0.7 14.8 0.2 4.38 84 130 Consumer Finance (2) 5.2 4.9 93.1 0.3 6.3 — 0.53 23 70 CCB 17.9 13.8 77.1 3.4 19.1 0.7 4.14 68 345 Corporate Centre 1.3 1.3 99.8 — 0.1 — 0.10 — — Total Drawn 206.7 180.8 87.5 22.9 11.1 3.0 1.49 232 916 Retail and Business Banking 22.0 21.5 — 0.5 — — — — 43 – Mortgages 8.3 8.2 — 0.1 — — — — 3 – EDB - Credit Cards 10.4 10.3 — 0.1 — — — — 10 – EDB - Other (1) 3.3 3.0 — 0.3 — — — — 30 Consumer Finance (2) — — — — — — — — — CCB 9.4 8.8 — 0.5 — 0.1 — — 35 Corporate Centre — — — — — — — — — Total Undrawn 31.4 30.3 — 1.0 — 0.1 — — 78 Total 238.1 211.1 — 23.9 — 3.1 — 232 994 2022 £bn £bn % £bn % £bn % £m £m Retail and Business Banking 194.6 178.0 91.5 14.6 7.4 2.0 1.08 113 504 – Mortgages 187.1 171.7 91.8 13.6 7.3 1.8 0.99 3 250 – EDB - Credit Cards 2.5 2.1 85.7 0.3 12.9 0.1 2.53 40 120 – EDB - Other (1) 5.0 4.2 82.8 0.7 13.0 0.1 4.30 70 134 Consumer Finance (2) 5.4 5.0 93.0 0.4 6.5 — 0.54 19 67 CCB 18.5 14.5 78.3 3.5 18.8 0.5 3.08 24 362 Corporate Centre 1.2 1.2 99.6 — 0.3 — 0.10 — — Total Drawn 219.7 198.7 90.4 18.5 8.4 2.5 1.24 156 933 Retail and Business Banking 21.8 21.2 — 0.5 — 0.1 — — 42 – Mortgages 8.0 7.9 — 0.1 — — — — 3 – EDB - Credit Cards 10.3 10.2 — 0.1 — — — — 10 – EDB - Other (1) 3.5 3.1 — 0.3 — 0.1 — — 29 Consumer Finance (2) 0.4 0.4 — — — — — — — CCB 9.7 9.3 — 0.4 — — — — 32 Corporate Centre — — — — — — — — — Total Undrawn 31.9 30.9 — 0.9 — 0.1 — — 74 Total 251.6 229.6 — 19.4 — 2.6 — 156 1,007 (1) EDB - Other includes £1.8bn of BBLS lending ( £1.7bn is BBLS with 100% Government guarantee), £2.1bn unsecured personal loans and £0.5bn overdrafts. (2) Consumer Finance - 87% ( 2022 : 84% ) of lending is collateralised on the vehicle. (3) Stage 3 ratio is the sum of Stage 3 drawn and Stage 3 undrawn assets divided by the sum of total drawn assets and Stage 3 undrawn assets. Arrears over 90 days past due 31 December 2023 31 December 2022 % % Mortgages 0.80 0.62 Credit Cards 0.51 0.49 UPL 0.73 0.61 Overdrafts 2.43 2.24 Business Banking 4.15 3.47 Consumer Finance 0.43 0.44 2023 2022 £m £m Mortgage loans and advances to customers 175,239 187,141 of which: – Stage 1 155,063 171,733 – Stage 2 18,160 13,576 – Stage 3 2,016 1,832 Loss allowances (1) 244 253 % % Stage 1 ratio (2) 88.49 91.76 Stage 2 ratio (2) 10.36 7.25 Stage 3 ratio 1.16 0.99 (1) The ECL allowance is for both on and off–balance sheet exposures. (2) Stage 1/Stage 2 exposures as a percentage of customer loans. Portfolio of particular interest (1) Total Interest-only Part interest- only, part repayment (2) Flexible LTV >100% Buy-to-let Other portfolio 2023 £m £m £m £m £m £m £m Mortgage portfolio 175,239 39,104 12,788 5,418 445 15,585 120,878 – Stage 1 155,063 32,244 11,077 4,420 276 13,887 109,509 – Stage 2 18,160 5,874 1,472 744 104 1,647 10,618 – Stage 3 2,016 986 239 254 65 51 751 Stage 3 ratio 1.16 % 2.54 % 1.88 % 5.01 % 14.54 % 0.33 % 0.62 % Properties in possession 23 12 3 2 5 1 8 Balance weighted LTV (indexed) 51 % 48 % 51 % 37 % 116 % 60 % 53 % 2022 Mortgage portfolio 187,141 41,098 13,759 6,765 372 16,799 129,299 – Stage 1 171,733 35,957 12,380 5,713 218 15,884 120,683 – Stage 2 13,576 4,265 1,161 839 102 876 7,916 – Stage 3 1,832 876 218 213 52 39 700 Stage 3 ratio 0.99 % 2.15 % 1.60 % 3.45 % 13.91 % 0.23 % 0.54 % Properties in possession 47 18 8 3 7 1 16 Balance weighted LTV (indexed) 50 % 47 % 49 % 36 % 117 % 58 % 52 % (1) Where a loan falls into more than one category, we include it in all the categories that apply. As a result, the sum of the mortgages in the segments of particular interest and the other portfolio does not agree to the total mortgage portfolio. (2) Mortgage balance includes both the interest-only part of £9,684m ( 2022 : £10,192m ) and the non-interest-only part of the loan. Business banking Other unsecured Personal loans Credit cards Overdrafts Total other unsecured Total 2023 £m £m £m £m £m £m Loans and advances to customers 1,819 2,064 2,674 471 5,209 7,028 of which: – Stage 1 1,574 1,743 2,283 207 4,233 5,807 – Stage 2 115 294 345 236 875 990 – Stage 3 130 27 46 28 101 231 Loss allowances (1) 16 66 140 78 284 300 Stage 3 undrawn exposures 2 37 39 Stage 3 ratio 7.25 % 2.65 % 3.83 % Gross write-offs (12 months) 11 119 130 2022 Loans and advances to customers 2,519 1,982 2,558 461 5,001 7,520 of which: – Stage 1 2,223 1,730 2,192 155 4,077 6,300 – Stage 2 133 231 329 282 842 975 – Stage 3 163 21 37 24 82 245 Loss allowances (1) 19 62 130 82 274 293 Stage 3 undrawn exposures 3 32 35 Stage 3 ratio 6.58 % 2.27 % 3.71 % Gross write-offs (12 months) 11 99 110 (1) The ECL allowance is for both on and off–balance sheet exposures. 2023 2022 £m £m Loans and advances to customers 5,228 5,384 of which: – Stage 1 4,870 5,005 – Stage 2 330 350 – Stage 3 28 29 Loss allowances (1) 70 67 Stage 3 ratio 0.53 % 0.54 % Gross write-offs 23 19 (1) The ECL allowance is for both on and off–balance sheet exposures. 2023 Committed exposure Watchlist Fully performing Enhanced monitoring Proactive management Stage 3 Total (1) Loss allowances £m £m £m £m £m £m SME and mid corporate 10,140 462 1,447 627 12,676 341 Commercial Real Estate 4,734 10 496 118 5,358 39 Social Housing 7,752 — 204 — 7,956 — 22,626 472 2,147 745 25,990 380 2022 SME and mid corporate 11,796 431 1,383 513 14,123 355 Commercial Real Estate 4,765 103 480 59 5,407 38 Social Housing 7,979 46 10 — 8,035 1 24,540 580 1,873 572 27,565 394 (1) Includes committed facilities and derivatives.
Disclosure of IFRS 9 Credit Quality	Stage 1 Stage 2 Stage 3 Total 2023 £m £m £m £m Exposures On-balance sheet Retail and Business Banking 160,870 19,150 2,247 182,267 – Mortgages 155,063 18,160 2,016 175,239 – EDB - Credit Cards 2,283 345 46 2,674 – EDB - Other 3,524 645 185 4,354 Consumer Finance 4,870 330 28 5,228 CCB 13,822 3,418 699 17,939 Corporate Centre 64,094 1 1 64,096 Total on-balance sheet 243,656 22,899 2,975 269,530 Off-balance sheet Retail and Business Banking (1) 21,598 433 59 22,090 – Mortgages (1) 8,189 120 20 8,329 – EDB - Credit Cards 10,295 114 33 10,442 – EDB - Other 3,114 199 6 3,319 Consumer Finance — — — — CCB 8,745 547 46 9,338 Corporate Centre 11 — — 11 Total off-balance sheet (2) 30,354 980 105 31,439 Total exposures 274,010 23,879 3,080 300,969 ECL On-balance sheet Retail and Business Banking 57 274 170 501 – Mortgages 22 110 109 241 – EDB - Credit Cards 17 87 26 130 – EDB - Other 18 77 35 130 Consumer Finance 21 30 19 70 CCB 64 118 163 345 Corporate Centre — — — — Total on-balance sheet 142 422 352 916 Off-balance sheet Retail and Business Banking 16 26 1 43 – Mortgages 2 1 — 3 – EDB - Credit Cards 4 6 — 10 – EDB - Other 10 19 1 30 Consumer Finance — — — — CCB 12 14 9 35 Corporate Centre — — — — Total off-balance sheet 28 40 10 78 Total ECL 170 462 362 994 Coverage ratio (3) % % % % On-balance sheet Retail and Business Banking — 1.4 7.5 0.3 – Mortgages — 0.6 5.4 0.1 – EDB - Credit Cards 0.8 25.2 57.7 4.9 – EDB - Other 0.5 11.9 18.8 3.0 Consumer Finance 0.4 9.0 68.5 1.3 CCB 0.5 3.5 23.4 1.9 Corporate Centre — — 10.0 — Total on-balance sheet 0.1 1.8 11.8 0.3 Off-balance sheet Retail and Business Banking 0.1 6.0 2.8 0.2 – Mortgages — 1.1 0.5 — – EDB - Credit Cards — 5.0 1.9 0.1 – EDB - Other 0.3 9.6 18.0 0.9 Consumer Finance — — — — CCB 0.1 2.5 20.2 0.4 Corporate Centre — — — — Total off-balance sheet 0.1 4.1 10.4 0.2 Total coverage 0.1 1.9 11.8 0.3 (1) Off-balance sheet exposures include £3.3 bn of residential mortgage offers in the pipeline. (2) Off-balance sheet amounts consist of contingent liabilities and commitments. For more, see Note 31 . (3) ECL as a percentage of the related exposure. Total on-balance sheet exposures at 31 December 2022 comprised £219.7 bn of customer loans, loans and advances to banks of £1.1 bn, £7.5 bn of sovereign assets measured at amortised cost, £6.0 bn of assets measured at FVOCI, and £46.6 bn of cash and balances at central banks. Stage 1 Stage 2 Stage 3 Total 2022 £m £m £m £m Exposures On-balance sheet Retail and Business Banking 178,033 14,551 2,077 194,661 – Mortgages 171,733 13,576 1,832 187,141 – EDB - Credit Cards 2,192 329 37 2,558 – EDB - Other 4,108 646 208 4,962 Consumer Finance 5,005 350 29 5,384 CCB 14,507 3,476 535 18,518 Corporate Centre 62,405 3 1 62,409 Total on-balance sheet 259,950 18,380 2,642 280,972 Off-balance sheet Retail and Business Banking (1) 21,176 490 56 21,722 – Mortgages (1) 7,899 109 21 8,029 – EDB - Credit Cards 10,137 122 29 10,288 – EDB - Other 3,140 259 6 3,405 Consumer Finance 356 — — 356 CCB 9,331 412 37 9,780 Corporate Centre — — — — Total off-balance sheet (2) 30,863 902 93 31,858 Total exposures 290,813 19,282 2,735 312,830 ECL On-balance sheet Retail and Business Banking 57 295 152 504 – Mortgages 24 131 95 250 – EDB - Credit Cards 14 85 21 120 – EDB - Other 19 79 36 134 Consumer Finance 19 27 21 67 CCB 69 155 138 362 Corporate Centre — — — — Total on-balance sheet 145 477 311 933 Off-balance sheet Retail and Business Banking 12 28 2 42 – Mortgages 2 1 — 3 – EDB - Credit Cards 3 6 1 10 – EDB - Other 7 21 1 29 Consumer Finance — — — — CCB 14 11 7 32 Corporate Centre — — — — Total off-balance sheet 26 39 9 74 Total ECL 171 516 320 1,007 Coverage ratio (3) % % % % On-balance sheet Retail and Business Banking — 2.0 7.3 0.3 – Mortgages — 1.0 5.2 0.1 – EDB - Credit Cards 0.6 25.8 56.8 4.7 – EDB - Other 0.5 12.2 17.3 2.7 Consumer Finance 0.4 7.7 72.4 1.2 CCB 0.5 4.5 25.8 2.0 Corporate Centre — — — — Total on-balance sheet 0.1 2.6 11.8 0.3 Off-balance sheet Retail and Business Banking 0.1 5.7 3.6 0.2 – Mortgages — 0.9 — — – EDB - Credit Cards — 4.9 3.4 0.1 – EDB - Other 0.2 8.1 16.7 0.9 Consumer Finance — — — — CCB 0.2 2.7 18.9 0.3 Corporate Centre — — — — Total off-balance sheet 0.1 4.3 9.7 0.2 Total coverage 0.1 2.7 11.7 0.3 (1) Off-balance sheet exposures include £2.8 bn of residential mortgage offers in the pipeline. (2) Off-balance sheet amounts consist of contingent liabilities and commitments. For more, see Note 31 . (3) ECL as a percentage of the related exposure.
Disclosure of Stage 2 Exposures by Classification	The following table analyses our Stage 2 exposures and ECL by the reason the exposure is classified as Stage 2. 2023 PD deterioration Forbearance ( 1) Other 30 DPD Secured affordability Unsecured affordability Mortgage Refinancing High risk corporate Total Retail and Business Banking - Mortgages Exposure £m 5,877 516 549 560 2,889 — 7,769 — 18,160 ECL £m 65 2 3 12 9 — 19 — 110 Coverage % 1.1 0.3 0.7 2.1 0.3 — 0.2 — 0.6 Retail and Business Banking EDB - Credit Cards Exposure £m 256 — 17 9 — 63 — — 345 ECL £m 63 — 5 4 — 15 — — 87 Coverage % 24.9 27.7 24.5 47.1 — 23.7 — — 25.2 Retail and Business Banking EDB - Other Exposure £m 288 — 19 169 — 169 — — 645 ECL £m 36 — 3 18 — 20 — — 77 Coverage % 12.3 — 16.2 10.8 — 11.7 — — 11.9 Consumer Finance Exposure £m 115 — 126 25 64 — — — 330 ECL £m 10 — 5 11 4 — — — 30 Coverage % 8.7 — 4.0 43.4 6.3 — — — 9.0 CCB Exposure £m 1,809 85 533 93 — — — 898 3,418 ECL £m 75 2 17 2 — — — 22 118 Coverage % 4.1 2.5 3.2 2.4 — — — 2.5 3.5 Corporate Centre Exposure £m — — — 1 — — — — 1 ECL £m — — — — — — — — — Coverage % — — — — — — — — — Total Drawn Exposure £m 8,345 601 1,244 857 2,953 232 7,769 898 22,899 ECL £m 249 4 33 47 13 35 19 22 422 Coverage % 3.0 0.7 2.7 5.5 0.4 15.0 0.2 2.5 1.8 Undrawn ECL £m 28 — 4 3 — 3 — 2 40 Total Reported Exposure £m 9,160 601 1,436 893 2,889 233 7,769 898 23,879 ECL £m 277 4 37 50 13 38 19 24 462 2022 Retail and Business Banking - Mortgages Exposure £m 7,310 449 393 463 4,961 — n/a — 13,576 ECL £m 85 2 7 10 27 — n/a — 131 Coverage % 1.2 0.4 1.8 2.2 0.5 — n/a — 1.0 Retail and Business Banking EDB - Credit Cards Exposure £m 240 — 22 8 — 59 n/a — 329 ECL £m 63 — 4 4 — 14 n/a — 85 Coverage % 26.3 — 18.2 50.0 — 23.7 n/a — 25.8 Retail and Business Banking EDB - Other Exposure £m 303 — 26 178 — 139 n/a — 646 ECL £m 42 — 6 14 — 17 n/a — 79 Coverage % 13.9 — 23.1 7.9 — 12.2 n/a — 12.2 Consumer Finance Exposure £m 159 — 164 27 — — n/a — 350 ECL £m 12 — 5 10 — — n/a — 27 Coverage % 7.5 — 3.0 37.0 — — n/a — 7.7 CCB Exposure £m 1,548 64 684 214 — — n/a 966 3,476 ECL £m 81 4 1 10 — — n/a 59 155 Coverage % 5.2 6.3 0.1 4.7 — — n/a 6.1 4.5 Corporate Centre Exposure £m — — — 3 — — n/a — 3 ECL £m — — — — — — n/a — — Coverage % — — — — — — n/a — — Total Drawn Exposure £m 9,560 513 1,289 893 4,961 198 n/a 966 18,380 ECL £m 283 6 23 48 27 31 n/a 59 477 Coverage % 3.0 1.2 1.8 5.4 0.5 15.7 n/a 6.1 2.6 Undrawn ECL £m 19 — 8 6 — 4 n/a 2 39 Total Reported Exposure £m 10,323 625 1,271 937 4,961 199 n/a 966 19,282 ECL £m 302 6 31 54 27 35 n/a 61 516 (1) Where the values of ECL and/or exposures are not nil, but round to nil when presented in £millions, the coverage ratio is still presented in the table. Where balances satisfy more than one of the criteria above for determining a SICR, we have assigned the corresponding gross carrying amount and ECL in order of the categories presented.
Disclosure of Stage 2 Exposures by Cure Period	2023 2022 Exposure ECL Coverage Exposure ECL Coverage £m £m % £m £m % Stage 2 Not in cure period 12,682 360 2.8 13,156 439 3.3 In cure period (for transfer to Stage 1) 11,197 102 0.9 6,126 77 1.3 23,879 462 1.9 19,282 516 2.7 Stage 3 Not in cure period 2,712 342 12.6 2,421 286 11.8 In cure period (for transfer to Stage 2) 368 20 5.4 314 34 10.8 3,080 362 11.8 2,735 320 11.7
Disclosure of ECL Reconciliation	The table below shows the relationships between disclosures in this Credit risk review section which refer to drawn exposures and the associated ECL , and the total assets as presented in the Consolidated Balance Sheet. The Credit risk review disclosures exclude Joint ventures, as they carry low credit risk and therefore have an immaterial ECL, and Other items, mainly accrued interest that we have not yet charged to the customer's account, and cash collateral. On-balance sheet Off-balance sheet Exposures Loss allowance Net carrying amount Exposures Loss allowance 2023 £m £m £m £m £m Retail and Business Banking 182,267 501 181,766 22,090 43 – Mortgages (1) 175,239 241 174,998 8,329 3 – EDB - Credit Cards (2) 2,674 130 2,544 10,442 10 – EDB - Other (3) 4,354 130 4,224 3,319 30 Consumer Finance 5,228 70 5,158 — — Corporate & Commercial Banking 17,939 345 17,594 9,338 35 Corporate Centre 64,096 — 64,096 11 — Total exposures presented in Credit Quality tables 269,530 916 268,614 31,439 78 Joint ventures 4,488 Other items 960 Adjusted net carrying amount 274,062 Assets classified at FVTPL 2,074 Non-financial assets (3) 5,947 Total assets per the Consolidated Balance Sheet 282,083 2022 Retail and Business Banking 194,661 504 194,157 21,722 42 – Mortgages (1) 187,141 250 186,891 8,029 3 – EDB - Credit Cards (2) 2,558 120 2,438 10,288 10 – EDB - Other (3) 4,962 134 4,828 3,405 29 Consumer Finance 5,384 67 5,317 356 — Corporate & Commercial Banking 18,518 362 18,156 9,780 32 Corporate Centre 62,409 — 62,409 — — Total exposures presented in Credit Quality tables 280,972 933 280,039 31,858 74 Joint ventures 4,165 Other items 904 Adjusted net carrying amount 285,108 Assets classified at FVTPL 2,873 Non-financial assets (3) 4,262 Total assets per the Consolidated Balance Sheet 292,243 (1) Off-balance sheet exposures include offers in the pipeline and undrawn flexible mortgages products. (2) Off-balance sheet exposures include credit cards. (3) Non-financial assets include £ 630 m (2022: £ 2,654 m ) of Macro hedge of interest rate risk. The following table shows changes in total on and off-balance sheet exposures, subject to ECL assessment, and the corresponding ECL, in the period. The table presents total gross carrying amounts and ECLs at a Santander UK group level. We present segmental views in the sections below. Stage 1 Stage 2 Stage 3 Total Exposures (1) ECL Exposures (1) ECL Exposures (1) ECL Exposures (1) ECL £m £m £m £m £m £m £m £m At 1 January 2023 290,813 171 19,282 516 2,735 320 312,830 1,007 Transfers from Stage 1 to Stage 2 (3) (13,160) (9) 13,160 9 — — — — Transfers from Stage 2 to Stage 1 (3) 5,974 111 (5,974) (111) — — — — Transfers to Stage 3 (3) (600) (6) (924) (38) 1,524 44 — — Transfers from Stage 3 (3) 28 1 306 15 (334) (16) — — Transfers of financial instruments (7,758) 97 6,568 (125) 1,190 28 — — Net ECL remeasurement on stage transfer (4) — (111) — 145 — 130 — 164 Change in economic scenarios (2) — 29 — (33) — 9 — 5 New lending and assets purchased (5) 25,306 28 562 45 59 20 25,927 93 Redemptions, repayments and assets sold (7) (34,246) (35) (3,030) (53) (886) (46) (38,162) (134) Changes in risk parameters and other movements (6) (105) (9) 497 (33) 394 133 786 91 Assets written off (7) — — — — (412) (232) (412) (232) At 31 December 2023 274,010 170 23,879 462 3,080 362 300,969 994 Net movement in the period (16,803) (1) 4,597 (54) 345 42 (11,861) (13) ECL (release)/charge to the Income Statement (1) (54) 274 219 Less: Discount unwind — — (21) (21) Less: Recoveries net of collection costs — — 8 8 Total ECL (release)/charge to the Income Statement (1) (54) 261 206 At 1 January 2022 298,285 133 18,013 330 3,021 403 319,319 866 Transfers from Stage 1 to Stage 2 (3) (9,100) (25) 9,100 25 — — — — Transfers from Stage 2 to Stage 1 (3) 7,207 133 (7,207) (133) — — — — Transfers to Stage 3 (3) (621) (4) (624) (32) 1,245 36 — — Transfers from Stage 3 (3) 10 1 758 150 (768) (151) — — Transfers of financial instruments (2,504) 105 2,027 10 477 (115) — — Net ECL remeasurement on stage transfer (4) — (110) — 98 — 110 — 98 Change in economic scenarios (2) — 37 — 123 — 3 — 163 New lending and assets purchased (5) 48,194 42 1,119 76 64 24 49,377 142 Redemptions, repayments and assets sold (7) (55,332) (35) (2,065) (60) (950) (35) (58,347) (130) Changes in risk parameters and other movements (6) 2,170 (1) 188 (61) 377 87 2,735 25 Assets written off (7) — — — — (254) (157) (254) (157) At 31 December 2022 290,813 171 19,282 516 2,735 320 312,830 1,007 Net movement in the period (7,472) 38 1,269 186 (286) (83) (6,489) 141 ECL charge/(release) to the Income Statement 38 186 74 298 Less: Discount unwind — — (13) (13) Less: Recoveries net of collection costs — — 36 36 Total ECL charge/(release) to the Income Statement 38 186 97 321 (1) Exposures that have attracted an ECL, and as reported in the Credit Quality table above. (2) Changes to assumptions in the period. Isolates the impact on ECL from changes to the economic variables for each scenario, the scenarios themselves, and the probability weights from all other movements. Also includes the impact of quarterly revaluation of collateral. The impact of changes in economics on exposure Stage allocations are shown in Transfers of financial instruments. (3) Total impact of facilities that moved Stage(s) in the period. This means, for example, that where risk parameter changes (model inputs) or model changes (methodology) result in a facility moving Stage, the full impact is reflected here (rather than in Other). Stage flow analysis only applies to facilities that existed at both the start and end of the period. Transfers between Stages are based on opening balances and ECL at the start of the period. (4) Relates to the revaluation of ECL following the transfer of an exposure from one Stage to another. (5) Exposures and ECL of facilities that did not exist at the start of the period but did at the end. Amounts in Stage 2 and 3 represent assets which deteriorated in the period after origination in Stage 1. (6) Residual movements on existing facilities that did not change Stage in the period, and which were not acquired in the period. Includes the net increase or decrease in the period of the mortgage pipeline, cash at central banks, the impact of changes in risk parameters in the period, unwind of discount rates and increases in ECL requirements of accounts which ultimately were written off in the period. (7) Exposures and ECL for facilities that existed at the start of the period but not at the end. The following tables show changes in total on and off-balance sheet exposures and ECL in the period. The footnotes to the Santander UK group level table on page 119 also apply to these tables. Stage 1 Stage 2 Stage 3 Total Exposures (1) ECL Exposures (1) ECL Exposures (1) ECL Exposures (1) ECL £m £m £m £m £m £m £m £m At 1 January 2023 179,632 26 13,685 132 1,853 95 195,170 253 Transfers from Stage 1 to Stage 2 (3) (11,006) (3) 11,006 3 — — — — Transfers from Stage 2 to Stage 1 (3) 4,838 30 (4,838) (30) — — — — Transfers to Stage 3 (3) (337) (3) (570) (15) 907 18 — — Transfers from Stage 3 (3) 14 — 279 9 (293) (9) — — Transfers of financial instruments (6,491) 24 5,877 (33) 614 9 — — Net ECL remeasurement on stage transfer (4) — (28) — 40 — 22 — 34 Change in economic scenarios (2) — — — (2) — 3 — 1 New lending and assets purchased (5) 12,957 4 154 3 5 1 13,116 8 Redemptions, repayments and assets sold (7) (23,522) (6) (1,765) (12) (417) (14) (25,704) (32) Changes in risk parameters and other movements (6) 676 4 329 (17) 35 4 1,040 (9) Assets written off (7) — — — — (54) (11) (54) (11) At 31 December 2023 163,252 24 18,280 111 2,036 109 183,568 244 Net movement in the period (16,380) (2) 4,595 (21) 183 14 (11,602) (9) ECL (release)/charge to the Income Statement (2) (21) 25 2 Less: Discount unwind — — (3) (3) Less: Recoveries net of collection costs — — 29 29 Total ECL (release)/charge to the Income Statement (2) (21) 51 28 At 1 January 2022 180,232 14 11,199 88 1,816 89 193,247 191 Transfers from Stage 1 to Stage 2 (3) (5,833) (1) 5,833 1 — — — — Transfers from Stage 2 to Stage 1 (3) 2,961 16 (2,961) (16) — — — — Transfers to Stage 3 (3) (278) (2) (448) (11) 726 13 — — Transfers from Stage 3 (3) 3 — 280 9 (283) (9) — — Transfers of financial instruments (3,147) 13 2,704 (17) 443 4 — — Net ECL remeasurement on stage transfer (4) — (15) — 40 — 8 — 33 Change in economic scenarios (2) — 1 — 21 — 2 — 24 New lending and assets purchased (5) 35,028 7 529 11 1 — 35,558 18 Redemptions, repayments and assets sold (7) (32,565) (3) (1,229) (11) (415) (12) (34,209) (26) Changes in risk parameters and other movements (6) 84 9 482 — 18 7 584 16 Assets written off (7) — — — — (10) (3) (10) (3) At 31 December 2022 179,632 26 13,685 132 1,853 95 195,170 253 Net movement in the period (600) 12 2,486 44 37 6 1,923 62 ECL charge/(release) to the Income Statement 12 44 9 65 Less: Discount unwind — — (2) (2) Less: Recoveries net of collection costs — — (1) (1) Total ECL charge/(release) to the Income Statement 12 44 6 62 The following tables show changes in total on and off-balance sheet exposures and ECL in the period. The footnotes to the Santander UK group level table on page 119 also apply to these tables. Stage 1 Stage 2 Stage 3 Total Exposures (1) ECL Exposures (1) ECL Exposures (1) ECL Exposures (1) ECL £m £m £m £m £m £m £m £m At 1 January 2023 23,838 83 3,888 166 572 145 28,298 394 Transfers from Stage 1 to Stage 2 (3) (1,376) (1) 1,376 1 — — — — Transfers from Stage 2 to Stage 1 (3) 512 10 (512) (10) — — — — Transfers to Stage 3 (3) (118) (3) (258) (8) 376 11 — — Transfers from Stage 3 (3) 1 — 9 1 (10) (1) — — Transfers of financial instruments (981) 6 615 (16) 366 10 — — Net ECL remeasurement on stage transfer (4) — (16) — 29 — 64 — 77 Change in economic scenarios (2) — 30 — (30) — 6 — 6 New lending and assets purchased (5) 7,257 5 132 6 38 10 7,427 21 Redemptions, repayments and assets sold (7) (6,713) (13) (869) (10) (193) (23) (7,775) (46) Changes in risk parameters and other movements (6) (834) (19) 199 (13) 137 28 (498) (4) Assets written off (7) — — — — (175) (68) (175) (68) At 31 December 2023 22,567 76 3,965 132 745 172 27,277 380 Net movement in the period (1,271) (7) 77 (34) 173 27 (1,021) (14) ECL (release)/charge to the Income Statement (7) (34) 95 54 Less: Discount unwind — — (9) (9) Less: Recoveries net of collection costs — — (5) (5) Total ECL (release)/charge to the Income Statement (7) (34) 81 40 Stage 1 Stage 2 Stage 3 Total Exposures (1) ECL Exposures (1) ECL Exposures (1) ECL Exposures (1) ECL £m £m £m £m £m £m £m £m At 1 January 2022 20,604 50 5,914 127 827 248 27,345 425 Transfers from Stage 1 to Stage 2 (3) (2,195) (14) 2,195 14 — — — — Transfers from Stage 2 to Stage 1 (3) 4,023 92 (4,023) (92) — — — — Transfers to Stage 3 (3) (172) (1) (111) (13) 283 14 — — Transfers from Stage 3 (3) — — 463 135 (463) (135) — — Transfers of financial instruments 1,656 77 (1,476) 44 (180) (121) — — Net ECL remeasurement on stage transfer (4) — (72) — (41) — 61 — (52) Change in economic scenarios (2) — 38 — 76 — — — 114 New lending and assets purchased (5) 8,629 16 228 19 43 12 8,900 47 Redemptions, repayments and assets sold (7) (9,019) (15) (584) (32) (53) (17) (9,656) (64) Changes in risk parameters and other movements (6) 1,968 (11) (194) (27) 21 (14) 1,795 (52) Assets written off (7) — — — — (86) (24) (86) (24) At 31 December 2022 23,838 83 3,888 166 572 145 28,298 394 Net movement in the period 3,234 33 (2,026) 39 (255) (103) 953 (31) ECL charge/(release) to the Income Statement 33 39 (79) (7) Less: Discount unwind — — (3) (3) Less: Recoveries net of collection costs — — 42 42 Total ECL charge/(release) to the Income Statement 33 39 (40) 32
Disclosure of Country Risk Exposures	The tables below show our total exposures, which are the total of balance sheet and off–balance sheet values. We calculate balance sheet values in line with IFRS (i.e. after netting allowed under IAS 32) except for credit provisions which we add back. Off–balance sheet values are undrawn facilities and letters of credit. We classify location by country of risk – the country where each client has its main business or assets. That is unless there is a full risk transfer guarantee in place. If so, we use the guarantor’s country of domicile. If a client has operations in many countries, we use their country of incorporation. The table below excludes balances with other Banco Santander group members. We show them separately in the section that immediately follows. 2023 2022 Financial institutions Financial institutions Government s Banks (1 ) Other Retail Corporat e Total (2) Governments Banks (1) Other Retail Corporat e Total (2) £bn £bn £bn £bn £bn £bn £bn £bn £bn £bn £bn £bn Eurozone Ireland — — 3.1 — 0.1 3.2 — — 2.3 — 0.1 2.4 Spain — — — — — — — — — — — — France 0.1 1.7 0.8 — — 2.6 0.1 0.8 0.5 — — 1.4 Germany — 0.2 0.3 — — 0.5 — 0.3 — — 0.1 0.4 Luxembourg — — 0.5 — 0.1 0.6 — — — — — — Other (3) 0.3 0.7 — — — 1.0 0.3 0.5 — — — 0.8 0.4 2.6 4.7 — 0.2 7.9 0.4 1.6 2.8 — 0.2 5.0 Other countries UK 40.8 1.7 7.2 208.4 25.0 283.1 46.6 1.8 6.2 220.2 26.8 301.6 US — 0.7 — — — 0.7 0.1 1.0 — — — 1.1 Japan 2.0 0.9 — — — 2.9 1.1 0.3 — — — 1.4 Switzerland 2.1 — — — — 2.1 1.2 — — — — 1.2 Other 0.1 1.2 0.2 1.3 0.7 3.5 0.1 0.8 0.2 1.3 0.5 2.9 45.0 4.5 7.4 209.7 25.7 292.3 49.1 3.9 6.4 221.5 27.3 308.2 Total 45.4 7.1 12.1 209.7 25.9 300.2 49.5 5.5 9.2 221.5 27.5 313.2 (1) Excludes balances with central banks. (2) Excludes cash at hand, interests in other entities, intangible assets, property, plant and equipment, tax assets, retirement benefit assets and other assets. (3) Includes The Netherlands £0.3 bn ( 2022 : £0.1 bn), Belgium £0.5 bn ( 2022 : £0.6 bn), and Finland £0.1 bn ( 2022 : £0.1 bn ).
Disclosure of Balances with Other Banco Santander Group Companies	At 31 December 2023 and 31 December 2022 , we had gross balances with other Banco Santander group members as follows: 2023 2022 Financial institutions Financial institutions Banks Other Corporate Total Banks Other Corporate Total £bn £bn £bn £bn £bn £bn £bn £bn Assets Spain 0.9 — — 0.9 1.4 — — 1.4 UK — 4.5 — 4.5 — 4.2 — 4.2 0.9 4.5 — 5.4 1.4 4.2 — 5.6 Liabilities Spain 2.3 0.1 — 2.4 1.7 0.1 — 1.8 UK — 0.9 — 0.9 — 1.2 — 1.2 2.3 1.0 — 3.3 1.7 1.3 — 3.0
Disclosure of Borrower Profile	Stock New business 2023 2022 2023 2022 £m % £m % £m % £m % Home movers (1) 73,075 42 77,708 41 5,009 41 12,221 36 Remortgagers (2) 49,084 28 53,936 29 3,901 32 10,644 31 First-time buyers 37,495 21 38,698 21 3,015 25 8,129 24 Buy-to-let 15,585 9 16,799 9 239 2 3,133 9 175,239 100 187,141 100 12,164 100 34,127 100 (1) 'Home movers’ include both existing customers moving house and taking out a new mortgage with us, and customers who switch their mortgage to us when they move house. (2) 'Remortgagers’ are new customers who are taking a new mortgage with us.
Disclosure of Interest Rate Profile of Mortgage Assets Stock	The interest rate profile of our maturing mortgage asset stock was: 2023 2022 £m % £m % Fixed rate 155,363 89 166,281 89 Of which maturing: – < 12 months 38,419 22 39,123 21 – Later than 1 year but no later than 3 years 66,451 38 39,056 21 – Later than 3 years but no later than 4 years 34,925 20 24,584 13 – Later than 4 years but no later than 5 years 11,126 6 25,290 14 – Later than 5 years 4,442 3 38,228 20 Variable rate 13,923 8 12,511 7 Standard Variable Rate (SVR) 3,942 2 5,682 3 Follow on Rate (FoR) 2,011 1 2,667 1 175,239 100 187,141 100
Disclosure of Geographic Distribution of Mortgage Assets Stock	Stock New business 2023 2022 2023 2022 Region £bn £bn £bn £bn London 44.6 47.8 2.9 8.3 Midlands and East Anglia 24.6 26.0 1.8 5.3 North 23.2 24.8 1.7 4.7 Northern Ireland 2.6 2.9 0.1 0.3 Scotland 6.4 6.8 0.6 1.2 South East excluding London 55.6 59.3 3.8 10.6 South West, Wales and other 18.2 19.5 1.3 3.7 175.2 187.1 12.2 34.1
Disclosure of Mortgage Loan Size	The split of our mortgage asset by size was: Mortgage loan size 2023 2022 >£1.0m 2 % 2 % £0.5m to £1.0m 10 % 10 % £0.25m to £0.5m 31 % 31 % <£0.25m 57 % 57 % Average loan size (stock) (1) £188k £184k Average loan size (new business) £228k £237k (1) Average initial advance of existing stock.
Disclosure of LTV Distribution of Mortgage Assets Stock	This table shows the LTV distribution for the gross carrying amount and the related ECL of our total mortgage portfolio and Stage 3 mortgages, and new business. We also show the collateral value and average LTV. We use our estimate of the property value at the balance sheet date and include fees that have been added to the loan. For flexible products, we only include the drawn amount, not undrawn limits. 2023 2022 Stock Stage 3 New Stock Stage 3 New Total ECL Total ECL Business Total ECL Total ECL Business LTV £m £m £m £m £m £m £m £m £m £m Up to 50% 79,949 31 1,110 12 2,616 88,841 37 1,116 14 4,890 >50-60% 33,402 24 348 10 1,604 36,356 29 284 11 4,014 >60-70% 31,261 40 248 16 1,977 34,350 50 197 16 6,104 >70-80% 18,847 50 139 20 2,736 17,977 46 110 15 10,094 >80-90% 8,917 35 67 15 2,318 7,369 29 42 9 6,002 >90-100% 2,418 20 39 11 900 1,876 17 32 9 2,999 >100% 445 44 65 25 13 372 45 52 21 24 175,239 244 2,016 109 12,164 187,141 253 1,833 95 34,127 Collateral value (1) 175,182 2,005 12,164 187,093 1,824 34,126 % % % % % % Average LTV - Balance weighted (2) 51 49 66 50 47 69 (1) Collateral value is limited to the balance of each loan and excludes the impact of any over-collateralisation. Includes collateral against loans in negative equity of £389m ( 2022 : £323m ). (2)
Disclosure of Loan Modifications	The following table sets out the financial assets that were forborne while they had a loss allowance measured at lifetime ECL. 2023 2022 £m £m Financial assets modified in the period: – Amortised cost before modification 351 317 – Net modification loss 5 7 Financial assets modified since initial recognition: – Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period 79 91 2023 2022 Term extension Interest-only Term extension Interest-only £m £m £m £m Stage 1 122 1,186 n/a n/a Stage 2 31 510 n/a n/a Stage 3 2 18 n/a n/a 155 1,714 n/a n/a The following table sets out the financial assets that were forborne while they had a loss allowance measured at lifetime ECL. Business banking Credit cards Overdrafts Total 2023 £m £m £m £m Financial assets modified in the period: – Amortised cost before modification — 13 8 21 – Net modification loss — 14 6 20 Financial assets modified since initial recognition: – Gross carrying amount of financial assets for which the loss allowance changed to 12m ECL in the period — 2 1 3 2022 Financial assets modified in the period: – Amortised cost before modification — 7 7 14 – Net modification loss — 7 6 13 Financial assets modified since initial recognition: – Gross carrying amount of financial assets for which the loss allowance changed to 12m ECL in the period — 3 1 4 The following table sets out the financial assets that were forborne while they had a loss allowance measured at lifetime ECL. 2023 2022 £m £m Financial assets modified in the period: – Amortised cost before modification 189 240 – Net modification loss 10 8 Financial assets modified since initial recognition: – Gross carrying amount of financial assets for which the loss allowance changed to 12-month ECL in the period 27 15
Disclosure of Forbearance Balances	The balances at 31 December 2023 and 31 December 2022 , analysed by their staging at the period-end and the forbearance we applied, were: Capitalisation Term extension Interest-only Concessionary interest rate Total Loss allowances 2023 £m £m £m £m £m £m Stage 2 327 388 212 11 938 8 Stage 3 285 150 64 172 671 30 612 538 276 183 1,609 38 Proportion of portfolio 0.3 % 0.3 % 0.2 % 0.1 % 0.9 % 2022 Stage 2 311 320 240 6 877 11 Stage 3 299 140 65 190 694 31 610 460 305 196 1,571 42 Proportion of portfolio 0.3 % 0.3 % 0.2 % 0.1 % 0.9 % (1) We base forbearance type on the first forbearance on the accounts. The balances at 31 December 2023 and 31 December 2022 were: Interest-only (2) Flexible LTV >100% Buy-to-Let 2023 £m £m £m £m Total 368 74 12 23 – Stage 2 219 55 3 16 – Stage 3 149 19 9 7 2022 Total 292 36 10 15 – Stage 2 112 19 1 11 – Stage 3 180 17 9 4 (1) Where a loan falls into more than one category, we have included it in all the categories that apply. (2) Comprises full interest-only loans and part interest-only, part repayment loans. The balances at 31 December 2023 and 31 December 2022 were: Other unsecured Business banking Personal loans Credit cards Overdrafts Total other unsecured Total 2023 £m £m £m £m £m £m Total 3 1 47 19 67 70 – Stage 2 — 1 5 2 8 8 – Stage 3 3 — 42 17 59 62 2022 Total 3 1 34 16 51 54 – Stage 2 — 1 6 2 9 9 – Stage 3 3 — 28 14 42 45 We only make forbearance arrangements for lending to customers. The balances at 31 December 2023 and 31 December 2022 , analysed by their staging at the period–end and the forbearance we applied, were: 2023 2022 £m £m Stock (1) – Term extension 113 98 – Interest-only 215 238 – Other payment rescheduling 264 219 592 555 Of which: – Stage 1 2 17 – Stage 2 159 173 – Stage 3 431 365 592 555 Proportion of portfolio 2.3% 2.0% (1) We base forbearance type on the first forbearance we applied. Tables only show accounts open at the period-end. Amounts are drawn balances and include off balance sheet balances.
Disclosure of Segments Exposure by Credit Rating	These tables show our credit risk exposure according to our internal rating scale (see the ‘Santander UK group level – credit risk review’ section) for each portfolio. On this scale, the higher the rating, the better the quality of the counterparty. Santander UK risk grade 9 8 7 6 5 4 3 to 1 Other (1) Total 2023 £m £m £m £m £m £m £m £m £m SME and mid corporate — 166 911 2,970 3,497 3,575 1,439 118 12,676 Commercial Real Estate — — 360 1,684 2,132 972 209 1 5,358 Social Housing 43 3,032 4,881 — — — — — 7,956 43 3,198 6,152 4,654 5,629 4,547 1,648 119 25,990 Of which: Stage 1 43 3,130 6,152 4,618 4,715 2,363 141 118 21,280 Stage 2 — 68 — 36 914 2,184 762 1 3,965 Stage 3 — — — — — — 745 — 745 2022 SME and mid corporate — 336 923 2,341 3,299 5,327 1,791 106 14,123 Commercial Real Estate — 2 111 2,044 2,128 936 185 1 5,407 Social Housing 44 4,028 3,956 6 — — — 1 8,035 44 4,366 4,990 4,391 5,427 6,263 1,976 108 27,565 Of which: Stage 1 39 4,364 4,944 4,202 4,773 4,289 386 108 23,105 Stage 2 5 2 46 189 654 1,974 1,018 — 3,888 Stage 3 — — — — — — 572 — 572 (1) Smaller exposures mainly in the commercial mortgage portfolio. We use scorecards for them, instead of a rating model. These tables show our credit risk exposure according to our internal rating scale (see the ‘Santander UK group level – credit risk review’ section) for each portfolio. On this scale, the higher the rating, the better the quality of the counterparty. Santander UK risk grade 9 8 7 6 5 4 3 to 1 Other (1) Total 2023 £m £m £m £m £m £m £m £m £m Sovereign and Supranational 48,338 1,895 — — — — — — 50,233 Structured Products 170 1,470 787 — — — — — 2,427 Financial Institutions 1,262 667 436 7 — — — — 2,372 Crown Dependencies — — — — — — — 1,256 1,256 49,770 4,032 1,223 7 — — — 1,256 56,288 Of which: Stage 1 49,770 4,032 1,223 7 — — — 1,254 56,286 Stage 2 — — — — — — — 1 1 Stage 3 — — — — — — — 1 1 2022 Sovereign and Supranational 53,910 1,077 — — — — — — 54,987 Structured Products 136 1,162 875 — — — — — 2,173 Financial Institutions 1,191 676 635 26 — — — — 2,528 Crown Dependencies — — — — — — — 1,141 1,141 55,237 2,915 1,510 26 — — — 1,141 60,829 Of which: Stage 1 55,237 2,915 1,510 26 — — — 1,137 60,825 Stage 2 — — — — — — — 3 3 Stage 3 — — — — — — — 1 1 (1) Smaller exposures mainly in the commercial mortgage portfolio , and Crown Dependencies residential mortgages portfolio. We use scorecards for them, instead of a rating model.
Disclosure of Segments Exposure by Geographical Distribution	We typically classify geographical location according to the counterparty’s country of domicile unless a full risk transfer guarantee is in place, in which case we use the guarantor’s country of domicile instead. At 31 December 2023 and 31 December 2022 this is mainly focused in the UK. We typically classify geographical location according to the counterparty’s country of domicile unless a full risk transfer guarantee is in place, in which case we use the guarantor’s country of domicile instead. 2023 2022 UK Europe US Rest of World Total UK Europe US Rest of World Total £m £m £m £m £m £m £m £m £m £m Sovereign and Supranational 45,367 2,062 — 2,804 50,233 50,806 1,886 83 2,212 54,987 Structured Products 1,430 243 — 754 2,427 1,379 422 4 368 2,173 Financial Institutions 892 1,004 282 194 2,372 1,075 1,036 230 187 2,528 Crown Dependencies — — — 1,256 1,256 — — — 1,141 1,141 47,689 3,309 282 5,008 56,288 53,260 3,344 317 3,908 60,829
Disclosure of Segments Exposures by Gross and Net Credit Exposure	Gross exposure Collateral Net exposure Stage 3 Stage 3 Stage 3 2023 £m £m £m SME and mid corporate 627 190 437 Commercial Real Estate 118 28 90 745 218 527 2022 SME and mid corporate 513 169 344 Commercial Real Estate 59 30 29 572 199 373

Market Risk (Tables)

Market Risk (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Market Risk Exposure [Abstract]
Summary of Key Non-Traded Market Risks	Our key non-traded market risks are: Key risks Description Interest rate risk Yield curve risk: comes from timing mismatches in repricing fixed and variable rate assets, liabilities and off-balance sheet instruments. It also comes from investing non-rate sensitive liabilities in interest-earning assets. Basis risk: comes from pricing assets using a different rate index to the liabilities that fund them. We are exposed to basis risks associated with Bank of England bank rate, reserve rate linked assets we deposit with central banks, and the Sterling Overnight Index Average (SONIA) rate. Since the cessation of LIBOR at the end of 2021, basis risk exposure has been immaterial. Spread risk Spread risk arises when the value of assets or liabilities which are accounted for at fair value (either through Other Comprehensive Income or through Profit and Loss) are affected by changes in the credit spread. We measure these spreads as the difference between the discount rate we use to value the asset or liability, and an underlying interest rate curve. Foreign exchange risk Our banking businesses operate mainly in sterling markets, so we do not create significant foreign exchange exposures. The only exception to this is money we raise in foreign currencies. For more on this, see ‘Wholesale funding’ in the ‘Liquidity risk’ section. Income statement volatility risk We measure most of the assets and liabilities in our banking book balance sheet at amortised cost. We sometimes manage their risk profile by using derivatives. As all derivatives are accounted for at fair value, the mismatch in their accounting treatment can lead to volatility in our Income Statement. This happens even if the derivative is an economic hedge of the asset or liability.
Summary of NII and EVE Sensitivities Measurement	Net Interest Income (NII) sensitivity – NII sensitivity is an income-based measure we use to forecast the changes to interest income and interest expense in different scenarios. It gives us a combined impact on net interest income over a given period – usually 12 or 36 months. – We calculate NII sensitivity as the change in NII for a defined set of instantaneous parallel and non-parallel shifts in the yield curve. EVE sensitivity – We calculate EVE sensitivity as the change in the net present value of all the interest rate sensitive items in the banking book balance sheet for a defined set of instantaneous parallel and non-parallel shifts in the yield curve.
Summary of Detailed Information about VaR	Value at Risk (VaR) (audited) VaR – VaR indicates the losses that we might suffer because of unfavourable changes in the markets under normal (non-stressed) market conditions. We run a historical simulation using historical daily price moves to find how much we might lose, normally at a 99% confidence level.
Summary of NII and EVE Sensitivity of Interest Rate Risk	The table below shows how our net interest income would be affected by a 100bps parallel shift (both up and down) applied instantaneously to the yield curve at 31 December 2023 and 31 December 2022 . Sensitivity to parallel shifts represents the amount of risk in a way that we think is both simple and scalable. 2023 2022 +100bps -100bps +100bps -100bps £m £m £m £m NII sensitivity (audited) (1) 218 (220) 238 (194) EVE sensitivity (303) 267 (501) 651 (1) Based on modelling assumptions of repricing behaviour.

Liquidity Risk (Tables)

Liquidity Risk (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Liquidity Risk Exposure [Abstract]
Summary of Reconciliation of Wholesale Funding to Balance Sheet	This table reconciles our wholesale funding to our balance sheet at 31 December 2023 and 31 December 2022 . Balance sheet line item Funding analysis Deposits by banks (1) Repurchas e agreement s - non trading Financial liabilities designated at fair value Debt securities in issue Subordinated liabilities Other equity instruments and non- controlling interests (2) 2023 £bn £bn £bn £bn £bn £bn £bn Deposits by banks 1.1 1.1 — — — — — Certificates of deposit and commercial paper 4.3 — — — 4.3 — — Senior unsecured – public benchmark 12.9 — — — 12.9 — — – privately placed 0.8 — — 0.6 0.2 — — Covered bonds 14.8 — — — 14.8 — — Securitisation and structured issuance 2.7 — — — 2.7 — — TFSME 17.0 17.0 — — — — — Subordinated liabilities and equity 4.4 — — — — 2.2 2.2 Total wholesale funding 58.0 18.1 — 0.6 34.9 2.2 2.2 Repos 8.4 — 8.4 — — — — Foreign exchange and hedge accounting 1.1 — — — 0.9 0.2 — Other 2.6 2.3 — 0.3 — — — Balance sheet total 70.1 20.4 8.4 0.9 35.8 2.4 2.2 2022 Deposits by banks 0.5 0.5 — — — — — Certificates of deposit and commercial paper 4.7 — — — 4.7 — — Senior unsecured – public benchmark 14.4 — — — 14.4 — — – privately placed 0.6 — — 0.4 0.2 — — Covered bonds 14.9 — — — 14.9 — — Securitisation and structured issuance 1.0 — — — 1.0 — — TFSME 25.0 25.0 — — — — — Subordinated liabilities and equity 4.1 — — — — 1.9 2.2 Total wholesale funding 65.2 25.5 — 0.4 35.2 1.9 2.2 Repos 8.0 — 8.0 — — — — Foreign exchange and hedge accounting 1.6 — — — 1.2 0.4 — Other 3.4 3.0 — 0.4 — — — Balance sheet total 78.2 28.5 8.0 0.8 36.4 2.3 2.2 (1) Consists of Perpetual Capital Securities (net of issuance costs) . See Note 33 to the Consolidated Financial Statements. (2) Other consists of items in the course of transmission and other deposits. See Note 24 to the Consolidated Financial Statements.
Summary of Sources of Wholesale Funding by Maturity	This table shows our main sources of wholesale funding. It does not include securities finance agreements. The table is based on exchange rates at issue and scheduled repayments and call dates. It does not reflect the final contractual maturity of the funding. For details of the maturities of financial liabilities and off-balance sheet commitments, see Note 39 to the Consolidated Financial Statements . ≤ 1 month >1 and ≤ 3 months >3 and ≤ 6 months >6 and ≤ 9 months >9 and ≤ 12 months Sub-total ≤ 1 year >1 and ≤ 2 years >2 and ≤ 5 years >5 years Total 2023 £bn £bn £bn £bn £bn £bn £bn £bn £bn £bn Santander UK Group Holdings plc (1) Senior unsecured – public benchmark — 1.6 — — — 1.6 2.5 6.8 0.5 11.4 – privately placed — — — — — — — 0.1 — 0.1 Subordinated liabilities and equity (incl. AT1) — — 0.5 — — 0.5 0.8 1.5 0.9 3.7 — 1.6 0.5 — — 2.1 3.3 8.4 1.4 15.2 Santander UK plc Deposits by banks 0.3 0.8 — — — 1.1 — — — 1.1 Certificates of deposit and commercial paper 1.0 3.3 — — — 4.3 — — — 4.3 Senior unsecured – public benchmark — 0.6 0.2 — — 0.8 0.4 — 0.3 1.5 – privately placed — — — 0.1 — 0.1 0.1 0.2 0.3 0.7 Covered bonds 0.1 1.0 0.9 0.4 1.0 3.4 1.1 9.2 1.1 14.8 Securitisation & structured issuance (2) — — — — 0.1 0.1 — 2.1 — 2.2 TFSME — — — — — — 17.0 — — 17.0 Subordinated liabilities — — — — — — — — 0.7 0.7 1.4 5.7 1.1 0.5 1.1 9.8 18.6 11.5 2.4 42.3 Other group entities Securitisation & structured issuance (3) — — — — — — 0.5 — — 0.5 31 December 2023 1.4 7.3 1.6 0.5 1.1 11.9 22.4 19.9 3.8 58.0 Of which: – Secured 0.1 1.0 0.9 0.4 1.1 3.5 18.6 11.3 1.1 34.5 – Unsecured 1.3 6.3 0.7 0.1 — 8.4 3.8 8.6 2.7 23.5 2022 Total at 31 December 2022 2.6 5.2 0.5 1.5 1.2 11.0 6.6 42.5 5.1 65.2 Of which: – Secured 0.1 1.0 0.2 0.9 — 2.2 3.5 34.0 1.2 40.9 – Unsecured 2.5 4.2 0.3 0.6 1.2 8.8 3.1 8.5 3.9 24.3 (1) 96% of senior unsecured debt issued from Santander UK Group Holdings plc has been downstreamed to Santander UK plc as ‘secondary non-preferential debt’ in line with the guidelines from the Bank of England for Internal MREL. (2) Includes funding from mortgage-backed securitisation vehicles where Santander UK plc is the asset originator. (3) Includes funding from asset-backed securitisation vehicles where entities other than Santander UK plc are the asset originator.
Summary of Wholesale Funding by Currency	This table shows our wholesale funding by major currency at 31 December 2023 and 31 December 2022 . 2023 2022 Sterling US Dollar Euro Other Sterling US Dollar Euro Other % % % % % % % % Santander UK Group Holdings plc Senior unsecured – public benchmark 24 59 16 1 18 58 24 — – privately placed — — — 100 — — 100 Subordinated liabilities and equity (incl. AT1) 88 12 — — 75 25 — — 40 47 13 — 28 51 20 1 Santander UK plc Deposits by banks 1 97 2 — 29 71 — — Certificates of deposit and commercial paper 29 70 — 1 56 42 2 — Senior unsecured – public benchmark 21 56 23 — 18 62 20 — – privately placed 98 — 2 — 95 — 5 — Covered bonds 54 5 39 2 43 12 45 — Securitisation & structured issuance 100 — — — 100 — — — TFSME 100 — — — 100 — — — Subordinated liabilities 76 24 — — 48 52 — — 71 14 15 — 74 12 14 — Other group entities Securitisation & structured issuance 1.00 — — — — — — — Total 63 22 14 1 63 21 16 —
Summary of External Term Issuance, Sterling Equivalent	In 2023 , our external term issuance (sterling equivalent) was: Sterling US Dollar Euro Other 2023 2022 £bn £bn £bn £bn £bn £bn Santander UK Group Holdings plc Senior unsecured – public benchmark 0.4 1.1 — — 1.5 3.9 Subordinated debt and equity (inc. AT1) 1.1 — — — 1.1 0.8 1.5 1.1 — — 2.6 4.7 Santander UK plc Securitisations and other secured funding 1.5 — — — 1.5 0.6 Covered bonds 1.5 — — 0.3 1.8 4.0 Senior unsecured – privately placed 0.3 — — — 0.3 0.1 3.3 — — 0.3 3.6 4.7 Other group entities Securitisations 0.5 — — — 0.5 — Total gross issuances 5.3 1.1 — 0.3 6.7 9.4
Summary of Balance Sheet Encumbered and Unencumbered Assets Explanatory	On-balance sheet encumbered and unencumbered assets (audited) Encumbered with counterparties other than central banks Assets positioned at central banks (3) Covered bonds Securitis- ations Other Total 2023 £m £m £m £m £m Cash and balances at central banks (1)(2) — — 1,480 1,480 847 Financial assets at FVTPL: – Derivative financial instruments — — — — — – Other financial assets at FVTPL — — — — — Financial assets at amortised cost: – Loans and advances to customers 21,880 5,208 55 27,143 58,489 – Loans and advances to banks — — 254 254 — – Repurchase agreements – non trading — — — — — – Other financial assets at amortised cost — — 14 14 — Financial assets at FVOCI — — 5,254 5,254 — Interests in other entities — — — — — Intangible assets — — — — — Property, plant and equipment — — — — — Current tax assets — — — — — Retirement benefit assets — — — — — Other assets — — — — — Total assets 21,880 5,208 7,057 34,145 59,336 2022 £m £m £m £m £m Cash and balances at central banks (1)(2) — — 1,330 1,330 911 Financial assets at FVTPL: – Derivative financial instruments — — — — — – Other financial assets at FVTPL — — — — — Financial assets at amortised cost: – Loans and advances to customers 21,304 2,851 46 24,201 68,535 – Loans and advances to banks — — 163 163 — – Repurchase agreements – non trading — — — — — – Other financial assets at amortised cost — — 35 35 — Financial assets at FVOCI — — 4,441 4,441 — Interests in other entities — — — — — Intangible assets — — — — — Property, plant and equipment — — — — — Current tax assets — — — — — Retirement benefit assets — — — — — Other assets — — — — — Total assets 21,304 2,851 6,015 30,170 69,446 (1) Encumbered cash and balances at central banks include minimum cash balances we have to hold at central banks for regulatory purposes. (2) Readily realisable cash and balances at central banks are amounts held at central banks as part of our liquidity management activities. (3) Comprises pre-positioned assets and encumbered assets.

Capital Risk (Tables)

Capital Risk (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Capital Risk Exposure [Abstract]
Summary of Regulatory Capital Resources	Regulatory capital resources (audited) This table shows our qualifying regulatory capital: 2023 2022 £m £m CET1 capital instruments and reserves: – Capital instruments 7,060 7,060 – Retained earnings 6,047 6,563 – Accumulated other reserves and non-controlling interests (337) (1,108) CET1 capital before regulatory adjustments 12,770 12,515 CET1 regulatory adjustments: – Additional value adjustments (unaudited) (15) (18) – Goodwill (net of tax) (1,129) (1,133) – Other intangibles (349) (351) – Fair value reserves related to gains or losses on cash flow hedges (1) 335 1,116 – Negative amounts resulting from the calculation of regulatory expected loss amounts (unaudited) (595) (517) – Gains or losses on liabilities valued at fair value resulting from changes in own credit standing (14) (27) – Defined benefit pension fund assets (520) (755) – NPE Backstop 0 (4) – Dividend accrual (3) (3) – IFRS 9 Transitional Adjustment (unaudited) 44 20 CET1 capital 10,524 10,843 AT1 capital instruments: – Capital instruments 2,196 2,196 AT1 capital 2,196 2,196 Tier 1 capital 12,720 13,039 Tier 2 capital instruments: – Capital instruments 2,193 2,111 – Amount of qualifying items subject to phase out from Tier 2 193 207 – Regulatory deductions for instruments issued by subsidiary undertakings or subject to CRDIV amortisation and repurchases (331) (857) Tier 2 capital 2,055 1,461 Total regulatory capital 14,775 14,500 (1) From H223, amount includes £1.3m for cashflow hedge reserves FVOCI.
Disclosure of Movements in Regulatory Capital	Movements in regulatory capital CET1 capital AT1 capital Tier 2 capital Total £m £m £m £m At 1 January 2023 10,843 2,196 1,461 14,500 – Retained earnings (516) — — (516) – Other reserves and non-controlling interests (1) 770 — — 770 – Additional value adjustments (unaudited) 3 — — 3 – Goodwill (net of tax) 4 — — 4 – Other intangibles 2 — — 2 – Fair value reserves related to gains and losses on cash flow hedges (1) (780) — — (780) – Negative amounts resulting from the calculation of regulatory expected loss amounts (unaudited) (78) — — (78) – Gains or losses on liabilities valued at fair value resulting from changes in own credit standing 13 — — 13 – Defined benefit pension fund assets 235 — — 235 – NPE Backstop 4 — — 4 – Capital instruments — — 82 82 – IFRS 9 Transitional Adjustment (unaudited) 24 — — 24 – Amount of qualifying items subject to phase out from Tier 2 — — (14) (14) - Deductions for instruments issued by subsidiary undertakings or subject to CRD IV amortisation — — 526 526 At 31 December 2023 10,524 2,196 2,055 14,775 (1) From H223, amount includes £1.3m for cashflow hedge reserves FVOCI.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Significant Accounting Policies [Abstract]
Schedule of Useful Lives or Depreciation Rates Used for Property, Plant and Equipment	Classes of property, plant and equipment are depreciated on a straight-line basis over their useful life, as follows: Owner-occupied properties Not exceeding 50 years Office fixtures and equipment 3 to 15 years Computer software 3 to 7 years Right-of-use assets Shorter of the lease term or the useful life of the underlying asset Operating lease assets - vehicles 1 to 4 years
Disclosure of Information about Key Judgements and Key Estimates	Key judgements – Determining an appropriate definition of default – Establishing the criteria for a significant increase in credit risk (SICR) and, for corporate borrowers, internal credit risk rating – Determining the need for any judgemental adjustments – Determining the need to assess corporate Stage 3 exposures individually Key estimates – Forward-looking multiple economic scenario assumptions – Probability weights assigned to multiple economic scenarios b) Provisions and contingent liabilities Key judgements – Determining whether a present obligation exists – Determining the likely outcome of future legal decisions Key estimates – Probability, timing, nature and amount of any outflows that may arise from past events Key judgements – Setting the criteria for constructing the corporate bond yield curve used to determine the discount rate – Determining the methodology for setting the inflation assumption Key estimates – Discount rate applied to future cash flows – Rate of price inflation – Expected lifetime of the schemes' members – Valuation of pension fund assets whose values are not based on market observable data Key judgements: – Determining the basis of goodwill impairment testing and the methodology for determining the carrying value of CGUs, including the need for planning assumptions and internal capital allocations Key estimates: – Forecast cash flows for cash generating units, including estimated allocations of regulatory capital – Growth rate beyond initial cash flow projections – Discount rates which factor in risk-free rates and applicable risk premiums All of these variables are subject to fluctuations in external market rates and economic conditions beyond management’s control

Segments (Tables)

Segments (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of operating segments [abstract]
Summary of Results by Segment	Results by segment 3 For the year ended 31 December Retail & Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 2023 £m £m £m £m £m Net interest income/(expense) 3,740 156 841 (70) 4,667 Non-interest income 177 192 135 5 509 Total operating income/(expense) 3,917 348 976 (65) 5,176 Operating expenses before credit impairment charges, provisions and charges (1,816) (141) (351) (177) (2,485) Credit impairment charges (150) (15) (40) (1) (206) Provisions for other liabilities and charges (233) (18) (15) (70) (336) Total operating credit impairment charges, provisions and charges (383) (33) (55) (71) (542) Profit/(loss) from continuing operations before tax 1,718 174 570 (313) 2,149 Revenue from external customers 3,670 663 712 131 5,176 Inter-segment revenue/(expense) 247 (315) 264 (196) — Total operating income/(expense) 3,917 348 976 (65) 5,176 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 493 — 49 — 542 – Insurance, protection and investments 47 — — — 47 – Credit cards 94 — — — 94 – Non-banking and other fees (2) 3 25 79 11 118 Total fee and commission income 637 25 128 11 801 Fee and commission expense (463) (6) (11) (25) (505) Net fee and commission income/(expense) 174 19 117 (14) 296 Customer loans 182,267 5,228 17,939 1,256 206,690 Customer deposits 158,329 — 24,066 11,168 193,563 Average number of full-time equivalent staff 16,330 816 2,376 184 19,706 (1) The disaggregation of fees and commission income as shown above is not included in reports provided to the chief operating decision maker but is provided to show the split by reportable segments. (2) Non-banking and other fees include mortgages (except mortgage account fees), consumer finance, commitment commission, asset finance, invoice finance and trade finance. (3) Total assets and total liabilities are no longer included in reports provided to the chief operating decision maker. Retail & Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 2022 £m £m £m £m £m Net interest income 3,689 180 580 23 4,472 Non-interest income/(expense) 197 195 146 (4) 534 Total operating income 3,886 375 726 19 5,006 Operating expenses before credit impairment charges, provisions and charges (1,683) (144) (342) (201) (2,370) Credit impairment charges (263) (27) (31) — (321) Provisions for other liabilities and charges (395) (6) (8) (12) (421) Total operating credit impairment charges, provisions and charges (658) (33) (39) (12) (742) Profit/(loss) from continuing operations before tax 1,545 198 345 (194) 1,894 Revenue/(expense) from external customers 4,153 513 732 (392) 5,006 Inter-segment (expense)/revenue (267) (138) (6) 411 — Total operating income 3,886 375 726 19 5,006 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 502 — 60 — 562 – Insurance, protection and investments 78 — — — 78 – Credit cards 95 — — — 95 – Non-banking and other fees (2) 2 20 77 2 101 Total fee and commission income 677 20 137 2 836 Fee and commission expense (483) (5) (18) (6) (512) Net fee and commission income/(expense) 194 15 119 (4) 324 31 December 2022 Customer loans 194,661 5,384 18,518 1,141 219,704 Customer deposits 161,748 — 24,798 9,930 196,476 Average number of full-time equivalent staff 15,212 531 2,336 194 18,273 Retail & Business Banking Consumer Finance Corporate & Commercial Banking Corporate & Investment Banking Corporate Centre Total 2021 £m £m £m £m £m £m Net interest income/(expense) 3,374 233 397 — (7) 3,997 Non-interest income 201 178 112 — 56 547 Total operating income 3,575 411 509 — 49 4,544 Operating expenses before credit impairment write-backs, provisions and charges (1,703) (163) (365) — (309) (2,540) Credit impairment write-backs 98 33 90 — 12 233 Provisions for other liabilities and charges (187) 4 (34) — (162) (379) Total operating credit impairment (charges)/write-backs, provisions and charges (89) 37 56 — (150) (146) Profit/(loss) from continuing operations before tax 1,783 285 200 — (410) 1,858 Revenue/(expense) from external customers 4,061 489 619 — (625) 4,544 Inter-segment (expense)/revenue (486) (78) (110) — 674 — Total operating income 3,575 411 509 — 49 4,544 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 428 — 50 — — 478 – Insurance, protection and investments 67 — — — — 67 – Credit card fees 73 — — — — 73 – Non-banking and other fees (2) 2 10 62 — 2 76 Total fee and commission income 570 10 112 — 2 694 Fee and commission expense (384) — (22) — (8) (414) Net fee and commission income/(expense) 186 10 90 — (6) 280 Customer loans 185,608 4,984 19,282 — 742 210,616 Customer deposits 156,991 — 26,466 — 8,719 192,176 Average number of full-time equivalent staff 16,149 670 2,281 528 216 19,844 (1) The disaggregation of fees and commission income as shown above is not included in reports provided to the chief operating decision maker but is provided to show the split by reportable segments. (2) Non-banking and other fees include mortgages (except mortgage account fees), consumer finance, commitment commission, asset finance, invoice finance and trade finance. (3) Total assets and total liabilities are no longer included in reports provided to the chief operating decision maker.
Summary Of Relationship Between Customer Liabilities and Deposits	The table below shows the relationships between Customer assets and Loans and advances to customers as presented in the Consolidated Balance Sheet. Customer assets exclude Joint ventures, as they carry low credit risk and therefore have an immaterial ECL, and Other items, mainly accrued interest that we have not yet charged to the customer's account, and cash collateral. It also shows the relationship between customer liabilities (see above) and Deposits by customers as presented in the Consolidated Balance Sheet. Assets Liabilities 2023 2022 2023 2022 £m £m £m £m Customer balances (gross) 206,690 219,704 193,563 196,476 Loan loss allowance (916) (933) — — Customer balances (net) 205,774 218,771 193,563 196,476 Intercompany balances 4,488 4,165 958 1,153 Accrued interest 747 647 834 237 Other items 213 257 (206) (553) Loans and advances to customers / Deposits by customers 211,222 223,840 195,149 197,313

Net Interest Income (Tables)

Net Interest Income (Tables)	12 Months Ended
	Dec. 31, 2023
Analysis of income and expense [abstract]
Summary of Net Interest Income	Group 2023 2022 2021 £m £m £m Interest and similar income: Loans and advances to customers 8,888 5,854 4,685 Loans and advances to banks 1,865 651 54 Reverse repurchase agreements – non-trading 625 149 35 Other 475 168 56 Total interest and similar income (1) 11,853 6,822 4,830 Interest expense and similar charges: Deposits by customers (3,283) (827) (331) Deposits by banks (1,167) (496) (23) Repurchase agreements – non-trading (538) (120) (3) Debt securities in issue (2,024) (795) (372) Subordinated liabilities (169) (108) (92) Other (5) (4) (12) Total interest expense and similar charges (2) (7,186) (2,350) (833) Net interest income 4,667 4,472 3,997 (1) Includes £230m ( 2022 : £87m , 2021 : £22m ) of interest income on financial assets at FVOCI. (2) Includes £707m ( 2022 : £6m , 2021 : £317m ) of interest expense on the effective part of derivatives hedging debt issuances and £3m ( 2022 : £3m , 2021 : £3m ) of interest expense on lease liabilities.

Net Fee and Commission Income (

Net Fee and Commission Income (Tables)	12 Months Ended
	Dec. 31, 2023
Fee and commission income (expense) [abstract]
Summary of Net Fee and Commission Income	Group 2023 2022 2021 £m £m £m Fee and commission income: Current account and debit card fees 542 562 478 Insurance, protection and investments 47 78 67 Credit cards 94 95 73 Non-banking and other fees (1) 118 101 76 Total fee and commission income 801 836 694 Total fee and commission expense (505) (512) (414) Net fee and commission income 296 324 280 (1) Non-banking and other fees include mortgages (except mortgage account fees), consumer finance, commitment commission, asset finance, invoice finance and trade finance.

Other Operating Income (Tables)

Other Operating Income (Tables)	12 Months Ended
	Dec. 31, 2023
Net Trading And Other Income [Abstract]
Summary of Net Trading and Other Income	Group 2023 2022 2021 £m £m £m Net (losses) on financial instruments designated at fair value through profit or loss (1) (33) (74) (68) Net gains on financial instruments mandatorily at fair value through profit or loss (2) 42 84 50 Hedge ineffectiveness 18 28 8 Net profit on sale of financial assets at fair value through other comprehensive income — — 6 Income from operating lease assets 118 129 136 Other 68 43 135 213 210 267 (1) Net (losses) on financial instruments designated at fair value through profit or loss include losses of £24m on deposits ( 2022 : £35m gains, 2021 £18m losses), losses of £32m on debt securities ( 2022 : £31m gains, 2021 : £nil ). (2) Net gains on financial instruments mandatorily at fair value through profit or loss include gains of £5m on debt securities ( 2022 : £13m gains, 2021 : £10m losses). Group 2023 2022 2021 £m £m £m Exchange rate differences in the consolidated income statement on items not at fair value through profit and loss 1,215 (2,147) 215 These are principally offset by related releases from the cash flow hedge reserve (1,231) 2,130 (357)

Operating Expenses Before Cre_3

Operating Expenses Before Credit Impairment Charges, Provisions and Charges (Tables)	12 Months Ended
	Dec. 31, 2023
Expenses by nature [abstract]
Disclosure Of Operating Expenses Before Credit Impairment Charges Provisions And Charges	For the year ended 31 December Group 2023 2022 2021 £m £m £m Staff costs: Wages and salaries 854 761 759 Performance-related payments 164 173 184 Social security costs 116 112 113 Pensions costs: – defined contribution plans 71 60 65 – defined benefit plans 13 28 38 Other share-based payments 4 1 1 Other personnel costs 42 44 42 1,264 1,179 1,202 Other administration expenses 931 894 831 Depreciation, amortisation and impairment 290 297 507 2,485 2,370 2,540
Summary of Deferred Performance Awards	Performance-related payments’ include bonuses paid in cash and share awards granted under the arrangements described in Note 36 . Included in this are equity- settled share-based payments, none of which related to option-based schemes. These are disclosed in the table below as ‘Shares awards’. Performance-related payments above include amounts related to deferred performance awards as follows: Costs recognised in 2023 Costs expected to be recognised in 2024 or later Arising from awards in current year Arising from awards in prior year Total Arising from awards in current year Arising from awards in prior year Total £m £m £m £m £m £m Cash 3 4 7 5 7 12 Shares 2 5 7 4 7 11 5 9 14 9 14 23
Disclosure of Amount of Bonus Awarded to Employees	The following table shows the amount of bonus awarded to employees for the performance year 2023 . In the case of deferred cash and shares awards, the final amount paid to an employee is influenced by forfeiture provisions and any performance conditions to which the awards are subject. The deferred shares award amount is based on the fair value of the awards at the date of grant. Expenses charged in the year Expenses deferred to future periods Total 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m Cash award – not deferred 142 148 — — 142 148 – deferred 7 8 12 14 19 22 Shares award – not deferred 8 9 — — 8 9 – deferred 7 8 11 14 18 22 Total discretionary bonus 164 173 23 28 187 201

Audit and Other Services (Table

Audit and Other Services (Tables)	12 Months Ended
	Dec. 31, 2023
Audit And Other Services [Abstract]
Summary of Audit and Other Services	Group 2023 2022 2021 £m £m £m Audit fees: Fees payable to the Company’s auditor and its associates for the audit of the Santander UK group’s annual accounts 15.0 12.8 12.1 Fees payable to the Company’s auditor and its associates for other services to the Santander UK group: – Audit of the Santander UK group’s subsidiaries 0.7 0.8 1.2 Total audit fees (1) 15.7 13.6 13.3 Non-audit fees: Audit-related assurance services 2.3 1.9 1.7 Other assurance services 0.8 0.8 0.5 Other non-audit services 0.2 0.2 0.2 Total non-audit fees 3.3 2.9 2.4 (1) 2023 audit fees included £0.7m ( 2022 : £0.6m , 2021 : £1.2m ) which related to the prior year.

Credit Impairment Charges and_2

Credit Impairment Charges and Provisions (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Summary of Impairment Charges and Provisions	Group 2023 2022 2021 £m £m £m Credit impairment charges/(write-backs): Loans and advances to customers 192 249 (186) Recoveries of loans and advances, net of collection costs 10 36 (17) Off-balance sheet credit exposures (See Note 29) 4 36 (30) 206 321 (233) Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 29) 335 424 388 Releases for residual value and voluntary termination 1 (3) (9) 336 421 379 542 742 146

Taxation (Tables)

Taxation (Tables)	12 Months Ended
	Dec. 31, 2023
Major components of tax expense (income) [abstract]
Disclosure of Income Tax and Deferred Taxes Explanatory	Group 2023 2022 2021 £m £m £m Current tax: UK corporation tax on profit for the year 474 524 400 Adjustments in respect of prior years (23) (88) (30) Total current tax 451 436 370 Deferred tax: Charge/(credit) for the year 109 (30) 101 Adjustments in respect of prior years (7) 65 14 Total deferred tax 102 35 115 Tax on profit from continuing operations 553 471 485
Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate	The tax on profit from continuing operations before tax differs from the theoretical amount that would arise using the basic corporation tax rate as follows: For the year ended 31 December Group 2023 2022 2021 £m £m £m Profit from continuing operations before tax 2,149 1,894 1,858 Tax calculated at a tax rate of 23.5% (2022:19%, 2021: 19%) 505 360 353 Bank surcharge on profits 84 123 106 Non-deductible preference dividends paid 9 9 9 Non-deductible UK Bank Levy 10 13 14 Non-deductible conduct remediation, fines and penalties 13 48 6 Other non-deductible costs and non-taxable income (5) 20 33 Effect of change in tax rate on deferred tax provision 2 (28) 8 Tax relief on dividends in respect of other equity instruments (35) (40) (40) Adjustment to prior year provisions (30) (34) (4) Tax on profit from continuing operations 553 471 485
Disclosure of Movement in Current Tax Assets and Liabilities	Movements in current tax assets and liabilities during the year were as follows: Group 2023 2022 £m £m Assets 484 351 At 1 January 484 351 Income statement charge (including discontinued operations) (451) (436) Other comprehensive income (charge)/credit (70) 159 Corporate income tax received 539 397 Other movements 5 13 507 484 Assets 507 484 At 31 December 507 484
Schedule of Deferred Taxes	The table below shows the deferred tax balances including the movement in the deferred tax account during the year. Deferred tax balances are presented in the balance sheet after offsetting assets and liabilities where the Santander UK group has the legal right to offset and intends to settle on a net basis. Group Fair value of financial instruments Pension remeasurement Cash flow hedges Fair value reserve Tax losses carried forward Accelerated tax depreciation Other temporary differences Total £m £m £m £m £m £m £m £m At 1 January 2023 27 (290) 305 (2) — 35 (105) (30) Income statement (charge)/credit (35) (63) — — — (17) 13 (102) Transfers/reclassifications — 2 (2) — — — — — Credited/(charged) to other comprehensive income — 167 (232) 5 — — 4 (56) At 31 December 2023 (8) (184) 71 3 — 18 (88) (188) At 1 January 2022 (123) (508) (7) (12) 8 68 1 (573) Income statement credit/(charge) 150 (49) — — (7) (33) (96) (35) Transfers/reclassifications — — 3 (1) (1) — (1) — Credited/(charged) to other comprehensive income — 267 309 11 — — (9) 578 At 31 December 2022 27 (290) 305 (2) — 35 (105) (30)

Dividends on Ordinary Shares (T

Dividends on Ordinary Shares (Tables)	12 Months Ended
	Dec. 31, 2023
Dividends On Ordinary Shares [Abstract]
Disclosure of Dividends on Ordinary Shares Declared and Paid	Dividends on ordinary shares declared and paid in the year were as follows: Group Group 2023 2022 2021 2023 2022 2021 Pence per share Pence per share Pence per share £m £m £m In respect of current year – first interim 5.86 5.62 4.05 414 397 286 – second interim 15.92 8.73 15.01 1,124 616 1,060 21.78 14.35 19.06 1,538 1,013 1,346

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of nature and extent of risks arising from financial instruments [abstract]
Disclosure of Notional Amounts and Fair Values of Derivatives	The table below includes the notional amounts of transactions outstanding at the balance sheet date; they do not represent actual exposures. Group 2023 2022 Fair value Fair value Notional amount Assets Liabilities Notional amount Assets Liabilities £m £m £m £m £m £m Derivatives held for trading: Exchange rate contracts 13,536 92 241 14,769 320 299 Interest rate contracts 28,806 398 626 31,599 473 792 Equity and credit contracts 810 143 25 954 142 25 Total derivatives held for trading 43,152 633 892 47,322 935 1,116 Derivatives held for hedging Designated as fair value hedges: Exchange rate contracts 1,145 29 2 538 12 4 Interest rate contracts 107,753 1,276 843 77,885 1,776 411 108,898 1,305 845 78,423 1,788 415 Designated as cash flow hedges: Exchange rate contracts 21,618 1,008 290 26,035 1,717 186 Interest rate contracts 51,881 554 911 25,971 164 1,463 Equity derivative contracts 59 19 — 51 8 1 73,558 1,581 1,201 52,057 1,889 1,650 Total derivatives held for hedging 182,456 2,886 2,046 130,480 3,677 2,065 Derivative netting (1) — (2,047) (2,047) — (2,173) (2,173) Total derivatives 225,608 1,472 891 177,802 2,439 1,008 (1) Derivative netting excludes the effect of cash collateral, which is offset against the gross derivative position. The amount of cash collateral received that had been offset against the gross derivative assets was £472m ( 2022 : £1,368m ) and the amount of cash collateral paid that had been offset against the gross derivative liabilities was £12m ( 2022 : £70m ).
Disclosure of Analysis of the Notional and Fair Values of Derivatives by Trading and Settlement Method	The table below analyses the notional and fair values of derivatives by trading and settlement method. Notional Traded over the counter Asset Liability Settled by central counterparties Not settled by central counterparties Total Traded over the counter Traded over the counter 2023 £m £m £m £m £m Exchange rate contracts — 36,299 36,299 1,129 533 Interest rate contracts 174,460 13,980 188,440 181 333 Equity and credit contracts — 869 869 162 25 174,460 51,148 225,608 1,472 891 2022 Exchange rate contracts — 41,342 41,342 2,049 489 Interest rate contracts 124,638 10,817 135,455 240 493 Equity and credit contracts — 1,005 1,005 150 26 124,638 53,164 177,802 2,439 1,008
Disclosure of Maturity Profile and Average Price/Rate of Hedging Instruments Used in Hedging Strategies	The following table sets out the maturity profile and average price/rate of the hedging instruments used in the Santander UK group’s hedging strategies: Group 2023 Hedging Instruments ≤1 month >1 and ≤3 months >3 and ≤12 months >1 and ≤5 years >5 years Total Fair value hedges: Interest rate risk Interest rate contracts - Nominal amount (£m) 3,612 7,141 32,241 60,803 3,008 106,805 Average fixed interest rate - GBP 2.38 % 3.19 % 3.42 % 3.89 % 3.99 % Average fixed interest rate - EUR 1.14 % 0.18 % 0.45 % 0.21 % 3.92 % Average fixed interest rate - USD 2.60 % 2.46 % 4.23 % 1.36 % 4.91 % Interest rate/FX risk Exchange rate contracts - Nominal amount (£m) — 18 — 1,041 86 1,145 Interest rate contracts - Nominal amount (£m) — 18 — 844 86 948 Average GBP - EUR exchange rate — 1.11 — 1.16 1.15 Average GBP - USD exchange rate — — — 1.32 — Average fixed interest rate - EUR — — — 2.77 % 3.48 % Average fixed interest rate - USD — — — 4.83 % — Cash flow hedges: Interest rate risk Interest rate contracts - Nominal amount (£m) 911 3,083 13,671 27,715 1,219 46,599 Average fixed interest rate - GBP 5.06 % 3.05 % 5.38 % 3.84 % 3.45 % FX risk Exchange rate contracts - Nominal amount (£m) 927 3,238 2,692 9,447 588 16,892 Interest rate contracts - Nominal amount (£m) — 2,199 — — 942 3,141 Average GBP - JPY exchange rate 154.14 153.95 167.85 — — Average GBP - CHF exchange rate 1.09 1.09 1.09 1.12 1.12 Average GBP - EUR exchange rate — 1.20 1.17 1.18 — Average GBP - USD exchange rate — 1.39 — 1.28 1.39 Equity risk Equity derivative contracts - Nominal amount (£m) — — 7 50 2 59 Interest rate/FX risk Exchange rate contracts - Nominal amount (£m) 87 785 500 2,896 458 4,726 Interest rate contracts - Nominal amount (£m) — — — 1,975 166 2,141 Average GBP - EUR exchange rate 1.18 — 1.25 1.20 1.19 Average GBP - USD exchange rate — 1.66 — 1.38 1.54 Average fixed interest rate - GBP 2.57 % 2.54 % 2.96 % 2.42 % 4.81 % 2022 Fair value hedges: Interest rate risk Interest rate contracts - Nominal amount (£m) 2,210 4,468 21,678 45,451 3,808 77,615 Average fixed interest rate - GBP 2.58 % 0.88 % 0.56 % 2.07 % 3.78 % Average fixed interest rate - EUR 1.77 % 1.60 % 0.77 % 0.28 % 3.09 % Average fixed interest rate - USD 1.35 % 3.47 % 3.51 % 2.00 % 4.92 % Interest rate/FX risk Exchange rate contracts - Nominal amount (£m) — — 66 465 7 538 Interest rate contracts - Nominal amount (£m) — — — 263 7 270 Average GBP - EUR exchange rate — — 1.20 1.16 1.10 Average GBP - USD exchange rate — — — 1.19 — Average fixed interest rate - EUR — — 3.42 % 2.06 % — Average fixed interest rate - USD — — — 4.63 % — Cash flow hedges: Interest rate risk Interest rate contracts - Nominal amount (£m) 1,042 2,191 1,940 13,060 1,076 19,309 Average fixed interest rate - GBP 1.77 % 2.29 % 1.98 % 2.35 % 1.84 % FX risk Exchange rate contracts - Nominal amount (£m) 2,301 3,135 2,381 10,606 1,163 19,586 Interest rate contracts - Nominal amount (£m) 415 — — 2,325 997 3,737 Average GBP - JPY exchange rate — 157.45 160.04 — — Average GBP - CHF exchange rate — 1.13 — — — Average GBP - EUR exchange rate — — 1.12 1.18 1.17 Average GBP - USD exchange rate 1.22 1.25 1.17 1.31 1.39 Equity risk Equity derivative contracts - Nominal amount (£m) — — 6 43 2 51 Interest rate/FX risk Exchange rate contracts - Nominal amount (£m) — — 1,173 4,626 650 6,449 Interest rate contracts - Nominal amount (£m) — — 585 2,132 208 2,925 Average GBP - EUR exchange rate — — 1.19 1.21 1.20 Average GBP - USD exchange rate — — 1.60 1.50 1.54 Average fixed interest rate - GBP — — 3.27 % 2.58 % 4.59 %
Net Gains or Losses Arising From Hedges Included in Operating Income	Net gains or losses arising from fair value and cash flow hedges included in other operating income Group 2023 2022 2021 £m £m £m Fair value hedging: (Losses)/gains on hedging instruments (1,878) 2,371 846 Gains/(losses) on hedged items attributable to hedged risks 1,893 (2,307) (804) Fair value hedging ineffectiveness 15 64 42 Cash flow hedging ineffectiveness 3 (36) (34) 18 28 8
Disclosure of Information about Hedging Ineffectiveness by Risk Category Explanatory	Hedge ineffectiveness can be analysed by risk category as follows: Group 2023 2022 2021 Change in FV of hedging instruments Change in FV of hedged items Recognised in income statement Change in FV of hedging instruments Change in FV of hedged items Recognised in income statement Change in FV of hedging instruments Change in FV of hedged items Recognised in income statement Fair value hedges: £m £m £m £m £m £m £m £m £m Interest rate risk (1,864) 1,874 10 2,382 (2,324) 58 868 (838) 30 Interest rate/FX risk (14) 19 5 (11) 17 6 (22) 34 12 (1,878) 1,893 15 2,371 (2,307) 64 846 (804) 42 Group Hedging Instruments Recognised in income statement Reclassified from reserves to income Income statement line item affected by reclassification Change in FV Recognised in OCI Cash flow hedges: £m £m £m £m 2023 Interest rate risk Net interest income 449 (447) 2 (464) FX risk Net interest income/other operating income (375) 377 2 (392) Equity risk Operating expenses 20 (20) — 13 Interest rate/FX risk Net interest income/other operating income (238) 237 (1) (388) (144) 147 3 (1,231) 2022 Interest rate risk Net interest income (1,150) 1,150 — (96) FX risk Net interest income/other operating income 1,602 (1,602) — 1,691 Equity risk Operating expenses 2 (2) — 2 Interest rate/FX risk Net interest income/other operating income (54) 18 (36) 533 400 (436) (36) 2,130 2021 Interest rate risk Net interest income (312) 306 (6) 70 FX risk Net interest income/other operating income (54) 54 — (158) Equity risk Operating expenses (1) 1 — 2 Interest rate/FX risk Net interest income/other operating income (542) 514 (28) (273) (909) 875 (34) (359)
Disclosure of Reconciliation by Risk Category of Components of Equity and Analysis of Other Comprehensive Income Items Resulting from Hedge Accounting Explanatory	The following table provides a reconciliation by risk category of components of equity and analysis of OCI items (before tax) resulting from hedge accounting. Group 2023 2022 £m £m Balance at 1 January (1,561) 133 Effective portion of changes in fair value: – Interest rate risk 447 (1,150) – Foreign currency risk (377) 1,602 – Equity risk 20 2 – Interest rate/foreign currency risk (237) (18) (147) 436 Income statement transfers: – Interest rate risk 464 96 – Foreign currency risk 392 (1,691) – Equity risk (13) (2) – Interest rate/foreign currency risk 388 (533) 1,231 (2,130) Balance at 31 December (477) (1,561)
Disclosure of detailed information about hedging instruments	Santander UK hedges its exposures to various risks, including interest rate risk and foreign currency risk, as set out in the following table. Group 2023 2022 Accumulated amount of FV hedge adjustments Change in value to calculate hedge ineffectiveness Accumulated amount of FV hedge adjustments Change in value to calculate hedge ineffectiveness Carrying value Hedged item Portfolio hedge of interest rate risks Of which Discontinued hedges Carrying value Hedged item Portfolio hedge of interest rate risks Of which Discontinued hedges £m £m £m £m £m £m £m £m £m £m Fair value hedges Interest rate risk: Loans and advances to customers 73,270 — (622) (435) 1,969 60,783 — (2,637) (651) (2,708) Other financial assets at amortised cost 152 1 (8) (8) 5 156 — (12) 2 (14) Reverse repurchase agreements – non trading 6,186 — — — 4 4,045 — (5) (1) — Other financial assets at FVOCI 2,013 (113) — (131) 82 2,325 (200) — 35 (227) Deposits by customers (15,052) — (10) — (15) (1,394) — 5 — 5 Debt securities in issue (5,065) 162 (75) (114) (170) (5,210) 355 (95) (172) 566 Subordinated liabilities (522) (27) (1) (42) (1) (250) (27) (6) (62) 54 Interest rate/FX risk: Other financial assets at FVOCI 989 4 — — 12 237 (21) — 1 (9) Debt securities in issue (214) (14) — (24) 8 (290) (18) — (37) 27 Subordinated liabilities — — — — (1) 1 1 — 1 (1) 61,757 13 (716) (754) 1,893 60,403 90 (2,750) (884) (2,307) Group 2023 2022 Change in value to calculate hedge ineffectiveness Cash flow hedge reserve Balances on cash flow hedge reserve for discontinued hedges Change in value to calculate hedge ineffectiveness Cash flow hedge reserve Balances on cash flow hedge reserve for discontinued hedges Hedged item balance sheet line item £m £m £m £m £m £m Cash flow hedges: Interest rate risk: Loans and advances to customers (163) (455) 1 925 (999) (1) Cash and balances at central banks (283) 100 (76) 233 (274) (106) Deposits by banks (1) (1) — (8) 7 — FX risk: Other financial assets at FVOCI (253) 1 — — (6) — Not applicable – highly probable forecast transactions 88 1 — (349) 2 — Deposits by customers (21) — — (74) — — Debt securities in issue 605 (9) — (1,142) (19) (2) Repurchase agreements - non trading (42) — — (37) — — Equity risk: Other liabilities (20) 10 — (2) 3 — Interest rate/FX risk: Debt securities in issue/loans and advances to customers 194 (114) — 55 (244) (3) Subordinated liabilities/loans and advances to customers 43 (10) 52 (37) (31) 77 147 (477) (23) (436) (1,561) (35)

Other Financial Assets at Fai_3

Other Financial Assets at Fair Value Through Profit or Loss (Tables)	12 Months Ended
	Dec. 31, 2023
Financial assets at fair value through profit or loss [abstract]
Summary of Other Financial Assets at Fair Value Through Profit or Loss	Group 2023 2022 £m £m Loans and advances to customers: Loans to housing associations 8 4 Other loans 347 335 355 339 Debt securities 168 16 Other debt instruments 49 69 Equity securities 30 10 602 434

Loans and Advances to Custome_2

Loans and Advances to Customers (Tables)	12 Months Ended
	Dec. 31, 2023
Net Loans And Advances To Customers [Abstract]
Summary of Net Loans and Advances to Customers	Group 2023 2022 £m £m Loans secured on residential properties 176,495 188,282 Corporate loans 18,454 19,057 Finance leases 4,530 4,645 Other unsecured loans 7,232 7,742 Accrued interest and other adjustments 960 904 Amounts due from fellow Banco Santander subsidiaries and joint ventures 4,488 4,165 Loans and advances to customers 212,159 224,795 Credit impairment loss allowances on loans and advances to customers (916) (933) Residual value and voluntary termination provisions on finance leases (21) (22) Net loans and advances to customers 211,222 223,840
Disclosure of Finance Lease and Hire Purchase Contract Receivables	Finance lease and hire purchase contract receivables may be analysed as follows: Group 2023 2022 Gross investment Unearned finance income Net investment Gross investment Unearned finance income Net investment £m £m £m £m £m £m No later than one year 1,502 (216) 1,286 1,493 (182) 1,311 Later than one year and not later than two years 1,426 (208) 1,218 1,367 (168) 1,199 Later than two years and not later than three years 1,331 (194) 1,137 1,190 (147) 1,043 Later than three years and not later than four years 882 (129) 753 1,044 (129) 915 Later than four years and not later than five years 99 (14) 85 143 (18) 125 Later than five years 60 (9) 51 59 (7) 52 5,300 (770) 4,530 5,296 (651) 4,645
Disclosure of Maturity Analysis of Operating Lease Payments	At 31 December 2023 and 2022 , the Santander UK group had contracted with lessees for the following future undiscounted minimum lease payments receivable under operating leases. Group 2023 2022 £m £m No later than one year 29 31 Later than one year and not later than two years 26 28 Later than two years and not later than three years 19 23 Later than three years and not later than four years 14 13 Later than four years and not later than five years 7 11 Later than five years 19 22 114 128

Securitisations and Covered B_2

Securitisations and Covered Bonds (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Securitisations And Covered Bonds [Abstract]
Disclosure of Analysis of Securitisations and Covered Bonds	The Santander UK group’s principal securitisation programmes and covered bond programme, together with the balances of the advances subject to securitisation (or for the covered bond programme assigned) and the carrying value of the notes in issue at 31 December 2023 and 2022 are listed below. Gross assets External notes in issue Notes issued to Santander UK plc/subsidiaries as collateral 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m Mortgage-backed master trust structures: – Holmes 3,242 1,646 2,119 790 300 176 – Fosse 2,048 2,028 100 100 1,382 1,365 5,290 3,674 2,219 890 1,682 1,541 Other asset-backed securitisation structures: – Motor — 6 — 7 — — – Repton 757 — 550 — — — 757 6 550 7 — — Total securitisation programmes 6,047 3,680 2,769 897 1,682 1,541 Covered bond programme: – Euro 35bn Global Covered Bond Programme 21,880 21,304 15,000 15,205 — — Total securitisation and covered bond programmes 27,927 24,984 17,769 16,102 1,682 1,541
Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme	The following table sets out the internal and external issuances and redemptions in 2023 and 2022 for each securitisation and covered bond programme. Internal issuances External issuances Internal redemptions External redemptions 2023 2022 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m £m £m Mortgage-backed master trust structures: – Holmes 241 — 1,500 600 121 100 186 200 – Fosse — — — — — — — 200 Other asset-backed securitisation structures: – Motor — — — — — — 7 33 – Repton — — 550 — — — — — Covered bond programme: – Euro 35bn Global Covered Bond Programme 1,100 — 1,844 4,200 16 100 1,897 1,700 1,341 — 3,894 4,800 137 200 2,090 2,133

Transfers of Financial Assets_2

Transfers of Financial Assets Not Qualifying for Derecognition (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of transferred financial assets that are not derecognised in their entirety [abstract]
Carrying Amount of Financial Assets that Did Not Qualify for Derecognition and their Associated Financial Liabilities	The following table analyses the carrying amount of financial assets that did not qualify for derecognition and their associated financial liabilities: Group 2023 2022 Assets Liabilities Assets Liabilities Nature of transaction £m £m £m £m Sale and repurchase agreements 14 (14) 120 (128) Securities lending agreements 3,136 (2,735) 2,871 (2,509) Securitisations (See Notes 14 and 26) 6,047 (2,769) 3,680 (897) 9,197 (5,518) 6,671 (3,534)

Reverse Repurchase Agreements_2

Reverse Repurchase Agreements - Non Trading (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Reserve Repurchase Agreements Non-Trading [Abstract]
Summary of Reverse Repurchase Agreements - Non Trading	Group 2023 2022 £m £m Agreements with banks 2,397 885 Agreements with customers 10,071 6,463 12,468 7,348

Other Financial Assets at Amo_3

Other Financial Assets at Amortised Cost (Tables)	12 Months Ended
	Dec. 31, 2023
Financial assets at fair value through profit or loss [abstract]
Summary of Other Financial Assets at Amortised Cost	Group 2023 2022 £m £m Asset backed securities — — Debt securities 152 156 152 156

Financial Assets at Fair Valu_2

Financial Assets at Fair Value Through Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2023
Financial assets at fair value through other comprehensive income [abstract]
Summary of Financial Assets at Fair Value Through Other Comprehensive Income	Group 2023 2022 £m £m Debt securities 8,481 6,024 8,481 6,024

Interests in Other Entities (Ta

Interests in Other Entities (Tables)	12 Months Ended
	Dec. 31, 2023
Investments accounted for using equity method [abstract]
Schedule of Interests in Other Entities	Group 2023 2022 £m £m Joint Ventures 245 252 245 252

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of detailed information about intangible assets [abstract]
Schedule of Goodwill	Group Cost Accumulated impairment Carrying amount £m £m £m At 31 December 2022 and 1 January 2023 and 31 December 2023 1,285 (86) 1,199
Schedule of Goodwill for Cash Generating Units	Carrying amount of Goodwill by CGU and key assumptions in the VIU calculation Goodwill Discount rate Growth rate beyond initial cash flow projections 2023 2022 2023 2022 2023 2022 CGU £m £m % % % % Personal Financial Services 1,169 1,169 16.7 16.6 1.6 1.6 Private Banking 30 30 14.6 15.3 1.6 1.6 1,199 1,199
Disclosure of Reasonably Possible Changes in Key Assumptions	Reasonably possible changes in key assumptions CGU Input Key assumptions Associated risks Reasonably possible change Personal Financial Services Cash flow projections – BoE Bank Rate – UK house price growth – UK mortgage loan market growth – UK unemployment rate – Position in the market – Regulatory capital levels. – Uncertain market outlook – Higher interest rate environment impact on customer affordability – Customer remediation and regulatory action outcomes – Uncertain regulatory capital requirements. – Cash flow projections decrease by 10% ( 2022 : 5% ) . Discount rate – Discount rate used is a reasonable estimate of a suitable market rate for the profile of the business. – Market rates of interest rise. – Discount rate increases by 100 basis points ( 2022 : 100 basis points ) . GDP growth rate – High oil / gas prices – Elevated wage growth – Weak productivity – Large government debt burden – Fragile business and consumer confidence – Inflation and interest rates stay higher for longer, hitting the disposable income of our customers – Affects the profitability of our customers – Limits the scope for tax cuts, hitting the disposable income of our customers – Affects business and consumer spending decisions of our customers – GDP Growth rate decreases by 10% ( 2022 : 10% ) At 31 December 2023 and 31 December 2022 , a reasonably possible change in the key assumptions in relation to the VIU calculation for the goodwill balance in the Personal Financial Services CGU would have resulted in a reduction in headroom as follows. Reduction in headroom 2023 2022 CGU Reasonably possible change £m £m Personal Financial Services Cash flow projections decrease by 10% ( 2022 : 5% ) (818) (538) Discount rate increases by 100 basis points ( 2022 : 100 basis points ) (663) (887) GDP Growth rate decreases by 10% ( 2022 : 10% ) (19) (31)
Disclosure of Sensitivity of VIU Changes to Current Assumptions to Achieve Nil Headroom	2023 Carrying value Value in use Headroom Increase in discount rate Decrease in GDP growth rate Decrease in cash flows CGU £m £m £m bps % % Personal Financial Services 7,513 8,178 665 101 4 8 2022 Personal Financial Services 8,860 10,752 1,892 239 13 18
Disclosure of Intangible Assets	b) Other intangibles Group Cost Accumulated amortisation / impairment Carrying amount £m £m £m At 1 January 2023 1,272 (921) 351 Additions 114 — 114 Disposals (36) 36 — Charge — (116) (116) At 31 December 2023 1,350 (1,001) 349 At 1 January 2022 1,346 (1,004) 342 Additions 112 — 112 Disposals (186) 186 — Charge — (100) (100) Impairment — (3) (3) At 31 December 2022 1,272 (921) 351

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, plant and equipment [abstract]
Disclosure of Detailed Information about Property, Plant and Equipment	Group Property Office fixtures and equipment Computer software Operating lease assets Right-of-use assets Total (1) £m £m £m £m £m £m Cost: At 1 January 2023 893 831 79 722 272 2,797 Additions 89 88 1 85 31 294 Reclassification (to)/from assets held for sale 8 — — — — 8 Disposals (66) (29) (5) (172) (35) (307) At 31 December 2023 924 890 75 635 268 2,792 Accumulated depreciation: At 1 January 2023 271 625 73 145 157 1,271 Charge for the period 17 63 1 64 30 175 Impairment during the period — — — — (11) (11) Disposals (61) (26) (5) (62) (1) (155) At 31 December 2023 227 662 69 147 175 1,280 Carrying amount 697 228 6 488 93 1,512 Cost: At 1 January 2022 981 1,056 437 755 258 3,487 Additions 62 87 4 185 39 377 Reclassification to assets held for sale (98) (13) — — — (111) Disposals (52) (299) (362) (218) (25) (956) At 31 December 2022 893 831 79 722 272 2,797 Accumulated depreciation: At 1 January 2022 335 863 435 160 139 1,932 Charge for the year 18 69 1 73 19 180 Impairment during the year 8 2 — — — 10 Reclassification to assets held for sale (49) (13) — — — (62) Disposals (41) (296) (363) (88) (1) (789) At 31 December 2022 271 625 73 145 157 1,271 Carrying amount 622 206 6 577 115 1,526 Property includes investment properties of £17m ( 2022 : £17m ) and assets under construction of £nil ( 2022 : £204m ). In September 2023, we completed the construction of a new head office in Milton Keynes.

Other Financial Liabilities a_3

Other Financial Liabilities at Fair Value Through Profit or Loss (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of financial liabilities [abstract]
Summary of Other Financial Liabilities at Fair Value Through Profit or Loss	Group 2023 2022 £m £m Structured Notes Programmes 369 375 Structured deposits 426 321 Zero Amortising Guaranteed Notes 104 107 899 803

Deposits by Customers (Tables)

Deposits by Customers (Tables)	12 Months Ended
	Dec. 31, 2023
Deposits from customers [abstract]
Schedule of Deposits by Customers	Group 2023 2022 £m £m Demand and time deposits (1) 194,191 196,160 Amounts due to fellow Banco Santander subsidiaries and joint ventures 958 1,153 195,149 197,313 (1) Includes capital amount guaranteed / protected equity index-linked deposits of £304m ( 2022 : £408m ).

Deposits by Banks (Tables)

Deposits by Banks (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Deposits From Banks [Abstract]
Schedule of Deposits by Banks	Group 2023 2022 £m £m Items in the course of transmission 732 701 Deposits held as collateral 888 1,758 Other deposits (1) 18,737 26,084 20,357 28,543 (1) Includes drawdown from the TFSME of £17.0bn ( 2022 : £25.0bn ).

Repurchase Agreements - Non T_2

Repurchase Agreements - Non Trading (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Repurchase Agreements 1 [Abstract]
Summary of Repurchase Agreements - Non Trading	Group 2023 2022 £m £m Agreements with banks 551 50 Agreements with customers 7,860 7,932 8,411 7,982

Debt Securities in Issue (Table

Debt Securities in Issue (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Securities In Issue [Abstract]
Summary of Debt Securities in Issue	Group 2023 2022 £m £m Medium-term notes: – US $30bn Euro Medium Term Note Programme 744 739 – Euro 30bn Euro Medium Term Note Programme 5,619 6,435 – US SEC-registered Debt Programme - Santander UK Group Holdings plc 6,130 7,083 - US SEC-registered Debt Programme - Santander UK plc 1,031 1,276 Medium-term notes 13,524 15,533 Euro 35bn Global Covered Bond Programme 15,000 15,205 US $20bn Commercial Paper Programmes 2,761 1,851 Certificates of deposit 1,530 2,874 Credit linked notes 194 60 Securitisation programmes 2,769 897 35,778 36,420

Subordinated Liabilities (Table

Subordinated Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
Subordinated liabilities [abstract]
Schedule of Subordinated Liabilities	Group 2023 2022 £m £m £325m Sterling preference shares 343 344 Undated subordinated liabilities 205 219 Dated subordinated liabilities 1,838 1,769 2,386 2,332
Disclosure of Undated Subordinated Liabilities Explanatory	Undated subordinated liabilities Group 2023 2022 First call date £m £m 10.0625% Exchangeable capital securities n/a 205 205 7.125% 30 Year Step-up perpetual callable subordinated notes 2030 — 14 205 219
Disclosure of Dated Subordinated Liabilities Explanatory	Dated subordinated liabilities Group 2023 2022 Maturity £m £m 5% Subordinated notes 2023 — 591 4.75% Subordinated notes 2025 326 608 7.95% Subordinated notes 2029 193 207 6.50% Subordinated notes 2030 1 22 5.875% Subordinated notes 2031 7 7 5.625% Subordinated notes 2045 222 334 7.869% Subordinated notes 2033 321 — 8.296% Subordinated notes 2033 768 — 1,838 1,769

Other Liabilities (Tables)

Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
Subclassifications of assets, liabilities and equities [abstract]
Disclosure Of Other Liabilities Explanatory	Group 2023 2022 £m £m Lease liabilities 114 129 Other 2,387 2,472 2,501 2,601

Provisions (Tables)

Provisions (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of other provisions [abstract]
Summary of Provisions Reconciliation	Group Customer remediation Litigation and other regulatory Bank Levy Property ECL on undrawn facilities and guarantees Restructuring Other Total £m £m £m £m £m £m £m £m At 1 January 2023 90 136 4 47 74 22 7 380 Additional provisions (See Note 8) 45 28 46 16 4 56 168 363 Provisions released (See Note 8) (8) — (8) (6) — — (1) (23) Utilisation and other (21) (32) (95) (10) — (46) (167) (371) Recharge (1) — — 20 — — — — 20 Reclassification from provisions to other assets — — 36 — — — — 36 At 31 December 2023 106 132 3 47 78 32 7 405 Recharge in respect of the UK Bank Levy paid on behalf of other UK entities in the Banco Santander group

Retirement Benefit Plans (Table

Retirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of net defined benefit liability (asset) [abstract]
Summary of Retirement Benefit Plans	The amounts recognised in the balance sheet were as follows: Group 2023 2022 £m £m Assets/(liabilities) Funded defined benefit pension scheme - surplus 723 1,051 Funded defined benefit pension scheme - deficit (41) — Unfunded pension and post-retirement medical benefits (25) (25) Total net assets 657 1,026
Disclosure of Total Defined Benefit Plan Amount Charged to the Income Statement	The total amount charged to the income statement was as follows: Group 2023 2022 2021 £m £m £m Net interest income (54) (31) (5) Current service cost 13 30 38 Past service and GMP costs 1 — — Past service curtailment costs — — 5 Administration costs 7 9 8 (33) 8 46
Summary of Amounts Recognised in Other Comprehensive Income	The amounts recognised in other comprehensive income were as follows: Group 2023 2022 2021 £m £m £m Return on plan assets (excluding amounts included in net interest expense) 352 5,531 (452) Actuarial (gains) arising from changes in demographic assumptions (51) (122) (17) Actuarial losses/(gains) arising from experience adjustments 91 481 (19) Actuarial losses/(gains) arising from changes in financial assumptions 206 (5,167) (775) Pension remeasurement 598 723 (1,263)
Disclosure of Movements in the Present Value of Defined Benefit Obligations	Movements in the present value of defined benefit scheme obligations were as follows: Group 2023 2022 £m £m At 1 January (7,937) (12,884) Current service cost paid by Santander UK plc (13) (29) Current service cost paid by other subsidiaries — (1) Interest cost (379) (241) Employer salary sacrifice contributions (1) (3) Past service cost (1) — Remeasurement due to actuarial movements arising from: – Changes in demographic assumptions 51 122 – Experience adjustments (91) (481) – Changes in financial assumptions (206) 5,167 Benefits paid 372 413 Derecognition of pension scheme liabilities arising from the wind up of the offshore scheme 4 — At 31 December (8,201) (7,937)
Disclosure of Movements in Fair Value of Schemes' Assets	Movements in the fair value of the schemes’ assets were as follows: Group 2023 2022 £m £m At 1 January 8,963 14,420 Interest income 433 272 Contributions paid by employer and scheme members 197 224 Administration costs paid (7) (9) Return on plan assets (excluding amounts included in net interest expense) (352) (5,531) Benefits paid (372) (413) Derecognition of pension scheme assets arising from the wind up of the offshore scheme (4) — At 31 December 8,858 8,963
Disclosure of Fair Value of Plan Assets	The composition and fair value of the schemes’ assets by category was: Group Quoted prices in active markets Prices not quoted in active markets Total Valuation 2023 £m % £m % £m % technique Overseas equities — — 980 11 980 11 A,C Corporate bonds 2,284 26 242 3 2,526 29 A,C Government fixed interest bonds 1,618 18 — — 1,618 18 A Government index-linked bonds 4,422 50 — — 4,422 50 A Property — — 1,080 12 1,080 12 B Derivatives — — (2) — (2) — A Cash — — 586 7 586 7 A Repurchase agreements (1) — — (3,062) (35) (3,062) (35) A Infrastructure — — 408 5 408 5 B,C Annuities — — 293 3 293 3 D Longevity swap — — (16) — (16) — D Other — — 25 — 25 — C 8,324 94 534 6 8,858 100 2022 Overseas equities — — 1,172 13 1,172 13 A,C Corporate bonds 1,991 22 244 3 2,235 25 A,C Government fixed interest bonds 1,138 13 — — 1,138 13 A Government index-linked bonds 5,525 62 — — 5,525 62 A Property — — 1,202 13 1,202 13 B Derivatives — — (78) (1) (78) (1) A Cash — — 1,340 15 1,340 15 A Repurchase agreements (1) — — (4,312) (48) (4,312) (48) A Infrastructure — — 426 5 426 5 B,C Annuities — — 298 3 298 3 D Longevity swap — — (12) — (12) — D Other — — 29 — 29 — C 8,654 97 309 3 8,963 100 (1) Sale and repurchase agreements net of purchase and resale agreements.
Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes	The principal actuarial assumptions used for the Scheme were: Group 2023 2022 2021 % % % To determine benefit obligations (1) : – Discount rate for scheme liabilities 4.6 4.9 1.9 – General price inflation 3.0 3.1 3.4 – General salary increase 1.0 1.0 1.0 – Expected rate of pension increase 3.0 3.0 3.2 Years Years Years Longevity at 60 for current pensioners, on the valuation date: – Males 27.0 27.4 27.5 – Females 29.8 30.1 30.1 Longevity at 60 for future pensioners currently aged 40, on the valuation date: – Males 28.6 28.9 29.0 – Females 31.3 31.6 31.6 (1) The discount rate and inflation related assumptions set out in the table above reflect the assumptions calculated based on the Scheme’s duration and cash flow profile as a whole. The actual assumptions used were determined for each section independently based on each section’s duration and cash flow profile.
Summary of Actuarial Assumption Sensitivities	The sensitivity analyses below have been determined based on reasonably possible changes of the respective assumptions occurring at the end of the reporting period, while holding all other assumptions constant. Group (Decrease)/increase 2023 2022 Assumption Change in pension obligation at period end from £m £m Discount rate 50 bps increase (507) (501) General price inflation 50 bps increase 385 374 Mortality Each additional year of longevity assumed 223 203
Disclosure of Defined Benefit Plan Expected Future Benefit Payments	The benefits expected to be paid in each of the next five years, and in the aggregate for the five years thereafter are: Year ending 31 December £m 2024 455 2025 389 2026 404 2027 428 2028 444 Five years ending 2033 2,398

Contingent Liabilities and Co_3

Contingent Liabilities and Commitments (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of contingent liabilities [abstract]
Summary of Contingent Liabilities and Commitments	Group 2023 2022 £m £m Guarantees given to third parties 452 448 Formal standby facilities, credit lines and other commitments 30,987 31,410 31,439 31,858

Share Capital (Tables)

Share Capital (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of classes of share capital [abstract]
Schedule of Share Capital Issued and Fully Paid	Group Ordinary shares of £1 each Issued and fully paid share capital No. £m At 31 December 2022, 1 January 2023 and 31 December 2023 7,060,000,000 7,060

Other Equity Instruments (Table

Other Equity Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of classes of share capital [abstract]
Summary of Other Equity Instruments	Group Interest rate 2023 2022 % Next call date £m £m AT1 securities: - £500m Fixed Rate Reset Perpetual AT1 Capital Securities 6.75 June 2024 496 496 - £500m Fixed Rate Reset Perpetual AT1 Capital Securities 6.30 March 2025 500 500 - £450m Fixed Rate Reset Perpetual AT1 Capital Securities 4.25 March 2026 450 450 - £750m Fixed Rate Reset Perpetual AT1 Capital Securities 6.50 June 2027 750 750 2,196 2,196

Notes to Cash Flows (Tables)

Notes to Cash Flows (Tables)	12 Months Ended
	Dec. 31, 2023
Cash Flows Explanatory Notes [Abstract]
Summary of Changes in Liabilities Arising from Financing Activities	The table below shows the changes in liabilities arising from financing activities. The changes in equity arising from financing activities are set out in the Consolidated Statement of Changes in Equity. Group Balance sheet line item Debt securities in issue Subordinated liabilities Other equity instruments Lease liabilities Dividends paid Total 2023 £m £m £m £m £m £m At 1 January 36,420 2,332 2,196 129 — 41,077 Proceeds from issue of debt securities 5,347 — — — — 5,347 Repayment of debt securities (5,438) — — — — (5,438) Proceeds from issue of subordinated liabilities — 1,050 — — — 1,050 Repayment of subordinated liabilities — (971) — — — (971) Principal elements of lease payments — — — (48) — (48) Dividends paid — — — — (1,671) (1,671) Liability-related other changes (159) 25 — 33 — (101) Non-cash changes: – Unrealised foreign exchange (750) (54) — — — (804) – Other changes 358 4 — — 1,671 2,033 At 31 December 35,778 2,386 2,196 114 — 40,474 2022 At 1 January 31,580 2,228 2,191 134 — 36,133 Proceeds from issue of debt securities 8,667 — — — — 8,667 Repayment of debt securities (4,482) — — — — (4,482) Repayment of subordinated liabilities — (40) — — — (40) Issue of other equity instruments — — 750 — — 750 Repurchase of other equity instruments — — (750) — — (750) Principal elements of lease payments — — — (26) — (26) Dividends paid — — — — (1,173) (1,173) Liability-related other changes (1,282) 2 5 21 — (1,254) Non-cash changes: – Unrealised foreign exchange 1,893 190 — — — 2,083 – Other changes 44 (47) — — 1,173 1,169 At 31 December 36,420 2,332 2,196 129 — 41,077 2021 At 1 January 43,679 2,556 2,241 100 — 48,576 Proceeds from issue of debt securities 2,847 — — — — 2,847 Repayment of debt securities (13,724) — — — — (13,724) Repayment of subordinated liabilities — (4) — — — (4) Issue of other equity instruments — — 450 — — 450 Repurchase of other equity instruments — — (500) — — (500) Principal elements of lease payments — — — (25) — (25) Dividends paid — — — — (1,506) (1,506) Liability-related other changes (473) (4) — 59 — (418) Non-cash changes: – Unrealised foreign exchange (930) 14 — — — (916) – Other changes 181 (334) — — 1,506 1,353 At 31 December 31,580 2,228 2,191 134 — 36,133

Assets Charged as Security fo_2

Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Assets Pledged As Security [Abstract]
Financial Assets Charged as Security Under On-Balance Sheet and Off-Balance	The financial assets below are analysed between those assets accounted for on-balance sheet and off-balance sheet. Group 2023 2022 £m £m On-balance sheet: Cash and balances at central banks 1,480 1,330 Loans and advances to banks 254 163 Loans and advances to customers - securitisations and covered bonds (See Note 14) 27,088 24,155 Loans and advances to customers - other 20,703 32,011 Other financial assets at amortised cost 14 35 Financial assets at fair value through other comprehensive income 5,253 4,441 Total on-balance sheet 54,792 62,135 Total off-balance sheet 10,184 9,184
Schedule of Collateral Held as Security For Assets	The collateral held as security for assets, analysed between those liabilities accounted for on balance sheet and off-balance sheet, was: Group 2023 2022 £m £m On-balance sheet: Deposits by banks 888 1,758 Total on-balance sheet 888 1,758 Total off-balance sheet 15,652 10,395

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Summary of Movement in Share Options	The table below summarises movements in the number of options, and changes in weighted average exercise price over the same period. 2023 2022 Number of options Weighted average exercise price Number of options Weighted average exercise price ‘000 £ ‘000 £ Outstanding at 1 January 29,988 2.00 25,993 2.25 Granted 7,175 2.78 13,068 1.89 Exercised (5,980) 1.70 (242) 1.69 Forfeited/expired (4,044) 2.53 (8,831) 2.59 Outstanding at 31 December 27,139 2.19 29,988 2.00 Exercisable at 31 December 868 1.84 3,439 3.22 The weighted average share price at the date the options were exercised was £3.22 ( 2022 : £2.34
Summary of Range of Exercise Prices and Weighted Average Remaining Contractual Life of the Options Outstanding	The following table summarises the range of exercise prices and weighted average remaining contractual life of the options at 31 December 2023 and 2022 . 2023 2022 Weighted average remaining contractual life Weighted average exercise price Weighted average remaining contractual life Weighted average exercise price Range of exercise prices Years £ Years £ £1 to £2 3 1.84 3 1.79 £2 to £3 3 2.65 2 2.56 £3 to £4 0 3.46 1 3.46 £4 to £5 0 — 0 4.02

Transactions with Directors a_3

Transactions with Directors and Other Key Management Personnel (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Remuneration Of Directors And Other Key Management Personnel [Abstract]
Summary of Remuneration of the Directors and Other Key Management Personnel	The remuneration of the Directors and Other Key Management Personnel (KMP) of the Santander UK group is set out in aggregate below. 2023 2022 2021 Directors’ remuneration £ £ £ Salaries and fees 4,008,772 4,037,116 3,828,333 Performance-related payments 1,002,607 3,701,569 3,431,294 Other fixed remuneration (pension and other allowances & non-cash benefits) 222,538 906,201 806,103 Expenses — 13,004 3,705 Total remuneration 5,233,917 8,657,890 8,069,435 2023 2022 2021 Directors' and Other Key Management Personnel compensation £ £ £ Short-term employee benefits 13,235,757 15,641,669 18,831,380 Post-employment benefits 611,769 740,333 913,842 Compensation for loss of office (1) — 1,540,400 — Total compensation 13,847,526 17,922,402 19,745,222 (1) Compensation for loss of office was not paid to Directors or KMPs in 2023 ( 2022 : three KMPs, £1,540,400 ; 2021 : nil ).
Summary of Transactions with Directors, Other Key Management Personnel	Directors, Other KMP (defined as the Executive Committee of Santander UK plc who served during the year) and their connected persons have undertaken the following transactions with the Santander UK group in the ordinary course of business. 2023 2022 No. £000 No. £000 Secured loans, unsecured loans and overdrafts At 1 January 6 647 4 27 Net movements — 244 2 620 At 31 December 6 891 6 647 Deposit, bank and instant access accounts and investments At 1 January 16 2,995 16 6,427 Net movements (3) (1,819) — (3,432) At 31 December 13 1,176 16 2,995

Related Party Disclosures (Tabl

Related Party Disclosures (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of transactions between related parties [abstract]
Summary of Transactions With Related Parties	Transactions with related parties during the year and balances outstanding at the year-end: Group Interest, fees and other income received Interest, fees and other expenses paid Amounts owed by related parties Amounts owed to related parties 2023 2022 2021 2023 2022 2021 2023 2022 2023 2022 £m £m £m £m £m £m £m £m £m £m Ultimate parent (12) (863) (210) 475 47 34 903 1,423 (2,250) (1,732) Fellow subsidiaries (28) (60) (47) 194 171 151 26 31 (251) (278) Joint ventures (183) (77) (34) 55 17 4 4,486 4,151 (781) (973) (223) (1,000) (291) 724 235 189 5,415 5,605 (3,282) (2,983)

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Abstract]
Disclosure of Analysis of Fair Value of Financial Instruments Carried at Amortised Cost	Group 2023 2022 Fair value Fair Carrying Fair value Fair Carrying Level 1 Level 2 Level 3 value value Level 1 Level 2 Level 3 value value £m £m £m £m £m £m £m £m £m £m Assets Loans and advances to customers — — 209,641 209,641 211,222 — — 216,451 216,451 223,840 Loans and advances to banks — 1,216 — 1,216 1,216 — 1,105 — 1,105 1,105 Reverse repurchase agreements - non trading — 12,470 — 12,470 12,468 — 7,341 — 7,341 7,348 Other financial assets at amortised cost 144 — — 144 152 144 — — 144 156 144 13,686 209,641 223,471 225,058 144 8,446 216,451 225,041 232,449 Liabilities Deposits by customers — 76 194,831 194,907 195,149 — 52 197,228 197,280 197,313 Deposits by banks — 20,371 37 20,408 20,357 — 27,997 54 28,051 28,543 Repurchase agreements - non trading — 8,413 — 8,413 8,411 — 7,982 — 7,982 7,982 Debt securities in issue 11,511 22,710 1,154 35,375 35,778 4,988 28,685 1,582 35,255 36,420 Subordinated liabilities 871 1,669 209 2,749 2,386 19 2,268 224 2,511 2,332 12,382 53,239 196,231 261,852 262,081 5,007 66,984 199,088 271,079 272,590
Disclosure of Analysis of Fair Value of Financial Instruments Measured at Fair Value on a Recurring Basis	The following tables summarise the fair values of the financial assets and liabilities accounted for at fair value at 31 December 2023 and 31 December 2022 , analysed by their levels in the fair value hierarchy - Level 1, Level 2 and Level 3. Group 2023 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Valuation £m £m £m £m £m £m £m £m technique Assets Derivative financial instruments Exchange rate contracts — 1,129 — 1,129 — 2,049 — 2,049 A Interest rate contracts — 2,227 1 2,228 — 2,406 7 2,413 A & C Equity and credit contracts — 127 35 162 — 103 47 150 B & D Netting — (2,047) — (2,047) — (2,173) — (2,173) — 1,436 36 1,472 — 2,385 54 2,439 Other financial assets at FVTPL Loans and advances to customers — 309 46 355 — 294 45 339 A Debt securities — 168 49 217 — 13 72 85 A, B & D Equity securities — — 30 30 — — 10 10 B — 477 125 602 — 307 127 434 Financial assets at FVOCI Debt securities 8,293 188 — 8,481 5,996 28 — 6,024 D 8,293 188 — 8,481 5,996 28 — 6,024 Total assets at fair value 8,293 2,101 161 10,555 5,996 2,720 181 8,897 Liabilities Derivative financial instruments Exchange rate contracts — 533 — 533 — 489 — 489 A Interest rate contracts — 2,379 1 2,380 — 2,662 4 2,666 A & C Equity and credit contracts — 16 9 25 — 18 8 26 B & D Netting — (2,047) — (2,047) — (2,173) — (2,173) — 881 10 891 — 996 12 1,008 Other financial liabilities at FVTPL Debt securities in issue — 369 — 369 — 372 3 375 A Structured deposits — 426 — 426 — 321 — 321 A Zero Amortising Guaranteed Notes — 104 — 104 — 107 — 107 D — 899 — 899 — 800 3 803 Total liabilities at fair value — 1,780 10 1,790 — 1,796 15 1,811
Summary of Fair Value Adjustment	The fair value adjustments are set out in the following table: Group 2023 2022 £m £m Risk-related: - Bid-offer and trade specific adjustments (6) (12) - Uncertainty 29 27 - Credit risk adjustment (2) (1) - Funding fair value adjustment 1 1 22 15 Day One profit (1) (1) 21 14
Disclosure of Analysis of Financial Instruments Valued Using Internal Models Based on Information Other than Market Data	The table below provides an analysis of financial instruments valued using internal models based on information other than market data together with further details on the valuation techniques used for each type of instrument. Each instrument is initially valued at transaction price: Group Balance sheet value Fair value movements recognised in profit/(loss) 2023 2022 2023 2022 2021 Balance sheet line item Category Financial instrument product type £m £m £m £m £m 1. Derivative assets Equity and credit contracts Reversionary property interests 35 30 12 (8) — 2. FVTPL assets Loans and advances to customers Roll-up mortgage portfolio 24 28 (2) (18) (5) 3. FVTPL assets Loans and advances to customers Other loans 22 17 4 (4) (2) 4. FVTPL assets Debt securities Reversionary property securities 49 70 (3) — 5 5. FVTPL assets Equity securities Unlisted equity shares 30 10 27 (10) 1 160 155 38 (40) (1) Other Level 3 assets 1 26 7 17 (6) Other Level 3 liabilities (10) (15) (1) 2 6 Total net assets 151 166 Total income/(expense) 44 (21) (1)
Summary of Reconciliation of Fair Value Measurement in Level 3 of the Fair Value Hierarchy	The following table sets out the movements in Level 3 financial instruments in 2023 : Group Assets Liabilities Derivatives Other financial assets at FVTPL Financial assets at FVOCI Total Derivatives Other financial liabilities at FVTPL Total £m £m £m £m £m £m £m At 1 January 2023 54 127 — 181 (12) (3) (15) Total gains/(losses) recognised: Fair value movements (2) 18 27 — 45 (1) — (1) Foreign exchange and other movements — (7) — (7) — — — Purchases — 1 — 1 — — — Transfers out (22) — — (22) — — — Netting (1) — (3) — (3) — — — Settlements (14) (20) — (34) 3 3 6 At 31 December 2023 36 125 — 161 (10) — (10) Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the year (2) 18 20 — 38 (1) — (1) At 1 January 2022 56 235 18 309 (32) (6) (38) Total gains/(losses) recognised: Fair value movements (2) 5 (28) — (23) 2 — 2 Foreign exchange and other movements — (2) — (2) — 1 1 Transfers in — — — — (2) — (2) Transfers out — (28) — (28) — — — Netting (1) — (8) — (8) — — — Sales — (5) — (5) — — — Settlements (7) (37) (18) (62) 20 2 22 At 31 December 2022 54 127 — 181 (12) (3) (15) Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the year (2) 5 (30) — (25) 2 1 3 This relates to the effect of netting on the fair value of the credit linked notes due to a legal right of set-off between the principal amounts of the senior notes and the associated cash deposits. For more, see ‘ii) Credit protection entities’ in Note 19 (2) Fair value movements relating to derivatives and other financial assets at FVTPL are recognised in other operating income in the income statement.
Disclosure of Effects of Changes in Significant Unobservable Assumptions to Reasonably Possible Alternatives Level Three	Favourable and unfavourable changes are determined on the basis of changes in the value of the instrument as a result of varying the levels of the unobservable input as described in the table below. The potential effects do not take into effect any hedged positions. Group Significant unobservable input Sensitivity Assumption value Favourable changes Unfavourable changes Fair value Range (1) Weighted average Shift 2023 £m Assumption description £m £m 1. Derivative assets – Equity and credit contracts: 35 HPI Forward growth rate -5% to 5% (0.20) % 1.0 % 2 (2) – Reversionary property derivatives HPI Spot rate (2) n/a 513 10.0 % 2 (4) 2. FVTPL – Loans and advances to customers: 24 HPI Forward growth rate -5% to 5% 1.31 % 1.0 % — — – Roll-up mortgage portfolio 3. FVTPL – Loans and advances to customers: 22 Credit spreads 0.13% - 2.54% 0.97 % 20.0 % — — – Other loans 4. FVTPL – Debt securities: 49 HPI Forward growth rate -5% to 5% (0.20) % 1.0 % — — – Reversionary property securities HPI Spot rate (2) n/a 513 10.0 % 2 (2) 5. FVTPL – equity securities: 30 Contingent litigation risk 0% - 100% 39.00 % 20.0 % 3 (3) – Unlisted equity shares 2022 1. Derivative assets – Equity and credit contracts: 30 HPI Forward growth rate -5% to 5% 0.53 % 1.0 % 4 (4) – Reversionary property derivatives HPI Spot rate (2) n/a 513 10.0 % 4 (4) 2. FVTPL – Loans and advances to customers: 28 HPI Forward growth rate -5% to 5% 1.39 % 1.0 % 1 (1) – Roll-up mortgage portfolio 3. FVTPL – Loans and advances to customers: 17 Credit spreads 0.19% to 2.04% 0.98 % 20.0 % — — – Other loans 4. FVTPL – Debt securities: 70 HPI Forward growth rate -5% to 5% 0.53 % 1.0 % 1 (1) – Reversionary property securities HPI Spot rate (2) n/a 513 10.0 % 3 (3) 5. FVTPL – equity securities: 10 Contingent litigation risk 0% to 100% 0.95 % 20.0 % 7 (7) – Unlisted equity shares 6. Derivative liabilities – Equity contracts: (8) HPI Forward growth rate -5% to 5% -0.92 % 1.0 % 1 (1) – Property-related options and forwards HPI Spot rate (2) n/a 491 10.0 % 2 (3) (1) The range of actual assumption values used to calculate the weighted average disclosure. (2) The HPI spot rate in the weighted average column represents the HPI spot rate index level at 31 December 2023 and 2022 .
Disclosure of Maturity Analysis of Undiscounted Cash Flows for Financial Liabilities and Off Balance Sheet Commitments	The table below analyses the maturities of the undiscounted cash flows relating to financial liabilities and off-balance sheet commitments of Santander UK based on the remaining period to the contractual maturity date at the balance sheet date. Deposits by customers largely consist of retail deposits. This table is not intended to show the liquidity of Santander UK. Group On demand Not later than 3 months Later than 3 months and not later than 1 year Later than 1 year and not later than 5 years Later than 5 years Total 2023 £m £m £m £m £m £m Financial liabilities Derivative financial instruments 1 221 53 480 236 991 Other financial liabilities at fair value through profit or loss — 8 7 538 520 1,073 Deposits by customers 181,492 4,826 5,987 2,946 286 195,537 Deposits by banks 1,479 806 1,518 18,087 — 21,890 Repurchase agreements – non trading — 8,418 8 — — 8,426 Debt securities in issue — 7,500 3,835 21,708 8,597 41,640 Subordinated liabilities — 27 83 876 2,470 3,456 Lease liabilities — — 30 73 25 128 Total financial liabilities 182,972 21,806 11,521 44,708 12,134 273,141 Off-balance sheet commitments given 3,805 15,205 1,408 7,399 3,622 31,439 2022 Financial liabilities Derivative financial instruments — 224 120 501 302 1,147 Other financial liabilities at fair value through profit or loss — — 98 443 437 978 Deposits by customers 181,744 4,969 7,927 2,471 332 197,443 Deposits by banks 2,067 948 659 26,140 — 29,814 Repurchase agreements – non trading — 7,984 3 — — 7,987 Debt securities in issue — 6,678 2,101 23,076 6,830 38,685 Subordinated liabilities — 35 691 1,149 1,400 3,275 Lease liabilities — — 32 82 28 142 Total financial liabilities 183,811 20,838 11,631 53,862 9,329 279,471 Off-balance sheet commitments given 19,111 787 898 7,508 3,554 31,858

Offsetting Financial Assets a_2

Offsetting Financial Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of offsetting of financial liabilities [abstract]
Summary of Information about Impact of Offsetting of Financial Assets and Liabilities	Santander UK engages in a variety of counterparty credit mitigation strategies in addition to netting and collateral arrangements. Therefore, the net amounts presented in the tables below do not purport to represent Santander UK’s actual credit exposure. Group Amounts subject to enforceable netting arrangements Effects of offsetting on balance sheet Related amounts not offset Assets not subject to enforceable netting arrangements (2) Gross amounts Amounts offset Net amounts on balance sheet Financial instruments Financial collateral (1) Net amount Balance sheet total (3) 2023 £m £m £m £m £m £m £m £m Assets Derivative financial assets 3,469 (2,047) 1,422 (479) (823) 120 50 1,472 Reverse repurchase, securities borrowing & similar agreements: - Amortised cost 15,625 (3,157) 12,468 (118) (12,350) — — 12,468 Loans and advances to customers and banks (4) 5,565 (805) 4,760 — (180) 4,580 207,678 212,438 24,659 (6,009) 18,650 (597) (13,353) 4,700 207,728 226,378 Liabilities Derivative financial liabilities 2,911 (2,047) 864 (479) (226) 159 27 891 Repurchase, securities lending & similar agreements: - Amortised cost 11,568 (3,157) 8,411 (118) (8,293) — — 8,411 Deposits by customers and banks (4) 2,370 (805) 1,565 — — 1,565 213,941 215,506 16,849 (6,009) 10,840 (597) (8,519) 1,724 213,968 224,808 2022 Assets Derivative financial assets 4,557 (2,173) 2,384 (526) (1,720) 138 55 2,439 Reverse repurchase, securities borrowing & similar agreements: - Amortised cost 8,826 (1,478) 7,348 (9) (7,339) — — 7,348 Loans and advances to customers and banks (4) 5,144 (908) 4,236 — — 4,236 220,709 224,945 18,527 (4,559) 13,968 (535) (9,059) 4,374 220,764 234,732 Liabilities Derivative financial liabilities 3,142 (2,173) 969 (526) (158) 285 39 1,008 Repurchase, securities lending & similar agreements: - Amortised cost 9,460 (1,478) 7,982 (9) (7,973) — — 7,982 Deposits by customers and banks (4) 3,265 (908) 2,357 — — 2,357 223,499 225,856 15,867 (4,559) 11,308 (535) (8,131) 2,642 223,538 234,846 (1) Financial collateral is reflected at its fair value but has been limited to the net balance sheet exposure so as not to include any over-collateralisation. (2) This column includes contractual rights of set-off that are subject to uncertainty under the laws of the relevant jurisdiction. (3) The balance sheet total is the sum of ‘Net amounts reported on the balance sheet’ that are subject to enforceable netting arrangements and ‘Amounts not subject to enforceable netting arrangements’. (4) The amounts offset within loans and advances to customers/banks or deposits by customers/banks relate to offset mortgages which are classified as either and that are subject to netting.

Interest Rate Benchmark Refor_2

Interest Rate Benchmark Reform (Tables)	12 Months Ended
	Dec. 31, 2023
Interest Rate Benchmark Reform [Abstract]
Schedule of Amounts Affected by IBOR Reform	The following tables show the notional amounts of assets, liabilities and off-balance sheet commitments at 31 December 2023 and 31 December 2022 affected by IBOR reform that have yet to transition to an alternative benchmark interest rate. Group GBP LIBOR USD LIBOR Total 2023 £m £m £m Assets Financial assets at amortised cost 6 — 6 6 — 6 2022 Assets Derivatives — 1,665 1,665 Financial assets at amortised cost 76 245 321 76 1,910 1,986 Liabilities Derivatives 66 1,846 1,912 Financial liabilities at amortised cost — 2,491 2,491 66 4,337 4,403 Off-balance sheet commitments given 2 — 2

Discontinued Operations and A_2

Discontinued Operations and Assets Held for Sale (Tables)	12 Months Ended
	Dec. 31, 2023
Discontinued Operations and Assets and Liabilities Held for Sale [Abstract]
Disclosure of Financial Performance Relating to Discontinued Operations	The financial performance and cash flow information relating to the discontinued operations were as follows: For the year ended 31 December 2023 2022 2021 £m £m £m Net interest income — — 33 Net fee and commission income — — 34 Other operating income — — 2 Total operating income — — 69 Operating expenses before credit impairment (charges)/write-backs, provisions and charges — — (32) Credit impairment (charges)/write-backs — — 11 Provisions for other liabilities and charges — — (4) Total operating credit impairment (charges)/write-backs, provisions and charges — — 7 Profit from discontinued operations before tax — — 44 Tax on profit from discontinued operations — — (12) Profit from discontinued operations after tax — — 32
Disclosure of Assets Classified as Held for Sale	At 31 December 2023 , assets held for sale comprised: 2023 2022 £m £m Assets Property, plant and equipment 13 49 Total assets held for sale 13 49

Accounting Policies - Parent (T

Accounting Policies - Parent (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Significant Accounting Policies [Line Items]
Disclosure of Information about Key Judgements and Key Estimates	Key judgements – Determining an appropriate definition of default – Establishing the criteria for a significant increase in credit risk (SICR) and, for corporate borrowers, internal credit risk rating – Determining the need for any judgemental adjustments – Determining the need to assess corporate Stage 3 exposures individually Key estimates – Forward-looking multiple economic scenario assumptions – Probability weights assigned to multiple economic scenarios b) Provisions and contingent liabilities Key judgements – Determining whether a present obligation exists – Determining the likely outcome of future legal decisions Key estimates – Probability, timing, nature and amount of any outflows that may arise from past events Key judgements – Setting the criteria for constructing the corporate bond yield curve used to determine the discount rate – Determining the methodology for setting the inflation assumption Key estimates – Discount rate applied to future cash flows – Rate of price inflation – Expected lifetime of the schemes' members – Valuation of pension fund assets whose values are not based on market observable data Key judgements: – Determining the basis of goodwill impairment testing and the methodology for determining the carrying value of CGUs, including the need for planning assumptions and internal capital allocations Key estimates: – Forecast cash flows for cash generating units, including estimated allocations of regulatory capital – Growth rate beyond initial cash flow projections – Discount rates which factor in risk-free rates and applicable risk premiums All of these variables are subject to fluctuations in external market rates and economic conditions beyond management’s control
Santander UK Group Holdings plc
Disclosure Of Significant Accounting Policies [Line Items]
Disclosure of Information about Key Judgements and Key Estimates	Key judgements: – Determining the basis of investment impairment testing methodology, including the need for planning assumptions and internal capital allocations Key estimates: – Forecast cash flows for investments, including estimated allocations of regulatory capital – Growth rate beyond initial cash flow projections – Discount rates which factor in risk-free rates and applicable risk premiums All of these variables are subject to fluctuations in external market rates and economic conditions beyond management’s control

Other Financial Assets at Fai_4

Other Financial Assets at Fair Value Through Profit or Loss - Parent (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Summary of Other Financial Assets at Fair Value Through Profit or Loss	Group 2023 2022 £m £m Loans and advances to customers: Loans to housing associations 8 4 Other loans 347 335 355 339 Debt securities 168 16 Other debt instruments 49 69 Equity securities 30 10 602 434
Santander UK Group Holdings plc
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Summary of Other Financial Assets at Fair Value Through Profit or Loss	2023 2022 £m £m Debt securities 9,591 7,888 9,591 7,888

Interests in Other Entities -_2

Interests in Other Entities - Parent (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of subsidiaries [line items]
Disclosure of Sensitivity of VIU Changes to Current Assumptions to Achieve Nil Headroom	2023 Carrying value Value in use Headroom Increase in discount rate Decrease in GDP growth rate Decrease in cash flows CGU £m £m £m bps % % Personal Financial Services 7,513 8,178 665 101 4 8 2022 Personal Financial Services 8,860 10,752 1,892 239 13 18
Santander UK Group Holdings plc
Disclosure of subsidiaries [line items]
Disclosure of Interests in Subsidiaries	2023 2022 £m £m Interests in ordinary shares of subsidiaries 11,635 11,635 £500m Fixed Rate Reset Perpetual AT1 Capital Securities 495 495 £750m Fixed Rate Reset Perpetual AT1 Capital Securities 750 750 £500m Fixed Rate Reset Perpetual AT1 Capital Securities 210 210 £500m Fixed Rate Reset Perpetual AT1 Capital Securities 500 500 £450m Fixed Rate Reset Perpetual AT1 Capital Securities 50 50 13,640 13,640 The Company’s interests in subsidiaries were as follows: Cost Impairment Carrying amount £m £m £m At 31 December 2023 11,645 (10) 11,635 At 31 December 2022 11,645 (10) 11,635
Disclosure of Key Assumptions in VIU Calculation	Carrying amount of investments and key assumptions in the VIU calculation Carrying amount of investment Discount rate Growth rate beyond initial cash flow projections 2023 2022 2023 2022 2023 2022 Investment £m £m % % % % Santander UK plc 11,268 11,268 16.7 16.9 1.6 1.6 Santander Financial Services plc 337 337 17.9 16.7 1.6 1.6 Other 30 30 11,635 11,635
Disclosure of Sensitivity of Key Assumptions in Calculating VIU for Investments	Reduction in headroom 2023 2022 Subsidiary Reasonably possible change £m £m Santander UK plc Cash flow projections decrease by 10% ( 2022 : 5% ) (1,261) (773) Discount rate increases by 100 basis points ( 2022 : 100 basis points ) (1,026) (1,212) GDP growth rate decreases by 10 basis points ( 2022 : 10 basis points ) (24) (42) Reduction in headroom 2023 2022 Subsidiary Reasonably possible change £m £m Santander Financial Services plc Cash flow projections decrease by 10% ( 2022 : 5% ) (50) (18) Discount rate increases by 100 basis points ( 2022 : 100 basis points ) (34) (29)
Disclosure of Sensitivity of VIU Changes to Current Assumptions to Achieve Nil Headroom	2023 Carrying value Value in use Headroom Increase in post tax discount rate Decrease in cash flows Subsidiary £m £m £m bps % Santander UK plc 11,268 12,610 1,342 135 11 2022 Santander UK plc 11,268 15,461 4,193 450 27 2023 Carrying value Value in use Headroom Increase in post tax discount rate Decrease in cash flows Subsidiary £m £m £m bps % Santander Financial Services plc 337 497 160 720 32 2022 Santander Financial Services plc 337 359 22 75 6

Other Financial Liabilities a_4

Other Financial Liabilities at Fair Value Through Profit or Loss - Parent (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Summary of Other Financial Liabilities at Fair Value Through Profit or Loss	Group 2023 2022 £m £m Structured Notes Programmes 369 375 Structured deposits 426 321 Zero Amortising Guaranteed Notes 104 107 899 803
Santander UK Group Holdings plc
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Summary of Other Financial Liabilities at Fair Value Through Profit or Loss	2023 2022 £m £m Medium-term notes 9,591 7,888 9,591 7,888

Debt Securities in Issue - Pa_2

Debt Securities in Issue - Parent (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Securities In Issue [Line Items]
Summary of Debt Securities in Issue	Group 2023 2022 £m £m Medium-term notes: – US $30bn Euro Medium Term Note Programme 744 739 – Euro 30bn Euro Medium Term Note Programme 5,619 6,435 – US SEC-registered Debt Programme - Santander UK Group Holdings plc 6,130 7,083 - US SEC-registered Debt Programme - Santander UK plc 1,031 1,276 Medium-term notes 13,524 15,533 Euro 35bn Global Covered Bond Programme 15,000 15,205 US $20bn Commercial Paper Programmes 2,761 1,851 Certificates of deposit 1,530 2,874 Credit linked notes 194 60 Securitisation programmes 2,769 897 35,778 36,420
Santander UK Group Holdings plc
Debt Securities In Issue [Line Items]
Summary of Debt Securities in Issue	The Company issues notes in the US from time to time pursuant to a shelf registration statement on Form F-3 filed with the SEC in 2021. 2023 2022 £m £m Medium-term notes: – Euro 30bn Euro Medium Term Note Programme 1,123 2,387 – US SEC-registered Debt Programme – Santander UK Group Holdings plc 788 2,511 1,911 4,898

Subordinated Liabilities - Pa_2

Subordinated Liabilities - Parent (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Subordinated Liabilities [Line Items]
Schedule of Subordinated Liabilities	Group 2023 2022 £m £m £325m Sterling preference shares 343 344 Undated subordinated liabilities 205 219 Dated subordinated liabilities 1,838 1,769 2,386 2,332
Santander UK Group Holdings plc
Disclosure Of Subordinated Liabilities [Line Items]
Schedule of Subordinated Liabilities	2023 2022 Dated subordinated liabilities Maturity £m £m 4.75% Subordinated notes 2025 326 608 5.625% Subordinated notes 2045 222 334 8.296% Subordinated notes 2033 767 — 7.869% Subordinated notes 2033 318 — 1,633 942

Notes to Cash Flows - Parent (T

Notes to Cash Flows - Parent (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Summary of Changes in Liabilities Arising from Financing Activities	The table below shows the changes in liabilities arising from financing activities. The changes in equity arising from financing activities are set out in the Consolidated Statement of Changes in Equity. Group Balance sheet line item Debt securities in issue Subordinated liabilities Other equity instruments Lease liabilities Dividends paid Total 2023 £m £m £m £m £m £m At 1 January 36,420 2,332 2,196 129 — 41,077 Proceeds from issue of debt securities 5,347 — — — — 5,347 Repayment of debt securities (5,438) — — — — (5,438) Proceeds from issue of subordinated liabilities — 1,050 — — — 1,050 Repayment of subordinated liabilities — (971) — — — (971) Principal elements of lease payments — — — (48) — (48) Dividends paid — — — — (1,671) (1,671) Liability-related other changes (159) 25 — 33 — (101) Non-cash changes: – Unrealised foreign exchange (750) (54) — — — (804) – Other changes 358 4 — — 1,671 2,033 At 31 December 35,778 2,386 2,196 114 — 40,474 2022 At 1 January 31,580 2,228 2,191 134 — 36,133 Proceeds from issue of debt securities 8,667 — — — — 8,667 Repayment of debt securities (4,482) — — — — (4,482) Repayment of subordinated liabilities — (40) — — — (40) Issue of other equity instruments — — 750 — — 750 Repurchase of other equity instruments — — (750) — — (750) Principal elements of lease payments — — — (26) — (26) Dividends paid — — — — (1,173) (1,173) Liability-related other changes (1,282) 2 5 21 — (1,254) Non-cash changes: – Unrealised foreign exchange 1,893 190 — — — 2,083 – Other changes 44 (47) — — 1,173 1,169 At 31 December 36,420 2,332 2,196 129 — 41,077 2021 At 1 January 43,679 2,556 2,241 100 — 48,576 Proceeds from issue of debt securities 2,847 — — — — 2,847 Repayment of debt securities (13,724) — — — — (13,724) Repayment of subordinated liabilities — (4) — — — (4) Issue of other equity instruments — — 450 — — 450 Repurchase of other equity instruments — — (500) — — (500) Principal elements of lease payments — — — (25) — (25) Dividends paid — — — — (1,506) (1,506) Liability-related other changes (473) (4) — 59 — (418) Non-cash changes: – Unrealised foreign exchange (930) 14 — — — (916) – Other changes 181 (334) — — 1,506 1,353 At 31 December 31,580 2,228 2,191 134 — 36,133
Santander UK Group Holdings plc
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Summary of Changes in Liabilities Arising from Financing Activities	In addition to the changes in equity arising from financing activities, as set out in the Company Statement of Changes in Equity, the table below shows the changes in liabilities arising from financing activities. 2023 2022 Balance sheet line item Balance sheet line item Debt securities in issue Other liabilities at FVTPL (1) Subordinate d liabilities Other equity instruments Dividend s paid Total Debt securitie s in issue Other liabilities at FVTPL (1) Subordinated liabilities Other equity instruments Dividends paid Total £m £m £m £m £m £m £m £m £m £m £m £m At 1 January 4,898 7,888 942 2,196 — 15,924 6,013 4,190 838 2,191 — 13,232 Proceeds from issue of debt securities — 1,528 — — — 1,528 — 3,889 — — — 3,889 Repayment of debt securities (2,870) — — — — (2,870) (1,446) — — — — (1,446) Proceeds from issue of subordinated liabilities — — 1,050 — — 1,050 — — — — — — Repayment of subordinated liabilities — — (360) — — (360) — — — — — — Issue of other equity instruments — — — — — — — — — 750 — 750 Repurchase of other equity instruments — — — — — — — — — (750) — (750) Dividends paid — — — — (1,671) (1,671) — — — — (1,156) (1,156) Liability-related other changes (23) 558 30 — — 565 (14) (191) 1 5 — (199) Non-cash changes: – Unrealised foreign (99) (383) (32) — — (514) 339 — 103 — — 442 – Other changes 5 — 3 — 1,671 1,679 6 — — — 1,156 1,162 At 31 December 1,911 9,591 1,633 2,196 — 15,331 4,898 7,888 942 2,196 — 15,924 (1) Liability-related other changes for Other liabilities at FVTPL are not part of the changes in liability arising from financing activities.

Credit Risk - Disclosure of Exp

Credit Risk - Disclosure of Exposures to Credit Risk by Segment (Details) - Maximum £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£)
Everyday Banking
Disclosure of credit risk exposure [line items]
Customers, annual turnover	£ 6.5
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Customers, annual turnover	£ 500

Credit Risk - Disclosure of Key

Credit Risk - Disclosure of Key Metrics to Measure and Control Credit Risk (Details) - Credit risk	12 Months Ended
	Dec. 31, 2023
Expected Credit Loss (ECL)
Disclosure of credit risk exposure [line items]
Methods used to measure risk	Expected Credit Loss (ECL)
Description of objectives, policies and processes for managing risk	ECL tells us what credit risk is expected to cost us either over the next 12 months or over the lifetime of the exposure where there is evidence of a SICR since origination. We explain how we calculate ECL below.
Stages 1, 2 and 3
Disclosure of credit risk exposure [line items]
Methods used to measure risk	Stages 1, 2 and 3
Description of objectives, policies and processes for managing risk	We assess each facility’s credit risk profile to determine which stage to allocate them to, and we monitor where there is a SICR and transfers between the Stages including monitoring of coverage ratios for each stage.
Stage 3 ratio
Disclosure of credit risk exposure [line items]
Methods used to measure risk	Stage 3 ratio
Description of objectives, policies and processes for managing risk	The Stage 3 ratio is the sum of Stage 3 drawn and Stage 3 undrawn assets divided by the sum of total drawn assets and Stage 3 undrawn assets. The Stage 3 ratio is a key indicator used to monitor underlying asset performance.
Expected Loss (EL)
Disclosure of credit risk exposure [line items]
Methods used to measure risk	Expected Loss (EL)
Description of objectives, policies and processes for managing risk	EL is based on the CRD IV regulatory capital rules and gives us another view of credit risk. It is the product of the probability of default, exposure at default and loss given default, and we include direct and indirect costs. We base it on our risk models and our assessment of each customer’s credit quality. The rest of our Risk review, impairments, losses and loss allowances refer to calculations in accordance with IFRS, unless we specifically say they relate to CRD IV. For our IFRS impairment accounting policy, see Note 1 to the Consolidated Financial Statements.

Credit Risk - Disclosure of K_2

Credit Risk - Disclosure of Key Differences between Regulatory EL and IFRS 9 ECL Models (Details) - Credit risk	12 Months Ended
	Dec. 31, 2023
Rating philosophy
Disclosure Of Securitisations And Covered Bonds [Line Items]
Methods used to measure risk	Rating philosophy
Rating philosophy | Basel advanced IRB EL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Mix of point-in-time, through-the-cycle or hybrid
Rating philosophy | IFRS 9 ECL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Point-in-time, forward-looking. Considers a range of economic scenarios
Parameters calibration
Disclosure Of Securitisations And Covered Bonds [Line Items]
Methods used to measure risk	Parameters calibration
Parameters calibration | Basel advanced IRB EL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Contains regulatory floors and downturn calibration
Parameters calibration | IFRS 9 ECL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Unbiased estimate, based on conditions known at the balance sheet date
Calculation timing
Disclosure Of Securitisations And Covered Bonds [Line Items]
Methods used to measure risk	Calculation timing
Calculation timing | Basel advanced IRB EL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Considers aggregation of possible default events in the next 12 months
Calculation timing | IFRS 9 ECL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Considers monthly calculation of parameters, for all possible future default dates. First 12 months are used for Stage 1, full lifetime for Stages 2 and 3
Probability of Default (PD)
Disclosure Of Securitisations And Covered Bonds [Line Items]
Methods used to measure risk	Probability of Default (PD)
Description of objectives, policies and processes for managing risk	The likelihood of a borrower defaulting in the following month, assuming it has not closed or defaulted since the reporting date. For each month in the forecast period, we estimate the monthly PD from a range of factors. These include the current risk grade for the exposure, which becomes less relevant further into the forecast period, as well as the expected evolution of the account risk with maturity and factors for changing economics. We support this with historical data analysis.
Probability of Default (PD) | Basel advanced IRB EL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	PD in the next 12 months
Probability of Default (PD) | IFRS 9 ECL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Includes forward-looking economic data and removes conservatism. PD in next 12 months for Stage 1, lifetime for Stages 2 and 3
Loss Given Default (LGD)
Disclosure Of Securitisations And Covered Bonds [Line Items]
Methods used to measure risk	Loss Given Default (LGD)
Description of objectives, policies and processes for managing risk	Our expected loss if a default event were to occur. We express it as a percentage and calculate it based on factors that we have observed to affect the likelihood and/or value of any subsequent write-offs, which vary according to whether the product is secured or unsecured. If the product is secured, we take into account collateral values as well as the historical discounts to market/book values due to forced sales type.
Loss Given Default (LGD) | Basel advanced IRB EL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Lifetime LGD for defaults in the next 12 months
Loss Given Default (LGD) | IFRS 9 ECL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Modelled without regulatory floors and exclusion of indirect costs
Exposure at default (EAD)
Disclosure Of Securitisations And Covered Bonds [Line Items]
Methods used to measure risk	Exposure at Default (EAD)
Description of objectives, policies and processes for managing risk	The amount we expect to be owed if a default event occurs. We determine EAD for each month of the forecast period by the expected payment profile, which varies by product. For amortising products, we base it on the borrower’s contractual repayments over the forecast period. We adjust this for any expected overpayments on Stage 1 accounts that the borrower may make and for any arrears we expect if the account was to default. For revolving products, or amortising products with an off-balance sheet element, we determine EAD using the balance at default and the contractual exposure limit. We vary these assumptions by product and base them on analysis of recent default data.
Exposure at default (EAD) | Basel advanced IRB EL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Exposure at the point of default if the customer defaults in the next 12 months
Exposure at default (EAD) | IFRS 9 ECL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Recognises ability for exposure to reduce from balance sheet date to default date
SICR
Disclosure Of Securitisations And Covered Bonds [Line Items]
Methods used to measure risk	SICR
SICR | Basel advanced IRB EL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Does not include SICR concept
SICR | IFRS 9 ECL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	Includes SICR concept
Discounting applied
Disclosure Of Securitisations And Covered Bonds [Line Items]
Methods used to measure risk	Discounting applied
Discounting applied | Basel advanced IRB EL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	At weighted average cost of capital to the default date
Discounting applied | IFRS 9 ECL
Disclosure Of Securitisations And Covered Bonds [Line Items]
Description of objectives, policies and processes for managing risk	At the effective interest rate (EIR) to the balance sheet date

Credit Risk - Schedule of Macro

Credit Risk - Schedule of Macroeconomic Assumptions for Each Five Scenarios (Details)	Dec. 31, 2023	Dec. 31, 2022
Upside
Disclosure of credit risk exposure [line items]
GDP growth, year 1	4.30%	7.50%
GDP growth, year 2	0.60%	4.40%
GDP growth, year 3	1%	(1.00%)
GDP growth, year 4	2.10%	0.80%
GDP growth, year 5	2.40%	2%
GDP growth, year 6	2.40%	2%
GDP growth, year 7	2.40%
GDP growth rate, five-year average	2.10%	1.20%
GDP growth rate, peak/(trough)	0%	6%
Bank of England base rate, year 1	3.50%	0.25%
Bank of England base rate, year 2	5.25%	3.50%
Bank of England base rate, year 3	4.25%	3.75%
Bank of England base rate, year 4	3.25%	3%
Bank of England base rate, year 5	2.75%	2.50%
Bank of England base rate, year 6	2.75%	2.25%
Bank of England base rate, year 7	2.75%
Bank of England base rate, five-year end period	2.75%	2.25%
Bank of England base rate, peak/(trough)	5.25%	3.75%
House price growth, year 1	5%	8.70%
House price growth, year 2	(1.70%)	7.60%
House price growth, year 3	2%	(8.80%)
House price growth, year 4	6.50%	(4.30%)
House price growth, year 5	5.10%	0.60%
House price growth, year 6	4%	4.10%
House price growth, year 7	3.60%
House price growth rate, five-year average	4.30%	(0.70%)
House price growth rate, peak/(trough)	(3.70%)	(12.80%)
Unemployment rate, year 1	3.70%	4%
Unemployment rate, year 2	4.30%	3.70%
Unemployment rate, year 3	4.30%	4.70%
Unemployment rate, year 4	3.70%	4.50%
Unemployment rate, year 5	3.40%	4.50%
Unemployment rate, year 6	3%	4.40%
Unemployment rate, year 7	3%
Unemployment rate, five-year end period	3%	4.20%
Unemployment rate, peak/(trough)	4.50%	4.70%
Base case
Disclosure of credit risk exposure [line items]
GDP growth, year 1	4.30%	7.50%
GDP growth, year 2	0.50%	4.40%
GDP growth, year 3	0.40%	(1.30%)
GDP growth, year 4	1.30%	0.50%
GDP growth, year 5	1.50%	1.60%
GDP growth, year 6	1.40%	1.50%
GDP growth, year 7	1.40%
GDP growth rate, five-year average	1.20%	0.80%
GDP growth rate, peak/(trough)	0%	3.80%
Bank of England base rate, year 1	3.50%	0.25%
Bank of England base rate, year 2	5.25%	3.50%
Bank of England base rate, year 3	4.50%	4%
Bank of England base rate, year 4	3.50%	3.25%
Bank of England base rate, year 5	3.25%	2.75%
Bank of England base rate, year 6	3%	2.50%
Bank of England base rate, year 7	3%
Bank of England base rate, five-year end period	3%	2.50%
Bank of England base rate, peak/(trough)	5.25%	4%
House price growth, year 1	5%	8.70%
House price growth, year 2	(2.20%)	7%
House price growth, year 3	(1.00%)	(10.00%)
House price growth, year 4	2.50%	0%
House price growth, year 5	3%	2%
House price growth, year 6	3%	3%
House price growth, year 7	3%
House price growth rate, five-year average	2%	(0.60%)
House price growth rate, peak/(trough)	(6.50%)	(11.20%)
Unemployment rate, year 1	3.70%	4%
Unemployment rate, year 2	4.30%	3.80%
Unemployment rate, year 3	4.80%	4.70%
Unemployment rate, year 4	4.40%	5.10%
Unemployment rate, year 5	4.30%	4.50%
Unemployment rate, year 6	4.30%	4.30%
Unemployment rate, year 7	4.20%
Unemployment rate, five-year end period	4.20%	4.30%
Unemployment rate, peak/(trough)	4.80%	5.10%
Downside 1
Disclosure of credit risk exposure [line items]
GDP growth, year 1	4.30%	7.50%
GDP growth, year 2	0.50%	4.30%
GDP growth, year 3	(0.10%)	(1.90%)
GDP growth, year 4	0.20%	(0.30%)
GDP growth, year 5	0.50%	0.50%
GDP growth, year 6	0.30%	0.40%
GDP growth, year 7	0.30%
GDP growth rate, five-year average	0.30%	(0.20%)
GDP growth rate, peak/(trough)	(0.20%)	(0.80%)
Bank of England base rate, year 1	3.50%	0.25%
Bank of England base rate, year 2	5.25%	3.50%
Bank of England base rate, year 3	5.25%	3.50%
Bank of England base rate, year 4	4%	2.75%
Bank of England base rate, year 5	3.25%	2.50%
Bank of England base rate, year 6	3%	2.25%
Bank of England base rate, year 7	3%
Bank of England base rate, five-year end period	3%	2.25%
Bank of England base rate, peak/(trough)	5.75%	3.50%
House price growth, year 1	5%	8.70%
House price growth, year 2	(4.70%)	7.60%
House price growth, year 3	(11.70%)	(10.00%)
House price growth, year 4	3.40%	(6.70%)
House price growth, year 5	2.10%	(3.10%)
House price growth, year 6	3%	(0.20%)
House price growth, year 7	3.10%
House price growth rate, five-year average	(0.80%)	(3.80%)
House price growth rate, peak/(trough)	(17.50%)	(19.00%)
Unemployment rate, year 1	3.70%	4%
Unemployment rate, year 2	4.30%	3.70%
Unemployment rate, year 3	4.80%	5.10%
Unemployment rate, year 4	4.90%	5.40%
Unemployment rate, year 5	5.20%	5.80%
Unemployment rate, year 6	5.40%	6.10%
Unemployment rate, year 7	5.30%
Unemployment rate, five-year end period	5.30%	6.10%
Unemployment rate, peak/(trough)	5.50%	6.10%
Downside 2
Disclosure of credit risk exposure [line items]
GDP growth, year 1	4.30%	7.50%
GDP growth, year 2	0.30%	3.70%
GDP growth, year 3	(3.30%)	(6.40%)
GDP growth, year 4	(1.40%)	(0.70%)
GDP growth, year 5	0.60%	1.70%
GDP growth, year 6	2.20%	1.50%
GDP growth, year 7	2.60%
GDP growth rate, five-year average	0.10%	(0.60%)
GDP growth rate, peak/(trough)	(5.10%)	(3.10%)
Bank of England base rate, year 1	3.50%	0.25%
Bank of England base rate, year 2	5.25%	3.50%
Bank of England base rate, year 3	3.75%	3.75%
Bank of England base rate, year 4	2%	3%
Bank of England base rate, year 5	2%	2.75%
Bank of England base rate, year 6	2.50%	2.50%
Bank of England base rate, year 7	2.50%
Bank of England base rate, five-year end period	2.50%	2.50%
Bank of England base rate, peak/(trough)	5.25%	4%
House price growth, year 1	5%	8.70%
House price growth, year 2	(7.80%)	7.60%
House price growth, year 3	(25.80%)	(15.80%)
House price growth, year 4	3.60%	(14.30%)
House price growth, year 5	1.60%	(4.10%)
House price growth, year 6	1.60%	4.70%
House price growth, year 7	1.80%
House price growth rate, five-year average	(5.40%)	(4.80%)
House price growth rate, peak/(trough)	(33.00%)	(30.70%)
Unemployment rate, year 1	3.70%	4%
Unemployment rate, year 2	4.40%	4.40%
Unemployment rate, year 3	8.50%	8.50%
Unemployment rate, year 4	8%	8%
Unemployment rate, year 5	7.40%	7.40%
Unemployment rate, year 6	6.80%	6.80%
Unemployment rate, year 7	6.20%
Unemployment rate, five-year end period	6.20%	6.20%
Unemployment rate, peak/(trough)	8.50%	8.50%
Stubborn Inflation
Disclosure of credit risk exposure [line items]
GDP growth, year 1	4.30%	7.50%
GDP growth, year 2	0.50%	4.20%
GDP growth, year 3	(1.80%)	(2.70%)
GDP growth, year 4	(0.90%)	(0.90%)
GDP growth, year 5	0.40%	0.20%
GDP growth, year 6	0.70%	0.60%
GDP growth, year 7	0.80%
GDP growth rate, five-year average	(0.20%)	(0.50%)
GDP growth rate, peak/(trough)	(2.80%)	(2.20%)
Bank of England base rate, year 1	3.50%	0.25%
Bank of England base rate, year 2	5.25%	3.50%
Bank of England base rate, year 3	6.50%	6%
Bank of England base rate, year 4	5%	5.50%
Bank of England base rate, year 5	3.75%	3.50%
Bank of England base rate, year 6	3%	3%
Bank of England base rate, year 7	3%
Bank of England base rate, five-year end period	3%	3%
Bank of England base rate, peak/(trough)	6.50%	6%
House price growth, year 1	5%	8.70%
House price growth, year 2	(6.30%)	7.60%
House price growth, year 3	(18.80%)	(10.90%)
House price growth, year 4	3.60%	(8.80%)
House price growth, year 5	1.60%	(4.90%)
House price growth, year 6	1.60%	(0.60%)
House price growth, year 7	1.80%
House price growth rate, five-year average	(3.30%)	(4.70%)
House price growth rate, peak/(trough)	(25.50%)	(23.10%)
Unemployment rate, year 1	3.70%	4%
Unemployment rate, year 2	4.30%	3.70%
Unemployment rate, year 3	5.60%	5.50%
Unemployment rate, year 4	5.90%	5.90%
Unemployment rate, year 5	6.20%	6.40%
Unemployment rate, year 6	6.10%	6.60%
Unemployment rate, year 7	5.80%
Unemployment rate, five-year end period	5.80%	6.40%
Unemployment rate, peak/(trough)	6.20%	6.60%
Weighted
Disclosure of credit risk exposure [line items]
GDP growth, year 1	4.30%	7.50%
GDP growth, year 2	0.50%	4.30%
GDP growth, year 3	(0.40%)	(2.20%)
GDP growth, year 4	0.60%	0%
GDP growth, year 5	1.10%	1.20%
GDP growth, year 6	1.40%	1.20%
GDP growth, year 7	1.40%
GDP growth rate, five-year average		0.30%
GDP growth rate, peak/(trough)	(1.10%)	1.30%
Bank of England base rate, year 1	3.50%	0.25%
Bank of England base rate, year 2	5.25%	3.50%
Bank of England base rate, year 3	4.88%	4.29%
Bank of England base rate, year 4	3.68%	3.59%
Bank of England base rate, year 5	3.18%	2.85%
Bank of England base rate, year 6	2.93%	2.55%
Bank of England base rate, year 7	2.93%
Bank of England base rate, five-year end period		2.55%
Bank of England base rate, peak/(trough)	5.55%	4.31%
House price growth, year 1	5%	8.70%
House price growth, year 2	(3.80%)	7.30%
House price growth, year 3	(7.80%)	(10.70%)
House price growth, year 4	3.30%	(4.40%)
House price growth, year 5	2.70%	(0.80%)
House price growth, year 6	2.70%	2%
House price growth, year 7	2.70%
House price growth rate, five-year average		(2.30%)
House price growth rate, peak/(trough)	(13.80%)	(16.80%)
Unemployment rate, year 1	3.70%	4%
Unemployment rate, year 2	4.30%	3.80%
Unemployment rate, year 3	5.30%	5.30%
Unemployment rate, year 4	5.10%	5.60%
Unemployment rate, year 5	5%	5.40%
Unemployment rate, year 6	4.90%	5.30%
Unemployment rate, year 7	4.70%
Unemployment rate, five-year end period		5.20%
Unemployment rate, peak/(trough)	5.50%	5.90%

Credit Risk - Disclosure of Sce

Credit Risk - Disclosure of Scenario Weights Applied To Scenarios (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Upside
Disclosure of credit risk exposure [line items]
Probability weightings of scenarios, percentage	10%	5%
Base case
Disclosure of credit risk exposure [line items]
Probability weightings of scenarios, percentage	50%	50%
Downside 1
Disclosure of credit risk exposure [line items]
Probability weightings of scenarios, percentage	10%	15%
Stubborn Inflation
Disclosure of credit risk exposure [line items]
Probability weightings of scenarios, percentage	20%	20%
Downside 2
Disclosure of credit risk exposure [line items]
Probability weightings of scenarios, percentage	10%	10%
Weighted
Disclosure of credit risk exposure [line items]
Probability weightings of scenarios, percentage	100%	100%

Credit Risk - Disclosure of Qua

Credit Risk - Disclosure of Quantitative Criteria of Credit Risk Exposure (Details) - Probability of Default (PD)	12 Months Ended
	Dec. 31, 2023
Mortgages
Disclosure of credit risk exposure [line items]
PD threshold for measuring significant increase in credit risk	0.30%
Consumer Finance
Disclosure of credit risk exposure [line items]
PD threshold for measuring significant increase in credit risk	3%
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
PD threshold for measuring significant increase in credit risk	0.30%
Personal loans | Everyday Banking
Disclosure of credit risk exposure [line items]
PD threshold for measuring significant increase in credit risk	0.30%
Credit cards | Everyday Banking
Disclosure of credit risk exposure [line items]
PD threshold for measuring significant increase in credit risk	3.40%
Overdrafts | Everyday Banking
Disclosure of credit risk exposure [line items]
PD threshold for measuring significant increase in credit risk	2.60%

Credit Risk - Disclosure of Q_2

Credit Risk - Disclosure of Qualitative Criteria of Credit Risk Exposure (Details)	12 Months Ended
	Dec. 31, 2023
Mortgages
Disclosure of credit risk exposure [line items]
Qualitative criteria for measuring SICR	– In forbearance– Default in last 24m– 30 Days past due (DPD) in last 12m– Bankrupt– £100+ arrears
Consumer Finance
Disclosure of credit risk exposure [line items]
Qualitative criteria for measuring SICR	– In forbearance– Deceased or Insolvent– Court ‘Return of goods’ order or Police watchlist– Agreement terminated– Payment holiday– Cash Collection
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Qualitative criteria for measuring SICR	– In forbearance– Default in last 12m– Watchlist: proactive management– Default at proxy origination
Corporate Centre
Disclosure of credit risk exposure [line items]
Qualitative criteria for measuring SICR	– Watchlist: proactive management
Personal loans | Everyday Banking
Disclosure of credit risk exposure [line items]
Qualitative criteria for measuring SICR	– In Collections– Default in last 12m– £50+ arrears
Credit cards | Everyday Banking
Disclosure of credit risk exposure [line items]
Qualitative criteria for measuring SICR	– In forbearance– Default in last 12m– In Collections– £100+ arrears– Behaviour score indicators
Overdrafts | Everyday Banking
Disclosure of credit risk exposure [line items]
Qualitative criteria for measuring SICR	– Fees suspended– Default in last 12m– Debit dormant >35 days– Any excess in month

Credit Risk - Group Level Credi

Credit Risk - Group Level Credit Risk Management, Additional Information (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£) cIIThreshold	Dec. 31, 2022 GBP (£)
Disclosure of credit risk exposure [line items]
Minimum ECL to recognise judgemental adjustments	£ 1
ECL	£ 994
Climate change, period covered for ECL calculations	5 years
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	£ 30	£ 95
Minimum | Stage 3
Disclosure of credit risk exposure [line items]
ECL under reasonably possible judgements	42
Maximum | Stage 3
Disclosure of credit risk exposure [line items]
ECL under reasonably possible judgements	209
JAs | Long-term indeterminate arrears | No delay in repossession
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	12
JAs | 12+ months in arrears | No delay in repossession
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	6
JAs | Model underestimation | Corrected model underestimation
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	13
JAs | Model underestimation | Model uplift estimation
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	65
JAs | Corporate single large exposure | One average losses
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	12
JAs | Corporate single large exposure | Three average losses
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	35
Affordability and cost of living JAs
Disclosure of credit risk exposure [line items]
ECL	100
Affordability and cost of living JAs | Secured affordability
Disclosure of credit risk exposure [line items]
Mortgages moved from stage 1 to stage 2	2,900
ECL	13
Affordability and cost of living JAs | Secured affordability | Minimum
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	£ 21
CII threshold | cIIThreshold	30
Affordability and cost of living JAs | Secured affordability | Maximum
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	£ 8
CII threshold | cIIThreshold	50
Affordability and cost of living JAs | Unsecured affordability
Disclosure of credit risk exposure [line items]
ECL	£ 38
Affordability and cost of living JAs | Unsecured affordability | Different sensitivities to PD uplifts | Minimum
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	31
Affordability and cost of living JAs | Unsecured affordability | Different sensitivities to PD uplifts | Maximum
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	47
Affordability and cost of living JAs | Corporate lending to segments affected by supply chain pressures
Disclosure of credit risk exposure [line items]
ECL	24
Affordability and cost of living JAs | Corporate lending to segments affected by supply chain pressures | Different sensitivities to PD uplifts | Minimum
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	16
Affordability and cost of living JAs | Corporate lending to segments affected by supply chain pressures | Different sensitivities to PD uplifts | Maximum
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	58
Affordability and cost of living JAs | SME debt burden
Disclosure of credit risk exposure [line items]
ECL	6
Affordability and cost of living JAs | Mortgage refinancing risk
Disclosure of credit risk exposure [line items]
Mortgages moved from stage 1 to stage 2	6,800
ECL	19
Affordability and cost of living JAs | Mortgage refinancing risk | Minimum
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	£ 9
Probability weighted interest rate	0.05
Affordability and cost of living JAs | Mortgage refinancing risk | Maximum
Disclosure of credit risk exposure [line items]
Judgemental adjustments under reasonably possible judgements	£ 22
Probability weighted interest rate	0.06

Credit Risk - Disclosure of ECL

Credit Risk - Disclosure of ECL by Segment (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
ECL	£ 994
ECL		£ 1,007
ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	810
ECL		710
Modelled ECL | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	682
ECL		598
Individually assessed | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	128
ECL		112
JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	84
ECL		167
Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	100
ECL		130
Total JAs
Disclosure of credit risk exposure [line items]
ECL	184
ECL		297
Long-term indeterminate arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	16
ECL		13
12+ months in arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	14
ECL		22
UPL loss floor | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	6
ECL		15
Model underestimation | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	36
ECL		57
Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	23
Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL		23
Other | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	(11)
ECL		37
Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	24
ECL		61
Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	13
ECL		27
Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	38
ECL		35
Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	19
SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	6
ECL		7
Mortgages
Disclosure of credit risk exposure [line items]
ECL	244
ECL		253
Mortgages | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	138
ECL		134
Mortgages | Modelled ECL | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	134
ECL		134
Mortgages | Individually assessed | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	4
ECL		0
Mortgages | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	78
ECL		92
Mortgages | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	28
ECL		27
Mortgages | Total JAs
Disclosure of credit risk exposure [line items]
ECL	106
ECL		119
Mortgages | Long-term indeterminate arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	16
ECL		13
Mortgages | 12+ months in arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	14
ECL		22
Mortgages | UPL loss floor | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Mortgages | Model underestimation | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	36
ECL		36
Mortgages | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
Mortgages | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL		0
Mortgages | Other | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	12
ECL		21
Mortgages | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Mortgages | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	9
ECL		27
Mortgages | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Mortgages | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	19
Mortgages | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Credit cards
Disclosure of credit risk exposure [line items]
ECL	140
ECL		130
Credit cards | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	123
ECL		112
Credit cards | Modelled ECL | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	123
ECL		112
Credit cards | Individually assessed | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Credit cards | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	1
ECL		3
Credit cards | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	16
ECL		15
Credit cards | Total JAs
Disclosure of credit risk exposure [line items]
ECL	17
ECL		18
Credit cards | Long-term indeterminate arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Credit cards | 12+ months in arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Credit cards | UPL loss floor | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Credit cards | Model underestimation | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		2
Credit cards | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
Credit cards | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL		0
Credit cards | Other | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	1
ECL		1
Credit cards | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Credit cards | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Credit cards | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	16
ECL		15
Credit cards | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Credit cards | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Other
Disclosure of credit risk exposure [line items]
ECL	160
ECL		164
Other | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	123
ECL		93
Other | Modelled ECL | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	123
ECL		93
Other | Individually assessed | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Other | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	9
ECL		44
Other | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	28
ECL		27
Other | Total JAs
Disclosure of credit risk exposure [line items]
ECL	37
ECL		71
Other | Long-term indeterminate arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Other | 12+ months in arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Other | UPL loss floor | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	6
ECL		15
Other | Model underestimation | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		19
Other | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
Other | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL		0
Other | Other | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	3
ECL		10
Other | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Other | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Other | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	22
ECL		20
Other | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Other | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	6
ECL		7
Consumer Finance
Disclosure of credit risk exposure [line items]
ECL	70	67
ECL		67
Consumer Finance | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	62
ECL		65
Consumer Finance | Modelled ECL | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	62
ECL		65
Consumer Finance | Individually assessed | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Consumer Finance | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	4
ECL		2
Consumer Finance | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	4
ECL		0
Consumer Finance | Total JAs
Disclosure of credit risk exposure [line items]
ECL	8
ECL		2
Consumer Finance | Long-term indeterminate arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Consumer Finance | 12+ months in arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Consumer Finance | UPL loss floor | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Consumer Finance | Model underestimation | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Consumer Finance | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
Consumer Finance | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL		0
Consumer Finance | Other | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	4
ECL		2
Consumer Finance | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Consumer Finance | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	4
ECL		0
Consumer Finance | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Consumer Finance | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Consumer Finance | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
ECL	380
ECL		393
Corporate & Commercial Banking | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	364
ECL		306
Corporate & Commercial Banking | Modelled ECL | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	240
ECL		194
Corporate & Commercial Banking | Individually assessed | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	124
ECL		112
Corporate & Commercial Banking | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	(8)
ECL		26
Corporate & Commercial Banking | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	24
ECL		61
Corporate & Commercial Banking | Total JAs
Disclosure of credit risk exposure [line items]
ECL	16
ECL		87
Corporate & Commercial Banking | Long-term indeterminate arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate & Commercial Banking | 12+ months in arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate & Commercial Banking | UPL loss floor | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate & Commercial Banking | Model underestimation | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate & Commercial Banking | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	23
Corporate & Commercial Banking | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL		23
Corporate & Commercial Banking | Other | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	(31)
ECL		3
Corporate & Commercial Banking | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	24
ECL		61
Corporate & Commercial Banking | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate & Commercial Banking | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate & Commercial Banking | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Corporate & Commercial Banking | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Modelled ECL | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Individually assessed | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Total JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Long-term indeterminate arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | 12+ months in arrears | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | UPL loss floor | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Model underestimation | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
Corporate Centre | Corporate single large exposure | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL		0
Corporate Centre | Other | JAs (excluding Affordability and Cost of Living JAs)
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
ECL		0
Corporate Centre | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Corporate Centre | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	£ 0
ECL		£ 0

Credit Risk - Disclosure of Bas

Credit Risk - Disclosure of Base Expected Credit Losses to Probability Weighted Estimated Credit Losses (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Exposure	£ 211,222	£ 223,840
ECL	994
Credit impairment loss allowances on loans and advances to customers		(1,007)
Mortgages
Disclosure of credit risk exposure [line items]
ECL	244
Credit impairment loss allowances on loans and advances to customers		(253)
Credit cards
Disclosure of credit risk exposure [line items]
ECL	140
Credit impairment loss allowances on loans and advances to customers		(130)
Other
Disclosure of credit risk exposure [line items]
ECL	160
Credit impairment loss allowances on loans and advances to customers		(164)
Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	5,228	5,384
ECL	70	67
Credit impairment loss allowances on loans and advances to customers		(67)
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
ECL	380
Credit impairment loss allowances on loans and advances to customers		(393)
Corporate Centre
Disclosure of credit risk exposure [line items]
ECL	0
Credit impairment loss allowances on loans and advances to customers		0
Upside
Disclosure of credit risk exposure [line items]
Exposure	300,969	312,830
ECL	£ 834
Credit impairment loss allowances on loans and advances to customers		£ (931)
Proportion of assets in Stage 2	6%	4%
Proportion of assets in Stage 3	1%	1%
Upside | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 204,357	£ 216,383
ECL	£ 420
Credit impairment loss allowances on loans and advances to customers		£ (490)
Proportion of assets in Stage 2	6%	4%
Proportion of assets in Stage 3	1%	1%
Upside | Mortgages
Disclosure of credit risk exposure [line items]
Exposure - of which: mortgages	£ 183,568	£ 195,170
ECL - of which: mortgages	£ 143	£ 215
Proportion of assets in Stage 2 - of which: mortgages	7%	4%
Proportion of assets in Stage 3 - of which: mortgages	1%	1%
Upside | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 13,116	£ 12,845
ECL	£ 132
Credit impairment loss allowances on loans and advances to customers		£ (122)
Proportion of assets in Stage 2	2%	2%
Proportion of assets in Stage 3	0%	0%
Upside | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 7,673	£ 8,368
ECL	£ 145
Credit impairment loss allowances on loans and advances to customers		£ (153)
Proportion of assets in Stage 2	7%	7%
Proportion of assets in Stage 3	2%	2%
Upside | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 5,228	£ 5,739
ECL	£ 68
Credit impairment loss allowances on loans and advances to customers		£ (65)
Proportion of assets in Stage 2	6%	6%
Proportion of assets in Stage 3	0%	1%
Upside | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 27,277	£ 28,299
ECL	£ 346
Credit impairment loss allowances on loans and advances to customers		£ (376)
Proportion of assets in Stage 2	13%	8%
Proportion of assets in Stage 3	3%	2%
Upside | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 64,107	£ 62,409
ECL	£ 0
Credit impairment loss allowances on loans and advances to customers		£ 0
Proportion of assets in Stage 2	0%	0%
Proportion of assets in Stage 3	0%	0%
Base case
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	£ 898
Credit impairment loss allowances on loans and advances to customers		£ (933)
Proportion of assets in Stage 2	6%	4%
Proportion of assets in Stage 3	1%	1%
Base case | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 204,357	£ 216,383
ECL	£ 467
Credit impairment loss allowances on loans and advances to customers		£ (498)
Proportion of assets in Stage 2	7%	4%
Proportion of assets in Stage 3	1%	1%
Base case | Mortgages
Disclosure of credit risk exposure [line items]
Exposure - of which: mortgages	£ 183,568	£ 195,170
ECL - of which: mortgages	£ 176	£ 219
Proportion of assets in Stage 2 - of which: mortgages	7%	4%
Proportion of assets in Stage 3 - of which: mortgages	1%	1%
Base case | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 13,116	£ 12,845
ECL	£ 138
Credit impairment loss allowances on loans and advances to customers		£ (123)
Proportion of assets in Stage 2	3%	2%
Proportion of assets in Stage 3	0%	0%
Base case | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 7,673	£ 8,368
ECL	£ 153
Credit impairment loss allowances on loans and advances to customers		£ (156)
Proportion of assets in Stage 2	8%	7%
Proportion of assets in Stage 3	2%	2%
Base case | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 5,228	£ 5,739
ECL	£ 69
Credit impairment loss allowances on loans and advances to customers		£ (66)
Proportion of assets in Stage 2	6%	6%
Proportion of assets in Stage 3	0%	1%
Base case | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 27,277	£ 28,299
ECL	£ 362
Credit impairment loss allowances on loans and advances to customers		£ (369)
Proportion of assets in Stage 2	14%	9%
Proportion of assets in Stage 3	3%	2%
Base case | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 64,107	£ 62,409
ECL	£ 0
Credit impairment loss allowances on loans and advances to customers		£ 0
Proportion of assets in Stage 2	0%	0%
Proportion of assets in Stage 3	0%	0%
Downside 1
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	£ 993
Credit impairment loss allowances on loans and advances to customers		£ (994)
Proportion of assets in Stage 2	6%	5%
Proportion of assets in Stage 3	1%	1%
Downside 1 | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 204,357	£ 216,383
ECL	£ 538
Credit impairment loss allowances on loans and advances to customers		£ (530)
Proportion of assets in Stage 2	7%	4%
Proportion of assets in Stage 3	1%	1%
Downside 1 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure - of which: mortgages	£ 183,568	£ 195,170
ECL - of which: mortgages	£ 236	£ 245
Proportion of assets in Stage 2 - of which: mortgages	7%	4%
Proportion of assets in Stage 3 - of which: mortgages	1%	1%
Downside 1 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 13,116	£ 12,845
ECL	£ 142
Credit impairment loss allowances on loans and advances to customers		£ (127)
Proportion of assets in Stage 2	3%	2%
Proportion of assets in Stage 3	0%	0%
Downside 1 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 7,673	£ 8,368
ECL	£ 160
Credit impairment loss allowances on loans and advances to customers		£ (158)
Proportion of assets in Stage 2	8%	7%
Proportion of assets in Stage 3	2%	2%
Downside 1 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 5,228	£ 5,739
ECL	£ 70
Credit impairment loss allowances on loans and advances to customers		£ (65)
Proportion of assets in Stage 2	6%	6%
Proportion of assets in Stage 3	0%	1%
Downside 1 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 27,277	£ 28,299
ECL	£ 385
Credit impairment loss allowances on loans and advances to customers		£ (399)
Proportion of assets in Stage 2	14%	9%
Proportion of assets in Stage 3	3%	2%
Downside 1 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 64,107	£ 62,409
ECL	£ 0
Credit impairment loss allowances on loans and advances to customers		£ 0
Proportion of assets in Stage 2	0%	0%
Proportion of assets in Stage 3	0%	0%
Downside 2
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	£ 1,412
Credit impairment loss allowances on loans and advances to customers		£ (1,384)
Proportion of assets in Stage 2	12%	11%
Proportion of assets in Stage 3	1%	1%
Downside 2 | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 204,357	£ 216,383
ECL	£ 891
Credit impairment loss allowances on loans and advances to customers		£ (831)
Proportion of assets in Stage 2	15%	10%
Proportion of assets in Stage 3	1%	1%
Downside 2 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure - of which: mortgages	£ 183,568	£ 195,170
ECL - of which: mortgages	£ 564	£ 502
Proportion of assets in Stage 2 - of which: mortgages	17%	11%
Proportion of assets in Stage 3 - of which: mortgages	1%	1%
Downside 2 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 13,116	£ 12,845
ECL	£ 150
Credit impairment loss allowances on loans and advances to customers		£ (142)
Proportion of assets in Stage 2	3%	3%
Proportion of assets in Stage 3	0%	0%
Downside 2 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 7,673	£ 8,368
ECL	£ 177
Credit impairment loss allowances on loans and advances to customers		£ (187)
Proportion of assets in Stage 2	9%	9%
Proportion of assets in Stage 3	2%	2%
Downside 2 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 5,228	£ 5,739
ECL	£ 72
Credit impairment loss allowances on loans and advances to customers		£ (69)
Proportion of assets in Stage 2	6%	6%
Proportion of assets in Stage 3	0%	1%
Downside 2 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 27,277	£ 28,299
ECL	£ 449
Credit impairment loss allowances on loans and advances to customers		£ (484)
Proportion of assets in Stage 2	20%	18%
Proportion of assets in Stage 3	3%	2%
Downside 2 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 64,107	£ 62,409
ECL	£ 0
Credit impairment loss allowances on loans and advances to customers		£ 0
Proportion of assets in Stage 2	0%	0%
Proportion of assets in Stage 3	0%	0%
Stubborn Inflation
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	£ 1,179
Credit impairment loss allowances on loans and advances to customers		£ (1,150)
Proportion of assets in Stage 2	7%	7%
Proportion of assets in Stage 3	1%	1%
Stubborn Inflation | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 204,357	£ 216,383
ECL	£ 692
Credit impairment loss allowances on loans and advances to customers		£ (648)
Proportion of assets in Stage 2	8%	6%
Proportion of assets in Stage 3	1%	1%
Stubborn Inflation | Mortgages
Disclosure of credit risk exposure [line items]
Exposure - of which: mortgages	£ 183,568	£ 195,170
ECL - of which: mortgages	£ 365	£ 325
Proportion of assets in Stage 2 - of which: mortgages	8%	6%
Proportion of assets in Stage 3 - of which: mortgages	1%	1%
Stubborn Inflation | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 13,116	£ 12,845
ECL	£ 150
Credit impairment loss allowances on loans and advances to customers		£ (140)
Proportion of assets in Stage 2	3%	3%
Proportion of assets in Stage 3	0%	0%
Stubborn Inflation | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 7,673	£ 8,368
ECL	£ 177
Credit impairment loss allowances on loans and advances to customers		£ (183)
Proportion of assets in Stage 2	9%	8%
Proportion of assets in Stage 3	2%	2%
Stubborn Inflation | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 5,228	£ 5,739
ECL	£ 72
Credit impairment loss allowances on loans and advances to customers		£ (68)
Proportion of assets in Stage 2	6%	6%
Proportion of assets in Stage 3	0%	1%
Stubborn Inflation | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 27,277	£ 28,299
ECL	£ 415
Credit impairment loss allowances on loans and advances to customers		£ (434)
Proportion of assets in Stage 2	17%	14%
Proportion of assets in Stage 3	3%	2%
Stubborn Inflation | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 64,107	£ 62,409
ECL	£ 0
Credit impairment loss allowances on loans and advances to customers		£ 0
Proportion of assets in Stage 2	0%	0%
Proportion of assets in Stage 3	0%	0%
Weighted
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	£ 994
Credit impairment loss allowances on loans and advances to customers		£ (1,007)
Proportion of assets in Stage 2	8%	7%
Proportion of assets in Stage 3	1%	1%
Weighted | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 204,357	£ 216,383
ECL	£ 544
Credit impairment loss allowances on loans and advances to customers		£ (546)
Proportion of assets in Stage 2	9%	7%
Proportion of assets in Stage 3	1%	1%
Weighted | Mortgages
Disclosure of credit risk exposure [line items]
Exposure - of which: mortgages	£ 183,568	£ 195,170
ECL - of which: mortgages	£ 244	£ 253
Proportion of assets in Stage 2 - of which: mortgages	10%	7%
Proportion of assets in Stage 3 - of which: mortgages	1%	1%
Weighted | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 13,116	£ 12,845
ECL	£ 140
Credit impairment loss allowances on loans and advances to customers		£ (130)
Proportion of assets in Stage 2	3%	3%
Proportion of assets in Stage 3	0%	0%
Weighted | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 7,673	£ 8,368
ECL	£ 160
Credit impairment loss allowances on loans and advances to customers		£ (163)
Proportion of assets in Stage 2	8%	8%
Proportion of assets in Stage 3	2%	2%
Weighted | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 5,228	£ 5,739
ECL	£ 70
Credit impairment loss allowances on loans and advances to customers		£ (67)
Proportion of assets in Stage 2	6%	6%
Proportion of assets in Stage 3	0%	1%
Weighted | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 27,277	£ 28,299
ECL	£ 380
Credit impairment loss allowances on loans and advances to customers		£ (394)
Proportion of assets in Stage 2	13%	12%
Proportion of assets in Stage 3	3%	2%
Weighted | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 64,107	£ 62,409
ECL	£ 0
Credit impairment loss allowances on loans and advances to customers		£ 0
Proportion of assets in Stage 2	0%	0%
Proportion of assets in Stage 3	0%	0%

Credit Risk - Schedule of Impac

Credit Risk - Schedule of Impact on Profit Before Tax of Applying an Immediate and Permanent House Price Increase or Decrease to Our Base Case Economic Scenario Explanatory (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [abstract]
Increase in profit before tax due to 20 percentage increase in HPI rate	£ 70	£ 48
Increase in profit before tax due to 10 percentage increase in HPI rate	38	32
Decrease in profit before tax due to 10 percentage decrease in HPI rate	(54)	(61)
Decrease in profit before tax due to 20 percentage decrease in HPI rate	£ (155)	£ (176)

Credit Risk - Disclosure of Fac

Credit Risk - Disclosure of Factors to Measure ECL (Details) - Credit risk	12 Months Ended
	Dec. 31, 2023
Survival rate (SR)
Disclosure of credit risk exposure [line items]
Factor	Survival rate (SR)
Description of objectives, policies and processes for managing risk	The probability that the exposure has not closed or defaulted since the reporting date.
Exposure at default (EAD)
Disclosure of credit risk exposure [line items]
Factor	Exposure at default (EAD)
Description of objectives, policies and processes for managing risk	The amount we expect to be owed if a default event occurs. We determine EAD for each month of the forecast period by the expected payment profile, which varies by product. For amortising products, we base it on the borrower’s contractual repayments over the forecast period. We adjust this for any expected overpayments on Stage 1 accounts that the borrower may make and for any arrears we expect if the account was to default. For revolving products, or amortising products with an off-balance sheet element, we determine EAD using the balance at default and the contractual exposure limit. We vary these assumptions by product and base them on analysis of recent default data.
Loss Given Default (LGD)
Disclosure of credit risk exposure [line items]
Factor	Loss given default (LGD)
Description of objectives, policies and processes for managing risk	Our expected loss if a default event were to occur. We express it as a percentage and calculate it based on factors that we have observed to affect the likelihood and/or value of any subsequent write-offs, which vary according to whether the product is secured or unsecured. If the product is secured, we take into account collateral values as well as the historical discounts to market/book values due to forced sales type.
Probability of Default (PD)
Disclosure of credit risk exposure [line items]
Factor	Probability of default (PD)
Description of objectives, policies and processes for managing risk	The likelihood of a borrower defaulting in the following month, assuming it has not closed or defaulted since the reporting date. For each month in the forecast period, we estimate the monthly PD from a range of factors. These include the current risk grade for the exposure, which becomes less relevant further into the forecast period, as well as the expected evolution of the account risk with maturity and factors for changing economics. We support this with historical data analysis.

Credit Risk - Disclosure of Max

Credit Risk - Disclosure of Maximum and Net Exposure to Credit Risk - IFRS 9 (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Collateral cash	£ (8,519)	£ (8,131)
Netting	(597)	(535)
Net exposure	300,969	312,830
Credit risk
Disclosure of credit risk exposure [line items]
Collateral cash	(100)	(100)
Collateral non-cash	(211,300)	(220,000)
Netting	(100)	0
Net exposure	94,000	96,700
Credit risk | Cash and balances at central banks
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Net exposure	40,500	46,600
Credit risk | Financial assets at amortised cost:
Disclosure of credit risk exposure [line items]
Collateral cash	(100)	(100)
Collateral non-cash	(211,300)	(220,000)
Netting	(100)	0
Net exposure	45,000	44,100
Credit risk | Retail Mortgages
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	(179,100)	(191,400)
Netting	0	0
Net exposure	5,500	4,600
Credit risk | Corporate loans
Disclosure of credit risk exposure [line items]
Collateral cash	(100)	(100)
Collateral non-cash	(15,300)	(16,500)
Netting	0	0
Net exposure	11,700	11,500
Credit risk | Finance leases
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	(4,500)	(4,800)
Netting	0	0
Net exposure	0	100
Credit risk | Accrued interest and other adjustments
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Net exposure	900	900
Credit risk | Other unsecured loans
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Net exposure	20,500	21,100
Credit risk | Amounts due from fellow Banco Santander group subsidiaries and JVs
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Net exposure	4,500	4,200
Credit risk | Total loans and advances to customers
Disclosure of credit risk exposure [line items]
Collateral cash	(100)	(100)
Collateral non-cash	(198,900)	(212,700)
Netting	0	0
Net exposure	43,100	42,400
Credit risk | Loans and advances to banks
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Net exposure	1,700	1,500
Credit risk | Reverse repurchase agreements – non trading
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	(12,400)	(7,300)
Netting	(100)	0
Net exposure	0	0
Credit risk | Other financial assets at amortised cost
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Net exposure	200	200
Credit risk | Financial assets at FVOCI
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Net exposure	8,500	6,000
Credit risk | Debt securities
Disclosure of credit risk exposure [line items]
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Net exposure	8,500	6,000
On-balance sheet | Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	274,100	285,100
On-balance sheet | Credit risk | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	275,000	286,000
On-balance sheet | Credit risk | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	900	900
On-balance sheet | Credit risk | Cash and balances at central banks
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	40,500	46,600
On-balance sheet | Credit risk | Cash and balances at central banks | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	40,500	46,600
On-balance sheet | Credit risk | Cash and balances at central banks | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
On-balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	225,100	232,500
On-balance sheet | Credit risk | Financial assets at amortised cost: | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	226,000	233,400
On-balance sheet | Credit risk | Financial assets at amortised cost: | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	900	900
On-balance sheet | Credit risk | Retail Mortgages
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	176,300	188,000
On-balance sheet | Credit risk | Retail Mortgages | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	176,500	188,300
On-balance sheet | Credit risk | Retail Mortgages | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	200	300
On-balance sheet | Credit risk | Corporate loans
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	18,200	18,800
On-balance sheet | Credit risk | Corporate loans | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	18,500	19,100
On-balance sheet | Credit risk | Corporate loans | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	300	300
On-balance sheet | Credit risk | Finance leases
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	4,500	4,500
On-balance sheet | Credit risk | Finance leases | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	4,600	4,600
On-balance sheet | Credit risk | Finance leases | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	100	100
On-balance sheet | Credit risk | Accrued interest and other adjustments
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	900	900
On-balance sheet | Credit risk | Accrued interest and other adjustments | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	900	900
On-balance sheet | Credit risk | Accrued interest and other adjustments | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
On-balance sheet | Credit risk | Other unsecured loans
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	6,800	7,500
On-balance sheet | Credit risk | Other unsecured loans | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	7,100	7,700
On-balance sheet | Credit risk | Other unsecured loans | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	300	200
On-balance sheet | Credit risk | Amounts due from fellow Banco Santander group subsidiaries and JVs
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	4,500	4,200
On-balance sheet | Credit risk | Amounts due from fellow Banco Santander group subsidiaries and JVs | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	4,500	4,200
On-balance sheet | Credit risk | Amounts due from fellow Banco Santander group subsidiaries and JVs | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
On-balance sheet | Credit risk | Total loans and advances to customers
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	211,200	223,900
On-balance sheet | Credit risk | Total loans and advances to customers | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	212,100	224,800
On-balance sheet | Credit risk | Total loans and advances to customers | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	900	900
On-balance sheet | Credit risk | Loans and advances to banks
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	1,200	1,100
On-balance sheet | Credit risk | Loans and advances to banks | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	1,200	1,100
On-balance sheet | Credit risk | Loans and advances to banks | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
On-balance sheet | Credit risk | Reverse repurchase agreements – non trading
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	12,500	7,300
On-balance sheet | Credit risk | Reverse repurchase agreements – non trading | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	12,500	7,300
On-balance sheet | Credit risk | Reverse repurchase agreements – non trading | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
On-balance sheet | Credit risk | Other financial assets at amortised cost
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	200	200
On-balance sheet | Credit risk | Other financial assets at amortised cost | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	200	200
On-balance sheet | Credit risk | Other financial assets at amortised cost | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
On-balance sheet | Credit risk | Financial assets at FVOCI
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	8,500	6,000
On-balance sheet | Credit risk | Financial assets at FVOCI | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	8,500	6,000
On-balance sheet | Credit risk | Financial assets at FVOCI | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
On-balance sheet | Credit risk | Debt securities
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	8,500	6,000
On-balance sheet | Credit risk | Debt securities | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	8,500	6,000
On-balance sheet | Credit risk | Debt securities | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	31,400	31,700
Off-balance sheet | Credit risk | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	31,500	31,800
Off-balance sheet | Credit risk | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	(100)	(100)
Off-balance sheet | Credit risk | Cash and balances at central banks
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Cash and balances at central banks | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Cash and balances at central banks | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	31,400	31,700
Off-balance sheet | Credit risk | Financial assets at amortised cost: | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	31,500	31,800
Off-balance sheet | Credit risk | Financial assets at amortised cost: | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	(100)	(100)
Off-balance sheet | Credit risk | Retail Mortgages
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	8,300	8,000
Off-balance sheet | Credit risk | Retail Mortgages | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	8,300	8,000
Off-balance sheet | Credit risk | Retail Mortgages | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Corporate loans
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	8,900	9,300
Off-balance sheet | Credit risk | Corporate loans | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	8,900	9,300
Off-balance sheet | Credit risk | Corporate loans | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Finance leases
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	400
Off-balance sheet | Credit risk | Finance leases | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	400
Off-balance sheet | Credit risk | Finance leases | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Accrued interest and other adjustments
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Accrued interest and other adjustments | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Accrued interest and other adjustments | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Other unsecured loans
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	13,700	13,600
Off-balance sheet | Credit risk | Other unsecured loans | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	13,800	13,700
Off-balance sheet | Credit risk | Other unsecured loans | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	(100)	(100)
Off-balance sheet | Credit risk | Amounts due from fellow Banco Santander group subsidiaries and JVs
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Amounts due from fellow Banco Santander group subsidiaries and JVs | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Amounts due from fellow Banco Santander group subsidiaries and JVs | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Total loans and advances to customers
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	30,900	31,300
Off-balance sheet | Credit risk | Total loans and advances to customers | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	31,000	31,400
Off-balance sheet | Credit risk | Total loans and advances to customers | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	(100)	(100)
Off-balance sheet | Credit risk | Loans and advances to banks
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	500	400
Off-balance sheet | Credit risk | Loans and advances to banks | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	500	400
Off-balance sheet | Credit risk | Loans and advances to banks | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Reverse repurchase agreements – non trading
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Reverse repurchase agreements – non trading | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Reverse repurchase agreements – non trading | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Other financial assets at amortised cost
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Other financial assets at amortised cost | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Other financial assets at amortised cost | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Financial assets at FVOCI
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Financial assets at FVOCI | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Financial assets at FVOCI | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Debt securities
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Debt securities | Gross amounts
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	0	0
Off-balance sheet | Credit risk | Debt securities | Accumulated impairment
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	£ 0	£ 0

Credit Risk - Disclosure of Dif

Credit Risk - Disclosure of Difference Between Maximum and Net Exposure to Credit Risk - IFRS 9 (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Collateral cash	£ (8,519)	£ (8,131)
Netting	(597)	(535)
Exposure	300,969	312,830
Credit risk
Disclosure of credit risk exposure [line items]
Collateral cash	(100)	(100)
Collateral non-cash	(211,300)	(220,000)
Netting	(100)	0
Exposure	94,000	96,700
Financial assets at fair value through profit loss | Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	2,100	2,800
Collateral cash	(800)	0
Collateral non-cash	0	(1,700)
Netting	(500)	(500)
Exposure	800	600
Derivative financial assets | Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	1,500	2,400
Collateral cash	(800)	0
Collateral non-cash	0	(1,700)
Netting	(500)	(500)
Exposure	200	200
Other financial assets at FVTPL | Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to balance sheet	600	400
Collateral cash	0	0
Collateral non-cash	0	0
Netting	0	0
Exposure	£ 600	£ 400

Credit Risk - Disclosure of Equ

Credit Risk - Disclosure of Equivalent Credit Rating Grade used by Standard and Poors Ratings Services (Details)	12 Months Ended
	Dec. 31, 2023
Mid range | Santander UK risk grade 9
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.01%
Mid range | Santander UK risk grade 8
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.032%
Mid range | Santander UK risk grade 7
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.10%
Mid range | Santander UK risk grade 6
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.316%
Mid range | Santander UK risk grade 5
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	1%
Mid range | Santander UK risk grade 4
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	3.162%
Mid range | Santander UK risk grade 3
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	10%
Mid range | Santander UK risk grade 2
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	31.623%
Mid range | Santander UK risk grade 1
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	100%
Lower range | Santander UK risk grade 9
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0%
Lower range | Santander UK risk grade 8
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.021%
Lower range | Santander UK risk grade 7
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.066%
Lower range | Santander UK risk grade 6
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.208%
Lower range | Santander UK risk grade 5
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.658%
Lower range | Santander UK risk grade 4
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	2.081%
Lower range | Santander UK risk grade 3
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	6.581%
Lower range | Santander UK risk grade 2
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	20.811%
Lower range | Santander UK risk grade 1
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	100%
Upper range | Santander UK risk grade 9
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.021%
Upper range | Santander UK risk grade 8
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.066%
Upper range | Santander UK risk grade 7
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.208%
Upper range | Santander UK risk grade 6
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	0.658%
Upper range | Santander UK risk grade 5
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	2.081%
Upper range | Santander UK risk grade 4
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	6.581%
Upper range | Santander UK risk grade 3
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	20.811%
Upper range | Santander UK risk grade 2
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	99.999%
Upper range | Santander UK risk grade 1
Disclosure of credit risk exposure [line items]
Standard and poors rating probability of default percent	100%

Credit Risk - Disclosure of Cre

Credit Risk - Disclosure of Credit Rating of Financial Assets Subject to Credit Risk (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of internal credit grades [line items]
Loss allowance	£ (994)
Allowance account for credit losses of financial assets		£ 1,007
Coverage	0.30%	0.30%
Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	£ 305,500	£ 316,700
Loss allowance	£ (1,000)
Allowance account for credit losses of financial assets		£ 1,000
Coverage	0.30%	0.30%
ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	£ 1,000	£ 1,000
Internal grade 9 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	59,900	65,400
Internal grade 9 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Internal grade 8 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	46,700	46,400
Internal grade 8 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Internal grade 7 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	93,500	94,400
Internal grade 7 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Internal grade 6 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	56,700	60,300
Internal grade 6 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Internal grade 5 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	19,300	20,100
Internal grade 5 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	200	200
Internal grade 4 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	10,100	11,400
Internal grade 4 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	300	200
Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	5,900	5,800
Internal grade 3 to 1 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	500	600
Other | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	14,400	13,900
Other | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	274,100	285,000
Loss allowance	£ (900)
Allowance account for credit losses of financial assets		£ 900
Coverage	0.30%	0.30%
On-balance sheet | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 225,100	£ 232,400
Loss allowance	£ (900)
Allowance account for credit losses of financial assets		£ 900
Coverage	0.40%	0.40%
On-balance sheet | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	£ 176,300	£ 188,000
Loss allowance	£ (200)
Allowance account for credit losses of financial assets		£ 300
Coverage	0.10%	0.20%
On-balance sheet | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	£ 156,300	£ 172,900
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	£ 18,100	£ 13,400
Loss allowance	£ (100)
Allowance account for credit losses of financial assets		£ 200
Coverage	0.50%	1.50%
On-balance sheet | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	£ 1,900	£ 1,700
Loss allowance	£ (100)
Allowance account for credit losses of financial assets		£ 100
Coverage	5%	5.90%
On-balance sheet | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	£ 900	£ 900
On-balance sheet | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	900	900
On-balance sheet | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	200	300
On-balance sheet | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	100	200
On-balance sheet | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	59,900	65,300
On-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	15,200	15,200
On-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	5,200	9,500
On-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	5,200	9,500
On-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 9 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 9 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 9 | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 9 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 9 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 9 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	40,400	39,200
On-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	36,500	37,000
On-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	33,100	34,100
On-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	32,000	33,800
On-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	1,100	300
On-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 8 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 8 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 8 | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 8 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 8 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 8 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	86,500	87,500
On-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	86,300	87,200
On-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	81,000	83,800
On-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	76,900	82,100
On-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	4,100	1,700
On-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 7 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 7 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 7 | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 7 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 7 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 7 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	49,900	53,800
On-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	49,900	53,800
On-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	42,000	45,600
On-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	36,700	41,600
On-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	5,300	4,000
On-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 6 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 6 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 6 | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 6 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 6 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 6 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	14,700	15,200
On-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	14,700	15,200
On-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	6,700	7,300
On-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	3,600	4,200
On-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	3,100	3,100
On-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 5 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Internal grade 5 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Internal grade 5 | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	100
On-balance sheet | Internal grade 5 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 5 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	100
On-balance sheet | Internal grade 5 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	8,400	9,300
On-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	8,400	9,300
On-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	3,800	3,800
On-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	500	500
On-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	3,200	3,200
On-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Internal grade 4 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Internal grade 4 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Internal grade 4 | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Internal grade 4 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 4 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Internal grade 4 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	5,500	5,400
On-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	5,500	5,400
On-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	3,400	3,100
On-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	1,400	1,300
On-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	1,900	1,700
On-balance sheet | Internal grade 3 to 1 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	500	500
On-balance sheet | Internal grade 3 to 1 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	500	500
On-balance sheet | Internal grade 3 to 1 | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Internal grade 3 to 1 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 3 to 1 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Internal grade 3 to 1 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Other | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	9,700	10,200
On-balance sheet | Other | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	9,500	10,200
On-balance sheet | Other | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	1,300	1,100
On-balance sheet | Other | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	1,300	1,100
On-balance sheet | Other | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other | ECL | Credit risk | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other | ECL | Credit risk | Stage 1 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other | ECL | Credit risk | Stage 2 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other | ECL | Credit risk | Stage 3 | Financial assets at amortised cost: | Mortgages
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	40,500	46,600
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Cash and balances at central banks | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	£ 40,500	£ 46,600
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Cash and balances at central banks | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	£ 0	£ 0
On-balance sheet | Cash and balances at central banks | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 9 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	40,500	46,600
On-balance sheet | Cash and balances at central banks | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	40,500	46,600
On-balance sheet | Cash and balances at central banks | Internal grade 9 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 9 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 8 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 8 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 8 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 7 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 7 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 7 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 6 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 6 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 6 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 5 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 5 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 5 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 4 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 4 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 4 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 3 to 1 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Internal grade 3 to 1 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Other | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Other | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Other | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Cash and balances at central banks | Other | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	211,200	223,800
Loss allowance	£ (900)
Allowance account for credit losses of financial assets		£ 900
Coverage	0.40%	0.40%
On-balance sheet | Total loans and advances to customers | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 186,100	£ 203,600
Loss allowance	£ (100)
Allowance account for credit losses of financial assets		£ 100
Coverage	0.10%	0%
On-balance sheet | Total loans and advances to customers | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 22,500	£ 17,900
Loss allowance	£ (400)
Allowance account for credit losses of financial assets		£ 500
Coverage	1.70%	2.80%
On-balance sheet | Total loans and advances to customers | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 2,600	£ 2,300
Loss allowance	£ (400)
Allowance account for credit losses of financial assets		£ 300
Coverage	13.30%	13%
On-balance sheet | Total loans and advances to customers | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 900	£ 900
On-balance sheet | Total loans and advances to customers | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Total loans and advances to customers | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	400	500
On-balance sheet | Total loans and advances to customers | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	400	300
On-balance sheet | Total loans and advances to customers | Internal grade 9 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	5,300	9,500
On-balance sheet | Total loans and advances to customers | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	5,300	9,500
On-balance sheet | Total loans and advances to customers | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 9 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 9 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 9 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 9 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 8 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	34,700	36,500
On-balance sheet | Total loans and advances to customers | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	33,600	36,200
On-balance sheet | Total loans and advances to customers | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	1,100	300
On-balance sheet | Total loans and advances to customers | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 8 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 8 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 8 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 8 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 7 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	85,600	87,100
On-balance sheet | Total loans and advances to customers | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	81,500	85,400
On-balance sheet | Total loans and advances to customers | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	4,100	1,700
On-balance sheet | Total loans and advances to customers | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 7 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 7 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 7 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 7 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 6 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	49,300	52,700
On-balance sheet | Total loans and advances to customers | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	43,900	48,400
On-balance sheet | Total loans and advances to customers | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	5,400	4,300
On-balance sheet | Total loans and advances to customers | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 6 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 6 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 6 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 6 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 5 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	14,700	15,200
On-balance sheet | Total loans and advances to customers | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	10,400	11,100
On-balance sheet | Total loans and advances to customers | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	4,300	4,100
On-balance sheet | Total loans and advances to customers | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 5 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Total loans and advances to customers | Internal grade 5 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Total loans and advances to customers | Internal grade 5 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Total loans and advances to customers | Internal grade 5 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 4 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	8,400	9,300
On-balance sheet | Total loans and advances to customers | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	2,800	4,000
On-balance sheet | Total loans and advances to customers | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	5,500	5,200
On-balance sheet | Total loans and advances to customers | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Total loans and advances to customers | Internal grade 4 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Total loans and advances to customers | Internal grade 4 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 4 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Total loans and advances to customers | Internal grade 4 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	5,500	5,400
On-balance sheet | Total loans and advances to customers | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	400	500
On-balance sheet | Total loans and advances to customers | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	2,400	2,600
On-balance sheet | Total loans and advances to customers | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	2,700	2,300
On-balance sheet | Total loans and advances to customers | Internal grade 3 to 1 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	500	500
On-balance sheet | Total loans and advances to customers | Internal grade 3 to 1 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Internal grade 3 to 1 | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	100	200
On-balance sheet | Total loans and advances to customers | Internal grade 3 to 1 | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	400	300
On-balance sheet | Total loans and advances to customers | Other | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	8,600	9,000
On-balance sheet | Total loans and advances to customers | Other | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	8,300	8,600
On-balance sheet | Total loans and advances to customers | Other | Exposures - On balance sheet | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	100	200
On-balance sheet | Total loans and advances to customers | Other | Exposures - On balance sheet | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Total loans and advances to customers | Other | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Other | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Other | ECL | Credit risk | Stage 2 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Total loans and advances to customers | Other | ECL | Credit risk | Stage 3 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	1,200	1,100
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Loans and advances to banks | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 1,200	£ 1,100
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Loans and advances to banks | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 0	£ 0
On-balance sheet | Loans and advances to banks | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 9 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Loans and advances to banks | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	100	100
On-balance sheet | Loans and advances to banks | Internal grade 9 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 9 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 8 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	(100)
On-balance sheet | Loans and advances to banks | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	(100)
On-balance sheet | Loans and advances to banks | Internal grade 8 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 8 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 7 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 7 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 7 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 6 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 6 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 6 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 5 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 5 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 5 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 4 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 4 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 4 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 3 to 1 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Internal grade 3 to 1 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Other | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	900	1,100
On-balance sheet | Loans and advances to banks | Other | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	900	1,100
On-balance sheet | Loans and advances to banks | Other | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Loans and advances to banks | Other | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	12,500	7,300
Loss allowance	0
Allowance account for credit losses of financial assets		£ 0
Coverage		0%
On-balance sheet | Reverse repurchase agreements – non trading | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	12,500	£ 7,300
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Reverse repurchase agreements – non trading | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 0	£ 0
On-balance sheet | Reverse repurchase agreements – non trading | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 9 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	9,600	5,400
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	9,600	5,400
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 9 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 9 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 8 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	1,600	600
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	1,600	600
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 8 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 8 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 7 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	700	100
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	700	100
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 7 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 7 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 6 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	600	1,100
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	600	1,100
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 6 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 6 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 5 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 5 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 5 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 4 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 4 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 4 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 3 to 1 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Internal grade 3 to 1 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Other | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	100
On-balance sheet | Reverse repurchase agreements – non trading | Other | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	100
On-balance sheet | Reverse repurchase agreements – non trading | Other | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Reverse repurchase agreements – non trading | Other | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Other financial assets at amortised cost | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 200	£ 200
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Other financial assets at amortised cost | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	£ 0	£ 0
On-balance sheet | Other financial assets at amortised cost | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 9 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Other financial assets at amortised cost | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	200	200
On-balance sheet | Other financial assets at amortised cost | Internal grade 9 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 9 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 8 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 8 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 8 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 7 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 7 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 7 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 6 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 6 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 6 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 5 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 5 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 5 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 4 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 4 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 4 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 3 to 1 | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Internal grade 3 to 1 | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Other | Exposures - On balance sheet | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Other | Exposures - On balance sheet | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Other | ECL | Credit risk | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Other financial assets at amortised cost | Other | ECL | Credit risk | Stage 1 | Financial assets at amortised cost:
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	8,500	6,000
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Financial assets at FVOCI | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	£ 8,500	£ 6,000
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
On-balance sheet | Financial assets at FVOCI | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	£ 0	£ 0
On-balance sheet | Financial assets at FVOCI | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 9 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	4,200	3,500
On-balance sheet | Financial assets at FVOCI | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	4,200	3,500
On-balance sheet | Financial assets at FVOCI | Internal grade 9 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 9 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 8 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	3,900	2,200
On-balance sheet | Financial assets at FVOCI | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	3,900	2,200
On-balance sheet | Financial assets at FVOCI | Internal grade 8 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 8 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 7 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	200	300
On-balance sheet | Financial assets at FVOCI | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	200	300
On-balance sheet | Financial assets at FVOCI | Internal grade 7 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 7 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 6 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 6 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 6 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 5 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 5 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 5 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 4 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 4 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 4 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 3 to 1 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Internal grade 3 to 1 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Other | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	200	0
On-balance sheet | Financial assets at FVOCI | Other | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	200	0
On-balance sheet | Financial assets at FVOCI | Other | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
On-balance sheet | Financial assets at FVOCI | Other | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	31,400	31,700
Loss allowance	£ (100)
Allowance account for credit losses of financial assets		£ 100
Coverage	0.30%	0.30%
Off-balance sheet | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	£ 30,300	£ 30,800
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
Off-balance sheet | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	£ 1,000	£ 800
Loss allowance	£ (100)
Allowance account for credit losses of financial assets		£ 100
Coverage	9.10%	12.50%
Off-balance sheet | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	£ 100	£ 100
Loss allowance	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage	0%	0%
Off-balance sheet | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	£ 100	£ 100
Off-balance sheet | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	100	100
Off-balance sheet | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	100
Off-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	100
Off-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 9 | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 9 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 9 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 9 | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 9 | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	6,300	7,200
Off-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	6,300	7,200
Off-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 8 | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 8 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 8 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 8 | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 8 | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	7,000	6,900
Off-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	6,900	6,800
Off-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	100	100
Off-balance sheet | Internal grade 7 | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 7 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 7 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 7 | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 7 | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	6,800	6,500
Off-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	6,700	6,400
Off-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	100	100
Off-balance sheet | Internal grade 6 | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 6 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 6 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 6 | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 6 | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	4,600	4,900
Off-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	4,400	4,700
Off-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	200	200
Off-balance sheet | Internal grade 5 | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 5 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 5 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 5 | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 5 | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	1,700	2,100
Off-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	1,200	1,700
Off-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	500	400
Off-balance sheet | Internal grade 4 | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 4 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	100	0
Off-balance sheet | Internal grade 4 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 4 | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	100	0
Off-balance sheet | Internal grade 4 | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	400	400
Off-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	100	200
Off-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	200	100
Off-balance sheet | Internal grade 3 to 1 | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	100	100
Off-balance sheet | Internal grade 3 to 1 | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	100
Off-balance sheet | Internal grade 3 to 1 | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Internal grade 3 to 1 | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	100
Off-balance sheet | Internal grade 3 to 1 | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Other | Exposures - On balance sheet | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	4,700	3,700
Off-balance sheet | Other | Exposures - On balance sheet | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	4,700	3,700
Off-balance sheet | Other | Exposures - On balance sheet | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Other | Exposures - On balance sheet | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Other | ECL | Credit risk
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Other | ECL | Credit risk | Stage 1
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Other | ECL | Credit risk | Stage 2
Disclosure of internal credit grades [line items]
Financial assets	0	0
Off-balance sheet | Other | ECL | Credit risk | Stage 3
Disclosure of internal credit grades [line items]
Financial assets	£ 0	£ 0

Credit Risk - Disclosure of C_2

Credit Risk - Disclosure of Credit Performance (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 211,222	£ 223,840
ECL	£ 994
Allowance account for credit losses of financial assets		£ 1,007
Unsecured personal loans
Disclosure of credit risk exposure [line items]
Percentage of arrears over ninety days past due	73%	61%
Overdrafts
Disclosure of credit risk exposure [line items]
Percentage of arrears over ninety days past due	243%	224%
Loans to customers
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 238,100	£ 251,600
12 month Gross write-offs	232	156
ECL	994
Allowance account for credit losses of financial assets		1,007
Loans to customers | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	206,700	219,700
12 month Gross write-offs	232	156
ECL	916
Allowance account for credit losses of financial assets		933
Loans to customers | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	31,400	31,900
12 month Gross write-offs	0	0
ECL	78
Allowance account for credit losses of financial assets		74
Loans to customers | Stage 1
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 211,100	£ 229,600
Exposure ratio	0%	0%
Loans to customers | Stage 1 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 180,800	£ 198,700
Exposure ratio	87.50%	90.40%
Loans to customers | Stage 1 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 30,300	£ 30,900
Exposure ratio	0%	0%
Loans to customers | Stage 2
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 23,900	£ 19,400
Exposure ratio	0%	0%
Loans to customers | Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 22,900	£ 18,500
Exposure ratio	11.10%	8.40%
Loans to customers | Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 1,000	£ 900
Exposure ratio	0%	0%
Loans to customers | Stage 3
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 3,100	£ 2,600
Exposure ratio	0%	0%
Loans to customers | Stage 3 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 3,000	£ 2,500
Exposure ratio	1.49%	1.24%
Loans to customers | Stage 3 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 100	£ 100
Exposure ratio	0%	0%
Retail and Business Banking
Disclosure of credit risk exposure [line items]
Percentage of arrears over ninety days past due	415%	347%
Retail and Business Banking | Loans to customers | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 182,300	£ 194,600
12 month Gross write-offs	141	113
ECL	501
Allowance account for credit losses of financial assets		504
Retail and Business Banking | Loans to customers | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	22,000	21,800
12 month Gross write-offs	0	0
ECL	43
Allowance account for credit losses of financial assets		42
Retail and Business Banking | Loans to customers | Stage 1 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 160,800	£ 178,000
Exposure ratio	88.30%	91.50%
Retail and Business Banking | Loans to customers | Stage 1 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 21,500	£ 21,200
Exposure ratio	0%	0%
Retail and Business Banking | Loans to customers | Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 19,200	£ 14,600
Exposure ratio	10.50%	7.40%
Retail and Business Banking | Loans to customers | Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 500	£ 500
Exposure ratio	0%	0%
Retail and Business Banking | Loans to customers | Stage 3 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 2,300	£ 2,000
Exposure ratio	1.27%	1.08%
Retail and Business Banking | Loans to customers | Stage 3 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 100
Exposure ratio	0%	0%
Mortgages
Disclosure of credit risk exposure [line items]
Percentage of arrears over ninety days past due	80%	62%
ECL	£ 244
Allowance account for credit losses of financial assets		£ 253
Mortgages | Loans to customers | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	175,200	187,100
12 month Gross write-offs	11	3
ECL	241
Allowance account for credit losses of financial assets		250
Mortgages | Loans to customers | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	8,300	8,000
12 month Gross write-offs	0	0
ECL	3
Allowance account for credit losses of financial assets		3
Mortgages | Loans to customers | Stage 1 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 155,000	£ 171,700
Exposure ratio	88.50%	91.80%
Mortgages | Loans to customers | Stage 1 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 8,200	£ 7,900
Exposure ratio	0%	0%
Mortgages | Loans to customers | Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 18,200	£ 13,600
Exposure ratio	10.40%	7.30%
Mortgages | Loans to customers | Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 100	£ 100
Exposure ratio	0%	0%
Mortgages | Loans to customers | Stage 3 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 2,000	£ 1,800
Exposure ratio	1.16%	0.99%
Mortgages | Loans to customers | Stage 3 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0%	0%
Credit cards
Disclosure of credit risk exposure [line items]
Percentage of arrears over ninety days past due	51%	49%
ECL	£ 140
Allowance account for credit losses of financial assets		£ 130
Credit cards | Loans to customers | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	2,700	2,500
12 month Gross write-offs	46	40
ECL	130
Allowance account for credit losses of financial assets		120
Credit cards | Loans to customers | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	10,400	10,300
12 month Gross write-offs	0	0
ECL	10
Allowance account for credit losses of financial assets		10
Credit cards | Loans to customers | Stage 1 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 2,300	£ 2,100
Exposure ratio	85.40%	85.70%
Credit cards | Loans to customers | Stage 1 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 10,300	£ 10,200
Exposure ratio	0%	0%
Credit cards | Loans to customers | Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 300	£ 300
Exposure ratio	12.90%	12.90%
Credit cards | Loans to customers | Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 100	£ 100
Exposure ratio	0%	0%
Credit cards | Loans to customers | Stage 3 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 100	£ 100
Exposure ratio	2.95%	2.53%
Credit cards | Loans to customers | Stage 3 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0%	0%
Other
Disclosure of credit risk exposure [line items]
ECL	£ 160
Allowance account for credit losses of financial assets		£ 164
Other | Loans to customers | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	4,400	5,000
12 month Gross write-offs	84	70
ECL	130
Allowance account for credit losses of financial assets		134
Other | Loans to customers | Total Drawn | BBLS
Disclosure of credit risk exposure [line items]
Loans and advances to customers	1,800
Other | Loans to customers | Total Drawn | BBLS 100% Government Guarantee
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 1,700
Government Guarantee, percentage	100%
Other | Loans to customers | Total Drawn | Unsecured personal loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 2,100
Other | Loans to customers | Total Drawn | Overdrafts
Disclosure of credit risk exposure [line items]
Loans and advances to customers	500
Other | Loans to customers | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	3,300	3,500
12 month Gross write-offs	0	0
ECL	30
Allowance account for credit losses of financial assets		29
Other | Loans to customers | Stage 1 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 3,500	£ 4,200
Exposure ratio	80.90%	82.80%
Other | Loans to customers | Stage 1 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 3,000	£ 3,100
Exposure ratio	0%	0%
Other | Loans to customers | Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 700	£ 700
Exposure ratio	14.80%	13%
Other | Loans to customers | Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 300	£ 300
Exposure ratio	0%	0%
Other | Loans to customers | Stage 3 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 200	£ 100
Exposure ratio	4.38%	4.30%
Other | Loans to customers | Stage 3 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 100
Exposure ratio	0%	0%
Consumer Finance
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 5,228	£ 5,384
12 month Gross write-offs	£ 23	£ 19
Percentage of arrears over ninety days past due	43%	44%
ECL	£ 70	£ 67
Allowance account for credit losses of financial assets		67
Consumer Finance | Loans to customers | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	5,200	5,400
12 month Gross write-offs	£ 23	19
Lending, percentage collateralised on vehicle	87%
ECL	£ 70
Allowance account for credit losses of financial assets		67
Consumer Finance | Loans to customers | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	0	400
12 month Gross write-offs	0	0
ECL	0
Allowance account for credit losses of financial assets		0
Consumer Finance | Loans to customers | Stage 1 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 4,900	£ 5,000
Exposure ratio	93.10%	93%
Consumer Finance | Loans to customers | Stage 1 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 400
Exposure ratio	0%	0%
Consumer Finance | Loans to customers | Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 300	£ 400
Exposure ratio	6.30%	6.50%
Consumer Finance | Loans to customers | Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0%	0%
Consumer Finance | Loans to customers | Stage 3 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0.53%	0.54%
Consumer Finance | Loans to customers | Stage 3 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0%	0%
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
ECL	£ 380
Allowance account for credit losses of financial assets		£ 393
Corporate & Commercial Banking | Loans to customers | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	17,900	18,500
12 month Gross write-offs	68	24
ECL	345
Allowance account for credit losses of financial assets		362
Corporate & Commercial Banking | Loans to customers | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	9,400	9,700
12 month Gross write-offs	0	0
ECL	35
Allowance account for credit losses of financial assets		32
Corporate & Commercial Banking | Loans to customers | Stage 1 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 13,800	£ 14,500
Exposure ratio	77.10%	78.30%
Corporate & Commercial Banking | Loans to customers | Stage 1 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 8,800	£ 9,300
Exposure ratio	0%	0%
Corporate & Commercial Banking | Loans to customers | Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 3,400	£ 3,500
Exposure ratio	19.10%	18.80%
Corporate & Commercial Banking | Loans to customers | Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 500	£ 400
Exposure ratio	0%	0%
Corporate & Commercial Banking | Loans to customers | Stage 3 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 700	£ 500
Exposure ratio	4.14%	3.08%
Corporate & Commercial Banking | Loans to customers | Stage 3 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 100	£ 0
Exposure ratio	0%	0%
Corporate Centre
Disclosure of credit risk exposure [line items]
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Corporate Centre | Loans to customers | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	1,300	1,200
12 month Gross write-offs	0	0
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | Loans to customers | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	0	0
12 month Gross write-offs	0	0
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | Loans to customers | Stage 1 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 1,300	£ 1,200
Exposure ratio	99.80%	99.60%
Corporate Centre | Loans to customers | Stage 1 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0%	0%
Corporate Centre | Loans to customers | Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0.10%	0.30%
Corporate Centre | Loans to customers | Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0%	0%
Corporate Centre | Loans to customers | Stage 3 | Total Drawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0.10%	0.10%
Corporate Centre | Loans to customers | Stage 3 | Total Undrawn
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 0	£ 0
Exposure ratio	0%	0%

Credit Risk - Disclosure of IFR

Credit Risk - Disclosure of IFRS 9 Credit Quality (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
Allowance account for credit losses of financial assets		1,007
ECL	994
Provision	405	380
Total ECL	£ 994	£ 1,007
Coverage ratio	0.30%	0.30%
Retail mortgage offers in pipeline	£ 3,300	£ 2,800
Mortgages
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		253
ECL	244
Credit cards
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		130
ECL	140
Other
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		164
ECL	160
Consumer Finance
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		67
ECL	70	67
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		393
ECL	380
Corporate Centre
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		0
ECL	0
Stage 1
Disclosure of credit risk exposure [line items]
Exposure	274,010	290,813
Total ECL	£ 170	£ 171
Coverage ratio	0.10%	0.10%
Stage 2
Disclosure of credit risk exposure [line items]
Exposure	£ 23,879	£ 19,282
Allowance account for credit losses of financial assets		516
ECL	462
Total ECL	£ 462	£ 516
Coverage ratio	1.90%	2.70%
Stage 2 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 18,160	£ 13,576
Allowance account for credit losses of financial assets		£ 131
ECL	£ 110
Coverage ratio	0.60%	1%
Stage 2 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 345	£ 329
Allowance account for credit losses of financial assets		£ 85
ECL	£ 87
Coverage ratio	25.20%	25.80%
Stage 2 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 645	£ 646
Allowance account for credit losses of financial assets		£ 79
ECL	£ 77
Coverage ratio	11.90%	12.20%
Stage 2 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 330	£ 350
Allowance account for credit losses of financial assets		£ 27
ECL	£ 30
Coverage ratio	9%	7.70%
Stage 2 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 3,418	£ 3,476
Allowance account for credit losses of financial assets		£ 155
ECL	£ 118
Coverage ratio	3.50%	4.50%
Stage 2 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 1	£ 3
Allowance account for credit losses of financial assets		£ 0
ECL	£ 0
Coverage ratio	0%	0%
Stage 3
Disclosure of credit risk exposure [line items]
Exposure	£ 3,080	£ 2,735
Total ECL	£ 362	£ 320
Coverage ratio	11.80%	11.70%
Stage 3 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 745	£ 572
On-balance sheet
Disclosure of credit risk exposure [line items]
Exposure	269,530	280,972
Allowance account for credit losses of financial assets		£ 933
ECL	£ 916
Coverage ratio	0.30%	0.30%
On-balance sheet | Customer loans
Disclosure of credit risk exposure [line items]
Exposure	£ 206,700	£ 219,700
On-balance sheet | Loans and advances to banks
Disclosure of credit risk exposure [line items]
Exposure	1,200	1,100
On-balance sheet | Sovereign assets measured at amortized cost
Disclosure of credit risk exposure [line items]
Exposure	12,600	7,500
On-balance sheet | Financial assets measured at fair value through other comprehensive income
Disclosure of credit risk exposure [line items]
Exposure	8,500	6,000
On-balance sheet | Cash and balances at central banks
Disclosure of credit risk exposure [line items]
Exposure	40,500	46,600
On-balance sheet | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	182,267	194,661
Allowance account for credit losses of financial assets		£ 504
ECL	£ 501
Coverage ratio	0.30%	0.30%
On-balance sheet | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 175,239	£ 187,141
Allowance account for credit losses of financial assets		£ 250
ECL	£ 241
Coverage ratio	0.10%	0.10%
On-balance sheet | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 2,674	£ 2,558
Allowance account for credit losses of financial assets		£ 120
ECL	£ 130
Coverage ratio	4.90%	4.70%
On-balance sheet | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 4,354	£ 4,962
Allowance account for credit losses of financial assets		£ 134
ECL	£ 130
Coverage ratio	3%	2.70%
On-balance sheet | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 5,228	£ 5,384
Allowance account for credit losses of financial assets		£ 67
ECL	£ 70
Coverage ratio	1.30%	1.20%
On-balance sheet | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 17,939	£ 18,518
Allowance account for credit losses of financial assets		£ 362
ECL	£ 345
Coverage ratio	1.90%	2%
On-balance sheet | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 64,096	£ 62,409
Allowance account for credit losses of financial assets		£ 0
ECL	£ 0
Coverage ratio	0%	0%
On-balance sheet | Stage 1
Disclosure of credit risk exposure [line items]
Exposure	£ 243,656	£ 259,950
Allowance account for credit losses of financial assets		£ 145
ECL	£ 142
Coverage ratio	0.10%	0.10%
On-balance sheet | Stage 1 | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 160,870	£ 178,033
Allowance account for credit losses of financial assets		£ 57
ECL	£ 57
Coverage ratio	0%	0%
On-balance sheet | Stage 1 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 155,063	£ 171,733
Allowance account for credit losses of financial assets		£ 24
ECL	£ 22
Coverage ratio	0%	0%
On-balance sheet | Stage 1 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 2,283	£ 2,192
Allowance account for credit losses of financial assets		£ 14
ECL	£ 17
Coverage ratio	0.80%	0.60%
On-balance sheet | Stage 1 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 3,524	£ 4,108
Allowance account for credit losses of financial assets		£ 19
ECL	£ 18
Coverage ratio	0.50%	0.50%
On-balance sheet | Stage 1 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 4,870	£ 5,005
Allowance account for credit losses of financial assets		£ 19
ECL	£ 21
Coverage ratio	0.40%	0.40%
On-balance sheet | Stage 1 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 13,822	£ 14,507
Allowance account for credit losses of financial assets		£ 69
ECL	£ 64
Coverage ratio	0.50%	0.50%
On-balance sheet | Stage 1 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 64,094	£ 62,405
Allowance account for credit losses of financial assets		£ 0
ECL	£ 0
Coverage ratio	0%	0%
On-balance sheet | Stage 2
Disclosure of credit risk exposure [line items]
Exposure	£ 22,899	£ 18,380
Allowance account for credit losses of financial assets		£ 477
ECL	£ 422
Coverage ratio	1.80%	2.60%
On-balance sheet | Stage 2 | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 19,150	£ 14,551
Allowance account for credit losses of financial assets		£ 295
ECL	£ 274
Coverage ratio	1.40%	2%
On-balance sheet | Stage 2 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 18,160	£ 13,576
Allowance account for credit losses of financial assets		£ 131
ECL	£ 110
Coverage ratio	0.60%	1%
On-balance sheet | Stage 2 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 345	£ 329
Allowance account for credit losses of financial assets		£ 85
ECL	£ 87
Coverage ratio	25.20%	25.80%
On-balance sheet | Stage 2 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 645	£ 646
Allowance account for credit losses of financial assets		£ 79
ECL	£ 77
Coverage ratio	11.90%	12.20%
On-balance sheet | Stage 2 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 330	£ 350
Allowance account for credit losses of financial assets		£ 27
ECL	£ 30
Coverage ratio	9%	7.70%
On-balance sheet | Stage 2 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 3,418	£ 3,476
Allowance account for credit losses of financial assets		£ 155
ECL	£ 118
Coverage ratio	3.50%	4.50%
On-balance sheet | Stage 2 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 1	£ 3
Allowance account for credit losses of financial assets		£ 0
ECL	£ 0
Coverage ratio	0%	0%
On-balance sheet | Stage 3
Disclosure of credit risk exposure [line items]
Exposure	£ 2,975	£ 2,642
Allowance account for credit losses of financial assets		£ 311
ECL	£ 352
Coverage ratio	11.80%	11.80%
On-balance sheet | Stage 3 | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 2,247	£ 2,077
Allowance account for credit losses of financial assets		£ 152
ECL	£ 170
Coverage ratio	7.50%	7.30%
On-balance sheet | Stage 3 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 2,016	£ 1,832
Allowance account for credit losses of financial assets		£ 95
ECL	£ 109
Coverage ratio	5.40%	5.20%
On-balance sheet | Stage 3 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 46	£ 37
Allowance account for credit losses of financial assets		£ 21
ECL	£ 26
Coverage ratio	57.70%	56.80%
On-balance sheet | Stage 3 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 185	£ 208
Allowance account for credit losses of financial assets		£ 36
ECL	£ 35
Coverage ratio	18.80%	17.30%
On-balance sheet | Stage 3 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 28	£ 29
Allowance account for credit losses of financial assets		£ 21
ECL	£ 19
Coverage ratio	68.50%	72.40%
On-balance sheet | Stage 3 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 699	£ 535
Allowance account for credit losses of financial assets		£ 138
ECL	£ 163
Coverage ratio	23.40%	25.80%
On-balance sheet | Stage 3 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 1	£ 1
Allowance account for credit losses of financial assets		£ 0
ECL	£ 0
Coverage ratio	10%	0%
Off-balance sheet
Disclosure of credit risk exposure [line items]
Exposure	£ 31,439	£ 31,858
Provision	£ 78	£ 74
Coverage ratio	0.20%	0.20%
Off-balance sheet | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 22,090	£ 21,722
Provision	£ 43	£ 42
Coverage ratio	0.20%	0.20%
Off-balance sheet | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 8,329	£ 8,029
Provision	£ 3	£ 3
Coverage ratio	0%	0%
Off-balance sheet | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 10,442	£ 10,288
Provision	£ 10	£ 10
Coverage ratio	0.10%	0.10%
Off-balance sheet | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 3,319	£ 3,405
Provision	£ 30	£ 29
Coverage ratio	0.90%	0.90%
Off-balance sheet | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 356
Provision	£ 0	£ 0
Coverage ratio	0%	0%
Off-balance sheet | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 9,338	£ 9,780
Provision	£ 35	£ 32
Coverage ratio	0.40%	0.30%
Off-balance sheet | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 11	£ 0
Provision	£ 0	£ 0
Coverage ratio	0%	0%
Off-balance sheet | Stage 1
Disclosure of credit risk exposure [line items]
Exposure	£ 30,354	£ 30,863
Provision	£ 28	£ 26
Coverage ratio	0.10%	0.10%
Off-balance sheet | Stage 1 | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 21,598	£ 21,176
Provision	£ 16	£ 12
Coverage ratio	0.10%	0.10%
Off-balance sheet | Stage 1 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 8,189	£ 7,899
Provision	£ 2	£ 2
Coverage ratio	0%	0%
Off-balance sheet | Stage 1 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 10,295	£ 10,137
Provision	£ 4	£ 3
Coverage ratio	0%	0%
Off-balance sheet | Stage 1 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 3,114	£ 3,140
Provision	£ 10	£ 7
Coverage ratio	0.30%	0.20%
Off-balance sheet | Stage 1 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 356
Provision	£ 0	£ 0
Coverage ratio	0%	0%
Off-balance sheet | Stage 1 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 8,745	£ 9,331
Provision	£ 12	£ 14
Coverage ratio	0.10%	0.20%
Off-balance sheet | Stage 1 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 11	£ 0
Provision	£ 0	£ 0
Coverage ratio	0%	0%
Off-balance sheet | Stage 2
Disclosure of credit risk exposure [line items]
Exposure	£ 980	£ 902
Provision	£ 40	£ 39
Coverage ratio	4.10%	4.30%
Off-balance sheet | Stage 2 | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 433	£ 490
Provision	£ 26	£ 28
Coverage ratio	6%	5.70%
Off-balance sheet | Stage 2 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 120	£ 109
Provision	£ 1	£ 1
Coverage ratio	1.10%	0.90%
Off-balance sheet | Stage 2 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 114	£ 122
Provision	£ 6	£ 6
Coverage ratio	5%	4.90%
Off-balance sheet | Stage 2 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 199	£ 259
Provision	£ 19	£ 21
Coverage ratio	9.60%	8.10%
Off-balance sheet | Stage 2 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
Provision	£ 0	£ 0
Coverage ratio	0%	0%
Off-balance sheet | Stage 2 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 547	£ 412
Provision	£ 14	£ 11
Coverage ratio	2.50%	2.70%
Off-balance sheet | Stage 2 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
Provision	£ 0	£ 0
Coverage ratio	0%	0%
Off-balance sheet | Stage 3
Disclosure of credit risk exposure [line items]
Exposure	£ 105	£ 93
Provision	£ 10	£ 9
Coverage ratio	10.40%	9.70%
Off-balance sheet | Stage 3 | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 59	£ 56
Provision	£ 1	£ 2
Coverage ratio	2.80%	3.60%
Off-balance sheet | Stage 3 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	£ 20	£ 21
Provision	£ 0	£ 0
Coverage ratio	0.50%	0%
Off-balance sheet | Stage 3 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 33	£ 29
Provision	£ 0	£ 1
Coverage ratio	1.90%	3.40%
Off-balance sheet | Stage 3 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 6	£ 6
Provision	£ 1	£ 1
Coverage ratio	18%	16.70%
Off-balance sheet | Stage 3 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
Provision	£ 0	£ 0
Coverage ratio	0%	0%
Off-balance sheet | Stage 3 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 46	£ 37
Provision	£ 9	£ 7
Coverage ratio	20.20%	18.90%
Off-balance sheet | Stage 3 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
Provision	£ 0	£ 0
Coverage ratio	0%	0%

Credit Risk - Disclosure of Sta

Credit Risk - Disclosure of Stage 2 Exposures by Classification (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	£ 994
Allowance account for credit losses of financial assets		£ 1,007
Coverage ratio	0.30%	0.30%
Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	£ 100
Allowance account for credit losses of financial assets		£ 130
Total JAs
Disclosure of credit risk exposure [line items]
ECL	184
Allowance account for credit losses of financial assets		297
Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	24
Allowance account for credit losses of financial assets		61
Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	13
Allowance account for credit losses of financial assets		27
Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	38
Allowance account for credit losses of financial assets		35
Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	19
SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	6
Allowance account for credit losses of financial assets		7
ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	810
Allowance account for credit losses of financial assets		710
ECL before JAs | Modelled ECL
Disclosure of credit risk exposure [line items]
ECL	682
Allowance account for credit losses of financial assets		598
ECL before JAs | Individually assessed
Disclosure of credit risk exposure [line items]
ECL	128
Allowance account for credit losses of financial assets		112
Mortgages
Disclosure of credit risk exposure [line items]
ECL	244
Allowance account for credit losses of financial assets		253
Mortgages | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	28
Allowance account for credit losses of financial assets		27
Mortgages | Total JAs
Disclosure of credit risk exposure [line items]
ECL	106
Allowance account for credit losses of financial assets		119
Mortgages | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Mortgages | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	9
Allowance account for credit losses of financial assets		27
Mortgages | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Mortgages | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	19
Mortgages | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Mortgages | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	138
Allowance account for credit losses of financial assets		134
Mortgages | ECL before JAs | Modelled ECL
Disclosure of credit risk exposure [line items]
ECL	134
Allowance account for credit losses of financial assets		134
Mortgages | ECL before JAs | Individually assessed
Disclosure of credit risk exposure [line items]
ECL	4
Allowance account for credit losses of financial assets		0
Credit cards
Disclosure of credit risk exposure [line items]
ECL	140
Allowance account for credit losses of financial assets		130
Credit cards | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	16
Allowance account for credit losses of financial assets		15
Credit cards | Total JAs
Disclosure of credit risk exposure [line items]
ECL	17
Allowance account for credit losses of financial assets		18
Credit cards | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Credit cards | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Credit cards | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	16
Allowance account for credit losses of financial assets		15
Credit cards | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Credit cards | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Credit cards | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	123
Allowance account for credit losses of financial assets		112
Credit cards | ECL before JAs | Modelled ECL
Disclosure of credit risk exposure [line items]
ECL	123
Allowance account for credit losses of financial assets		112
Credit cards | ECL before JAs | Individually assessed
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Other
Disclosure of credit risk exposure [line items]
ECL	160
Allowance account for credit losses of financial assets		164
Other | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	28
Allowance account for credit losses of financial assets		27
Other | Total JAs
Disclosure of credit risk exposure [line items]
ECL	37
Allowance account for credit losses of financial assets		71
Other | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Other | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Other | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	22
Allowance account for credit losses of financial assets		20
Other | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Other | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	6
Allowance account for credit losses of financial assets		7
Other | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	123
Allowance account for credit losses of financial assets		93
Other | ECL before JAs | Modelled ECL
Disclosure of credit risk exposure [line items]
ECL	123
Allowance account for credit losses of financial assets		93
Other | ECL before JAs | Individually assessed
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Consumer Finance
Disclosure of credit risk exposure [line items]
ECL	70	67
Allowance account for credit losses of financial assets		67
Consumer Finance | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	4
Allowance account for credit losses of financial assets		0
Consumer Finance | Total JAs
Disclosure of credit risk exposure [line items]
ECL	8
Allowance account for credit losses of financial assets		2
Consumer Finance | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Consumer Finance | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	4
Allowance account for credit losses of financial assets		0
Consumer Finance | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Consumer Finance | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Consumer Finance | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Consumer Finance | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	62
Allowance account for credit losses of financial assets		65
Consumer Finance | ECL before JAs | Modelled ECL
Disclosure of credit risk exposure [line items]
ECL	62
Allowance account for credit losses of financial assets		65
Consumer Finance | ECL before JAs | Individually assessed
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
ECL	380
Allowance account for credit losses of financial assets		393
Corporate & Commercial Banking | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	24
Allowance account for credit losses of financial assets		61
Corporate & Commercial Banking | Total JAs
Disclosure of credit risk exposure [line items]
ECL	16
Allowance account for credit losses of financial assets		87
Corporate & Commercial Banking | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	24
Allowance account for credit losses of financial assets		61
Corporate & Commercial Banking | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate & Commercial Banking | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate & Commercial Banking | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Corporate & Commercial Banking | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate & Commercial Banking | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	364
Allowance account for credit losses of financial assets		306
Corporate & Commercial Banking | ECL before JAs | Modelled ECL
Disclosure of credit risk exposure [line items]
ECL	240
Allowance account for credit losses of financial assets		194
Corporate & Commercial Banking | ECL before JAs | Individually assessed
Disclosure of credit risk exposure [line items]
ECL	124
Allowance account for credit losses of financial assets		112
Corporate Centre
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | Total JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | Corporate lending to segments affected by supply chain pressures | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | Secured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | Unsecured affordability | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | Mortgage refinancing risk | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Corporate Centre | SME debt burden | Affordability and Cost of Living JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | ECL before JAs
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | ECL before JAs | Modelled ECL
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Corporate Centre | ECL before JAs | Individually assessed
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
Stage 2
Disclosure of credit risk exposure [line items]
Exposure	23,879	19,282
ECL	£ 462
Allowance account for credit losses of financial assets		£ 516
Coverage ratio	1.90%	2.70%
Stage 2 | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	£ 22,899	£ 18,380
ECL	£ 422
Allowance account for credit losses of financial assets		£ 477
Coverage ratio	1.80%	2.60%
Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 40
Allowance account for credit losses of financial assets		£ 39
Stage 2 | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	18,160	13,576
ECL	£ 110
Allowance account for credit losses of financial assets		£ 131
Coverage ratio	0.60%	1%
Stage 2 | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 345	£ 329
ECL	£ 87
Allowance account for credit losses of financial assets		£ 85
Coverage ratio	25.20%	25.80%
Stage 2 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 645	£ 646
ECL	£ 77
Allowance account for credit losses of financial assets		£ 79
Coverage ratio	11.90%	12.20%
Stage 2 | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 330	£ 350
ECL	£ 30
Allowance account for credit losses of financial assets		£ 27
Coverage ratio	9%	7.70%
Stage 2 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 3,418	£ 3,476
ECL	£ 118
Allowance account for credit losses of financial assets		£ 155
Coverage ratio	3.50%	4.50%
Stage 2 | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 1	£ 3
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | PD deterioration
Disclosure of credit risk exposure [line items]
Exposure	£ 9,160	£ 10,323
ECL	277
Allowance account for credit losses of financial assets		302
Stage 2 | PD deterioration | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	8,345	9,560
ECL	£ 249
Allowance account for credit losses of financial assets		£ 283
Coverage ratio	3%	3%
Stage 2 | PD deterioration | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 28
Allowance account for credit losses of financial assets		£ 19
Stage 2 | PD deterioration | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	5,877	7,310
ECL	£ 65
Allowance account for credit losses of financial assets		£ 85
Coverage ratio	1.10%	1.20%
Stage 2 | PD deterioration | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 256	£ 240
ECL	£ 63
Allowance account for credit losses of financial assets		£ 63
Coverage ratio	24.90%	26.30%
Stage 2 | PD deterioration | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 288	£ 303
ECL	£ 36
Allowance account for credit losses of financial assets		£ 42
Coverage ratio	12.30%	13.90%
Stage 2 | PD deterioration | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 115	£ 159
ECL	£ 10
Allowance account for credit losses of financial assets		£ 12
Coverage ratio	8.70%	7.50%
Stage 2 | PD deterioration | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 1,809	£ 1,548
ECL	£ 75
Allowance account for credit losses of financial assets		£ 81
Coverage ratio	4.10%	5.20%
Stage 2 | PD deterioration | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Forbearance
Disclosure of credit risk exposure [line items]
Exposure	£ 601	£ 625
ECL	4
Allowance account for credit losses of financial assets		6
Stage 2 | Forbearance | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	601	513
ECL	£ 4
Allowance account for credit losses of financial assets		£ 6
Coverage ratio	0.70%	1.20%
Stage 2 | Forbearance | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Stage 2 | Forbearance | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	516	449
ECL	£ 2
Allowance account for credit losses of financial assets		£ 2
Coverage ratio	0.30%	0.40%
Stage 2 | Forbearance | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	27.70%	0%
Stage 2 | Forbearance | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Forbearance | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Forbearance | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 85	£ 64
ECL	£ 2
Allowance account for credit losses of financial assets		£ 4
Coverage ratio	2.50%	6.30%
Stage 2 | Forbearance | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 1,436	£ 1,271
ECL	37
Allowance account for credit losses of financial assets		31
Stage 2 | Other | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	1,244	1,289
ECL	£ 33
Allowance account for credit losses of financial assets		£ 23
Coverage ratio	2.70%	1.80%
Stage 2 | Other | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 4
Allowance account for credit losses of financial assets		£ 8
Stage 2 | Other | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	549	393
ECL	£ 3
Allowance account for credit losses of financial assets		£ 7
Coverage ratio	0.70%	1.80%
Stage 2 | Other | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 17	£ 22
ECL	£ 5
Allowance account for credit losses of financial assets		£ 4
Coverage ratio	24.50%	18.20%
Stage 2 | Other | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 19	£ 26
ECL	£ 3
Allowance account for credit losses of financial assets		£ 6
Coverage ratio	16.20%	23.10%
Stage 2 | Other | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 126	£ 164
ECL	£ 5
Allowance account for credit losses of financial assets		£ 5
Coverage ratio	4%	3%
Stage 2 | Other | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 533	£ 684
ECL	£ 17
Allowance account for credit losses of financial assets		£ 1
Coverage ratio	3.20%	0.10%
Stage 2 | Other | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | 30 DPD
Disclosure of credit risk exposure [line items]
Exposure	£ 893	£ 937
ECL	50
Allowance account for credit losses of financial assets		54
Stage 2 | 30 DPD | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	857	893
ECL	£ 47
Allowance account for credit losses of financial assets		£ 48
Coverage ratio	5.50%	5.40%
Stage 2 | 30 DPD | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 3
Allowance account for credit losses of financial assets		£ 6
Stage 2 | 30 DPD | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	560	463
ECL	£ 12
Allowance account for credit losses of financial assets		£ 10
Coverage ratio	2.10%	2.20%
Stage 2 | 30 DPD | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 9	£ 8
ECL	£ 4
Allowance account for credit losses of financial assets		£ 4
Coverage ratio	47.10%	50%
Stage 2 | 30 DPD | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 169	£ 178
ECL	£ 18
Allowance account for credit losses of financial assets		£ 14
Coverage ratio	10.80%	7.90%
Stage 2 | 30 DPD | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 25	£ 27
ECL	£ 11
Allowance account for credit losses of financial assets		£ 10
Coverage ratio	43.40%	37%
Stage 2 | 30 DPD | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 93	£ 214
ECL	£ 2
Allowance account for credit losses of financial assets		£ 10
Coverage ratio	2.40%	4.70%
Stage 2 | 30 DPD | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 1	£ 3
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Secured affordability
Disclosure of credit risk exposure [line items]
Exposure	£ 2,889	£ 4,961
ECL	13
Allowance account for credit losses of financial assets		27
Stage 2 | Secured affordability | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	2,953	4,961
ECL	£ 13
Allowance account for credit losses of financial assets		£ 27
Coverage ratio	0.40%	0.50%
Stage 2 | Secured affordability | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Stage 2 | Secured affordability | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	2,889	4,961
ECL	£ 9
Allowance account for credit losses of financial assets		£ 27
Coverage ratio	0.30%	0.50%
Stage 2 | Secured affordability | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Secured affordability | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Secured affordability | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 64	£ 0
ECL	£ 4
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	6.30%	0%
Stage 2 | Secured affordability | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Secured affordability | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Unsecured affordability
Disclosure of credit risk exposure [line items]
Exposure	£ 233	£ 199
ECL	38
Allowance account for credit losses of financial assets		35
Stage 2 | Unsecured affordability | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	232	198
ECL	£ 35
Allowance account for credit losses of financial assets		£ 31
Coverage ratio	15%	15.70%
Stage 2 | Unsecured affordability | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 3
Allowance account for credit losses of financial assets		£ 4
Stage 2 | Unsecured affordability | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	0	0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Unsecured affordability | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 63	£ 59
ECL	£ 15
Allowance account for credit losses of financial assets		£ 14
Coverage ratio	23.70%	23.70%
Stage 2 | Unsecured affordability | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 169	£ 139
ECL	£ 20
Allowance account for credit losses of financial assets		£ 17
Coverage ratio	11.70%	12.20%
Stage 2 | Unsecured affordability | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Unsecured affordability | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Unsecured affordability | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | Mortgage Refinancing
Disclosure of credit risk exposure [line items]
Exposure	£ 7,769
ECL	19
Stage 2 | Mortgage Refinancing | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	7,769
ECL	£ 19
Coverage ratio	0.20%
Stage 2 | Mortgage Refinancing | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 0
Stage 2 | Mortgage Refinancing | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	7,769
ECL	£ 19
Coverage ratio	0.20%
Stage 2 | Mortgage Refinancing | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 0
ECL	£ 0
Coverage ratio	0%
Stage 2 | Mortgage Refinancing | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 0
ECL	£ 0
Coverage ratio	0%
Stage 2 | Mortgage Refinancing | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 0
ECL	£ 0
Coverage ratio	0%
Stage 2 | Mortgage Refinancing | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 0
ECL	£ 0
Coverage ratio	0%
Stage 2 | Mortgage Refinancing | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0
ECL	£ 0
Coverage ratio	0%
Stage 2 | High risk corporate
Disclosure of credit risk exposure [line items]
Exposure	£ 898	£ 966
ECL	24
Allowance account for credit losses of financial assets		61
Stage 2 | High risk corporate | Total Drawn
Disclosure of credit risk exposure [line items]
Exposure	898	966
ECL	£ 22
Allowance account for credit losses of financial assets		£ 59
Coverage ratio	2.50%	6.10%
Stage 2 | High risk corporate | Total Undrawn
Disclosure of credit risk exposure [line items]
ECL	£ 2
Allowance account for credit losses of financial assets		£ 2
Stage 2 | High risk corporate | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	0	0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | High risk corporate | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | High risk corporate | Other
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | High risk corporate | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%
Stage 2 | High risk corporate | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	£ 898	£ 966
ECL	£ 22
Allowance account for credit losses of financial assets		£ 59
Coverage ratio	2.50%	6.10%
Stage 2 | High risk corporate | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	£ 0	£ 0
ECL	£ 0
Allowance account for credit losses of financial assets		£ 0
Coverage ratio	0%	0%

Credit Risk - Disclosure of S_2

Credit Risk - Disclosure of Stage 2 Decomposition Cure and Not Cure Explanatory (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	£ 994
Allowance account for credit losses of financial assets		£ 1,007
Coverage	0.30%	0.30%
Stage 2
Disclosure of credit risk exposure [line items]
Exposure	£ 23,879	£ 19,282
ECL	£ 462
Allowance account for credit losses of financial assets		£ 516
Coverage	1.90%	2.70%
Not in cure period | Stage 2
Disclosure of credit risk exposure [line items]
Exposure	£ 12,682	£ 13,156
ECL	£ 360
Allowance account for credit losses of financial assets		£ 439
Coverage	2.80%	3.30%
In cure period (for transfer to Stage 1) | Stage 2
Disclosure of credit risk exposure [line items]
Exposure	£ 11,197	£ 6,126
ECL	£ 102
Allowance account for credit losses of financial assets		£ 77
Coverage	0.90%	1.30%

Credit Risk - Disclosure of S_3

Credit Risk - Disclosure of Stage 3 Decomposition Cure and Not Cure Explanatory (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	£ 994
ECL		£ 1,007
Coverage	0.30%	0.30%
Stage 3
Disclosure of credit risk exposure [line items]
Exposure	£ 3,080	£ 2,735
ECL	£ 362
ECL		£ 320
Coverage	11.80%	11.70%
Stage 3 | Not in cure period
Disclosure of credit risk exposure [line items]
Exposure	£ 2,712	£ 2,421
ECL	£ 342
ECL		£ 286
Coverage	12.60%	11.80%
Stage 3 | In cure period (for transfer to Stage 2)
Disclosure of credit risk exposure [line items]
Exposure	£ 368	£ 314
ECL	£ 20
ECL		£ 34
Coverage	5.40%	10.80%

Credit Risk - Disclosure of Rec

Credit Risk - Disclosure of Reconciliation of Exposures, ECL and Net Carrying Amounts (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
ECL	994
Allowance account for credit losses of financial assets		1,007
Assets classified at FVTPL	285	122
Total assets	282,083	292,243
Provisions	405	380
Macro hedge of interest rate risk	(630)	(2,654)
Mortgages
Disclosure of credit risk exposure [line items]
ECL	244
Allowance account for credit losses of financial assets		253
Credit cards
Disclosure of credit risk exposure [line items]
ECL	140
Allowance account for credit losses of financial assets		130
Other
Disclosure of credit risk exposure [line items]
ECL	160
Allowance account for credit losses of financial assets		164
Consumer Finance
Disclosure of credit risk exposure [line items]
ECL	70	67
Allowance account for credit losses of financial assets		67
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
ECL	380
Allowance account for credit losses of financial assets		393
Corporate Centre
Disclosure of credit risk exposure [line items]
ECL	0
Allowance account for credit losses of financial assets		0
On-balance sheet
Disclosure of credit risk exposure [line items]
Exposure	269,530	280,972
ECL	916
Allowance account for credit losses of financial assets		933
Net carrying amount	268,614	280,039
Joint ventures	4,488	4,165
Other items	960	904
Adjusted net carrying amount	274,062	285,108
Assets classified at FVTPL	2,074	2,873
Non-financial assets	5,947	4,262
Total assets	282,083	292,243
On-balance sheet | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	182,267	194,661
ECL	501
Allowance account for credit losses of financial assets		504
Net carrying amount	181,766	194,157
On-balance sheet | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	175,239	187,141
ECL	241
Allowance account for credit losses of financial assets		250
Net carrying amount	174,998	186,891
On-balance sheet | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	2,674	2,558
ECL	130
Allowance account for credit losses of financial assets		120
Net carrying amount	2,544	2,438
On-balance sheet | Other
Disclosure of credit risk exposure [line items]
Exposure	4,354	4,962
ECL	130
Allowance account for credit losses of financial assets		134
Net carrying amount	4,224	4,828
On-balance sheet | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	5,228	5,384
ECL	70
Allowance account for credit losses of financial assets		67
Net carrying amount	5,158	5,317
On-balance sheet | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	17,939	18,518
ECL	345
Allowance account for credit losses of financial assets		362
Net carrying amount	17,594	18,156
On-balance sheet | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	64,096	62,409
ECL	0
Allowance account for credit losses of financial assets		0
Net carrying amount	64,096	62,409
Off-balance sheet
Disclosure of credit risk exposure [line items]
Exposure	31,439	31,858
Provisions	78	74
Off-balance sheet | Retail and Business Banking
Disclosure of credit risk exposure [line items]
Exposure	22,090	21,722
Provisions	43	42
Off-balance sheet | Mortgages
Disclosure of credit risk exposure [line items]
Exposure	8,329	8,029
Provisions	3	3
Off-balance sheet | Credit cards
Disclosure of credit risk exposure [line items]
Exposure	10,442	10,288
Provisions	10	10
Off-balance sheet | Other
Disclosure of credit risk exposure [line items]
Exposure	3,319	3,405
Provisions	30	29
Off-balance sheet | Consumer Finance
Disclosure of credit risk exposure [line items]
Exposure	0	356
Provisions	0	0
Off-balance sheet | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	9,338	9,780
Provisions	35	32
Off-balance sheet | Corporate Centre
Disclosure of credit risk exposure [line items]
Exposure	11	0
Provisions	£ 0	£ 0

Credit Risk - Disclosure of E_2

Credit Risk - Disclosure of ECL Reconciliation (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	£ 1,007
Ending balance	994	£ 1,007
Less: Recoveries net of collection costs	(10)	(36)	£ 17
ECL
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	1,007	866
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	0	0
Transfers from Stage 3	0	0
Transfers of financial instruments	0	0
Net ECL remeasurement on stage transfer	164	98
Change in economic scenarios	5	163
New lending and assets purchased	93	142
Redemptions, repayments and assets sold	(134)	(130)
Changes in risk parameters and other movements	91	25
Assets written off	(232)	(157)
Ending balance	994	1,007	866
Net movement in the period	(13)	141
ECL (release)/charge to the Income Statement	219	298
Less: Discount unwind	(21)	(13)
Less: Recoveries net of collection costs	8	36
Total ECL (release)/charge to the Income Statement	206	321
Stage 1
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	171
Ending balance	170	171
Stage 2
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	516
Ending balance	462	516
Stage 3
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	320
Ending balance	362	320
Exposures - On balance sheet
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	312,830	319,319
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	0	0
Transfers from Stage 3	0	0
Transfers of financial instruments	0	0
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	25,927	49,377
Redemptions, repayments and assets sold	(38,162)	(58,347)
Changes in risk parameters and other movements	786	2,735
Assets written off	(412)	(254)
Ending balance	300,969	312,830	319,319
Net movement in the period	(11,861)	(6,489)
Financial instruments not credit-impaired | Subject to 12-month ECL | Stage 1
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	171	133
Transfers from Stage 1 to Stage 2	(9)	(25)
Transfers from Stage 2 to Stage 1	111	133
Transfers to Stage 3	(6)	(4)
Transfers from Stage 3	1	1
Transfers of financial instruments	97	105
Net ECL remeasurement on stage transfer	(111)	(110)
Change in economic scenarios	29	37
New lending and assets purchased	28	42
Redemptions, repayments and assets sold	(35)	(35)
Changes in risk parameters and other movements	(9)	(1)
Assets written off	0	0
Ending balance	170	171	133
Net movement in the period	(1)	38
ECL (release)/charge to the Income Statement	(1)	38
Less: Discount unwind	0	0
Less: Recoveries net of collection costs	0	0
Total ECL (release)/charge to the Income Statement	(1)	38
Financial instruments not credit-impaired | Subject to 12-month ECL | Stage 1
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	290,813	298,285
Transfers from Stage 1 to Stage 2	(13,160)	(9,100)
Transfers from Stage 2 to Stage 1	5,974	7,207
Transfers to Stage 3	(600)	(621)
Transfers from Stage 3	28	10
Transfers of financial instruments	(7,758)	(2,504)
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	25,306	48,194
Redemptions, repayments and assets sold	(34,246)	(55,332)
Changes in risk parameters and other movements	(105)	2,170
Assets written off	0	0
Ending balance	274,010	290,813	298,285
Net movement in the period	(16,803)	(7,472)
Financial instruments not credit-impaired | Subject to Lifetime ECL | Stage 2
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	516	330
Transfers from Stage 1 to Stage 2	9	25
Transfers from Stage 2 to Stage 1	(111)	(133)
Transfers to Stage 3	(38)	(32)
Transfers from Stage 3	15	150
Transfers of financial instruments	(125)	10
Net ECL remeasurement on stage transfer	145	98
Change in economic scenarios	(33)	123
New lending and assets purchased	45	76
Redemptions, repayments and assets sold	(53)	(60)
Changes in risk parameters and other movements	(33)	(61)
Assets written off	0	0
Ending balance	462	516	330
Net movement in the period	(54)	186
ECL (release)/charge to the Income Statement	(54)	186
Less: Discount unwind	0	0
Less: Recoveries net of collection costs	0	0
Total ECL (release)/charge to the Income Statement	(54)	186
Financial instruments not credit-impaired | Subject to Lifetime ECL | Stage 2
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	19,282	18,013
Transfers from Stage 1 to Stage 2	13,160	9,100
Transfers from Stage 2 to Stage 1	(5,974)	(7,207)
Transfers to Stage 3	(924)	(624)
Transfers from Stage 3	306	758
Transfers of financial instruments	6,568	2,027
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	562	1,119
Redemptions, repayments and assets sold	(3,030)	(2,065)
Changes in risk parameters and other movements	497	188
Assets written off	0	0
Ending balance	23,879	19,282	18,013
Net movement in the period	4,597	1,269
Financial instruments credit-impaired | Subject to Lifetime ECL | Stage 3
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	320	403
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	44	36
Transfers from Stage 3	(16)	(151)
Transfers of financial instruments	28	(115)
Net ECL remeasurement on stage transfer	130	110
Change in economic scenarios	9	3
New lending and assets purchased	20	24
Redemptions, repayments and assets sold	(46)	(35)
Changes in risk parameters and other movements	133	87
Assets written off	(232)	(157)
Ending balance	362	320	403
Net movement in the period	42	(83)
ECL (release)/charge to the Income Statement	274	74
Less: Discount unwind	(21)	(13)
Less: Recoveries net of collection costs	8	36
Total ECL (release)/charge to the Income Statement	261	97
Financial instruments credit-impaired | Subject to Lifetime ECL | Stage 3
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	2,735	3,021
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	1,524	1,245
Transfers from Stage 3	(334)	(768)
Transfers of financial instruments	1,190	477
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	59	64
Redemptions, repayments and assets sold	(886)	(950)
Changes in risk parameters and other movements	394	377
Assets written off	(412)	(254)
Ending balance	3,080	2,735	£ 3,021
Net movement in the period	£ 345	£ (286)

Credit Risk - Disclosure of Cou

Credit Risk - Disclosure of Country Risk Exposure (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
Total
Disclosure of credit risk exposure [line items]
Exposure	300,200	313,200
Governments
Disclosure of credit risk exposure [line items]
Exposure	45,400	49,500
Banks
Disclosure of credit risk exposure [line items]
Exposure	7,100	5,500
Other
Disclosure of credit risk exposure [line items]
Exposure	12,100	9,200
Retail
Disclosure of credit risk exposure [line items]
Exposure	209,700	221,500
Corporate
Disclosure of credit risk exposure [line items]
Exposure	25,900	27,500
Eurozone | Netherlands
Disclosure of credit risk exposure [line items]
Exposure	300	100
Eurozone | Belgium
Disclosure of credit risk exposure [line items]
Exposure	500	600
Eurozone | Finland
Disclosure of credit risk exposure [line items]
Exposure	100	100
Eurozone | Total
Disclosure of credit risk exposure [line items]
Exposure	7,900	5,000
Eurozone | Total | Ireland
Disclosure of credit risk exposure [line items]
Exposure	3,200	2,400
Eurozone | Total | Spain
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Total | France
Disclosure of credit risk exposure [line items]
Exposure	2,600	1,400
Eurozone | Total | Germany
Disclosure of credit risk exposure [line items]
Exposure	500	400
Eurozone | Total | Luxembourg
Disclosure of credit risk exposure [line items]
Exposure	600	0
Eurozone | Total | Other
Disclosure of credit risk exposure [line items]
Exposure	1,000	800
Eurozone | Governments
Disclosure of credit risk exposure [line items]
Exposure	400	400
Eurozone | Governments | Ireland
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Governments | Spain
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Governments | France
Disclosure of credit risk exposure [line items]
Exposure	100	100
Eurozone | Governments | Germany
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Governments | Luxembourg
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Governments | Other
Disclosure of credit risk exposure [line items]
Exposure	300	300
Eurozone | Banks
Disclosure of credit risk exposure [line items]
Exposure	2,600	1,600
Eurozone | Banks | Ireland
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Banks | Spain
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Banks | France
Disclosure of credit risk exposure [line items]
Exposure	1,700	800
Eurozone | Banks | Germany
Disclosure of credit risk exposure [line items]
Exposure	200	300
Eurozone | Banks | Luxembourg
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Banks | Other
Disclosure of credit risk exposure [line items]
Exposure	700	500
Eurozone | Other
Disclosure of credit risk exposure [line items]
Exposure	4,700	2,800
Eurozone | Other | Ireland
Disclosure of credit risk exposure [line items]
Exposure	3,100	2,300
Eurozone | Other | Spain
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Other | France
Disclosure of credit risk exposure [line items]
Exposure	800	500
Eurozone | Other | Germany
Disclosure of credit risk exposure [line items]
Exposure	300	0
Eurozone | Other | Luxembourg
Disclosure of credit risk exposure [line items]
Exposure	500	0
Eurozone | Other | Other
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Retail
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Retail | Ireland
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Retail | Spain
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Retail | France
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Retail | Germany
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Retail | Luxembourg
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Retail | Other
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Corporate
Disclosure of credit risk exposure [line items]
Exposure	200	200
Eurozone | Corporate | Ireland
Disclosure of credit risk exposure [line items]
Exposure	100	100
Eurozone | Corporate | Spain
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Corporate | France
Disclosure of credit risk exposure [line items]
Exposure	0	0
Eurozone | Corporate | Germany
Disclosure of credit risk exposure [line items]
Exposure	0	100
Eurozone | Corporate | Luxembourg
Disclosure of credit risk exposure [line items]
Exposure	100	0
Eurozone | Corporate | Other
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Total | UK
Disclosure of credit risk exposure [line items]
Exposure	283,100	301,600
Other countries | Total | US
Disclosure of credit risk exposure [line items]
Exposure	700	1,100
Other countries | Total | Switzerland
Disclosure of credit risk exposure [line items]
Exposure	2,100	1,200
Other countries | Total | Japan
Disclosure of credit risk exposure [line items]
Exposure	2,900	1,400
Other countries | Total | Other
Disclosure of credit risk exposure [line items]
Exposure	3,500	2,900
Other countries | Governments | UK
Disclosure of credit risk exposure [line items]
Exposure	40,800	46,600
Other countries | Governments | US
Disclosure of credit risk exposure [line items]
Exposure	0	100
Other countries | Governments | Switzerland
Disclosure of credit risk exposure [line items]
Exposure	2,100	1,200
Other countries | Governments | Japan
Disclosure of credit risk exposure [line items]
Exposure	2,000	1,100
Other countries | Governments | Other
Disclosure of credit risk exposure [line items]
Exposure	100	100
Other countries | Banks | UK
Disclosure of credit risk exposure [line items]
Exposure	1,700	1,800
Other countries | Banks | US
Disclosure of credit risk exposure [line items]
Exposure	700	1,000
Other countries | Banks | Switzerland
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Banks | Japan
Disclosure of credit risk exposure [line items]
Exposure	900	300
Other countries | Banks | Other
Disclosure of credit risk exposure [line items]
Exposure	1,200	800
Other countries | Other | UK
Disclosure of credit risk exposure [line items]
Exposure	7,200	6,200
Other countries | Other | US
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Other | Switzerland
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Other | Japan
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Other | Other
Disclosure of credit risk exposure [line items]
Exposure	200	200
Other countries | Retail | UK
Disclosure of credit risk exposure [line items]
Exposure	208,400	220,200
Other countries | Retail | US
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Retail | Switzerland
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Retail | Japan
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Retail | Other
Disclosure of credit risk exposure [line items]
Exposure	1,300	1,300
Other countries | Corporate | UK
Disclosure of credit risk exposure [line items]
Exposure	25,000	26,800
Other countries | Corporate | US
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Corporate | Switzerland
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Corporate | Japan
Disclosure of credit risk exposure [line items]
Exposure	0	0
Other countries | Corporate | Other
Disclosure of credit risk exposure [line items]
Exposure	700	500
All countries excluding Eurozone countries | Total
Disclosure of credit risk exposure [line items]
Exposure	292,300	308,200
All countries excluding Eurozone countries | Governments
Disclosure of credit risk exposure [line items]
Exposure	45,000	49,100
All countries excluding Eurozone countries | Banks
Disclosure of credit risk exposure [line items]
Exposure	4,500	3,900
All countries excluding Eurozone countries | Other
Disclosure of credit risk exposure [line items]
Exposure	7,400	6,400
All countries excluding Eurozone countries | Retail
Disclosure of credit risk exposure [line items]
Exposure	209,700	221,500
All countries excluding Eurozone countries | Corporate
Disclosure of credit risk exposure [line items]
Exposure	£ 25,700	£ 27,300

Credit Risk - Disclosure of Bal

Credit Risk - Disclosure of Balances with Other Banco Santander Companies (Details) - Santander UK Group Holdings plc - GBP (£) £ in Billions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about financial instruments [line items]
Financial assets	£ 5.4	£ 5.6
Financial liabilities	3.3	3
Spain
Disclosure of detailed information about financial instruments [line items]
Financial assets	0.9	1.4
Financial liabilities	2.4	1.8
UK
Disclosure of detailed information about financial instruments [line items]
Financial assets	4.5	4.2
Financial liabilities	0.9	1.2
Banks
Disclosure of detailed information about financial instruments [line items]
Financial assets	0.9	1.4
Financial liabilities	2.3	1.7
Banks | Spain
Disclosure of detailed information about financial instruments [line items]
Financial assets	0.9	1.4
Financial liabilities	2.3	1.7
Banks | UK
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
Financial liabilities	0	0
Other
Disclosure of detailed information about financial instruments [line items]
Financial assets	4.5	4.2
Financial liabilities	1	1.3
Other | Spain
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
Financial liabilities	0.1	0.1
Other | UK
Disclosure of detailed information about financial instruments [line items]
Financial assets	4.5	4.2
Financial liabilities	0.9	1.2
Corporate
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
Financial liabilities	0	0
Corporate | Spain
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
Financial liabilities	0	0
Corporate | UK
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
Financial liabilities	£ 0	£ 0

Credit Risk - Disclosure of Bor

Credit Risk - Disclosure of Borrower Profile (Details) - Credit risk - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 175,239	£ 187,141
Percentage of residential mortgage loans	100%	100%
New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 12,164	£ 34,127
Percentage of residential mortgage loans	100%	100%
Home movers | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 73,075	£ 77,708
Percentage of residential mortgage loans	42%	41%
Home movers | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 5,009	£ 12,221
Percentage of residential mortgage loans	41%	36%
Remortgagers | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 49,084	£ 53,936
Percentage of residential mortgage loans	28%	29%
Remortgagers | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 3,901	£ 10,644
Percentage of residential mortgage loans	32%	31%
First-time buyers | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 37,495	£ 38,698
Percentage of residential mortgage loans	21%	21%
First-time buyers | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 3,015	£ 8,129
Percentage of residential mortgage loans	25%	24%
Buy-to-let | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 15,585	£ 16,799
Percentage of residential mortgage loans	9%	9%
Buy-to-let | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 239	£ 3,133
Percentage of residential mortgage loans	2%	9%

Credit Risk - Homes Credit Risk

Credit Risk - Homes Credit Risk Review, Additional Information (Details) £ in Thousands	12 Months Ended
	Dec. 31, 2023 GBP (£)	Dec. 31, 2022 GBP (£)
Disclosure of credit risk exposure [line items]
Advances and flexible mortgage drawdowns	£ 800,000	£ 1,200,000
Percentage of customers with a maturing mortgage retained	77%	81%
Average LTV of mortgage total new lending, in London	65%	66%
Re-priced new business and internal transfers	£ 45,000,000
New mortgages reaching end of incentive period within a year	£ 39,000,000
Percentage of new business mortgages that are prime UK retail mortgages	0.85
Average new loan size	£ 228	£ 237
Percentage of new business mortgages that are unsecured retail mortgages	0.03
Proportion of mortgage portfolio in forbearance	0.009	0.009
Proportion of accounts in forbearance in excess of six months since last contractual payment	0.81	0.85
Weighted average LTV of accounts in forbearance	0.44	0.43
Weighted average portfolio LTV	0.51	0.50
Carrying value of mortgages classified as multiple forbearance	£ 121,000	£ 152,000
Mortgages modified since January 2008	£ 1,600,000	£ 1,900,000
Average LTV	0.24	0.24
Percentage of customers that made last six months payments	0.93	0.94
Percentage of accounts ninety days or more in arrears	0.0171	0.0153
Maximum
Disclosure of credit risk exposure [line items]
Percentage of internal transfer customers in arrears	0.01
Internal remortgages
Disclosure of credit risk exposure [line items]
Internal remortgages	£ 31,900,000	£ 25,300,000

Credit Risk - Disclosure of Int

Credit Risk - Disclosure of Interest Rate Profile of Mortgage Assets Stock (Details) - Stock - Credit risk - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 175,239	£ 187,141
Percentage of residential mortgage loans	100%	100%
Fixed rate
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 155,363	£ 166,281
Percentage of residential mortgage loans	89%	89%
Fixed rate | No later than one year
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 38,419	£ 39,123
Percentage of residential mortgage loans	22%	21%
Fixed rate | Later than 1 year but no later than 3 years
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 66,451	£ 39,056
Percentage of residential mortgage loans	38%	21%
Fixed rate | Later than 3 years but no later than 4 years
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 34,925	£ 24,584
Percentage of residential mortgage loans	20%	13%
Fixed rate | Later than 4 years but no later than 5 years
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 11,126	£ 25,290
Percentage of residential mortgage loans	6%	14%
Fixed rate | Later than five years
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 4,442	£ 38,228
Percentage of residential mortgage loans	3%	20%
Variable rate
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 13,923	£ 12,511
Percentage of residential mortgage loans	8%	7%
Standard Variable Rate (SVR)
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 3,942	£ 5,682
Percentage of residential mortgage loans	2%	3%
Follow on Rate (FoR)
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 2,011	£ 2,667
Percentage of residential mortgage loans	1%	1%

Credit Risk - Disclosure of Geo

Credit Risk - Disclosure of Geographic Distribution of Mortgage Assets Stock (Details) - Credit risk - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 175,239	£ 187,141
New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	12,164	34,127
London | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	44,600	47,800
London | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	2,900	8,300
Midlands and East Anglia | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	24,600	26,000
Midlands and East Anglia | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	1,800	5,300
North | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	23,200	24,800
North | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	1,700	4,700
Northern Ireland | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	2,600	2,900
Northern Ireland | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	100	300
Scotland | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	6,400	6,800
Scotland | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	600	1,200
South East excluding London | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	55,600	59,300
South East excluding London | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	3,800	10,600
South West, Wales and other | Stock
Disclosure of credit risk exposure [line items]
Residential mortgage loans	18,200	19,500
South West, Wales and other | New business
Disclosure of credit risk exposure [line items]
Residential mortgage loans	£ 1,300	£ 3,700

Credit Risk - Disclosure of Mor

Credit Risk - Disclosure of Mortgage Loan Size (Details) - Credit risk - GBP (£) £ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Stock
Disclosure of credit risk exposure [line items]
Mortgage loans average size	£ 188	£ 184
New business
Disclosure of credit risk exposure [line items]
Mortgage loans average size	£ 228	£ 237
Over £1.0m
Disclosure of credit risk exposure [line items]
Mortgage loan size, percentage	2%	2%
£0.5m to £1.0m
Disclosure of credit risk exposure [line items]
Mortgage loan size, percentage	10%	10%
£0.25m to £0.5m
Disclosure of credit risk exposure [line items]
Mortgage loan size, percentage	31%	31%
Below £0.25m
Disclosure of credit risk exposure [line items]
Mortgage loan size, percentage	57%	57%

Credit Risk - Disclosure of LTV

Credit Risk - Disclosure of LTV Distribution of Mortgage Assets Stock (Details) - Credit risk - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	£ 175,239	£ 187,141
Collateral value, stock	175,182	187,093
Loan-to-value, stage 3	2,016	1,833
Collateral value, stage 3	2,005	1,824
Loan-to-value, new business	12,164	34,127
Collateral value, new business	12,164	34,126
Collateral against loans in negative equity	389	323
ECL
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	244	253
Loan-to-value, stage 3	109	95
Up to 50%
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	79,949	88,841
Loan-to-value, stage 3	1,110	1,116
Loan-to-value, new business	2,616	4,890
Up to 50% | ECL
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	31	37
Loan-to-value, stage 3	12	14
>50-60%
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	33,402	36,356
Loan-to-value, stage 3	348	284
Loan-to-value, new business	1,604	4,014
>50-60% | ECL
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	24	29
Loan-to-value, stage 3	10	11
>60-70%
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	31,261	34,350
Loan-to-value, stage 3	248	197
Loan-to-value, new business	1,977	6,104
>60-70% | ECL
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	40	50
Loan-to-value, stage 3	16	16
>70-80%
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	18,847	17,977
Loan-to-value, stage 3	139	110
Loan-to-value, new business	2,736	10,094
>70-80% | ECL
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	50	46
Loan-to-value, stage 3	20	15
>80-90%
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	8,917	7,369
Loan-to-value, stage 3	67	42
Loan-to-value, new business	2,318	6,002
>80-90% | ECL
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	35	29
Loan-to-value, stage 3	15	9
>90-100%
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	2,418	1,876
Loan-to-value, stage 3	39	32
Loan-to-value, new business	900	2,999
>90-100% | ECL
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	20	17
Loan-to-value, stage 3	11	9
>100%
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	445	372
Loan-to-value, stage 3	65	52
Loan-to-value, new business	13	24
>100% | ECL
Disclosure of credit risk exposure [line items]
Loan-to-value, stock	44	45
Loan-to-value, stage 3	£ 25	£ 21
Average LTV - Balance weighted
Disclosure of credit risk exposure [line items]
Percentage of loan to value, stock	51%	50%
Percentage of loan to value, stage 3	49%	47%
Percentage of loan to value, new business	66%	69%

Credit Risk - Disclosure of C_3

Credit Risk - Disclosure of Credit Performance by Segment (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 211,222	£ 223,840
Allowance account for credit losses of financial assets		1,007
ECL	994
Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	175,239	187,141
Everyday Banking
Disclosure of credit risk exposure [line items]
Loans and advances to customers	7,028	7,520
Allowance account for credit losses of financial assets		£ 293
ECL	£ 300
Stage 3 ratio	3.83%	3.71%
12 month Gross write-offs	£ 130	£ 110
Everyday Banking | Business banking
Disclosure of credit risk exposure [line items]
Loans and advances to customers	1,819	2,519
Allowance account for credit losses of financial assets		£ 19
ECL	£ 16
Stage 3 ratio	7.25%	6.58%
12 month Gross write-offs	£ 11	£ 11
Everyday Banking | Other unsecured loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	5,209	5,001
Allowance account for credit losses of financial assets		£ 274
ECL	£ 284
Stage 3 ratio	2.65%	2.27%
12 month Gross write-offs	£ 119	£ 99
Everyday Banking | Personal loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	2,064	1,982
Allowance account for credit losses of financial assets		62
ECL	66
Everyday Banking | Credit cards
Disclosure of credit risk exposure [line items]
Loans and advances to customers	2,674	2,558
Allowance account for credit losses of financial assets		130
ECL	140
Everyday Banking | Overdrafts
Disclosure of credit risk exposure [line items]
Loans and advances to customers	471	461
Allowance account for credit losses of financial assets		82
ECL	78
Everyday Banking | Total Undrawn
Disclosure of credit risk exposure [line items]
Stage 3 undrawn exposures	39
Stage 3 undrawn exposures		35
Everyday Banking | Total Undrawn | Business banking
Disclosure of credit risk exposure [line items]
Stage 3 undrawn exposures	2
Stage 3 undrawn exposures		3
Everyday Banking | Total Undrawn | Other unsecured loans
Disclosure of credit risk exposure [line items]
Stage 3 undrawn exposures	37
Stage 3 undrawn exposures		32
Consumer Finance
Disclosure of credit risk exposure [line items]
Loans and advances to customers	5,228	5,384
Allowance account for credit losses of financial assets		67
ECL	£ 70	£ 67
Stage 3 ratio	0.53%	0.54%
12 month Gross write-offs	£ 23	£ 19
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		393
ECL	380
Maximum exposure to credit risk	25,990	27,565
Loss allowances	380	394
Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	12,676	14,123
Loss allowances	341	355
Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	5,358	5,407
Loss allowances	39	38
Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	7,956	8,035
Loss allowances	0	1
Corporate & Commercial Banking | Fully performing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	22,626	24,540
Corporate & Commercial Banking | Fully performing | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	10,140	11,796
Corporate & Commercial Banking | Fully performing | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	4,734	4,765
Corporate & Commercial Banking | Fully performing | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	7,752	7,979
Corporate & Commercial Banking | Enhanced monitoring
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	472	580
Corporate & Commercial Banking | Enhanced monitoring | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	462	431
Corporate & Commercial Banking | Enhanced monitoring | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	10	103
Corporate & Commercial Banking | Enhanced monitoring | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	46
Corporate & Commercial Banking | Proactive management
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,147	1,873
Corporate & Commercial Banking | Proactive management | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,447	1,383
Corporate & Commercial Banking | Proactive management | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	496	480
Corporate & Commercial Banking | Proactive management | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	204	10
Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	745	572
Corporate & Commercial Banking | Stage 3 | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	627	513
Corporate & Commercial Banking | Stage 3 | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	118	59
Corporate & Commercial Banking | Stage 3 | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Stage 1 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	155,063	171,733
Stage 1 | Everyday Banking
Disclosure of credit risk exposure [line items]
Loans and advances to customers	5,807	6,300
Stage 1 | Everyday Banking | Business banking
Disclosure of credit risk exposure [line items]
Loans and advances to customers	1,574	2,223
Stage 1 | Everyday Banking | Other unsecured loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	4,233	4,077
Stage 1 | Everyday Banking | Personal loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	1,743	1,730
Stage 1 | Everyday Banking | Credit cards
Disclosure of credit risk exposure [line items]
Loans and advances to customers	2,283	2,192
Stage 1 | Everyday Banking | Overdrafts
Disclosure of credit risk exposure [line items]
Loans and advances to customers	207	155
Stage 1 | Consumer Finance
Disclosure of credit risk exposure [line items]
Loans and advances to customers	4,870	5,005
Stage 1 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	21,280	23,105
Stage 2
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		516
ECL	462
Stage 2 | Total Undrawn
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		39
ECL	40
Stage 2 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	18,160	13,576
Stage 2 | Everyday Banking
Disclosure of credit risk exposure [line items]
Loans and advances to customers	990	975
Stage 2 | Everyday Banking | Business banking
Disclosure of credit risk exposure [line items]
Loans and advances to customers	115	133
Stage 2 | Everyday Banking | Other unsecured loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	875	842
Stage 2 | Everyday Banking | Personal loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	294	231
Stage 2 | Everyday Banking | Credit cards
Disclosure of credit risk exposure [line items]
Loans and advances to customers	345	329
Stage 2 | Everyday Banking | Overdrafts
Disclosure of credit risk exposure [line items]
Loans and advances to customers	236	282
Stage 2 | Consumer Finance
Disclosure of credit risk exposure [line items]
Loans and advances to customers	330	350
Allowance account for credit losses of financial assets		27
ECL	30
Stage 2 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Allowance account for credit losses of financial assets		155
ECL	118
Maximum exposure to credit risk	3,965	3,888
Stage 3 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 2,016	£ 1,832
Stage 3 ratio	1.16%	0.99%
Stage 3 | Everyday Banking
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 231	£ 245
Stage 3 | Everyday Banking | Business banking
Disclosure of credit risk exposure [line items]
Loans and advances to customers	130	163
Stage 3 | Everyday Banking | Other unsecured loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	101	82
Stage 3 | Everyday Banking | Personal loans
Disclosure of credit risk exposure [line items]
Loans and advances to customers	27	21
Stage 3 | Everyday Banking | Credit cards
Disclosure of credit risk exposure [line items]
Loans and advances to customers	46	37
Stage 3 | Everyday Banking | Overdrafts
Disclosure of credit risk exposure [line items]
Loans and advances to customers	28	24
Stage 3 | Consumer Finance
Disclosure of credit risk exposure [line items]
Loans and advances to customers	28	29
Stage 3 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	745	572
Credit risk | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	175,239	187,141
Allowance account for credit losses of financial assets		£ 253
ECL	£ 244
Stage 3 ratio	1.16%	0.99%
Credit risk | Stage 1 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 155,063	£ 171,733
Credit risk | Stage 2 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	18,160	13,576
Credit risk | Stage 3 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 2,016	£ 1,832

Credit Risk - Disclosure of E_3

Credit Risk - Disclosure of ECL Reconciliation by Segment (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	£ 1,007
Ending balance	994	£ 1,007
Less: Recoveries net of collection costs	(10)	(36)	£ 17
ECL (release)/charge to the Income Statement from continued operations	206
Consumer Finance
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
ECL (release)/charge to the Income Statement from continued operations	15
Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
ECL (release)/charge to the Income Statement from continued operations	40
Corporate Centre
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
ECL (release)/charge to the Income Statement from continued operations	1
Stage 1
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	171
Ending balance	170	171
Stage 1 | Subject to 12-month ECL | Financial instruments not credit-impaired
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	290,813	298,285
Transfers from Stage 1 to Stage 2	(13,160)	(9,100)
Transfers from Stage 2 to Stage 1	5,974	7,207
Transfers to Stage 3	(600)	(621)
Transfers from Stage 3	28	10
Transfers of financial instruments	(7,758)	(2,504)
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	25,306	48,194
Redemptions, repayments and assets sold	(34,246)	(55,332)
Changes in risk parameters and other movements	(105)	2,170
Assets written off	0	0
Ending balance	274,010	290,813	298,285
Net movement in the period	(16,803)	(7,472)
Stage 1 | Subject to 12-month ECL | Financial instruments not credit-impaired | Mortgages
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	179,632	180,232
Transfers from Stage 1 to Stage 2	(11,006)	(5,833)
Transfers from Stage 2 to Stage 1	4,838	2,961
Transfers to Stage 3	(337)	(278)
Transfers from Stage 3	14	3
Transfers of financial instruments	(6,491)	(3,147)
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	12,957	35,028
Redemptions, repayments and assets sold	(23,522)	(32,565)
Changes in risk parameters and other movements	676	84
Assets written off	0	0
Ending balance	163,252	179,632	180,232
Net movement in the period	(16,380)	(600)
Stage 1 | Subject to 12-month ECL | Financial instruments not credit-impaired | Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	23,838	20,604
Transfers from Stage 1 to Stage 2	(1,376)	(2,195)
Transfers from Stage 2 to Stage 1	512	4,023
Transfers to Stage 3	(118)	(172)
Transfers from Stage 3	1	0
Transfers of financial instruments	(981)	1,656
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	7,257	8,629
Redemptions, repayments and assets sold	(6,713)	(9,019)
Changes in risk parameters and other movements	(834)	1,968
Assets written off	0	0
Ending balance	22,567	23,838	20,604
Net movement in the period	(1,271)	3,234
Stage 2
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	516
Ending balance	462	516
Stage 2 | Subject to Lifetime ECL | Financial instruments not credit-impaired
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	19,282	18,013
Transfers from Stage 1 to Stage 2	13,160	9,100
Transfers from Stage 2 to Stage 1	(5,974)	(7,207)
Transfers to Stage 3	(924)	(624)
Transfers from Stage 3	306	758
Transfers of financial instruments	6,568	2,027
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	562	1,119
Redemptions, repayments and assets sold	(3,030)	(2,065)
Changes in risk parameters and other movements	497	188
Assets written off	0	0
Ending balance	23,879	19,282	18,013
Net movement in the period	4,597	1,269
Stage 2 | Subject to Lifetime ECL | Financial instruments not credit-impaired | Mortgages
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	13,685	11,199
Transfers from Stage 1 to Stage 2	11,006	5,833
Transfers from Stage 2 to Stage 1	(4,838)	(2,961)
Transfers to Stage 3	(570)	(448)
Transfers from Stage 3	279	280
Transfers of financial instruments	5,877	2,704
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	154	529
Redemptions, repayments and assets sold	(1,765)	(1,229)
Changes in risk parameters and other movements	329	482
Assets written off	0	0
Ending balance	18,280	13,685	11,199
Net movement in the period	4,595	2,486
Stage 2 | Subject to Lifetime ECL | Financial instruments not credit-impaired | Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	3,888	5,914
Transfers from Stage 1 to Stage 2	1,376	2,195
Transfers from Stage 2 to Stage 1	(512)	(4,023)
Transfers to Stage 3	(258)	(111)
Transfers from Stage 3	9	463
Transfers of financial instruments	615	(1,476)
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	132	228
Redemptions, repayments and assets sold	(869)	(584)
Changes in risk parameters and other movements	199	(194)
Assets written off	0	0
Ending balance	3,965	3,888	5,914
Net movement in the period	77	(2,026)
Stage 3
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	320
Ending balance	362	320
Stage 3 | Subject to Lifetime ECL | Financial instruments credit-impaired
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	2,735	3,021
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	1,524	1,245
Transfers from Stage 3	(334)	(768)
Transfers of financial instruments	1,190	477
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	59	64
Redemptions, repayments and assets sold	(886)	(950)
Changes in risk parameters and other movements	394	377
Assets written off	(412)	(254)
Ending balance	3,080	2,735	3,021
Net movement in the period	345	(286)
Stage 3 | Subject to Lifetime ECL | Financial instruments credit-impaired | Mortgages
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	1,853	1,816
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	907	726
Transfers from Stage 3	(293)	(283)
Transfers of financial instruments	614	443
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	5	1
Redemptions, repayments and assets sold	(417)	(415)
Changes in risk parameters and other movements	35	18
Assets written off	(54)	(10)
Ending balance	2,036	1,853	1,816
Net movement in the period	183	37
Stage 3 | Subject to Lifetime ECL | Financial instruments credit-impaired | Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	572	827
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	376	283
Transfers from Stage 3	(10)	(463)
Transfers of financial instruments	366	(180)
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	38	43
Redemptions, repayments and assets sold	(193)	(53)
Changes in risk parameters and other movements	137	21
Assets written off	(175)	(86)
Ending balance	745	572	827
Net movement in the period	173	(255)
Exposures - On balance sheet
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	312,830	319,319
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	0	0
Transfers from Stage 3	0	0
Transfers of financial instruments	0	0
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	25,927	49,377
Redemptions, repayments and assets sold	(38,162)	(58,347)
Changes in risk parameters and other movements	786	2,735
Assets written off	(412)	(254)
Ending balance	300,969	312,830	319,319
Net movement in the period	(11,861)	(6,489)
Exposures - On balance sheet | Mortgages
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	195,170	193,247
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	0	0
Transfers from Stage 3	0	0
Transfers of financial instruments	0	0
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	13,116	35,558
Redemptions, repayments and assets sold	(25,704)	(34,209)
Changes in risk parameters and other movements	1,040	584
Assets written off	(54)	(10)
Ending balance	183,568	195,170	193,247
Net movement in the period	(11,602)	1,923
Exposures - On balance sheet | Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	28,298	27,345
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	0	0
Transfers from Stage 3	0	0
Transfers of financial instruments	0	0
Net ECL remeasurement on stage transfer	0	0
Change in economic scenarios	0	0
New lending and assets purchased	7,427	8,900
Redemptions, repayments and assets sold	(7,775)	(9,656)
Changes in risk parameters and other movements	(498)	1,795
Assets written off	(175)	(86)
Ending balance	27,277	28,298	27,345
Net movement in the period	(1,021)	953
Stage 1 | Subject to 12-month ECL | Financial instruments not credit-impaired
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	171	133
Transfers from Stage 1 to Stage 2	(9)	(25)
Transfers from Stage 2 to Stage 1	111	133
Transfers to Stage 3	(6)	(4)
Transfers from Stage 3	1	1
Transfers of financial instruments	97	105
Net ECL remeasurement on stage transfer	(111)	(110)
Change in economic scenarios	29	37
New lending and assets purchased	28	42
Redemptions, repayments and assets sold	(35)	(35)
Changes in risk parameters and other movements	(9)	(1)
Assets written off	0	0
Ending balance	170	171	133
Net movement in the period	(1)	38
ECL (release)/charge to the Income Statement	(1)	38
Less: Discount unwind	0	0
Less: Recoveries net of collection costs	0	0
Stage 1 | Subject to 12-month ECL | Financial instruments not credit-impaired | Mortgages
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	26	14
Transfers from Stage 1 to Stage 2	(3)	(1)
Transfers from Stage 2 to Stage 1	30	16
Transfers to Stage 3	(3)	(2)
Transfers from Stage 3	0	0
Transfers of financial instruments	24	13
Net ECL remeasurement on stage transfer	(28)	(15)
Change in economic scenarios	0	1
New lending and assets purchased	4	7
Redemptions, repayments and assets sold	(6)	(3)
Changes in risk parameters and other movements	4	9
Assets written off	0	0
Ending balance	24	26	14
Net movement in the period	(2)	12
ECL (release)/charge to the Income Statement	(2)	12
Less: Discount unwind	0	0
Less: Recoveries net of collection costs	0	0
ECL (release)/charge to the Income Statement from continued operations	(2)	12
Stage 1 | Subject to 12-month ECL | Financial instruments not credit-impaired | Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	83	50
Transfers from Stage 1 to Stage 2	(1)	(14)
Transfers from Stage 2 to Stage 1	10	92
Transfers to Stage 3	(3)	(1)
Transfers from Stage 3	0	0
Transfers of financial instruments	6	77
Net ECL remeasurement on stage transfer	(16)	(72)
Change in economic scenarios	30	38
New lending and assets purchased	5	16
Redemptions, repayments and assets sold	(13)	(15)
Changes in risk parameters and other movements	(19)	(11)
Assets written off	0	0
Ending balance	76	83	50
Net movement in the period	(7)	33
ECL (release)/charge to the Income Statement	(7)	33
Less: Discount unwind	0	0
Less: Recoveries net of collection costs	0	0
ECL (release)/charge to the Income Statement from continued operations	(7)	33
Stage 2 | Subject to Lifetime ECL | Financial instruments not credit-impaired
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	516	330
Transfers from Stage 1 to Stage 2	9	25
Transfers from Stage 2 to Stage 1	(111)	(133)
Transfers to Stage 3	(38)	(32)
Transfers from Stage 3	15	150
Transfers of financial instruments	(125)	10
Net ECL remeasurement on stage transfer	145	98
Change in economic scenarios	(33)	123
New lending and assets purchased	45	76
Redemptions, repayments and assets sold	(53)	(60)
Changes in risk parameters and other movements	(33)	(61)
Assets written off	0	0
Ending balance	462	516	330
Net movement in the period	(54)	186
ECL (release)/charge to the Income Statement	(54)	186
Less: Discount unwind	0	0
Less: Recoveries net of collection costs	0	0
Stage 2 | Subject to Lifetime ECL | Financial instruments not credit-impaired | Mortgages
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	132	88
Transfers from Stage 1 to Stage 2	3	1
Transfers from Stage 2 to Stage 1	(30)	(16)
Transfers to Stage 3	(15)	(11)
Transfers from Stage 3	9	9
Transfers of financial instruments	(33)	(17)
Net ECL remeasurement on stage transfer	40	40
Change in economic scenarios	(2)	21
New lending and assets purchased	3	11
Redemptions, repayments and assets sold	(12)	(11)
Changes in risk parameters and other movements	(17)	0
Assets written off	0	0
Ending balance	111	132	88
Net movement in the period	(21)	44
ECL (release)/charge to the Income Statement	(21)	44
Less: Discount unwind	0	0
Less: Recoveries net of collection costs	0	0
ECL (release)/charge to the Income Statement from continued operations	(21)	44
Stage 2 | Subject to Lifetime ECL | Financial instruments not credit-impaired | Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	166	127
Transfers from Stage 1 to Stage 2	1	14
Transfers from Stage 2 to Stage 1	(10)	(92)
Transfers to Stage 3	(8)	(13)
Transfers from Stage 3	1	135
Transfers of financial instruments	(16)	44
Net ECL remeasurement on stage transfer	29	(41)
Change in economic scenarios	(30)	76
New lending and assets purchased	6	19
Redemptions, repayments and assets sold	(10)	(32)
Changes in risk parameters and other movements	(13)	(27)
Assets written off	0	0
Ending balance	132	166	127
Net movement in the period	(34)	39
ECL (release)/charge to the Income Statement	(34)	39
Less: Discount unwind	0	0
Less: Recoveries net of collection costs	0	0
ECL (release)/charge to the Income Statement from continued operations	(34)	39
Stage 3 | Subject to Lifetime ECL | Financial instruments credit-impaired
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	320	403
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	44	36
Transfers from Stage 3	(16)	(151)
Transfers of financial instruments	28	(115)
Net ECL remeasurement on stage transfer	130	110
Change in economic scenarios	9	3
New lending and assets purchased	20	24
Redemptions, repayments and assets sold	(46)	(35)
Changes in risk parameters and other movements	133	87
Assets written off	(232)	(157)
Ending balance	362	320	403
Net movement in the period	42	(83)
ECL (release)/charge to the Income Statement	274	74
Less: Discount unwind	(21)	(13)
Less: Recoveries net of collection costs	8	36
Stage 3 | Subject to Lifetime ECL | Financial instruments credit-impaired | Mortgages
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	95	89
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	18	13
Transfers from Stage 3	(9)	(9)
Transfers of financial instruments	9	4
Net ECL remeasurement on stage transfer	22	8
Change in economic scenarios	3	2
New lending and assets purchased	1	0
Redemptions, repayments and assets sold	(14)	(12)
Changes in risk parameters and other movements	4	7
Assets written off	(11)	(3)
Ending balance	109	95	89
Net movement in the period	14	6
ECL (release)/charge to the Income Statement	25	9
Less: Discount unwind	(3)	(2)
Less: Recoveries net of collection costs	29	(1)
ECL (release)/charge to the Income Statement from continued operations	51	6
Stage 3 | Subject to Lifetime ECL | Financial instruments credit-impaired | Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	145	248
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	11	14
Transfers from Stage 3	(1)	(135)
Transfers of financial instruments	10	(121)
Net ECL remeasurement on stage transfer	64	61
Change in economic scenarios	6	0
New lending and assets purchased	10	12
Redemptions, repayments and assets sold	(23)	(17)
Changes in risk parameters and other movements	28	(14)
Assets written off	(68)	(24)
Ending balance	172	145	248
Net movement in the period	27	(103)
ECL (release)/charge to the Income Statement	95	(79)
Less: Discount unwind	(9)	(3)
Less: Recoveries net of collection costs	(5)	42
ECL (release)/charge to the Income Statement from continued operations	81	(40)
ECL
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	1,007	866
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	0	0
Transfers from Stage 3	0	0
Transfers of financial instruments	0	0
Net ECL remeasurement on stage transfer	164	98
Change in economic scenarios	5	163
New lending and assets purchased	93	142
Redemptions, repayments and assets sold	(134)	(130)
Changes in risk parameters and other movements	91	25
Assets written off	(232)	(157)
Ending balance	994	1,007	866
Net movement in the period	(13)	141
ECL (release)/charge to the Income Statement	219	298
Less: Discount unwind	(21)	(13)
Less: Recoveries net of collection costs	8	36
ECL | Mortgages
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	253	191
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	0	0
Transfers from Stage 3	0	0
Transfers of financial instruments	0	0
Net ECL remeasurement on stage transfer	34	33
Change in economic scenarios	1	24
New lending and assets purchased	8	18
Redemptions, repayments and assets sold	(32)	(26)
Changes in risk parameters and other movements	(9)	16
Assets written off	(11)	(3)
Ending balance	244	253	191
Net movement in the period	(9)	62
ECL (release)/charge to the Income Statement	2	65
Less: Discount unwind	(3)	(2)
Less: Recoveries net of collection costs	29	(1)
ECL (release)/charge to the Income Statement from continued operations	28	62
ECL | Corporate & Commercial Banking
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]
Beginning balance	394	425
Transfers from Stage 1 to Stage 2	0	0
Transfers from Stage 2 to Stage 1	0	0
Transfers to Stage 3	0	0
Transfers from Stage 3	0	0
Transfers of financial instruments	0	0
Net ECL remeasurement on stage transfer	77	(52)
Change in economic scenarios	6	114
New lending and assets purchased	21	47
Redemptions, repayments and assets sold	(46)	(64)
Changes in risk parameters and other movements	(4)	(52)
Assets written off	(68)	(24)
Ending balance	380	394	£ 425
Net movement in the period	(14)	(31)
ECL (release)/charge to the Income Statement	54	(7)
Less: Discount unwind	(9)	(3)
Less: Recoveries net of collection costs	(5)	42
ECL (release)/charge to the Income Statement from continued operations	£ 40	£ 32

Credit Risk - Disclosure of Loa

Credit Risk - Disclosure of Loan Modification by Segment (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	£ 30	£ 95
Everyday Banking
Disclosure of credit risk exposure [line items]
Amortised cost before modification	21	14
Net modification loss	20	13
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	3	4
Everyday Banking | Business banking
Disclosure of credit risk exposure [line items]
Amortised cost before modification	0	0
Net modification loss	0	0
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	0	0
Everyday Banking | Credit cards
Disclosure of credit risk exposure [line items]
Amortised cost before modification	13	7
Net modification loss	14	7
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	2	3
Everyday Banking | Overdrafts
Disclosure of credit risk exposure [line items]
Amortised cost before modification	8	7
Net modification loss	6	6
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	1	1
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Amortised cost before modification	189	240
Net modification loss	10	8
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	27	15
Mortgages
Disclosure of credit risk exposure [line items]
Amortised cost before modification	351	317
Net modification loss	5	7
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	£ 79	£ 91
Mortgages | Credit risk
Disclosure of credit risk exposure [line items]
Stage 2 ratio	10.36%	7.25%

Credit Risk - Disclosure of For

Credit Risk - Disclosure of Forbearance Balances by Segment (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Mortgages
Disclosure of credit risk exposure [line items]
Capitalisation	£ 612	£ 610
Term extension	538	460
Interest-only	276	305
Concessionary interest rate	183	196
Forbearance	1,609	1,571
Loss allowances	£ 38	£ 42
Loans capitalisation forbearance Percentage	0.30%	0.30%
Loans term extension forbearance percentage	0.30%	0.30%
Loans interest only forbearance percentage	0.20%	0.20%
Loans concessionary interest rate forbearance percentage	0.10%	0.10%
Loans forbearance percentage	0.90%	0.90%
Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	£ 70	£ 54
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Capitalisation	264	219
Term extension	113	98
Interest-only	215	238
Forbearance	£ 592	£ 555
Proportion of portfolio	2.30%	2%
Stage 1 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Forbearance	£ 2	£ 17
Stage 2 | Mortgages
Disclosure of credit risk exposure [line items]
Capitalisation	327	311
Term extension	388	320
Interest-only	212	240
Concessionary interest rate	11	6
Forbearance	938	877
Loss allowances	8	11
Stage 2 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	8	9
Stage 2 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Forbearance	159	173
Stage 3 | Mortgages
Disclosure of credit risk exposure [line items]
Capitalisation	285	299
Term extension	150	140
Interest-only	64	65
Concessionary interest rate	172	190
Forbearance	671	694
Loss allowances	30	31
Stage 3 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	62	45
Stage 3 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Forbearance	431	365
Business banking | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	3	3
Business banking | Stage 2 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	0	0
Business banking | Stage 3 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	3	3
Total other unsecured | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	67	51
Total other unsecured | Stage 2 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	8	9
Total other unsecured | Stage 3 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	59	42
Personal loans | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	1	1
Personal loans | Stage 2 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	1	1
Personal loans | Stage 3 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	0	0
Credit cards | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	47	34
Credit cards | Stage 2 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	5	6
Credit cards | Stage 3 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	42	28
Overdrafts | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	19	16
Overdrafts | Stage 2 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	2	2
Overdrafts | Stage 3 | Everyday Banking
Disclosure of credit risk exposure [line items]
Forbearance	£ 17	£ 14

Credit Risk - Disclosure of Oth

Credit Risk - Disclosure of Other Loan Modification by Segment (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	£ 30	£ 95
Mortgages
Disclosure of credit risk exposure [line items]
Amortised cost before modification	351	317
Net modification loss	5	7
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	79	91
Everyday Banking
Disclosure of credit risk exposure [line items]
Amortised cost before modification	21	14
Net modification loss	20	13
Gross carrying amount of financial assets for which the loss allowance changed to 12 months ECL in the period	3	4
Other loans | Mortgages | Term extension
Disclosure of credit risk exposure [line items]
Amortised cost before modification	155
Other loans | Mortgages | Term extension | Stage 1
Disclosure of credit risk exposure [line items]
Amortised cost before modification	122
Other loans | Mortgages | Term extension | Stage 2
Disclosure of credit risk exposure [line items]
Amortised cost before modification	31
Other loans | Mortgages | Term extension | Stage 3
Disclosure of credit risk exposure [line items]
Amortised cost before modification	£ 2
Other loans | Mortgages | Interest-only
Disclosure of credit risk exposure [line items]
Amortised cost before modification		1,714
Other loans | Mortgages | Interest-only | Stage 1
Disclosure of credit risk exposure [line items]
Amortised cost before modification		1,186
Other loans | Mortgages | Interest-only | Stage 2
Disclosure of credit risk exposure [line items]
Amortised cost before modification		510
Other loans | Mortgages | Interest-only | Stage 3
Disclosure of credit risk exposure [line items]
Amortised cost before modification		£ 18

Credit Risk - Disclosure of Hom

Credit Risk - Disclosure of Homes Portfolios of Particular Interest by Credit Performance (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 211,222	£ 223,840
ECL	994
Allowance account for credit losses of financial assets		1,007
Properties in possession	£ 23	£ 47
Balance weighted LTV (indexed)	51%	50%
Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 175,239	£ 187,141
Mortgages | Credit risk
Disclosure of credit risk exposure [line items]
Loans and advances to customers	175,239	187,141
ECL	£ 244
Allowance account for credit losses of financial assets		£ 253
Stage 1 ratio	88.49%	91.76%
Stage 2 ratio	10.36%	7.25%
Stage 3 ratio	1.16%	0.99%
Interest-only
Disclosure of credit risk exposure [line items]
Properties in possession	£ 12	£ 18
Balance weighted LTV (indexed)	48%	47%
Interest-only | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 39,104	£ 41,098
Part interest-only, part repayment
Disclosure of credit risk exposure [line items]
Properties in possession	£ 3	£ 8
Balance weighted LTV (indexed)	51%	49%
Mortgage loan including interest-only part	£ 9,684	£ 10,192
Part interest-only, part repayment | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	12,788	13,759
Flexible
Disclosure of credit risk exposure [line items]
Properties in possession	£ 2	£ 3
Balance weighted LTV (indexed)	37%	36%
Flexible | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 5,418	£ 6,765
LTV >100%
Disclosure of credit risk exposure [line items]
Properties in possession	£ 5	£ 7
Balance weighted LTV (indexed)	116%	117%
LTV >100% | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 445	£ 372
Buy-to-let
Disclosure of credit risk exposure [line items]
Properties in possession	£ 1	£ 1
Balance weighted LTV (indexed)	60%	58%
Buy-to-let | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 15,585	£ 16,799
Other portfolio
Disclosure of credit risk exposure [line items]
Properties in possession	£ 8	£ 16
Balance weighted LTV (indexed)	53%	52%
Other portfolio | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 120,878	£ 129,299
Stage 1 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	155,063	171,733
Stage 1 | Mortgages | Credit risk
Disclosure of credit risk exposure [line items]
Loans and advances to customers	155,063	171,733
Stage 1 | Interest-only | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	32,244	35,957
Stage 1 | Part interest-only, part repayment | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	11,077	12,380
Stage 1 | Flexible | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	4,420	5,713
Stage 1 | LTV >100% | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	276	218
Stage 1 | Buy-to-let | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	13,887	15,884
Stage 1 | Other portfolio | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	109,509	120,683
Stage 2
Disclosure of credit risk exposure [line items]
ECL	462
Allowance account for credit losses of financial assets		516
Stage 2 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	18,160	13,576
Stage 2 | Mortgages | Credit risk
Disclosure of credit risk exposure [line items]
Loans and advances to customers	18,160	13,576
Stage 2 | Interest-only | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	5,874	4,265
Stage 2 | Part interest-only, part repayment | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	1,472	1,161
Stage 2 | Flexible | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	744	839
Stage 2 | LTV >100% | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	104	102
Stage 2 | Buy-to-let | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	1,647	876
Stage 2 | Other portfolio | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	10,618	7,916
Stage 3 | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 2,016	£ 1,832
Stage 3 ratio	1.16%	0.99%
Stage 3 | Mortgages | Credit risk
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 2,016	£ 1,832
Stage 3 | Interest-only | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 986	£ 876
Stage 3 ratio	2.54%	2.15%
Stage 3 | Part interest-only, part repayment | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 239	£ 218
Stage 3 ratio	1.88%	1.60%
Stage 3 | Flexible | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 254	£ 213
Stage 3 ratio	5.01%	3.45%
Stage 3 | LTV >100% | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 65	£ 52
Stage 3 ratio	14.54%	13.91%
Stage 3 | Buy-to-let | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 51	£ 39
Stage 3 ratio	0.33%	0.23%
Stage 3 | Other portfolio | Mortgages
Disclosure of credit risk exposure [line items]
Loans and advances to customers	£ 751	£ 700
Stage 3 ratio	0.62%	0.54%

Credit Risk - Disclosure of H_2

Credit Risk - Disclosure of Homes Portfolios of Particular Interest by Forbearance Balances (Details) - Mortgages - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Forbearance	£ 1,609	£ 1,571
Stage 2
Disclosure of credit risk exposure [line items]
Forbearance	938	877
Stage 3
Disclosure of credit risk exposure [line items]
Forbearance	671	694
Interest-only
Disclosure of credit risk exposure [line items]
Forbearance	368	292
Interest-only | Stage 2
Disclosure of credit risk exposure [line items]
Forbearance	219	112
Interest-only | Stage 3
Disclosure of credit risk exposure [line items]
Forbearance	149	180
Flexible
Disclosure of credit risk exposure [line items]
Forbearance	74	36
Flexible | Stage 2
Disclosure of credit risk exposure [line items]
Forbearance	55	19
Flexible | Stage 3
Disclosure of credit risk exposure [line items]
Forbearance	19	17
LTV >100%
Disclosure of credit risk exposure [line items]
Forbearance	12	10
LTV >100% | Stage 2
Disclosure of credit risk exposure [line items]
Forbearance	3	1
LTV >100% | Stage 3
Disclosure of credit risk exposure [line items]
Forbearance	9	9
Buy-to-let
Disclosure of credit risk exposure [line items]
Forbearance	23	15
Buy-to-let | Stage 2
Disclosure of credit risk exposure [line items]
Forbearance	16	11
Buy-to-let | Stage 3
Disclosure of credit risk exposure [line items]
Forbearance	£ 7	£ 4

Credit Risk - Disclosure of Seg

Credit Risk - Disclosure of Segments Exposure by Credit Rating (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	£ 25,990	£ 27,565
Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	21,280	23,105
Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	3,965	3,888
Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	745	572
Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	12,676	14,123
Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	5,358	5,407
Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	7,956	8,035
Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	56,288	60,829
Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	56,286	60,825
Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1	3
Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1	1
Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	50,233	54,987
Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,427	2,173
Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,372	2,528
Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,256	1,141
Internal grade 9 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	43	44
Internal grade 9 | Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	43	39
Internal grade 9 | Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	5
Internal grade 9 | Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 9 | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 9 | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 9 | Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	43	44
Internal grade 9 | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	49,770	55,237
Internal grade 9 | Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	49,770	55,237
Internal grade 9 | Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 9 | Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 9 | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	48,338	53,910
Internal grade 9 | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	170	136
Internal grade 9 | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,262	1,191
Internal grade 9 | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 8 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	3,198	4,366
Internal grade 8 | Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	3,130	4,364
Internal grade 8 | Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	68	2
Internal grade 8 | Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 8 | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	166	336
Internal grade 8 | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	2
Internal grade 8 | Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	3,032	4,028
Internal grade 8 | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	4,032	2,915
Internal grade 8 | Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	4,032	2,915
Internal grade 8 | Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 8 | Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 8 | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,895	1,077
Internal grade 8 | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,470	1,162
Internal grade 8 | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	667	676
Internal grade 8 | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 7 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	6,152	4,990
Internal grade 7 | Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	6,152	4,944
Internal grade 7 | Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	46
Internal grade 7 | Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 7 | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	911	923
Internal grade 7 | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	360	111
Internal grade 7 | Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	4,881	3,956
Internal grade 7 | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,223	1,510
Internal grade 7 | Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,223	1,510
Internal grade 7 | Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 7 | Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 7 | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 7 | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	787	875
Internal grade 7 | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	436	635
Internal grade 7 | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 6 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	4,654	4,391
Internal grade 6 | Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	4,618	4,202
Internal grade 6 | Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	36	189
Internal grade 6 | Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 6 | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,970	2,341
Internal grade 6 | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,684	2,044
Internal grade 6 | Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	6
Internal grade 6 | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	7	26
Internal grade 6 | Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	7	26
Internal grade 6 | Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 6 | Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 6 | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 6 | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 6 | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	7	26
Internal grade 6 | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	5,629	5,427
Internal grade 5 | Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	4,715	4,773
Internal grade 5 | Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	914	654
Internal grade 5 | Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	3,497	3,299
Internal grade 5 | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,132	2,128
Internal grade 5 | Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 5 | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	4,547	6,263
Internal grade 4 | Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,363	4,289
Internal grade 4 | Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,184	1,974
Internal grade 4 | Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	3,575	5,327
Internal grade 4 | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	972	936
Internal grade 4 | Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 4 | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,648	1,976
Internal grade 3 to 1 | Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	141	386
Internal grade 3 to 1 | Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	762	1,018
Internal grade 3 to 1 | Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	745	572
Internal grade 3 to 1 | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,439	1,791
Internal grade 3 to 1 | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	209	185
Internal grade 3 to 1 | Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Internal grade 3 to 1 | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Other | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	119	108
Other | Corporate & Commercial Banking | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	118	108
Other | Corporate & Commercial Banking | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1	0
Other | Corporate & Commercial Banking | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Other | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	118	106
Other | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1	1
Other | Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	1
Other | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,256	1,141
Other | Corporate Centre | Stage 1
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,254	1,137
Other | Corporate Centre | Stage 2
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1	3
Other | Corporate Centre | Stage 3
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1	1
Other | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Other | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Other | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Other | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	£ 1,256	£ 1,141

Credit Risk - Disclosure of S_4

Credit Risk - Disclosure of Segments Exposure by Geographical Distribution (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	£ 25,990	£ 27,565
Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	12,676	14,123
Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	5,358	5,407
Corporate & Commercial Banking | Social Housing
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	7,956	8,035
Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	56,288	60,829
Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	50,233	54,987
Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,427	2,173
Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,372	2,528
Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,256	1,141
UK | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	47,689	53,260
UK | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	45,367	50,806
UK | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,430	1,379
UK | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	892	1,075
UK | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Europe | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	3,309	3,344
Europe | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,062	1,886
Europe | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	243	422
Europe | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	1,004	1,036
Europe | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
US | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	282	317
US | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	83
US | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	4
US | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	282	230
US | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	0	0
Rest of World | Corporate Centre
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	5,008	3,908
Rest of World | Corporate Centre | Sovereign and Supranational
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,804	2,212
Rest of World | Corporate Centre | Structured Products
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	754	368
Rest of World | Corporate Centre | Financial Institutions
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	194	187
Rest of World | Corporate Centre | Crown Dependencies
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	£ 1,256	£ 1,141

Credit Risk - Disclosure of S_5

Credit Risk - Disclosure of Segments Exposure by Gross and Net Credit Exposure (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of credit risk exposure [line items]
Exposure	£ 300,969	£ 312,830
Stage 3
Disclosure of credit risk exposure [line items]
Exposure	3,080	2,735
Stage 3 | Corporate & Commercial Banking
Disclosure of credit risk exposure [line items]
Exposure	745	572
Collateral	218	199
Net exposure	527	373
Stage 3 | Corporate & Commercial Banking | SME and mid corporate
Disclosure of credit risk exposure [line items]
Exposure	627	513
Collateral	190	169
Net exposure	437	344
Stage 3 | Corporate & Commercial Banking | Commercial Real Estate
Disclosure of credit risk exposure [line items]
Exposure	118	59
Collateral	28	30
Net exposure	£ 90	£ 29

Market Risk - Summary of Detail

Market Risk - Summary of Detailed Information about VaR (Details)	Dec. 31, 2023
Disclosure Of Market Risk Exposure [Abstract]
VaR, confidence level	99%

Market Risk - Additional Inform

Market Risk - Additional Information (Details)	Dec. 31, 2023
Disclosure Of Market Risk Exposure [Abstract]
VaR, losses greater than VaR estimate, percentage of trading days	1%

Liquidity Risk - Summary of Rec

Liquidity Risk - Summary of Reconciliation of Wholesale Funding to Balance Sheet (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Deposits by banks	£ 20,357	£ 28,543
Deposits by customers	195,149	197,313
Repurchase agreements - non trading	8,411	7,982
Debt securities in issue	35,778	36,420
Subordinated liabilities	2,386	2,332
Other equity interest	2,196	2,196
Liquidity risk
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	70,100	78,200
Deposits by banks	20,400	28,500
Repurchase agreements - non trading	8,400	8,000
Financial liabilities designated at fair value	900	800
Debt securities in issue	35,800	36,400
Subordinated liabilities	2,400	2,300
Other equity instruments and non-controlling interests	2,200	2,200
Liquidity risk | Repos
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	8,400	8,000
Deposits by banks	0	0
Repurchase agreements - non trading	8,400	8,000
Financial liabilities designated at fair value	0	0
Debt securities in issue	0	0
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Foreign exchange and hedge accounting
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	1,100	1,600
Deposits by banks	0	0
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	0	0
Debt securities in issue	900	1,200
Subordinated liabilities	200	400
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Other
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	2,600	3,400
Deposits by banks	2,300	3,000
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	300	400
Debt securities in issue	0	0
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Wholesale funding
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	58,000	65,200
Deposits by banks	18,100	25,500
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	600	400
Debt securities in issue	34,900	35,200
Subordinated liabilities	2,200	1,900
Other equity instruments and non-controlling interests	2,200	2,200
Liquidity risk | Wholesale funding | Deposits by banks
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	1,100	500
Deposits by banks	1,100	500
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	0	0
Debt securities in issue	0	0
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Wholesale funding | Certificates of deposit and commercial paper
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	4,300	4,700
Deposits by banks	0	0
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	0	0
Debt securities in issue	4,300	4,700
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Wholesale funding | Senior unsecured – public benchmark
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	12,900	14,400
Deposits by banks	0	0
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	0	0
Debt securities in issue	12,900	14,400
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Wholesale funding | Senior unsecured – privately placed
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	800	600
Deposits by banks	0	0
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	600	400
Debt securities in issue	200	200
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Wholesale funding | Covered bonds
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	14,800	14,900
Deposits by banks	0	0
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	0	0
Debt securities in issue	14,800	14,900
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Wholesale funding | Securitisation and structured issuance
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	2,700	1,000
Deposits by banks	0	0
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	0	0
Debt securities in issue	2,700	1,000
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Wholesale funding | TFSME
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	17,000	25,000
Deposits by banks	17,000	25,000
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	0	0
Debt securities in issue	0	0
Subordinated liabilities	0	0
Other equity instruments and non-controlling interests	0	0
Liquidity risk | Wholesale funding | Subordinated liabilities and equity
Reconciliation Of Wholesale Funding To Balance Sheet [line items]
Funding analysis	4,400	4,100
Deposits by banks	0	0
Repurchase agreements - non trading	0	0
Financial liabilities designated at fair value	0	0
Debt securities in issue	0	0
Subordinated liabilities	2,200	1,900
Other equity instruments and non-controlling interests	£ 2,200	£ 2,200

Liquidity Risk - Summary of Sou

Liquidity Risk - Summary of Sources of Wholesale Funding by Maturity (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	£ 58,000	£ 65,200
Deposits by banks	20,357	28,543
Subordinated liabilities	2,386	2,332
Of which secured	34,500	40,900
Of which unsecured	23,500	24,300
Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	11,400
Senior unsecured – privately placed	100
Subordinated liabilities and equity (incl. AT1)	3,700
Wholesale fund amount	£ 15,200
Unsecured debt issued	96%
Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	£ 1,500
Senior unsecured – privately placed	700
Wholesale fund amount	42,300
Deposits by banks	1,100
Certificates of deposit and commercial paper	4,300
Covered bonds	14,800
Securitisation and structured issuance	2,200
TFSME	17,000
Subordinated liabilities	700
Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	500
≤ 1 month
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	1,400	2,600
Of which secured	100	100
Of which unsecured	1,300	2,500
≤ 1 month | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	0
Senior unsecured – privately placed	0
Subordinated liabilities and equity (incl. AT1)	0
Wholesale fund amount	0
≤ 1 month | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	0
Senior unsecured – privately placed	0
Wholesale fund amount	1,400
Deposits by banks	300
Certificates of deposit and commercial paper	1,000
Covered bonds	100
Securitisation and structured issuance	0
TFSME	0
Subordinated liabilities	0
≤ 1 month | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	0
>1 and ≤ 3 months
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	7,300	5,200
Of which secured	1,000	1,000
Of which unsecured	6,300	4,200
>1 and ≤ 3 months | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	1,600
Senior unsecured – privately placed	0
Subordinated liabilities and equity (incl. AT1)	0
Wholesale fund amount	1,600
>1 and ≤ 3 months | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	600
Senior unsecured – privately placed	0
Wholesale fund amount	5,700
Deposits by banks	800
Certificates of deposit and commercial paper	3,300
Covered bonds	1,000
Securitisation and structured issuance	0
TFSME	0
Subordinated liabilities	0
>1 and ≤ 3 months | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	0
>3 and ≤ 6 months
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	1,600	500
Of which secured	900	200
Of which unsecured	700	300
>3 and ≤ 6 months | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	0
Senior unsecured – privately placed	0
Subordinated liabilities and equity (incl. AT1)	500
Wholesale fund amount	500
>3 and ≤ 6 months | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	200
Senior unsecured – privately placed	0
Wholesale fund amount	1,100
Deposits by banks	0
Certificates of deposit and commercial paper	0
Covered bonds	900
Securitisation and structured issuance	0
TFSME	0
Subordinated liabilities	0
>3 and ≤ 6 months | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	0
>6 and ≤ 9 months
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	500	1,500
Of which secured	400	900
Of which unsecured	100	600
>6 and ≤ 9 months | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	0
Senior unsecured – privately placed	0
Subordinated liabilities and equity (incl. AT1)	0
Wholesale fund amount	0
>6 and ≤ 9 months | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	0
Senior unsecured – privately placed	100
Wholesale fund amount	500
Deposits by banks	0
Certificates of deposit and commercial paper	0
Covered bonds	400
Securitisation and structured issuance	0
TFSME	0
Subordinated liabilities	0
>6 and ≤ 9 months | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	0
>9 and ≤ 12 months
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	1,100	1,200
Of which secured	1,100	0
Of which unsecured	0	1,200
>9 and ≤ 12 months | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	0
Senior unsecured – privately placed	0
Subordinated liabilities and equity (incl. AT1)	0
Wholesale fund amount	0
>9 and ≤ 12 months | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	0
Senior unsecured – privately placed	0
Wholesale fund amount	1,100
Deposits by banks	0
Certificates of deposit and commercial paper	0
Covered bonds	1,000
Securitisation and structured issuance	100
TFSME	0
Subordinated liabilities	0
>9 and ≤ 12 months | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	0
No later than one year
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	11,900	11,000
Of which secured	3,500	2,200
Of which unsecured	8,400	8,800
No later than one year | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	1,600
Senior unsecured – privately placed	0
Subordinated liabilities and equity (incl. AT1)	500
Wholesale fund amount	2,100
No later than one year | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	800
Senior unsecured – privately placed	100
Wholesale fund amount	9,800
Deposits by banks	1,100
Certificates of deposit and commercial paper	4,300
Covered bonds	3,400
Securitisation and structured issuance	100
TFSME	0
Subordinated liabilities	0
No later than one year | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	0
Later than 1 year but no later than 3 years
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	22,400	6,600
Of which secured	18,600	3,500
Of which unsecured	3,800	3,100
Later than 1 year but no later than 3 years | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	2,500
Senior unsecured – privately placed	0
Subordinated liabilities and equity (incl. AT1)	800
Wholesale fund amount	3,300
Later than 1 year but no later than 3 years | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	400
Senior unsecured – privately placed	100
Wholesale fund amount	18,600
Deposits by banks	0
Certificates of deposit and commercial paper	0
Covered bonds	1,100
Securitisation and structured issuance	0
TFSME	17,000
Subordinated liabilities	0
Later than 1 year but no later than 3 years | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	500
>2 and ≤ 5 years
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	19,900	42,500
Of which secured	11,300	34,000
Of which unsecured	8,600	8,500
>2 and ≤ 5 years | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	6,800
Senior unsecured – privately placed	100
Subordinated liabilities and equity (incl. AT1)	1,500
Wholesale fund amount	8,400
>2 and ≤ 5 years | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	0
Senior unsecured – privately placed	200
Wholesale fund amount	11,500
Deposits by banks	0
Certificates of deposit and commercial paper	0
Covered bonds	9,200
Securitisation and structured issuance	2,100
TFSME	0
Subordinated liabilities	0
>2 and ≤ 5 years | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	0
>5 years
Disclosure Of Sources Of Wholesale Funding [Line Items]
Wholesale fund amount	3,800	5,100
Of which secured	1,100	1,200
Of which unsecured	2,700	£ 3,900
>5 years | Santander UK Group Holdings plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	500
Senior unsecured – privately placed	0
Subordinated liabilities and equity (incl. AT1)	900
Wholesale fund amount	1,400
>5 years | Santander UK plc
Disclosure Of Sources Of Wholesale Funding [Line Items]
Senior unsecured – public benchmark	300
Senior unsecured – privately placed	300
Wholesale fund amount	2,400
Deposits by banks	0
Certificates of deposit and commercial paper	0
Covered bonds	1,100
Securitisation and structured issuance	0
TFSME	0
Subordinated liabilities	700
>5 years | Other group entities
Disclosure Of Sources Of Wholesale Funding [Line Items]
Securitisation and structured issuance	£ 0

Liquidity Risk - Summary of Who

Liquidity Risk - Summary of Wholesale Funding by Currency (Details) - Liquidity risk	Dec. 31, 2023	Dec. 31, 2022
Sterling
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	63%	63%
Sterling | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	40%	28%
Sterling | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	71%	74%
Sterling | Senior unsecured – public benchmark | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	24%	18%
Sterling | Senior unsecured – public benchmark | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	21%	18%
Sterling | Senior unsecured – privately placed | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%
Sterling | Senior unsecured – privately placed | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	98%	95%
Sterling | Subordinated liabilities and equity | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	88%	75%
Sterling | Deposits by banks | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	1%	29%
Sterling | Certificates of deposit and commercial paper | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	29%	56%
Sterling | Covered bonds | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	54%	43%
Sterling | Securitisation and structured issuance | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	100%	100%
Sterling | Securitisation and structured issuance | Other group entities
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	100%	0%
Sterling | TFSME | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	100%	100%
Sterling | Subordinated liabilities | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	76%	48%
US Dollar
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	22%	21%
US Dollar | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	47%	51%
US Dollar | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	14%	12%
US Dollar | Senior unsecured – public benchmark | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	59%	58%
US Dollar | Senior unsecured – public benchmark | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	56%	62%
US Dollar | Senior unsecured – privately placed | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
US Dollar | Senior unsecured – privately placed | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
US Dollar | Subordinated liabilities and equity | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	12%	25%
US Dollar | Deposits by banks | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	97%	71%
US Dollar | Certificates of deposit and commercial paper | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	70%	42%
US Dollar | Covered bonds | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	5%	12%
US Dollar | Securitisation and structured issuance | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
US Dollar | Securitisation and structured issuance | Other group entities
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
US Dollar | TFSME | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
US Dollar | Subordinated liabilities | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	24%	52%
Euro
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	14%	16%
Euro | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	13%	20%
Euro | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	15%	14%
Euro | Senior unsecured – public benchmark | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	16%	24%
Euro | Senior unsecured – public benchmark | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	23%	20%
Euro | Senior unsecured – privately placed | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Euro | Senior unsecured – privately placed | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	2%	5%
Euro | Subordinated liabilities and equity | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Euro | Deposits by banks | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	2%	0%
Euro | Certificates of deposit and commercial paper | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	2%
Euro | Covered bonds | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	39%	45%
Euro | Securitisation and structured issuance | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Euro | Securitisation and structured issuance | Other group entities
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Euro | TFSME | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Euro | Subordinated liabilities | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	1%	0%
Other | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	1%
Other | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other | Senior unsecured – public benchmark | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	1%	0%
Other | Senior unsecured – public benchmark | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other | Senior unsecured – privately placed | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	100%	100%
Other | Senior unsecured – privately placed | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other | Subordinated liabilities and equity | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other | Deposits by banks | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other | Certificates of deposit and commercial paper | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	1%	0%
Other | Covered bonds | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	2%	0%
Other | Securitisation and structured issuance | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other | Securitisation and structured issuance | Other group entities
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other | TFSME | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%
Other | Subordinated liabilities | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Percentage of wholesale funding by major currencies	0%	0%

Liquidity Risk - Summary of Ext

Liquidity Risk - Summary of External Term Issuance, Sterling Equivalent (Details) - Liquidity risk - GBP (£) £ in Billions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about borrowings [line items]
Borrowings	£ 6.7	£ 9.4
Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Borrowings	2.6	4.7
Santander UK Group Holdings plc | Senior unsecured – public benchmark
Disclosure of detailed information about borrowings [line items]
Borrowings	1.5	3.9
Santander UK Group Holdings plc | Subordinated liabilities and equity
Disclosure of detailed information about borrowings [line items]
Borrowings	1.1	0.8
Santander UK plc
Disclosure of detailed information about borrowings [line items]
Borrowings	3.6	4.7
Santander UK plc | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	1.5	0.6
Santander UK plc | Covered bonds
Disclosure of detailed information about borrowings [line items]
Borrowings	1.8	4
Santander UK plc | Senior unsecured – privately placed
Disclosure of detailed information about borrowings [line items]
Borrowings	0.3	0.1
Other group entities | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	0.5	£ 0
Sterling
Disclosure of detailed information about borrowings [line items]
Borrowings	5.3
Sterling | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Borrowings	1.5
Sterling | Santander UK Group Holdings plc | Senior unsecured – public benchmark
Disclosure of detailed information about borrowings [line items]
Borrowings	0.4
Sterling | Santander UK Group Holdings plc | Subordinated liabilities and equity
Disclosure of detailed information about borrowings [line items]
Borrowings	1.1
Sterling | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Borrowings	3.3
Sterling | Santander UK plc | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	1.5
Sterling | Santander UK plc | Covered bonds
Disclosure of detailed information about borrowings [line items]
Borrowings	1.5
Sterling | Santander UK plc | Senior unsecured – privately placed
Disclosure of detailed information about borrowings [line items]
Borrowings	0.3
Sterling | Other group entities | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	0.5
US Dollar
Disclosure of detailed information about borrowings [line items]
Borrowings	1.1
US Dollar | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Borrowings	1.1
US Dollar | Santander UK Group Holdings plc | Senior unsecured – public benchmark
Disclosure of detailed information about borrowings [line items]
Borrowings	1.1
US Dollar | Santander UK Group Holdings plc | Subordinated liabilities and equity
Disclosure of detailed information about borrowings [line items]
Borrowings	0
US Dollar | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Borrowings	0
US Dollar | Santander UK plc | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	0
US Dollar | Santander UK plc | Covered bonds
Disclosure of detailed information about borrowings [line items]
Borrowings	0
US Dollar | Santander UK plc | Senior unsecured – privately placed
Disclosure of detailed information about borrowings [line items]
Borrowings	0
US Dollar | Other group entities | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro | Santander UK Group Holdings plc | Senior unsecured – public benchmark
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro | Santander UK Group Holdings plc | Subordinated liabilities and equity
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro | Santander UK plc | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro | Santander UK plc | Covered bonds
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro | Santander UK plc | Senior unsecured – privately placed
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Euro | Other group entities | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Other
Disclosure of detailed information about borrowings [line items]
Borrowings	0.3
Other | Santander UK Group Holdings plc
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Other | Santander UK Group Holdings plc | Senior unsecured – public benchmark
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Other | Santander UK Group Holdings plc | Subordinated liabilities and equity
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Other | Santander UK plc
Disclosure of detailed information about borrowings [line items]
Borrowings	0.3
Other | Santander UK plc | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Other | Santander UK plc | Covered bonds
Disclosure of detailed information about borrowings [line items]
Borrowings	0.3
Other | Santander UK plc | Senior unsecured – privately placed
Disclosure of detailed information about borrowings [line items]
Borrowings	0
Other | Other group entities | Securitisations and other secured funding
Disclosure of detailed information about borrowings [line items]
Borrowings	£ 0

Liquidity Risk - Summary of Bal

Liquidity Risk - Summary of Balance Sheet Encumbered and Unencumbered Assets Explanatory (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Encumbered And Unencumbered Assets [Line Items]
Cash and balances at central banks	£ 40,523	£ 46,635	£ 50,494
Financial assets at fair value through profit or loss [abstract]
Derivative financial instruments	1,472	2,439
Other financial assets at fair value through profit or loss	602	434
Financial Assets At Amortised Cost [Abstract]
Loans and advances to customers	211,222	223,840
Loans and advances to banks	1,216	1,105
Reverse repurchase agreements - non-trading	12,468	7,348
Financial assets at fair value through other comprehensive income	8,481	6,024
Interests in other entities	245	252
Intangible assets	1,548	1,550
Property, plant and equipment	1,512	1,526
Current tax assets	507	484	£ 351
Retirement benefit assets	723	1,051
Other assets	2,029	2,004
Total assets	282,083	292,243
Liquidity risk | Assets positioned at central banks
Disclosure Of Encumbered And Unencumbered Assets [Line Items]
Cash and balances at central banks	847	911
Financial assets at fair value through profit or loss [abstract]
Derivative financial instruments	0	0
Other financial assets at fair value through profit or loss	0	0
Financial Assets At Amortised Cost [Abstract]
Loans and advances to customers	58,489	68,535
Loans and advances to banks	0	0
Reverse repurchase agreements - non-trading	0	0
Other financial assets at amortised cost	0	0
Financial assets at fair value through other comprehensive income	0	0
Interests in other entities	0	0
Intangible assets	0	0
Property, plant and equipment	0	0
Current tax assets	0	0
Retirement benefit assets	0	0
Total assets	59,336	69,446
Liquidity risk | Assets positioned at central banks | Other assets
Financial Assets At Amortised Cost [Abstract]
Other assets	0	0
Total | Liquidity risk
Disclosure Of Encumbered And Unencumbered Assets [Line Items]
Cash and balances at central banks	1,480	1,330
Financial assets at fair value through profit or loss [abstract]
Derivative financial instruments	0	0
Other financial assets at fair value through profit or loss	0	0
Financial Assets At Amortised Cost [Abstract]
Loans and advances to customers	27,143	24,201
Loans and advances to banks	254	163
Reverse repurchase agreements - non-trading	0	0
Other financial assets at amortised cost	14	35
Financial assets at fair value through other comprehensive income	5,254	4,441
Interests in other entities	0	0
Intangible assets	0	0
Property, plant and equipment	0	0
Current tax assets	0	0
Retirement benefit assets	0	0
Total assets	34,145	30,170
Total | Liquidity risk | Other assets
Financial Assets At Amortised Cost [Abstract]
Other assets	0	0
Covered bonds | Liquidity risk
Disclosure Of Encumbered And Unencumbered Assets [Line Items]
Cash and balances at central banks	0	0
Financial assets at fair value through profit or loss [abstract]
Derivative financial instruments	0	0
Other financial assets at fair value through profit or loss	0	0
Financial Assets At Amortised Cost [Abstract]
Loans and advances to customers	21,880	21,304
Loans and advances to banks	0	0
Reverse repurchase agreements - non-trading	0	0
Other financial assets at amortised cost	0	0
Financial assets at fair value through other comprehensive income	0	0
Interests in other entities	0	0
Intangible assets	0	0
Property, plant and equipment	0	0
Current tax assets	0	0
Retirement benefit assets	0	0
Total assets	21,880	21,304
Covered bonds | Liquidity risk | Other assets
Financial Assets At Amortised Cost [Abstract]
Other assets	0	0
Securitis- ations | Liquidity risk
Disclosure Of Encumbered And Unencumbered Assets [Line Items]
Cash and balances at central banks	0	0
Financial assets at fair value through profit or loss [abstract]
Derivative financial instruments	0	0
Other financial assets at fair value through profit or loss	0	0
Financial Assets At Amortised Cost [Abstract]
Loans and advances to customers	5,208	2,851
Loans and advances to banks	0	0
Reverse repurchase agreements - non-trading	0	0
Other financial assets at amortised cost	0	0
Financial assets at fair value through other comprehensive income	0	0
Interests in other entities	0	0
Intangible assets	0	0
Property, plant and equipment	0	0
Current tax assets	0	0
Retirement benefit assets	0	0
Total assets	5,208	2,851
Securitis- ations | Liquidity risk | Other assets
Financial Assets At Amortised Cost [Abstract]
Other assets	0	0
Other | Liquidity risk
Disclosure Of Encumbered And Unencumbered Assets [Line Items]
Cash and balances at central banks	1,480	1,330
Financial assets at fair value through profit or loss [abstract]
Derivative financial instruments	0	0
Other financial assets at fair value through profit or loss	0	0
Financial Assets At Amortised Cost [Abstract]
Loans and advances to customers	55	46
Loans and advances to banks	254	163
Reverse repurchase agreements - non-trading	0	0
Other financial assets at amortised cost	14	35
Financial assets at fair value through other comprehensive income	5,254	4,441
Interests in other entities	0	0
Intangible assets	0	0
Property, plant and equipment	0	0
Current tax assets	0	0
Retirement benefit assets	0	0
Total assets	7,057	6,015
Other | Liquidity risk | Other assets
Financial Assets At Amortised Cost [Abstract]
Other assets	£ 0	£ 0

Liquidity Risk - Additional Inf

Liquidity Risk - Additional Information (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Currency Composition Of Wholesale Funds [Line Items]
Notional amount	£ 225,608	£ 177,802
Multi-currency medium term funding
Disclosure Of Currency Composition Of Wholesale Funds [Line Items]
Notional amount	5,600
Multi-currency medium term funding, MREL issuance
Disclosure Of Currency Composition Of Wholesale Funds [Line Items]
Notional amount	1,500
Multi-currency medium term funding, other secured issuance
Disclosure Of Currency Composition Of Wholesale Funds [Line Items]
Notional amount	4,100
Tier 2 securities | Banco Santander
Disclosure Of Currency Composition Of Wholesale Funds [Line Items]
Notional amount	£ 1,100

Capital Risk - Additional Infor

Capital Risk - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Capital Risk Exposure [Abstract]
Possible occurence of adverse economic stress	20 years
Possible occurence of very severe economic stress	100 years

Capital Risk - Summary of Regul

Capital Risk - Summary of Regulatory Capital Resources (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	£ 10,524	£ 10,843
AT1 capital	2,196	2,196
Tier 1 capital	12,720	13,039
Tier 2 capital	2,055	1,461
Total regulatory capital	14,775	14,500
CET1 capital before regulatory adjustments
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	12,770	12,515
– Capital instruments
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	7,060	7,060
AT1 capital	2,196	2,196
Tier 2 capital	2,193	2,111
– Retained earnings
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	6,047	6,563
– Accumulated other reserves and non-controlling interests
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	(337)	(1,108)
– Goodwill (net of tax)
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	(1,129)	(1,133)
– Other intangibles
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	(349)	(351)
– Fair value reserves related to gains or losses on cash flow hedges
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	335	1,116
– Gains or losses on liabilities valued at fair value resulting from changes in own credit standing
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	(14)	(27)
– Defined benefit pension fund assets
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	(520)	(755)
– NPE Backstop
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	0	(4)
– Dividend accrual
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital	(3)	(3)
– Regulatory deductions for instruments issued by subsidiary undertakings
Disclosure Of Regulatory Capital Resources [Line Items]
Tier 2 capital	(331)	(857)
– Amount of qualifying items subject to phase out from Tier 2
Disclosure Of Regulatory Capital Resources [Line Items]
Tier 2 capital	£ 193	£ 207

Capital Risk - Disclosure of Mo

Capital Risk - Disclosure of Movements in Regulatory Capital (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£)
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	£ 10,843
CET1 capital, ending period	10,524
AT1 capital, beginning period	2,196
AT1 capital, ending period	2,196
Tier 2 capital, beginning period	1,461
Tier 2 capital, ending period	2,055
Regulatory capital, beginning period	14,500
Regulatory capital, ending period	14,775
– Retained earnings
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	6,563
Increase (decrease) in CET1 capital	(516)
CET1 capital, ending period	6,047
Increase (decrease) in AT1 capital	0
Increase (decrease) in Tier 2 capital	0
Increase (decrease) in regulatory capital	(516)
– Accumulated other reserves and non-controlling interests
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	(1,108)
Increase (decrease) in CET1 capital	770
CET1 capital, ending period	(337)
Increase (decrease) in AT1 capital	0
Increase (decrease) in Tier 2 capital	0
Increase (decrease) in regulatory capital	770
– Goodwill (net of tax)
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	(1,133)
Increase (decrease) in CET1 capital	4
CET1 capital, ending period	(1,129)
Increase (decrease) in AT1 capital	0
Increase (decrease) in Tier 2 capital	0
Increase (decrease) in regulatory capital	4
– Other intangibles
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	(351)
Increase (decrease) in CET1 capital	2
CET1 capital, ending period	(349)
Increase (decrease) in AT1 capital	0
Increase (decrease) in Tier 2 capital	0
Increase (decrease) in regulatory capital	2
– Fair value reserves related to gains or losses on cash flow hedges
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	1,116
Increase (decrease) in CET1 capital	(780)
CET1 capital, ending period	335
Increase (decrease) in AT1 capital	0
Increase (decrease) in Tier 2 capital	0
Increase (decrease) in regulatory capital	(780)
– Gains or losses on liabilities valued at fair value resulting from changes in own credit standing
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	(27)
Increase (decrease) in CET1 capital	13
CET1 capital, ending period	(14)
Increase (decrease) in AT1 capital	0
Increase (decrease) in Tier 2 capital	0
Increase (decrease) in regulatory capital	13
– Defined benefit pension fund assets
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	(755)
Increase (decrease) in CET1 capital	235
CET1 capital, ending period	(520)
Increase (decrease) in AT1 capital	0
Increase (decrease) in Tier 2 capital	0
Increase (decrease) in regulatory capital	235
– NPE Backstop
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	(4)
Increase (decrease) in CET1 capital	4
CET1 capital, ending period	0
Increase (decrease) in AT1 capital	0
Increase (decrease) in Tier 2 capital	0
Increase (decrease) in regulatory capital	4
– Capital instruments
Disclosure Of Regulatory Capital Resources [Line Items]
CET1 capital, beginning period	7,060
Increase (decrease) in CET1 capital	0
CET1 capital, ending period	7,060
AT1 capital, beginning period	2,196
Increase (decrease) in AT1 capital	0
AT1 capital, ending period	2,196
Tier 2 capital, beginning period	2,111
Increase (decrease) in Tier 2 capital	82
Tier 2 capital, ending period	2,193
Increase (decrease) in regulatory capital	82
– Amount of qualifying items subject to phase out from Tier 2
Disclosure Of Regulatory Capital Resources [Line Items]
Increase (decrease) in CET1 capital	0
Increase (decrease) in AT1 capital	0
Tier 2 capital, beginning period	207
Increase (decrease) in Tier 2 capital	(14)
Tier 2 capital, ending period	193
Increase (decrease) in regulatory capital	(14)
- Deductions for instruments issued by subsidiary undertakings or subject to CRD IV amortisation
Disclosure Of Regulatory Capital Resources [Line Items]
Increase (decrease) in CET1 capital	0
Increase (decrease) in AT1 capital	0
Tier 2 capital, beginning period	(857)
Increase (decrease) in Tier 2 capital	526
Tier 2 capital, ending period	(331)
Increase (decrease) in regulatory capital	£ 526

Accounting Policies - Additiona

Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 area
Disclosure of detailed information about financial instruments [line items]
Climate change objective, number of main focus areas	3
Climate change, period covered for ECL calculations	5 years
180 Days | Unsecured Debt
Disclosure of detailed information about financial instruments [line items]
Written off period for past due	180 days

Accounting Policies - Summary o

Accounting Policies - Summary of Useful Lives or Depreciation Rates Used for Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2023
Other intangible | Minimum
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	3 years
Other intangible | Maximum
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	7 years
Computer software | Minimum
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	3 years
Computer software | Maximum
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	7 years

Accounting Policies - Summary_2

Accounting Policies - Summary of Useful Lives or Depreciation Rates Used for Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2023
Owner-occupied properties
Disclosure of detailed information about property, plant and equipment [line items]
Useful lives or depreciation rates, property, plant and equipment	50 years
Minimum | Office fixtures and equipment
Disclosure of detailed information about property, plant and equipment [line items]
Useful lives or depreciation rates, property, plant and equipment	3 years
Minimum | Computer software
Disclosure of detailed information about property, plant and equipment [line items]
Useful lives or depreciation rates, property, plant and equipment	3 years
Minimum | Operating lease assets
Disclosure of detailed information about property, plant and equipment [line items]
Useful lives or depreciation rates, property, plant and equipment	1 year
Maximum | Office fixtures and equipment
Disclosure of detailed information about property, plant and equipment [line items]
Useful lives or depreciation rates, property, plant and equipment	15 years
Maximum | Computer software
Disclosure of detailed information about property, plant and equipment [line items]
Useful lives or depreciation rates, property, plant and equipment	7 years
Maximum | Operating lease assets
Disclosure of detailed information about property, plant and equipment [line items]
Useful lives or depreciation rates, property, plant and equipment	4 years

Segments - Additional Informati

Segments - Additional Information (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£) business_unit segment
Disclosure of operating segments [line items]
Number of segments | segment	4
Retail and Business Banking
Disclosure of operating segments [line items]
Number of business units | business_unit	2
Corporate & Commercial Banking | Minimum
Disclosure of operating segments [line items]
Customers, annual turnover	£ 2
Corporate & Commercial Banking | Maximum
Disclosure of operating segments [line items]
Customers, annual turnover	500
Corporate & Investment Banking
Disclosure of operating segments [line items]
Customers, annual turnover	£ 500

Segments - Summary of Results b

Segments - Summary of Results by Segment (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£) employee	Dec. 31, 2022 GBP (£) employee	Dec. 31, 2021 GBP (£) employee
Disclosure of operating segments [line items]
Net interest income/(expense)	£ 4,667	£ 4,472	£ 3,997
Non-interest income/(expense)	509	534	547
Total operating income	5,176	5,006	4,544
Operating expenses before credit impairment charges, provisions and charges	(2,485)	(2,370)	(2,540)
Impairment Loss On Financial Assets 1	(206)
ECL (release)/charge to the Income Statement from continued operations		321	(233)
Provisions for other liabilities and charges	(336)	(421)	(379)
Total operating credit impairment charges, provisions and charges	(542)	(742)	(146)
Profit from continuing operations before tax	2,149	1,894	1,858
Revenue/(expense) from external customers	5,176	5,006	4,544
Revenue and other operating income	5,176	5,006	4,544
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	542	562	478
Insurance, protection and investments	47	78	67
Credit cards	94	95	73
Non-banking and other fees	118	101	76
Total fee and commission income	801	836	694
Fee and commission expense	(505)	(512)	(414)
Net fee and commission income	296	324	280
Customer loans	206,690	219,704	210,616
Customer deposits	£ 193,563	£ 196,476	£ 192,176
Average number of full-time equivalent staff | employee	19,706	18,273	19,844
Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Revenue and other operating income	£ 0	£ 0	£ 0
Retail and Business Banking
Disclosure of operating segments [line items]
Net interest income/(expense)	3,740	3,689	3,374
Non-interest income/(expense)	177	197	201
Total operating income	3,917	3,886	3,575
Operating expenses before credit impairment charges, provisions and charges	(1,816)	(1,683)	(1,703)
Impairment Loss On Financial Assets 1	(150)
ECL (release)/charge to the Income Statement from continued operations		263	(98)
Provisions for other liabilities and charges	(233)	(395)	(187)
Total operating credit impairment charges, provisions and charges	(383)	(658)	(89)
Profit from continuing operations before tax	1,718	1,545	1,783
Revenue/(expense) from external customers	3,670	4,153	4,061
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	493	502	428
Insurance, protection and investments	47	78	67
Credit cards	94	95	73
Non-banking and other fees	3	2	2
Total fee and commission income	637	677	570
Fee and commission expense	(463)	(483)	(384)
Net fee and commission income	174	194	186
Customer loans	182,267	194,661	185,608
Customer deposits	£ 158,329	£ 161,748	£ 156,991
Average number of full-time equivalent staff | employee	16,330	15,212	16,149
Retail and Business Banking | Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Revenue and other operating income	£ 247	£ (267)	£ (486)
Consumer Finance
Disclosure of operating segments [line items]
Net interest income/(expense)	156	180	233
Non-interest income/(expense)	192	195	178
Total operating income	348	375	411
Operating expenses before credit impairment charges, provisions and charges	(141)	(144)	(163)
Impairment Loss On Financial Assets 1	(15)
ECL (release)/charge to the Income Statement from continued operations		27	(33)
Provisions for other liabilities and charges	(18)	(6)	4
Total operating credit impairment charges, provisions and charges	(33)	(33)	37
Profit from continuing operations before tax	174	198	285
Revenue/(expense) from external customers	663	513	489
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	0	0	0
Insurance, protection and investments	0	0	0
Credit cards	0	0	0
Non-banking and other fees	25	20	10
Total fee and commission income	25	20	10
Fee and commission expense	(6)	(5)	0
Net fee and commission income	19	15	10
Customer loans	5,228	5,384	4,984
Customer deposits	£ 0	£ 0	£ 0
Average number of full-time equivalent staff | employee	816	531	670
Consumer Finance | Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Revenue and other operating income	£ (315)	£ (138)	£ (78)
Corporate & Commercial Banking
Disclosure of operating segments [line items]
Net interest income/(expense)	841	580	397
Non-interest income/(expense)	135	146	112
Total operating income	976	726	509
Operating expenses before credit impairment charges, provisions and charges	(351)	(342)	(365)
Impairment Loss On Financial Assets 1	(40)
ECL (release)/charge to the Income Statement from continued operations		31	(90)
Provisions for other liabilities and charges	(15)	(8)	(34)
Total operating credit impairment charges, provisions and charges	(55)	(39)	56
Profit from continuing operations before tax	570	345	200
Revenue/(expense) from external customers	712	732	619
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	49	60	50
Insurance, protection and investments	0	0	0
Credit cards	0	0	0
Non-banking and other fees	79	77	62
Total fee and commission income	128	137	112
Fee and commission expense	(11)	(18)	(22)
Net fee and commission income	117	119	90
Customer loans	17,939	18,518	19,282
Customer deposits	£ 24,066	£ 24,798	£ 26,466
Average number of full-time equivalent staff | employee	2,376	2,336	2,281
Corporate & Commercial Banking | Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Revenue and other operating income	£ 264	£ (6)	£ (110)
Corporate & Investment Banking
Disclosure of operating segments [line items]
Net interest income/(expense)			0
Non-interest income/(expense)			0
Total operating income			0
Operating expenses before credit impairment charges, provisions and charges			0
ECL (release)/charge to the Income Statement from continued operations			0
Provisions for other liabilities and charges			0
Total operating credit impairment charges, provisions and charges			0
Profit from continuing operations before tax			0
Revenue/(expense) from external customers			0
Revenue from external customers includes the following fee and commission income
Current account and debit card fees			0
Insurance, protection and investments			0
Credit cards			0
Non-banking and other fees			0
Total fee and commission income			0
Fee and commission expense			0
Net fee and commission income			0
Customer loans			0
Customer deposits			£ 0
Average number of full-time equivalent staff | employee			528
Corporate & Investment Banking | Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Revenue and other operating income			£ 0
Corporate Centre
Disclosure of operating segments [line items]
Net interest income/(expense)	(70)	23	(7)
Non-interest income/(expense)	5	(4)	56
Total operating income	(65)	19	49
Operating expenses before credit impairment charges, provisions and charges	(177)	(201)	(309)
Impairment Loss On Financial Assets 1	(1)
ECL (release)/charge to the Income Statement from continued operations		0	(12)
Provisions for other liabilities and charges	(70)	(12)	(162)
Total operating credit impairment charges, provisions and charges	(71)	(12)	(150)
Profit from continuing operations before tax	(313)	(194)	(410)
Revenue/(expense) from external customers	131	(392)	(625)
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	0	0	0
Insurance, protection and investments	0	0	0
Credit cards	0	0	0
Non-banking and other fees	11	2	2
Total fee and commission income	11	2	2
Fee and commission expense	(25)	(6)	(8)
Net fee and commission income	(14)	(4)	(6)
Customer loans	1,256	1,141	742
Customer deposits	£ 11,168	£ 9,930	£ 8,719
Average number of full-time equivalent staff | employee	184	194	216
Corporate Centre | Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Revenue and other operating income	£ (196)	£ 411	£ 674

Segments - Summary Of Relations

Segments - Summary Of Relationship Between Customer Liabilities and Deposits (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets
Customer balances (gross)	£ 206,690	£ 219,704
Loan loss allowance	(916)	(933)
Customer balances (net)	205,774	218,771
Intercompany balances	4,488	4,165
Accrued interest	747	647
Other items	213	257
Net loans and advances to customers	211,222	223,840
Liabilities
Customer balances (gross)	193,563	196,476
Customer balances (net)	193,563	196,476
Accrued interest	834	237
Other items	(206)	(553)
Deposits by customers	195,149	197,313
Intercompany
Assets
Intercompany balances	4,488	4,165
Liabilities
Intercompany balances	£ 958	£ 1,153

Net Interest Income (Details)

Net Interest Income (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest and similar income:
Loans and advances to customers	£ 8,888	£ 5,854	£ 4,685
Loans and advances to banks	1,865	651	54
Reverse repurchase agreements – non-trading	625	149	35
Other	475	168	56
Total interest and similar income	11,853	6,822	4,830
Interest expense and similar charges:
Deposits by customers	(3,283)	(827)	(331)
Deposits by banks	(1,167)	(496)	(23)
Repurchase agreements – non-trading	(538)	(120)	(3)
Debt securities in issue	(2,024)	(795)	(372)
Subordinated liabilities	(169)	(108)	(92)
Other	(5)	(4)	(12)
Total interest expense and similar charges	(7,186)	(2,350)	(833)
Net interest income	4,667	4,472	3,997
Interest revenue for financial assets measured at fair value through other comprehensive income	230	87	22
Interest expense on derivatives hedging debt issuances	707	6	£ 317
Interest expense on lease liabilities	£ 3	£ 3

Net Fee and Commission Income_2

Net Fee and Commission Income (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Fee And Commission Income [Line Items]
Total fee and commission income	£ 801	£ 836	£ 694
Total fee and commission expense	(505)	(512)	(414)
Net fee and commission income	296	324	280
Current account and debit card fees
Net Fee And Commission Income [Line Items]
Total fee and commission income	542	562	478
Insurance, protection and investments
Net Fee And Commission Income [Line Items]
Total fee and commission income	47	78	67
Credit cards
Net Fee And Commission Income [Line Items]
Total fee and commission income	94	95	73
Non-banking and other fees
Net Fee And Commission Income [Line Items]
Total fee and commission income	£ 118	£ 101	£ 76

Other Operating Income - Summar

Other Operating Income - Summary of Net Trading and Other Income (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Trading And Other Income [Line Items]
Net gains/(losses) on financial instruments designated at fair value through profit or loss	£ (33)	£ (74)	£ (68)
Net gains/(losses) on financial instruments mandatorily at fair value through profit or loss	42	84	50
Hedge ineffectiveness	18	28	8
Net profit on sale of financial assets at fair value through other comprehensive income	0	0	6
Income from operating lease assets	118	129	136
Other	68	43	135
Other operating income (expense)	213	210	267
Exchange rate differences in the consolidated income statement on items not at fair value through profit and loss	1,215	(2,147)	215
These are principally offset by related releases from the cash flow hedge reserve	(1,231)	2,130	(357)
Deposits
Net Trading And Other Income [Line Items]
Net gains/(losses) on financial instruments designated at fair value through profit or loss	(24)	35	(18)
Debt securities
Net Trading And Other Income [Line Items]
Net gains/(losses) on financial instruments designated at fair value through profit or loss	(32)	31	0
Net gains/(losses) on financial instruments mandatorily at fair value through profit or loss	£ 5	£ 13	£ (10)

Other Operating Income - Additi

Other Operating Income - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Trading And Other Income [Abstract]
Gains (losses) on embedded derivatives bifurcated from certain equity index-linked deposits	£ (12)	£ 14	£ (15)
Gains (losses) on economic hedging of embedded derivatives bifurcated from certain equity index-linked deposits	12	(14)	15
Net gain on equity index-linked deposits and the related economic hedges	0	0	0
Exchange rate differences in the consolidated income statement on items not at fair value through profit and loss	1,215	(2,147)	215
These are principally offset by related releases from the cash flow hedge reserve	(1,231)	2,130	£ (357)
Losses on disposals of property, plant and equipment	£ (7)
Gains on disposals of property, plant and equipment		£ 73

Operating Expenses Before Cre_4

Operating Expenses Before Credit Impairment Charges, Provisions and Charges - Summary of Operating Expenses Before Credit Impairment Losses, Provisions and Charges (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Staff costs:
Wages and salaries	£ 854	£ 761	£ 759
Performance-related payments	164	173	184
Social security costs	116	112	113
Pension costs, defined contribution plans	71	60	65
Pension costs, defined benefit plans	13	28	38
Other share-based payments	4	1	1
Other personnel costs	42	44	42
Staff costs	1,264	1,179	1,202
Other administration expenses	931	894	831
Depreciation, amortisation and impairment	290	297	507
Total operating expenses before impairment losses, provisions and charges	£ 2,485	£ 2,370	£ 2,540

Operating Expenses Before Cre_5

Operating Expenses Before Credit Impairment Charges, Provisions and Charges - Summary of Deferred Performance Awards (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Deferred Performance Awards [Line Items]
Cash	£ 19	£ 22
Shares	18	22
Expenses charged in the year
Disclosure Of Deferred Performance Awards [Line Items]
Cash	7	8
Shares	7	8
Deferred performance awards	14
Expenses charged in the year | Arising from awards in current year
Disclosure Of Deferred Performance Awards [Line Items]
Cash	3
Shares	2
Deferred performance awards	5
Expenses charged in the year | Arising from awards in prior year
Disclosure Of Deferred Performance Awards [Line Items]
Cash	4
Shares	5
Deferred performance awards	9
Expenses deferred to future periods
Disclosure Of Deferred Performance Awards [Line Items]
Cash	12	14
Shares	11	£ 14
Deferred performance awards	23
Expenses deferred to future periods | Arising from awards in current year
Disclosure Of Deferred Performance Awards [Line Items]
Cash	5
Shares	4
Deferred performance awards	9
Expenses deferred to future periods | Arising from awards in prior year
Disclosure Of Deferred Performance Awards [Line Items]
Cash	7
Shares	7
Deferred performance awards	£ 14

Operating Expenses Before Cre_6

Operating Expenses Before Credit Impairment Charges, Provisions and Charges - Summary of Amount of Bonus Awarded to Employees (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Amount Of Bonus Awarded To Employees [Line Items]
Cash award – not deferred	£ 142	£ 148
Cash award – deferred	19	22
Shares award – not deferred	8	9
Shares award – deferred	18	22
Total discretionary bonus	187	201
Expenses charged in the year
Disclosure Of Amount Of Bonus Awarded To Employees [Line Items]
Cash award – not deferred	142	148
Cash award – deferred	7	8
Shares award – not deferred	8	9
Shares award – deferred	7	8
Total discretionary bonus	164	173
Expenses deferred to future periods
Disclosure Of Amount Of Bonus Awarded To Employees [Line Items]
Cash award – not deferred	0	0
Cash award – deferred	12	14
Shares award – not deferred	0	0
Shares award – deferred	11	14
Total discretionary bonus	£ 23	£ 28

Operating Expenses Before Cre_7

Operating Expenses Before Credit Impairment Charges, Provisions and Charges - Additional Information (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£) employee	Dec. 31, 2022 GBP (£) employee	Dec. 31, 2021 GBP (£) employee
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Average number of full-time equivalent staff | employee	19,706	18,273	19,844
Expense relating to short-term leases	£ 19	£ 21	£ 23
Right-of-use assets
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Depreciation for lease assets	30	19	20
Operating lease assets	93	115	119
Branch and head office site closures
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Impairment during the period	25	10	88
Operating lease assets
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Depreciation, property, plant and equipment	64	73	81
Property, plant and equipment	£ 488	£ 577	£ 595

Audit and Other Services - Summ

Audit and Other Services - Summary of Audit and Other Services (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Audit fees:
Fees payable to the Company’s auditor and its associates for the audit of the Santander UK group’s annual accounts	£ 15	£ 12.8	£ 12.1
Audit of the Santander UK group’s subsidiaries	0.7	0.8	1.2
Total audit fees	15.7	13.6	13.3
Non-audit fees:
Audit-related assurance services	2.3	1.9	1.7
Other assurance services	0.8	0.8	0.5
Other non-audit services	0.2	0.2	0.2
Total non-audit fees	3.3	2.9	2.4
Prior year audit services
Non-audit fees:
Auditors fee	£ 0.7	£ 0.6	£ 1.2

Audit and Other Services - Addi

Audit and Other Services - Additional Information (Details) - GBP (£)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Audit Fees And Non Audit Fees [Line Items]
Audit fees payable for statutory audit	£ 15,700,000	£ 13,600,000	£ 13,300,000
Non-audit fees - Audit fees per US Securities and Exchange Commission guidance	1,700,000	1,500,000	1,200,000
Non-audit fees - Audit related fees per US Securities and Exchange Commission guidance	1,600,000	1,400,000	1,200,000
Non-audit fees - All other fees per US Securities and Exchange Commission guidance	37,000	0	0
Incremental work, audit of Banco Santander
Disclosure Of Audit Fees And Non Audit Fees [Line Items]
Audit fees payable for statutory audit	1,600,000	1,600,000	1,400,000
Santander UK Group Holdings plc
Disclosure Of Audit Fees And Non Audit Fees [Line Items]
Audit fees payable for statutory audit	600,000	600,000	500,000
Corporate and other borrowers
Disclosure Of Audit Fees And Non Audit Fees [Line Items]
Audit fees payable for statutory audit	£ 0	£ 0	£ 27,000

Credit Impairment Charges and_3

Credit Impairment Charges and Provisions - Summary of Impairment Losses and Provisions (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Loans and advances to customers	£ 192	£ 249	£ (186)
Recoveries of loans and advances, net of collection costs	10	36	(17)
Off-balance sheet credit exposures (See Note 29)	4	36	(30)
Impairment loss on financial assets	206
Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 29)	335	424	388
Releases for residual value and voluntary termination	1	(3)	(9)
Provisions for other liabilities and charges	336	421	379
Total operating credit impairment (charges)/write-backs, provisions and charges	£ 542	£ 742	£ 146

Credit Impairment Charges and_4

Credit Impairment Charges and Provisions - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Impairment losses on loans and advances to banks	£ 0	£ 0	£ 0
Impairment losses on non-trading reverse repurchase agreements	0	0	0
Impairment losses on other financial assets at amortised cost	0	0	0
Impairment losses on financial assets at FVOCI	£ 0	£ 0	£ 0

Taxation - Disclosure of Income

Taxation - Disclosure of Income Tax and Deferred Taxes Explanatory (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current tax:
UK corporation tax on profit for the year	£ 474	£ 524	£ 400
Adjustments in respect of prior years	(23)	(88)	(30)
Total current tax	451	436	370
Deferred tax:
Charge/(credit) for the year	109	(30)	101
Adjustments in respect of prior years	(7)	65	14
Total deferred tax	102	35	115
Tax on profit from continuing operations	£ 553	£ 471	£ 485

Taxation - Additional Informati

Taxation - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Expense Benefits [Line Items]
Effective tax rate (percentage)	25.70%	24.90%	26.10%
Unrecognised capital losses carried forward	£ 0	£ 0
Banking entities
Income Tax Expense Benefits [Line Items]
Applicable tax rate (percentage)	28%	27%	27%
Non-banking entities
Income Tax Expense Benefits [Line Items]
Applicable tax rate (percentage)	24%	19%	19%

Taxation - Schedule of Tax on P

Taxation - Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Major components of tax expense (income) [abstract]
Effective tax rate (percentage)	25.70%	24.90%	26.10%
Profit from continuing operations before tax	£ 2,149	£ 1,894	£ 1,858
Tax calculated at a tax rate of 23.5% (2022:19%, 2021: 19%)	505	360	353
Bank surcharge on profits	84	123	106
Non-deductible preference dividends paid	9	9	9
Non-deductible UK Bank Levy	10	13	14
Non-deductible conduct remediation, fines and penalties	13	48	6
Other non-deductible costs and non-taxable income	(5)	20	33
Effect of change in tax rate on deferred tax provision	2	(28)	8
Tax relief on dividends in respect of other equity instruments	(35)	(40)	(40)
Adjustment to prior year provisions	(30)	(34)	(4)
Tax on profit from continuing operations	£ 553	£ 471	£ 485

Taxation - Disclosure of Moveme

Taxation - Disclosure of Movements in Current Tax Assets and Liabilities (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Major components of tax expense (income) [abstract]
Assets	£ 484	£ 351
Beginning balance	484	351
Income statement charge (including discontinued operations)	(451)	(436)
Other comprehensive income (charge)/credit	(70)	159
Corporate income tax received	539	397
Other movements	5	13
Ending balance	507	484
Assets	£ 507	£ 484

Taxation - Disclosure of Deferr

Taxation - Disclosure of Deferred Tax Assets and Liabilities Including Movement in Deferred Tax Account (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Beginning balance	£ (30)	£ (573)
Income statement (charge)/credit	102	35
Transfers/reclassifications	0	0
Credited/(charged) to other comprehensive income	(56)	578
Ending balance	(188)	(30)
Fair value of financial instruments
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Beginning balance	27	(123)
Income statement (charge)/credit	35	(150)
Transfers/reclassifications	0	0
Credited/(charged) to other comprehensive income	0	0
Ending balance	(8)	27
Pension remeasurement
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Beginning balance	(290)	(508)
Income statement (charge)/credit	63	49
Transfers/reclassifications	2	0
Credited/(charged) to other comprehensive income	167	267
Ending balance	(184)	(290)
Cash flow hedges
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Beginning balance	305	(7)
Income statement (charge)/credit	0	0
Transfers/reclassifications	(2)	3
Credited/(charged) to other comprehensive income	(232)	309
Ending balance	71	305
Fair value reserve
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Beginning balance	(2)	(12)
Income statement (charge)/credit	0	0
Transfers/reclassifications	0	(1)
Credited/(charged) to other comprehensive income	5	11
Ending balance	3	(2)
Tax losses carried forward
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Beginning balance	0	8
Income statement (charge)/credit	0	7
Transfers/reclassifications	0	(1)
Credited/(charged) to other comprehensive income	0	0
Ending balance	0	0
Accelerated tax depreciation
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Beginning balance	35	68
Income statement (charge)/credit	17	33
Transfers/reclassifications	0	0
Credited/(charged) to other comprehensive income	0	0
Ending balance	18	35
Other temporary differences
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Beginning balance	(105)	1
Income statement (charge)/credit	(13)	96
Transfers/reclassifications	0	(1)
Credited/(charged) to other comprehensive income	4	(9)
Ending balance	£ (88)	£ (105)

Dividends on Ordinary Shares _2

Dividends on Ordinary Shares - Disclosure of Dividends on Ordinary Shares Declared and Paid (Details) - GBP (£) £ / shares in Units, £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Dividends On Ordinary Shares [Line Items]
Dividend per share	£ 21.78	£ 14.35	£ 19.06
Dividends	£ 1,538	£ 1,013	£ 1,346
First interim
Disclosure Of Dividends On Ordinary Shares [Line Items]
Dividend per share	£ 5.86	£ 5.62	£ 4.05
Dividends	£ 414	£ 397	£ 286
Second interim
Disclosure Of Dividends On Ordinary Shares [Line Items]
Dividend per share	£ 15.92	£ 8.73	£ 15.01
Dividends	£ 1,124	£ 616	£ 1,060

Dividends on Ordinary Shares _3

Dividends on Ordinary Shares - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Dividends On Ordinary Shares [Line Items]
Dividends declared and paid	£ 1,538	£ 1,013	£ 1,346
Special dividend
Disclosure Of Dividends On Ordinary Shares [Line Items]
Dividends declared and paid	£ 750	£ 300

Derivative Financial Instrume_3

Derivative Financial Instruments - Notional Amounts of Transactions Outstanding (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about hedges
Notional amount	£ 225,608	£ 177,802
Assets	1,472	2,439
Liabilities	891	1,008
Cash collateral received subject to enforceable master netting arrangement or similar agreement not set off against financial assets	13,353	9,059
Collateral cash	8,519	8,131
Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	43,152	47,322
Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	182,456	130,480
Fair value hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	108,898	78,423
Cash flow hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	73,558	52,057
Exchange rate contracts
Disclosure of detailed information about hedges
Notional amount	36,299	41,342
Exchange rate contracts | Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	13,536	14,769
Exchange rate contracts | Fair value hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	1,145	538
Exchange rate contracts | Cash flow hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	21,618	26,035
Interest rate contracts
Disclosure of detailed information about hedges
Notional amount	188,440	135,455
Interest rate contracts | Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	28,806	31,599
Interest rate contracts | Fair value hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	107,753	77,885
Interest rate contracts | Cash flow hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	51,881	25,971
Equity and credit contracts
Disclosure of detailed information about hedges
Notional amount	869	1,005
Equity and credit contracts | Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	810	954
Equity derivative contracts | Cash flow hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	59	51
Derivative assets
Disclosure of detailed information about hedges
Cash collateral received subject to enforceable master netting arrangement or similar agreement not set off against financial assets	472	1,368
Derivative liabilities
Disclosure of detailed information about hedges
Collateral cash	12	70
Fair value
Disclosure of detailed information about hedges
Assets	1,472	2,439
Liabilities	891	1,008
Fair value | Group entities
Disclosure of detailed information about hedges
Assets	802	1,346
Liabilities	298	246
Fair value | Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	633	935
Liabilities	892	1,116
Fair value | Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	2,886	3,677
Liabilities	2,046	2,065
Fair value | Fair value hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	1,305	1,788
Liabilities	845	415
Fair value | Cash flow hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	1,581	1,889
Liabilities	1,201	1,650
Fair value | Exchange rate contracts | Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	92	320
Liabilities	241	299
Fair value | Exchange rate contracts | Fair value hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	29	12
Liabilities	2	4
Fair value | Exchange rate contracts | Cash flow hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	1,008	1,717
Liabilities	290	186
Fair value | Interest rate contracts | Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	398	473
Liabilities	626	792
Fair value | Interest rate contracts | Fair value hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	1,276	1,776
Liabilities	843	411
Fair value | Interest rate contracts | Cash flow hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	554	164
Liabilities	911	1,463
Fair value | Equity and credit contracts | Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	143	142
Liabilities	25	25
Fair value | Equity derivative contracts | Cash flow hedges | Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	19	8
Liabilities	0	1
Fair value | Derivative netting
Disclosure of detailed information about hedges
Assets	(2,047)	(2,173)
Liabilities	£ (2,047)	£ (2,173)

Derivative Financial Instrume_4

Derivative Financial Instruments - Analysis of the Notional and Fair Values of Derivatives by Trading and Settlement Method (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	£ 225,608	£ 177,802
Exchange rate contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	36,299	41,342
Interest rate contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	188,440	135,455
Equity and credit contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	869	1,005
Settled by central counterparties
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	174,460	124,638
Settled by central counterparties | Exchange rate contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	0	0
Settled by central counterparties | Interest rate contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	174,460	124,638
Settled by central counterparties | Equity and credit contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	0	0
Not settled by central counterparties
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	51,148	53,164
Not settled by central counterparties | Exchange rate contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	36,299	41,342
Not settled by central counterparties | Interest rate contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	13,980	10,817
Not settled by central counterparties | Equity and credit contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional amount	869	1,005
Traded over the counter
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Asset	1,472	2,439
Liability	891	1,008
Traded over the counter | Exchange rate contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Asset	1,129	2,049
Liability	533	489
Traded over the counter | Interest rate contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Asset	181	240
Liability	333	493
Traded over the counter | Equity and credit contracts
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Asset	162	150
Liability	£ 25	£ 26

Derivative Financial Instrume_5

Derivative Financial Instruments - Summary of Maturity Profile and Average Price/Rate of Hedging Instruments Used in Hedging Strategies (Details) £ in Millions	Dec. 31, 2023 GBP (£)	Dec. 31, 2022 GBP (£)
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 225,608	£ 177,802
Interest rate contracts
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	188,440	135,455
Interest rate contracts | Interest rate risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	106,805	77,615
Interest rate contracts | Interest rate risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	46,599	19,309
Interest rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	948	270
Interest rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	2,141	2,925
Interest rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	3,141	3,737
Exchange rate contracts
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	36,299	41,342
Exchange rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	1,145	538
Exchange rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	4,726	6,449
Exchange rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	16,892	19,586
Equity derivative contracts | Equity risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	59	51
≤1 month | Interest rate contracts | Interest rate risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 3,612	£ 2,210
≤1 month | Interest rate contracts | Interest rate risk | Fair value hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0238	0.0258
≤1 month | Interest rate contracts | Interest rate risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0114	0.0177
≤1 month | Interest rate contracts | Interest rate risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0260	0.0135
≤1 month | Interest rate contracts | Interest rate risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 911	£ 1,042
≤1 month | Interest rate contracts | Interest rate risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0506	0.0177
≤1 month | Interest rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 0
≤1 month | Interest rate contracts | Interest rate/FX risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0	0
≤1 month | Interest rate contracts | Interest rate/FX risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0	0
≤1 month | Interest rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 0
≤1 month | Interest rate contracts | Interest rate/FX risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0257	0
≤1 month | Interest rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 415
≤1 month | Exchange rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 0
Average GBP - EUR exchange rate	0	0
Average GBP - USD exchange rate	0	0
≤1 month | Exchange rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 87	£ 0
Average GBP - EUR exchange rate	1.18	0
Average GBP - USD exchange rate	0	0
≤1 month | Exchange rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 927	£ 2,301
Average GBP - EUR exchange rate	0	0
Average GBP - USD exchange rate	0	1.22
Average GBP - JPY exchange rate	154.14	0
Average GBP - CHF exchange rate	1.09	0
≤1 month | Equity derivative contracts | Equity risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 0
>1 and ≤ 3 months | Interest rate contracts | Interest rate risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 7,141	£ 4,468
>1 and ≤ 3 months | Interest rate contracts | Interest rate risk | Fair value hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0319	0.0088
>1 and ≤ 3 months | Interest rate contracts | Interest rate risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0018	0.0160
>1 and ≤ 3 months | Interest rate contracts | Interest rate risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0246	0.0347
>1 and ≤ 3 months | Interest rate contracts | Interest rate risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 3,083	£ 2,191
>1 and ≤ 3 months | Interest rate contracts | Interest rate risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0305	0.0229
>1 and ≤ 3 months | Interest rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 18	£ 0
>1 and ≤ 3 months | Interest rate contracts | Interest rate/FX risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0	0
>1 and ≤ 3 months | Interest rate contracts | Interest rate/FX risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0	0
>1 and ≤ 3 months | Interest rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 0
>1 and ≤ 3 months | Interest rate contracts | Interest rate/FX risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0254	0
>1 and ≤ 3 months | Interest rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 2,199	£ 0
>1 and ≤ 3 months | Exchange rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 18	£ 0
Average GBP - EUR exchange rate	1.11	0
Average GBP - USD exchange rate	0	0
>1 and ≤ 3 months | Exchange rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 785	£ 0
Average GBP - EUR exchange rate	0	0
Average GBP - USD exchange rate	1.66	0
>1 and ≤ 3 months | Exchange rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 3,238	£ 3,135
Average GBP - EUR exchange rate	1.20	0
Average GBP - USD exchange rate	1.39	1.25
Average GBP - JPY exchange rate	153.95	157.45
Average GBP - CHF exchange rate	1.09	1.13
>1 and ≤ 3 months | Equity derivative contracts | Equity risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 0
>3 and ≤12 months | Interest rate contracts | Interest rate risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 32,241	£ 21,678
>3 and ≤12 months | Interest rate contracts | Interest rate risk | Fair value hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0342	0.0056
>3 and ≤12 months | Interest rate contracts | Interest rate risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0045	0.0077
>3 and ≤12 months | Interest rate contracts | Interest rate risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0423	0.0351
>3 and ≤12 months | Interest rate contracts | Interest rate risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 13,671	£ 1,940
>3 and ≤12 months | Interest rate contracts | Interest rate risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0538	0.0198
>3 and ≤12 months | Interest rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 0
>3 and ≤12 months | Interest rate contracts | Interest rate/FX risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0	0.0342
>3 and ≤12 months | Interest rate contracts | Interest rate/FX risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0	0
>3 and ≤12 months | Interest rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 585
>3 and ≤12 months | Interest rate contracts | Interest rate/FX risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0296	0.0327
>3 and ≤12 months | Interest rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 0
>3 and ≤12 months | Exchange rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 66
Average GBP - EUR exchange rate	0	1.20
Average GBP - USD exchange rate	0	0
>3 and ≤12 months | Exchange rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 500	£ 1,173
Average GBP - EUR exchange rate	1.25	1.19
Average GBP - USD exchange rate	0	1.60
>3 and ≤12 months | Exchange rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 2,692	£ 2,381
Average GBP - EUR exchange rate	1.17	1.12
Average GBP - USD exchange rate	0	1.17
Average GBP - JPY exchange rate	167.85	160.04
Average GBP - CHF exchange rate	1.09	0
>3 and ≤12 months | Equity derivative contracts | Equity risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 7	£ 6
>1 and ≤5 years | Interest rate contracts | Interest rate risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 60,803	£ 45,451
>1 and ≤5 years | Interest rate contracts | Interest rate risk | Fair value hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0389	0.0207
>1 and ≤5 years | Interest rate contracts | Interest rate risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0021	0.0028
>1 and ≤5 years | Interest rate contracts | Interest rate risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0136	0.0200
>1 and ≤5 years | Interest rate contracts | Interest rate risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 27,715	£ 13,060
>1 and ≤5 years | Interest rate contracts | Interest rate risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0384	0.0235
>1 and ≤5 years | Interest rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 844	£ 263
>1 and ≤5 years | Interest rate contracts | Interest rate/FX risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0277	0.0206
>1 and ≤5 years | Interest rate contracts | Interest rate/FX risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0483	0.0463
>1 and ≤5 years | Interest rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 1,975	£ 2,132
>1 and ≤5 years | Interest rate contracts | Interest rate/FX risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0242	0.0258
>1 and ≤5 years | Interest rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 0	£ 2,325
>1 and ≤5 years | Exchange rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 1,041	£ 465
Average GBP - EUR exchange rate	1.16	1.16
Average GBP - USD exchange rate	1.32	1.19
>1 and ≤5 years | Exchange rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 2,896	£ 4,626
Average GBP - EUR exchange rate	1.20	1.21
Average GBP - USD exchange rate	1.38	1.50
>1 and ≤5 years | Exchange rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 9,447	£ 10,606
Average GBP - EUR exchange rate	1.18	1.18
Average GBP - USD exchange rate	1.28	1.31
Average GBP - JPY exchange rate	0	0
Average GBP - CHF exchange rate	1.12	0
>1 and ≤5 years | Equity derivative contracts | Equity risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 50	£ 43
>5 years | Interest rate contracts | Interest rate risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 3,008	£ 3,808
>5 years | Interest rate contracts | Interest rate risk | Fair value hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0399	0.0378
>5 years | Interest rate contracts | Interest rate risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0392	0.0309
>5 years | Interest rate contracts | Interest rate risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0491	0.0492
>5 years | Interest rate contracts | Interest rate risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 1,219	£ 1,076
>5 years | Interest rate contracts | Interest rate risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0345	0.0184
>5 years | Interest rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 86	£ 7
>5 years | Interest rate contracts | Interest rate/FX risk | Fair value hedges | Euro
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0348	0
>5 years | Interest rate contracts | Interest rate/FX risk | Fair value hedges | US Dollar
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0	0
>5 years | Interest rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 166	£ 208
>5 years | Interest rate contracts | Interest rate/FX risk | Cash flow hedges | Sterling
Disclosure of nature and extent of risks arising from financial instruments [line items]
Average fixed interest rate	0.0481	0.0459
>5 years | Interest rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 942	£ 997
>5 years | Exchange rate contracts | Interest rate/FX risk | Fair value hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 86	£ 7
Average GBP - EUR exchange rate	1.15	1.10
Average GBP - USD exchange rate	0	0
>5 years | Exchange rate contracts | Interest rate/FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 458	£ 650
Average GBP - EUR exchange rate	1.19	1.20
Average GBP - USD exchange rate	1.54	1.54
>5 years | Exchange rate contracts | FX risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 588	£ 1,163
Average GBP - EUR exchange rate	0	1.17
Average GBP - USD exchange rate	1.39	1.39
Average GBP - JPY exchange rate	0	0
Average GBP - CHF exchange rate	1.12	0
>5 years | Equity derivative contracts | Equity risk | Cash flow hedges
Disclosure of nature and extent of risks arising from financial instruments [line items]
Notional amount	£ 2	£ 2

Derivative Financial Instrume_6

Derivative Financial Instruments - Summary of Net Gains or Losses Arising from Fair Value and Cash Flow Hedges Included in Net Trading and Other Income (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of detailed information about hedges
Hedge ineffectiveness	£ 18	£ 28	£ 8
Fair value and cash flow hedges
Disclosure of detailed information about hedges
(Losses)/gains on hedging instruments	(1,878)	2,371	846
Gains/(losses) on hedged items attributable to hedged risks	1,893	(2,307)	(804)
Fair value hedging ineffectiveness	15	64	42
Cash flow hedging ineffectiveness	3	(36)	(34)
Hedge ineffectiveness	£ 18	£ 28	£ 8

Derivative Financial Instrume_7

Derivative Financial Instruments - Summary of Information About Hedging Ineffectiveness by Risk Category (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair value hedges
Disclosure of detailed information about hedges
Change in FV of hedging instruments	£ (1,878)	£ 2,371	£ 846
Change in FV of hedged items	1,893	(2,307)	(804)
Recognised in income statement	15	64	42
Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Change in FV of hedging instruments	(1,864)	2,382	868
Change in FV of hedged items	1,874	(2,324)	(838)
Recognised in income statement	10	58	30
Fair value hedges | Interest rate/FX risk
Disclosure of detailed information about hedges
Change in FV of hedging instruments	(14)	(11)	(22)
Change in FV of hedged items	19	17	34
Recognised in income statement	5	6	12
Cash flow hedges
Disclosure of detailed information about hedges
Change in FV of hedging instruments	(144)	400	(909)
Change in FV of hedged items	147	(436)
Recognised in OCI	147	(436)	875
Recognised in income statement	3	(36)	(34)
Reclassified from reserves to income	(1,231)	2,130	(359)
Cash flow hedges | Interest rate risk
Disclosure of detailed information about hedges
Change in FV of hedging instruments	449	(1,150)	(312)
Recognised in OCI	(447)	1,150	306
Recognised in income statement	2	0	(6)
Reclassified from reserves to income	(464)	(96)	70
Cash flow hedges | FX risk
Disclosure of detailed information about hedges
Change in FV of hedging instruments	(375)	1,602	(54)
Recognised in OCI	377	(1,602)	54
Recognised in income statement	2	0	0
Reclassified from reserves to income	(392)	1,691	(158)
Cash flow hedges | Equity risk
Disclosure of detailed information about hedges
Change in FV of hedging instruments	20	2	(1)
Recognised in OCI	(20)	(2)	1
Recognised in income statement	0	0	0
Reclassified from reserves to income	13	2	2
Cash flow hedges | Interest rate/FX risk
Disclosure of detailed information about hedges
Change in FV of hedging instruments	(238)	(54)	(542)
Recognised in OCI	237	18	514
Recognised in income statement	(1)	(36)	(28)
Reclassified from reserves to income	£ (388)	£ 533	£ (273)

Derivative Financial Instrume_8

Derivative Financial Instruments - Additional Information (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of nature and extent of risks arising from financial instruments [abstract]
Ceased cash flow hedge accounting	£ 0	£ 10

Derivative Financial Instrume_9

Derivative Financial Instruments - Summary of Reconciliation by Risk Category of Components of Equity and Analysis of Other Comprehensive Income Items Resulting from Hedge Accounting (Details) - Cash flow hedges - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about hedges
Beginning Balance	£ (1,561)	£ 133
Effective portion of changes in fair value:	(147)	436
Income statement transfers:	1,231	(2,130)
Ending Balance	(477)	(1,561)
Interest rate risk
Disclosure of detailed information about hedges
Effective portion of changes in fair value:	447	(1,150)
Income statement transfers:	464	96
Foreign currency risk
Disclosure of detailed information about hedges
Effective portion of changes in fair value:	(377)	1,602
Income statement transfers:	392	(1,691)
Equity risk
Disclosure of detailed information about hedges
Effective portion of changes in fair value:	20	2
Income statement transfers:	(13)	(2)
Interest rate/FX risk
Disclosure of detailed information about hedges
Effective portion of changes in fair value:	(237)	(18)
Income statement transfers:	£ 388	£ (533)

Derivative Financial Instrum_10

Derivative Financial Instruments - Summary of Details of Hedged Exposures by Hedging Strategies (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair value hedges
Disclosure of detailed information about hedges
Carrying value of assets	£ 61,757	£ 60,403
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item liabilities	13	90
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks assets	(716)	(2,750)
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	(754)	(884)
Change in value to calculate hedge ineffectiveness	1,893	(2,307)	£ (804)
Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	1,874	(2,324)	(838)
Fair value hedges | Interest rate/FX risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	19	17	34
Cash flow hedges
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	147	(436)
Cash flow hedge reserve	(477)	(1,561)	£ 133
Balances on cash flow hedge reserve for discontinued hedges	(23)	(35)
Deposits by customers | Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Carrying value of liabilities	(15,052)	(1,394)
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item liabilities	0	0
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks liabilities	(10)	5
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	0	0
Change in value to calculate hedge ineffectiveness	(15)	5
Deposits by customers | Cash flow hedges | FX risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	(21)	(74)
Cash flow hedge reserve	0	0
Balances on cash flow hedge reserve for discontinued hedges	0	0
Deposits by banks | Cash flow hedges | Interest rate risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	(1)	(8)
Cash flow hedge reserve	(1)	7
Balances on cash flow hedge reserve for discontinued hedges	0	0
Debt securities in issue | Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Carrying value of liabilities	(5,065)	(5,210)
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item liabilities	162	355
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks liabilities	(75)	(95)
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	(114)	(172)
Change in value to calculate hedge ineffectiveness	(170)	566
Debt securities in issue | Fair value hedges | Interest rate/FX risk
Disclosure of detailed information about hedges
Carrying value of liabilities	(214)	(290)
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item liabilities	(14)	(18)
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks liabilities	0	0
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	(24)	(37)
Change in value to calculate hedge ineffectiveness	8	27
Debt securities in issue | Cash flow hedges | FX risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	605	(1,142)
Cash flow hedge reserve	(9)	(19)
Balances on cash flow hedge reserve for discontinued hedges	0	(2)
Subordinated liabilities | Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Carrying value of liabilities	(522)	(250)
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item liabilities	(27)	(27)
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks liabilities	(1)	(6)
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	(42)	(62)
Change in value to calculate hedge ineffectiveness	(1)	54
Subordinated liabilities | Fair value hedges | Interest rate/FX risk
Disclosure of detailed information about hedges
Carrying value of liabilities	0	(1)
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item liabilities	0	1
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks liabilities	0	0
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	0	1
Change in value to calculate hedge ineffectiveness	(1)	(1)
Repurchase agreements - non trading | Cash flow hedges | FX risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	(42)	(37)
Cash flow hedge reserve	0	0
Balances on cash flow hedge reserve for discontinued hedges	0	0
Other liabilities | Cash flow hedges | Equity risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	(20)	(2)
Cash flow hedge reserve	10	3
Balances on cash flow hedge reserve for discontinued hedges	0	0
Total loans and advances to customers | Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Carrying value of assets	73,270	60,783
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item assets	0	0
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks assets	(622)	(2,637)
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	(435)	(651)
Change in value to calculate hedge ineffectiveness	1,969	(2,708)
Total loans and advances to customers | Cash flow hedges | Interest rate risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	(163)	925
Cash flow hedge reserve	(455)	(999)
Balances on cash flow hedge reserve for discontinued hedges	1	(1)
Other financial assets at amortised cost | Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Carrying value of assets	152	156
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item assets	1	0
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks assets	(8)	(12)
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	(8)	2
Change in value to calculate hedge ineffectiveness	5	(14)
Reverse repurchase agreements – non trading | Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Carrying value of assets	6,186	4,045
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item assets	0	0
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks assets	0	(5)
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	0	(1)
Change in value to calculate hedge ineffectiveness	4	0
Other financial assets at FVOCI | Fair value hedges | Interest rate risk
Disclosure of detailed information about hedges
Carrying value of assets	2,013	2,325
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item assets	(113)	(200)
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks assets	0	0
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	(131)	35
Change in value to calculate hedge ineffectiveness	82	(227)
Other financial assets at FVOCI | Fair value hedges | Interest rate/FX risk
Disclosure of detailed information about hedges
Carrying value of assets	989	237
Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item assets	4	(21)
Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks assets	0	0
Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges	0	1
Change in value to calculate hedge ineffectiveness	12	(9)
Cash and balances at central banks | Cash flow hedges | Interest rate risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	(283)	233
Cash flow hedge reserve	100	(274)
Balances on cash flow hedge reserve for discontinued hedges	(76)	(106)
Other financial assets at FVOCI | Cash flow hedges | FX risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	(253)	0
Cash flow hedge reserve	1	(6)
Balances on cash flow hedge reserve for discontinued hedges	0	0
Not applicable – highly probable forecast transactions | Cash flow hedges | FX risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	88	(349)
Cash flow hedge reserve	1	2
Balances on cash flow hedge reserve for discontinued hedges	0	0
Debt securities in issue/loans and advances to customers | Debt securities in issue/loans and advances to customers | Cash flow hedges | Interest rate/FX risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	194	55
Cash flow hedge reserve	(114)	(244)
Balances on cash flow hedge reserve for discontinued hedges	0	(3)
Subordinated liabilities/loans and advances to customers | Subordinated liabilities/loans and advances to customers | Cash flow hedges | Interest rate/FX risk
Disclosure of detailed information about hedges
Change in value to calculate hedge ineffectiveness	43	(37)
Cash flow hedge reserve	(10)	(31)
Balances on cash flow hedge reserve for discontinued hedges	£ 52	£ 77

Other Financial Assets at Fai_5

Other Financial Assets at Fair Value Through Profit or Loss - Summary of Other Financial Assets at Fair Value Through Profit or Loss (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Debt securities	£ 602	£ 434
Total loans and advances to customers
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Debt securities	355	339
Total loans and advances to customers | Loans to housing associations
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Debt securities	8	4
Total loans and advances to customers | Other loans
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Debt securities	347	335
Debt securities
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Debt securities	168	16
Other debt instruments
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Debt securities	49	69
Equity securities
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Debt securities	£ 30	£ 10

Other Financial Assets at Fai_6

Other Financial Assets at Fair Value Through Profit or Loss - Additional Information (Details) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Financial assets designated at FVTPL	£ 317,000	£ 312,000
Financial assets mandatorily at FVTPL	285,000	122,000
Net (loss)/gain attributable to changes in credit risk for loans and advances at fair value through profit or loss	0
Net (loss)/gain attributable to changes in credit risk for loans and advances at fair value through profit or loss		(1,000)	£ 0
Cumulative net loss attributable to changes in credit risk for loans and advances at fair value through profit or loss	(3,000)
Cumulative net loss attributable to changes in credit risk for loans and advances at fair value through profit or loss		£ (3,000)	£ (2,000)
Santander Equity Investments Limited (SEIL)
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Gains (losses) on financial assets at fair value through profit or loss	£ 46,000

Loans and Advances to Custome_3

Loans and Advances to Customers - Summary of Net Loans and Advances to Customers (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Net Loans And Advances To Customers [Abstract]
Loans secured on residential properties	£ 176,495	£ 188,282
Corporate loans	18,454	19,057
Finance leases	4,530	4,645
Other unsecured loans	7,232	7,742
Accrued interest and other adjustments	960	904
Amounts due from fellow Banco Santander subsidiaries and joint ventures	4,488	4,165
Loans and advances to customers	212,159	224,795
Credit impairment loss allowances on loans and advances to customers	(916)	(933)
Residual value and voluntary termination provisions on finance leases	(21)	(22)
Net loans and advances to customers	£ 211,222	£ 223,840

Loans and Advances to Custome_4

Loans and Advances to Customers - Summary of Finance Lease and Hire Purchase Contract Receivables (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Finance Lease And Hire Purchase Contract Receivables [Line Items]
Gross investment	£ 5,300	£ 5,296
Unearned finance income	(770)	(651)
Net investment	4,530	4,645
No later than one year
Disclosure Of Finance Lease And Hire Purchase Contract Receivables [Line Items]
Gross investment	1,502	1,493
Unearned finance income	(216)	(182)
Net investment	1,286	1,311
Later than one year and not later than two years
Disclosure Of Finance Lease And Hire Purchase Contract Receivables [Line Items]
Gross investment	1,426	1,367
Unearned finance income	(208)	(168)
Net investment	1,218	1,199
Later than two years and not later than three years
Disclosure Of Finance Lease And Hire Purchase Contract Receivables [Line Items]
Gross investment	1,331	1,190
Unearned finance income	(194)	(147)
Net investment	1,137	1,043
Later than three years and not later than four years
Disclosure Of Finance Lease And Hire Purchase Contract Receivables [Line Items]
Gross investment	882	1,044
Unearned finance income	(129)	(129)
Net investment	753	915
Later than four years and not later than five years
Disclosure Of Finance Lease And Hire Purchase Contract Receivables [Line Items]
Gross investment	99	143
Unearned finance income	(14)	(18)
Net investment	85	125
Later than five years
Disclosure Of Finance Lease And Hire Purchase Contract Receivables [Line Items]
Gross investment	60	59
Unearned finance income	(9)	(7)
Net investment	£ 51	£ 52

Loans and Advances to Custome_5

Loans and Advances to Customers - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Loans And Advances To Customers [Abstract]
Unguaranteed residual value of leases	£ 1,830	£ 1,761
Contingent rent income	0	0	£ 0
Finance income on the net investment in finance leases	£ 266	£ 230	£ 243

Loans and Advances to Custome_6

Loans and Advances to Customers - Disclosure of Maturity Analysis of Operating Lease Payments (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of maturity analysis of operating lease payments [line items]
Undiscounted operating lease payments to be received	£ 114	£ 128
No later than one year
Disclosure of maturity analysis of operating lease payments [line items]
Undiscounted operating lease payments to be received	29	31
Later than one year and not later than two years
Disclosure of maturity analysis of operating lease payments [line items]
Undiscounted operating lease payments to be received	26	28
Later than two years and not later than three years
Disclosure of maturity analysis of operating lease payments [line items]
Undiscounted operating lease payments to be received	19	23
Later than three years and not later than four years
Disclosure of maturity analysis of operating lease payments [line items]
Undiscounted operating lease payments to be received	14	13
Later than four years and not later than five years
Disclosure of maturity analysis of operating lease payments [line items]
Undiscounted operating lease payments to be received	7	11
Later than five years
Disclosure of maturity analysis of operating lease payments [line items]
Undiscounted operating lease payments to be received	£ 19	£ 22

Securitisations and Covered B_3

Securitisations and Covered Bonds - Analysis of Securitisations and Covered Bonds (Details) £ in Millions	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 EUR (€)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	£ 27,927		£ 24,984
External notes in issue	17,769		16,102
Notes issued to Santander UK plc/subsidiaries as collateral	1,682		1,541
Notional amount	225,608		177,802
Euro 35bn Global Covered Bond Programme
Disclosure Of Securitisations And Covered Bonds [Line Items]
Notional amount | €		€ 35,000,000,000		€ 35,000,000,000
Securitisation programmes
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	6,047		3,680
External notes in issue	2,769		897
Notes issued to Santander UK plc/subsidiaries as collateral	1,682		1,541
Securitisation programmes | Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	5,290		3,674
External notes in issue	2,219		890
Notes issued to Santander UK plc/subsidiaries as collateral	1,682		1,541
Securitisation programmes | Other asset-backed securitisation structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	757		6
External notes in issue	550		7
Notes issued to Santander UK plc/subsidiaries as collateral	0		0
Holmes | Securitisation programmes | Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	3,242		1,646
External notes in issue	2,119		790
Notes issued to Santander UK plc/subsidiaries as collateral	300		176
Fosse | Securitisation programmes | Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	2,048		2,028
External notes in issue	100		100
Notes issued to Santander UK plc/subsidiaries as collateral	1,382		1,365
Motor | Securitisation programmes | Other asset-backed securitisation structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	0		6
External notes in issue	0		7
Notes issued to Santander UK plc/subsidiaries as collateral	0		0
Euro 35bn Global Covered Bond Programme | Covered bond programme
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	21,880		21,304
External notes in issue	15,000		15,205
Notes issued to Santander UK plc/subsidiaries as collateral	0		0
Repton | Securitisation programmes | Other asset-backed securitisation structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	757		0
External notes in issue	550		0
Notes issued to Santander UK plc/subsidiaries as collateral	£ 0		£ 0

Securitisations and Covered B_4

Securitisations and Covered Bonds - Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Internal
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	£ 1,341	£ 0
Internal and external redemptions	137	200
Internal | Mortgage-backed master trust structures | Holmes
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	241	0
Internal and external redemptions	121	100
Internal | Mortgage-backed master trust structures | Fosse
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	0
Internal | Other asset-backed securitisation structures | Motor
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	0
Internal | Other asset-backed securitisation structures | Repton
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	0
Internal | Covered bond programme | Euro 35bn Global Covered Bond Programme
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	1,100	0
Internal and external redemptions	16	100
External
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	3,894	4,800
Internal and external redemptions	2,090	2,133
External | Mortgage-backed master trust structures | Holmes
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	1,500	600
Internal and external redemptions	186	200
External | Mortgage-backed master trust structures | Fosse
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	200
External | Other asset-backed securitisation structures | Motor
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	7	33
External | Other asset-backed securitisation structures | Repton
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	550	0
Internal and external redemptions	0	0
External | Covered bond programme | Euro 35bn Global Covered Bond Programme
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	1,844	4,200
Internal and external redemptions	£ 1,897	£ 1,700

Securitisations and Covered B_5

Securitisations and Covered Bonds - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
External
Disclosure Of Gross Asset Securitised [Line Items]
Internal and external issuances	£ 3,894	£ 4,800
Holmes
Disclosure Of Gross Asset Securitised [Line Items]
Beneficial interest in residential mortgage loans	2,396	796
Cash deposits	80	112
Fosse
Disclosure Of Gross Asset Securitised [Line Items]
Beneficial interest in residential mortgage loans	1,393	1,465
Cash deposits	108	108
Repton | External | Other asset-backed securitisation structures
Disclosure Of Gross Asset Securitised [Line Items]
Internal and external issuances	£ 550	£ 0

Transfers of Financial Assets_3

Transfers of Financial Assets Not Qualifying for Derecognition (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of continuing involvement in derecognised financial assets [line items]
Carrying amount of financial assets not derecognised in their entirety	£ 9,197	£ 6,671
Carrying amount of associated financial liabilities	(5,518)	(3,534)
Sale and repurchase agreements
Disclosure of continuing involvement in derecognised financial assets [line items]
Carrying amount of financial assets not derecognised in their entirety	14	120
Carrying amount of associated financial liabilities	(14)	(128)
Securities lending agreements
Disclosure of continuing involvement in derecognised financial assets [line items]
Carrying amount of financial assets not derecognised in their entirety	3,136	2,871
Carrying amount of associated financial liabilities	(2,735)	(2,509)
Securitisations (See Notes 14 and 26)
Disclosure of continuing involvement in derecognised financial assets [line items]
Carrying amount of financial assets not derecognised in their entirety	6,047	3,680
Carrying amount of associated financial liabilities	£ (2,769)	£ (897)

Reverse Repurchase Agreements_3

Reverse Repurchase Agreements - Non Trading (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non-trading	£ 12,468	£ 7,348
Agreements with banks
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non-trading	2,397	885
Agreements with customers
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non-trading	£ 10,071	£ 6,463

Other Financial Assets at Amo_4

Other Financial Assets at Amortised Cost (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at amortised cost	£ 152	£ 156
Other financial assets
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at amortised cost	152	156
Other financial assets | Asset backed securities
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at amortised cost	0	0
Other financial assets | Debt securities
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at amortised cost	£ 152	£ 156

Financial Assets at Fair Valu_3

Financial Assets at Fair Value Through Other Comprehensive Income (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Financial Assets At Fair Value Through Other Comprehensive Income [Line Items]
Financial assets at fair value through other comprehensive income	£ 8,481	£ 6,024
Debt securities
Disclosure Of Financial Assets At Fair Value Through Other Comprehensive Income [Line Items]
Financial assets at fair value through other comprehensive income	£ 8,481	£ 6,024

Interests in Other Entities - S

Interests in Other Entities - Schedule of Interests in Other Entities (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Investments accounted for using equity method [abstract]
Joint ventures	£ 245	£ 252

Interests In Other Entities - A

Interests In Other Entities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 GBP (£)	Dec. 31, 2022 GBP (£)
Disclosure of subsidiaries [line items]
Ownership interest in share capital	100%
Joint ventures	£ 245,000,000	£ 252,000,000
Number of credit protection vehicles	4	4
Senior credit linked notes issued	£ 0	£ 180,000,000
Junior credit linked notes issued	185,000,000	465,000,000
Santander (UK) Common Investment Fund
Disclosure of subsidiaries [line items]
Defined benefit assets and obligations	8,551,000,000	8,646,000,000
Joint ventures
Disclosure of subsidiaries [line items]
Profit after tax	43,000,000	36,000,000
Joint ventures	245,000,000	252,000,000
Commitments and contingent liabilities	£ 0	£ 0

Intangible Assets - Schedule of

Intangible Assets - Schedule of Goodwill (Details) £ in Millions	Dec. 31, 2023 GBP (£)
Disclosure Of Goodwill [Line Items]
Goodwill at beginning of period	£ 1,199
Goodwill at end of period	1,199
Cost
Disclosure Of Goodwill [Line Items]
Goodwill at beginning of period	1,285
Goodwill at end of period	1,285
Accumulated impairment
Disclosure Of Goodwill [Line Items]
Goodwill at beginning of period	(86)
Goodwill at end of period	£ (86)

Intangible Assets - Additional

Intangible Assets - Additional Information (Details) - GBP (£)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about intangible assets [abstract]
Goodwill impairment recognised	£ 0	£ 0
Computer software	157,000,000	149,000,000
Internally generated computer software	35,000,000	33,000,000
Impairment charge	£ 0	£ 3,000,000

Intangible Assets - Schedule _2

Intangible Assets - Schedule of Goodwill for Cash Generating Units (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of information for cash-generating units [line items]
Goodwill	£ 1,199	£ 1,199
Personal Financial Services
Disclosure of information for cash-generating units [line items]
Goodwill	£ 1,169	£ 1,169
Discount rate	16.70%	16.60%
Growth rate beyond initial cash flow projections	1.60%	1.60%
Private Banking
Disclosure of information for cash-generating units [line items]
Goodwill	£ 30	£ 30
Discount rate	14.60%	15.30%
Growth rate beyond initial cash flow projections	1.60%	1.60%

Intangible Assets - Disclosure

Intangible Assets - Disclosure of Reasonably Possible Changes in Key Assumptions (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Goodwill [Line Items]
Value in use estimate, impairment increase sensitivity for GDP growth rate adjustment	£ (19)	£ (31)
Personal Financial Services
Disclosure Of Goodwill [Line Items]
Value in use estimate, increase (decrease) in cash flows	(10.00%)	(5.00%)
Increase (decrease) in discount rate applied to cash flow projections	1%	1%
Increase (decrease) in GDP growth rate applied to cash flow projections	(10.00%)	(10.00%)
Value in use estimate, impairment increase sensitivity for cash flows adjustment	£ (818)	£ (538)
Value in use estimate, impairment increase sensitivity for discount rate adjustment	£ (663)	£ (887)

Intangible Assets - Sensitivity

Intangible Assets - Sensitivity of VIU Changes to Current Assumptions (Details) - Personal Financial Services - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Goodwill [Line Items]
Carrying value	£ 7,513	£ 8,860
Value in use	8,178	10,752
Headroom	£ 665	£ 1,892
Increase in discount rate	101%	239%
Decrease in GDP growth rate	0.04	0.13
Decrease in cash flows	8%	18%

Intangible Assets - Schedule _3

Intangible Assets - Schedule of Other Intangibles (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about intangible assets [line items]
Other intangibles at beginning of period	£ 351	£ 342
Additions	114	112
Disposals	0	0
Charge	(116)	(100)
Impairment	0	(3)
Other intangibles at end of period	349	351
Cost
Disclosure of detailed information about intangible assets [line items]
Other intangibles at beginning of period	1,272	1,346
Additions	114	112
Disposals	(36)	(186)
Charge	0	0
Impairment		0
Other intangibles at end of period	1,350	1,272
Accumulated amortisation / impairment
Disclosure of detailed information about intangible assets [line items]
Other intangibles at beginning of period	(921)	(1,004)
Additions	0	0
Disposals	36	186
Charge	116	100
Impairment		3
Other intangibles at end of period	£ (1,001)	£ (921)

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	£ 1,526
Property, plant and equipment including right-of-use assets at the end of the period	1,512	£ 1,526
Investment property	17	17
Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	2,797	3,487
Additions	294	377
Reclassification (to)/from assets held for sale	8
Disposals	(307)	(956)
Reclassification to assets held for sale		(111)
Property, plant and equipment including right-of-use assets at the end of the period	2,792	2,797
Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	(1,271)	(1,932)
Additions	(175)	(180)
Disposals	155	789
Reclassification to assets held for sale		62
Property, plant and equipment including right-of-use assets at the end of the period	(1,280)	(1,271)
Accumulated impairment
Disclosure of detailed information about property, plant and equipment [line items]
Impairment during the period	(11)	10
Property
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	622
Property, plant and equipment including right-of-use assets at the end of the period	697	622
Property | Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	893	981
Additions	89	62
Reclassification (to)/from assets held for sale	8
Disposals	(66)	(52)
Reclassification to assets held for sale		(98)
Property, plant and equipment including right-of-use assets at the end of the period	924	893
Property | Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	(271)	(335)
Additions	(17)	(18)
Disposals	61	41
Reclassification to assets held for sale		49
Property, plant and equipment including right-of-use assets at the end of the period	(227)	(271)
Property | Accumulated impairment
Disclosure of detailed information about property, plant and equipment [line items]
Impairment during the period	0	8
Office fixtures and equipment
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	206
Property, plant and equipment including right-of-use assets at the end of the period	228	206
Office fixtures and equipment | Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	831	1,056
Additions	88	87
Reclassification (to)/from assets held for sale	0
Disposals	(29)	(299)
Reclassification to assets held for sale		(13)
Property, plant and equipment including right-of-use assets at the end of the period	890	831
Office fixtures and equipment | Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	(625)	(863)
Additions	(63)	(69)
Disposals	26	296
Reclassification to assets held for sale		13
Property, plant and equipment including right-of-use assets at the end of the period	(662)	(625)
Office fixtures and equipment | Accumulated impairment
Disclosure of detailed information about property, plant and equipment [line items]
Impairment during the period	0	2
Computer software
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	6
Property, plant and equipment including right-of-use assets at the end of the period	6	6
Computer software | Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	79	437
Additions	1	4
Reclassification (to)/from assets held for sale	0
Disposals	(5)	(362)
Reclassification to assets held for sale		0
Property, plant and equipment including right-of-use assets at the end of the period	75	79
Computer software | Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	(73)	(435)
Additions	(1)	(1)
Disposals	5	363
Reclassification to assets held for sale		0
Property, plant and equipment including right-of-use assets at the end of the period	(69)	(73)
Computer software | Accumulated impairment
Disclosure of detailed information about property, plant and equipment [line items]
Impairment during the period	0	0
Operating lease assets
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	577
Property, plant and equipment including right-of-use assets at the end of the period	488	577
Operating lease assets | Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	722	755
Additions	85	185
Reclassification (to)/from assets held for sale	0
Disposals	(172)	(218)
Reclassification to assets held for sale		0
Property, plant and equipment including right-of-use assets at the end of the period	635	722
Operating lease assets | Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	(145)	(160)
Additions	(64)	(73)
Disposals	62	88
Reclassification to assets held for sale		0
Property, plant and equipment including right-of-use assets at the end of the period	(147)	(145)
Operating lease assets | Accumulated impairment
Disclosure of detailed information about property, plant and equipment [line items]
Impairment during the period	0	0
Right-of-use assets
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	115
Property, plant and equipment including right-of-use assets at the end of the period	93	115
Right-of-use assets | Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	272	258
Additions	31	39
Reclassification (to)/from assets held for sale	0
Disposals	(35)	(25)
Reclassification to assets held for sale		0
Property, plant and equipment including right-of-use assets at the end of the period	268	272
Right-of-use assets | Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment including right-of-use assets at the beginning of the period	(157)	(139)
Additions	(30)	(19)
Disposals	1	1
Reclassification to assets held for sale		0
Property, plant and equipment including right-of-use assets at the end of the period	(175)	(157)
Right-of-use assets | Accumulated impairment
Disclosure of detailed information about property, plant and equipment [line items]
Impairment during the period	£ (11)	£ 0

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about property, plant and equipment [line items]
Investment property	£ 17	£ 17
Head Office, Milton Keynes
Disclosure of detailed information about property, plant and equipment [line items]
Expenditures		£ 204

Other Financial Liabilities a_5

Other Financial Liabilities at Fair Value Through Profit or Loss - Summary of Other Financial Liabilities at Fair Value Through Profit or Loss (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other financial liabilities at fair value through profit or loss	£ 899	£ 803
Structured Notes Programmes
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other financial liabilities at fair value through profit or loss	369	375
Structured deposits
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other financial liabilities at fair value through profit or loss	426	321
Zero Amortising Guaranteed Notes
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other financial liabilities at fair value through profit or loss	£ 104	£ 107

Other Financial Liabilities a_6

Other Financial Liabilities at Fair Value Through Profit or Loss - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of financial liabilities [abstract]
Increase (decrease) in fair value of financial liability, attributable to changes in credit risk of liability	£ (21)	£ 25	£ (12)
Accumulated increase (decrease) in fair value of financial liability, attributable to changes in credit risk of liability	(6)	15	£ (10)
Difference between carrying amount of financial liability and amount contractually required to pay at maturity to holder of obligation	£ 97	£ (138)

Deposits by Customers (Details)

Deposits by Customers (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	£ 195,149	£ 197,313
Demand and time deposits
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	194,191	196,160
Amounts due to fellow Banco Santander subsidiaries and joint ventures
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	958	1,153
Equity index linked deposits
Disclosure Of Deposits From Customers [Line Items]
Capital amount guaranteed or protected	£ 304	£ 408

Deposits by Banks (Details)

Deposits by Banks (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	£ 20,357	£ 28,543
Drawdown from TFSME	17,000	25,000
Items in the course of transmission
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	732	701
Deposits held as collateral
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	888	1,758
Other deposits
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	£ 18,737	£ 26,084

Repurchase Agreements - Non T_3

Repurchase Agreements - Non Trading (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non-trading	£ 8,411	£ 7,982
Agreements with banks
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non-trading	551	50
Agreements with customers
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non-trading	£ 7,860	£ 7,932

Debt Securities in Issue (Detai

Debt Securities in Issue (Details) £ in Millions	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 EUR (€)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Dec. 31, 2022 USD ($)
Debt Securities In Issue [Line Items]
Debt securities	£ 35,778			£ 36,420
Notional amount	225,608			177,802
Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities	13,524			15,533
Euro 35bn Global Covered Bond Programme
Debt Securities In Issue [Line Items]
Debt securities	15,000			15,205
Notional amount | €		€ 35,000,000,000			€ 35,000,000,000
US $20bn Commercial Paper Programmes
Debt Securities In Issue [Line Items]
Debt securities	2,761			1,851
Notional amount | $			$ 20,000,000,000			$ 20,000,000,000
Certificates of deposit
Debt Securities In Issue [Line Items]
Debt securities	1,530			2,874
Credit linked notes
Debt Securities In Issue [Line Items]
Credit linked notes	194			60
Securitisation programmes
Debt Securities In Issue [Line Items]
Debt securities	2,769			897
– US$30bn Euro Medium Term Note Programme | Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities	744			739
Notional amount | $			$ 30,000,000,000			$ 30,000,000,000
– Euro 30bn Euro Medium Term Note Programme | Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities	5,619			6,435
Notional amount | €		€ 30,000,000,000			€ 30,000,000,000
– US SEC-registered Debt Programme - Santander UK Group Holdings plc | Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities	6,130			7,083
- US SEC-registered Debt Programme - Santander UK plc | Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities	£ 1,031			£ 1,276

Subordinated Liabilities - Sche

Subordinated Liabilities - Schedule of Subordinated Liabilities (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Subordinated liabilities [abstract]
£325m Sterling preference shares	£ 343	£ 344
Undated subordinated liabilities	205	219
Dated subordinated liabilities	1,838	1,769
Subordinated liabilities	2,386	2,332
£325m Sterling preference shares, notional amount	£ 325	£ 325

Subordinated Liabilities - Addi

Subordinated Liabilities - Additional Information (Details) - GBP (£)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Subordinated Liabilities [Line Items]
Defaults of principal, interest or other breaches with respect to subordinated liabilities	£ 0	£ 0
Repayment or purchase of subordinated liabilities before stated maturity allowed	£ 0	£ 0
Par value per share (in GBP per share)	£ 1	£ 1	£ 1
Loss on repurchase of subordinated liabilities	£ 4,000,000	£ (5,000,000)
10.375% non-cumulative non-redeemable sterling preference shares
Disclosure Of Subordinated Liabilities [Line Items]
Par value per share (in GBP per share)	£ 1
7.125% 30 Year Step-up perpetual callable subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	7.125%	7.125%
10.0625% Exchangeable capital securities
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	10.0625%	10.0625%
10.375% exchangeable subordinated capital securities
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	10.375%

Subordinated Liabilities - Summ

Subordinated Liabilities - Summary of Undated Subordinated Liabilities (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Subordinated Liabilities [Line Items]
Undated subordinated liabilities	£ 205	£ 219
10.0625% Exchangeable capital securities
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	10.0625%	10.0625%
First call date	n/a	n/a
Undated subordinated liabilities	£ 205	£ 205
7.125% 30 Year Step-up perpetual callable subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	7.125%	7.125%
Notes maturity, year	30 years	30 years
First call date	2030	2030
Undated subordinated liabilities	£ 0	£ 14

Subordinated Liabilities - Su_2

Subordinated Liabilities - Summary of Dated Subordinated Liabilities (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Subordinated Liabilities [Line Items]
Dated subordinated liabilities	£ 1,838	£ 1,769
5% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	5%	5%
Maturity	2023	2023
Dated subordinated liabilities	£ 0	£ 591
4.75% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	4.75%	4.75%
Maturity	2025	2025
Dated subordinated liabilities	£ 326	£ 608
7.95% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	7.95%	7.95%
Maturity	2029	2029
Dated subordinated liabilities	£ 193	£ 207
6.50% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	6.50%	6.50%
Maturity	2030	2030
Dated subordinated liabilities	£ 1	£ 22
5.875% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	5.875%	5.875%
Maturity	2031	2031
Dated subordinated liabilities	£ 7	£ 7
5.625% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	5.625%	5.625%
Maturity	2045	2045
Dated subordinated liabilities	£ 222	£ 334
7.869% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	7.869%
Maturity	2033
Dated subordinated liabilities	£ 321	0
8.296% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	8.296%
Maturity	2033
Dated subordinated liabilities	£ 768	£ 0

Other Liabilities (Details)

Other Liabilities (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Subclassifications of assets, liabilities and equities [abstract]
Lease liabilities	£ 114	£ 129
Other	2,387	2,472
Other liabilities	£ 2,501	£ 2,601

Provisions - Summary of Provisi

Provisions - Summary of Provisions Reconciliation (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£)
Disclosure of other provisions [line items]
Beginning balance	£ 380
Additional provisions (See Note 8)	363
Provisions released (See Note 8)	(23)
Utilisation and other	(371)
Recharge	20
Reclassification from provisions to other assets	36
Ending balance	405
Customer remediation
Disclosure of other provisions [line items]
Beginning balance	90
Additional provisions (See Note 8)	45
Provisions released (See Note 8)	(8)
Utilisation and other	(21)
Recharge	0
Reclassification from provisions to other assets	0
Ending balance	106
Litigation and other regulatory
Disclosure of other provisions [line items]
Beginning balance	136
Additional provisions (See Note 8)	28
Provisions released (See Note 8)	0
Utilisation and other	(32)
Recharge	0
Reclassification from provisions to other assets	0
Ending balance	132
Bank Levy
Disclosure of other provisions [line items]
Beginning balance	4
Additional provisions (See Note 8)	46
Provisions released (See Note 8)	(8)
Utilisation and other	(95)
Recharge	20
Reclassification from provisions to other assets	36
Ending balance	3
Property
Disclosure of other provisions [line items]
Beginning balance	47
Additional provisions (See Note 8)	16
Provisions released (See Note 8)	(6)
Utilisation and other	(10)
Recharge	0
Reclassification from provisions to other assets	0
Ending balance	47
ECL on undrawn facilities and guarantees
Disclosure of other provisions [line items]
Beginning balance	74
Additional provisions (See Note 8)	4
Provisions released (See Note 8)	0
Utilisation and other	0
Recharge	0
Reclassification from provisions to other assets	0
Ending balance	78
Restructuring
Disclosure of other provisions [line items]
Beginning balance	22
Additional provisions (See Note 8)	56
Provisions released (See Note 8)	0
Utilisation and other	(46)
Recharge	0
Reclassification from provisions to other assets	0
Ending balance	32
Other
Disclosure of other provisions [line items]
Beginning balance	7
Additional provisions (See Note 8)	168
Provisions released (See Note 8)	(1)
Utilisation and other	(167)
Recharge	0
Reclassification from provisions to other assets	0
Ending balance	£ 7

Provisions - Additional Informa

Provisions - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of other provisions [line items]
Provisions	£ 405	£ 380
Additional provisions	363
No later than one year
Disclosure of other provisions [line items]
Provisions	220	130
Customer remediation
Disclosure of other provisions [line items]
Provisions	106	£ 90
Net provision	37
Additional provisions	£ 45
Regulatory related UK Bank Levy | No later than one year
Disclosure of other provisions [line items]
Bank Levy rate	0.10%	0.10%
Regulatory related UK Bank Levy | More than one year
Disclosure of other provisions [line items]
Bank Levy rate	0.05%	0.05%
Restructuring
Disclosure of other provisions [line items]
Provisions	£ 32	£ 22
Additional provisions	56
Provisions for costs related to transformation programs	51
Operational risk provisions
Disclosure of other provisions [line items]
Additional provisions	163
Fraud losses
Disclosure of other provisions [line items]
Additional provisions	136
Legal provision
Disclosure of other provisions [line items]
Additional provisions	12
Regulatory fees
Disclosure of other provisions [line items]
Additional provisions	16
Customer remediation- mortgage book
Disclosure of other provisions [line items]
Additional provisions	45
Customer remediation- interest refund
Disclosure of other provisions [line items]
Additional provisions	30
Customer remediation- early repayment charges
Disclosure of other provisions [line items]
Additional provisions	10
Property Transformation Charges
Disclosure of other provisions [line items]
Additional provisions	£ 4

Retirement Benefit Plans - Summ

Retirement Benefit Plans - Summary of Retirement Benefit Plans (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets/(liabilities)
Total net assets	£ 657	£ 1,026
Unfunded pension and post-retirement medical benefits
Assets/(liabilities)
Surplus (deficit) in plan	(25)	(25)
Surplus | Funded defined benefit pension scheme
Assets/(liabilities)
Surplus (deficit) in plan	723	1,051
Deficit | Funded defined benefit pension scheme
Assets/(liabilities)
Surplus (deficit) in plan	£ (41)	£ 0

Retirement Benefit Plans - Addi

Retirement Benefit Plans - Additional Information (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£) section director	Dec. 31, 2022 GBP (£) director	Dec. 31, 2021 GBP (£)	Mar. 31, 2021	May 31, 2020	Aug. 31, 2019 GBP (£)	Mar. 01, 2015
Disclosure of defined benefit plans [line items]
Defined contribution expense	£ 71	£ 60	£ 65
Number of legally segregated sections | section	7
Percentage of employee covered defined benefit pension schemes	7%	10%
Number of directors selected | director	6	6
Number of directors nominated | director	4	4
Actuarial valuation deficit						£ 183
Percentage of the SMA section pensioner liabilities insured					100%
Percentage of the SPI section pensioner liabilities insured					50%
Contribution to scheme based on agreement	£ 194	£ 218
Period over which the spot rate remain constant	50 years
Percentage of pension pay increase	3%	3%	3.20%				1%
Percentage improvements in membership profile retirement benefits plan	0.25%
Improvements to life expectancy of female employees	1.25%
Improvements to life expectancy of male employees	1.25%
Average duration of defined benefit obligation	13.8 years	14.2 years
Longevity swap
Disclosure of defined benefit plans [line items]
Percentage of pensioner liabilities covered by longevity swap				85%
Minimum
Disclosure of defined benefit plans [line items]
Forward curve term	30 years
Maximum
Disclosure of defined benefit plans [line items]
Forward curve term	50 years
General price inflation
Disclosure of defined benefit plans [line items]
Percentage of reasonably possible increase in actuarial assumption	0.50%
Deficit Repair Contributions
Disclosure of defined benefit plans [line items]
Contribution to scheme based on agreement	£ 164	£ 178
Currency futures
Disclosure of defined benefit plans [line items]
Gross notional value	£ 859	£ 985

Retirement Benefit Plans - Tota

Retirement Benefit Plans - Total Defined Benefit Plan Amount Charged to Income Statement (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of net defined benefit liability (asset) [abstract]
Net interest income	£ (54)	£ (31)	£ (5)
Current service cost	13	30	38
Past service and GMP costs	1	0	0
Past service curtailment costs	0	0	5
Administration costs	7	9	8
Total	£ (33)	£ 8	£ 46

Retirement Benefit Plans - Su_2

Retirement Benefit Plans - Summary of Amounts Recognised in Other Comprehensive Income (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of net defined benefit liability (asset) [abstract]
Return on plan assets (excluding amounts included in net interest expense)	£ 352	£ 5,531	£ (452)
Actuarial (gains) arising from changes in demographic assumptions	(51)	(122)	(17)
Actuarial losses/(gains) arising from experience adjustments	91	481	(19)
Actuarial losses/(gains) arising from changes in financial assumptions	206	(5,167)	(775)
Pension remeasurement	598
Pension remeasurement	£ 598	£ 723	£ (1,263)

Retirement Benefit Plans - Disc

Retirement Benefit Plans - Disclosure of Movements in Present Value of Defined Benefit Obligations (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of net defined benefit liability (asset) [line items]
Net defined benefit liability (asset) at the end of the period	£ 657	£ 1,026
Current service cost	13	30	£ 38
Interest cost	54	31	5
Remeasurement due to actuarial movements arising from:
– Changes in demographic assumptions	(51)	(122)	(17)
– Experience adjustments	91	481	(19)
– Changes in financial assumptions	206	(5,167)	(775)
Present value of defined benefit obligations
Disclosure of net defined benefit liability (asset) [line items]
Net defined benefit liability (asset) at the end of the period	(8,201)	(7,937)	£ (12,884)
Current service cost	(13)	(29)
Current service cost paid by other subsidiaries	0	(1)
Interest cost	(379)	(241)
Employer salary sacrifice contributions	(1)	(3)
Past service cost	(1)	0
Remeasurement due to actuarial movements arising from:
– Changes in demographic assumptions	51	122
– Experience adjustments	(91)	(481)
– Changes in financial assumptions	(206)	5,167
Benefits paid	372	413
Derecognition of pension scheme liabilities arising from the wind up of the offshore scheme	£ 4	£ 0

Retirement Benefit Plans - Di_2

Retirement Benefit Plans - Disclosure of Movements in Fair Value of Scheme Assets (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of net defined benefit liability (asset) [line items]
Net defined benefit liability (asset)	£ 1,026
Interest income	54	£ 31	£ 5
Return on plan assets (excluding amounts included in net interest expense)	352	5,531	(452)
Net defined benefit liability (asset) at the end of the period	657	1,026
Fair value of scheme assets
Disclosure of net defined benefit liability (asset) [line items]
Net defined benefit liability (asset)	8,963	14,420
Interest income	433	272
Contributions paid by employer and scheme members	197	224
Administration costs paid	(7)	(9)
Return on plan assets (excluding amounts included in net interest expense)	(352)	(5,531)
Benefits paid	(372)	(413)
Derecognition of pension scheme liabilities arising from the wind up of the offshore scheme	(4)	0
Net defined benefit liability (asset) at the end of the period	£ 8,858	£ 8,963	£ 14,420

Retirement Benefit Plans - Su_3

Retirement Benefit Plans - Summary of Composition and Fair Value of Plan Assets (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of net defined benefit liability (asset) [line items]
Overseas equities	£ 980	£ 1,172
Corporate bonds	2,526	2,235
Government fixed interest bonds	1,618	1,138
Government index-linked bonds	4,422	5,525
Property	1,080	1,202
Derivatives	(2)	(78)
Cash	586	1,340
Repurchase agreements	(3,062)	(4,312)
Infrastructure	408	426
Annuities	293	298
Longevity swap	(16)	(12)
Other	25	29
Total	£ 8,858	£ 8,963
Overseas equities, percentage	11%	13%
Corporate bonds, percentage	29%	25%
Government fixed interest bonds, percentage	18%	13%
Government index-linked bonds, percentage	50%	62%
Property, percentage	12%	13%
Derivatives, percentage	0%	(1.00%)
Cash, percentage	7%	15%
Repurchase agreements, percentage	(35.00%)	(48.00%)
Infrastructure, percentage	5%	5%
Annuities, percentage	3%	3%
Longevity swap, percentage	0%	0%
Other, percentage	0%	0%
Total, percentage	100%	100%
Quoted prices in active markets
Disclosure of net defined benefit liability (asset) [line items]
Overseas equities	£ 0	£ 0
Corporate bonds	2,284	1,991
Government fixed interest bonds	1,618	1,138
Government index-linked bonds	4,422	5,525
Property	0	0
Derivatives	0	0
Cash	0	0
Repurchase agreements	0	0
Infrastructure	0	0
Annuities	0	0
Longevity swap	0	0
Other	0	0
Total	£ 8,324	£ 8,654
Overseas equities, percentage	0%	0%
Corporate bonds, percentage	26%	22%
Government fixed interest bonds, percentage	18%	13%
Government index-linked bonds, percentage	50%	62%
Property, percentage	0%	0%
Derivatives, percentage	0%	0%
Cash, percentage	0%	0%
Repurchase agreements, percentage	0%	0%
Infrastructure, percentage	0%	0%
Annuities, percentage	0%	0%
Longevity swap, percentage	0%	0%
Other, percentage	0%	0%
Total, percentage	94%	97%
Prices not quoted in active markets
Disclosure of net defined benefit liability (asset) [line items]
Overseas equities	£ 980	£ 1,172
Corporate bonds	242	244
Government fixed interest bonds	0	0
Government index-linked bonds	0	0
Property	1,080	1,202
Derivatives	(2)	(78)
Cash	586	1,340
Repurchase agreements	(3,062)	(4,312)
Infrastructure	408	426
Annuities	293	298
Longevity swap	(16)	(12)
Other	25	29
Total	£ 534	£ 309
Overseas equities, percentage	11%	13%
Corporate bonds, percentage	3%	3%
Government fixed interest bonds, percentage	0%	0%
Government index-linked bonds, percentage	0%	0%
Property, percentage	12%	13%
Derivatives, percentage	0%	(1.00%)
Cash, percentage	7%	15%
Repurchase agreements, percentage	(35.00%)	(48.00%)
Infrastructure, percentage	5%	5%
Annuities, percentage	3%	3%
Longevity swap, percentage	0%	0%
Other, percentage	0%	0%
Total, percentage	6%	3%

Retirement Benefit Plans - Su_4

Retirement Benefit Plans - Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Mar. 01, 2015
Disclosure of net defined benefit liability (asset) [abstract]
– Discount rate for scheme liabilities	4.60%	4.90%	1.90%
– General price inflation	3%	3.10%	3.40%
– General salary increase	1%	1%	1%
– Expected rate of pension increase	3%	3%	3.20%	1%
Longevity at 60 for current pensioners, on the valuation date:
– Males	27 years	27 years 4 months 24 days	27 years 6 months
– Females	29 years 9 months 18 days	30 years 1 month 6 days	30 years 1 month 6 days
Longevity at 60 for future pensioners currently aged 40, on the valuation date:
– Males	28 years 7 months 6 days	28 years 10 months 24 days	29 years
– Females	31 years 3 months 18 days	31 years 7 months 6 days	31 years 7 months 6 days

Retirement Benefit Plans - Su_5

Retirement Benefit Plans - Summary of Actuarial Assumption Sensitivities (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Discount rate
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Percentage of reasonably possible increase in actuarial assumption	0.50%
Description of changes in methods and assumptions	bps increase
Increase (decrease) in defined benefit obligation	£ (507)	£ (501)
General price inflation
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Percentage of reasonably possible increase in actuarial assumption	0.50%
Description of changes in methods and assumptions	bps increase
Increase (decrease) in defined benefit obligation	£ 385	374
Mortality
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Description of changes in methods and assumptions	Each additional year of longevity assumed
Increase (decrease) in defined benefit obligation	£ 223	£ 203

Retirement Benefit Plans - Di_3

Retirement Benefit Plans - Disclosure of Benefits Expected To Be Paid (Details) £ in Millions	Dec. 31, 2023 GBP (£)
No later than one year
Disclosure of net defined benefit liability (asset) [line items]
Benefits expected to be paid	£ 455
Later than one year and not later than two years
Disclosure of net defined benefit liability (asset) [line items]
Benefits expected to be paid	389
Later than two years and not later than three years
Disclosure of net defined benefit liability (asset) [line items]
Benefits expected to be paid	404
Later than three years and not later than four years
Disclosure of net defined benefit liability (asset) [line items]
Benefits expected to be paid	428
Later than four years and not later than five years
Disclosure of net defined benefit liability (asset) [line items]
Benefits expected to be paid	444
Five years ending 2033
Disclosure of net defined benefit liability (asset) [line items]
Benefits expected to be paid	£ 2,398

Contingent Liabilities and Co_4

Contingent Liabilities and Commitments - Summary of Contingent Liabilities and Commitments (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of contingent liabilities [line items]
Guarantees and formal standby facilities, credit lines and other commitments	£ 31,439	£ 31,858
Contingent liability for guarantees
Disclosure of contingent liabilities [line items]
Guarantees given to third parties	452	448
Loan commitments
Disclosure of contingent liabilities [line items]
Formal standby facilities, credit lines and other commitments	£ 30,987	£ 31,410

Contingent Liabilities and Co_5

Contingent Liabilities and Commitments - Additional Information (Details) £ in Millions		12 Months Ended
	Nov. 02, 2015	Dec. 31, 2023 EUR (€)	Jun. 29, 2023 GBP (£)	Oct. 21, 2022 GBP (£)
Disclosure of contingent liabilities [line items]
Capital support arrangements, risk-weighted exposures of regulated entities		0%
Minimum
Disclosure of contingent liabilities [line items]
Losses on litigation settlements		€ 1,000,000,000
Maximum
Disclosure of contingent liabilities [line items]
Santander UK liability under indemnity cap		39,850,000
AXA France
Disclosure of contingent liabilities [line items]
Amount claimed by other party | £			£ 552	£ 670
UK&I Banks
Disclosure of contingent liabilities [line items]
Preferred stock issued, threshold value		€ 0
Visa Europe Ltd
Disclosure of contingent liabilities [line items]
Visa Europe Ltd sale to Visa Inc	100%

Share Capital (Details)

Share Capital (Details) - GBP (£) £ / shares in Units, £ in Millions	Dec. 31, 2023	Jan. 01, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of classes of share capital [abstract]
Ordinary shares, price per share (in GBP per share)	£ 1		£ 1	£ 1
Number of shares issued and fully paid (in shares)	7,060,000,000	7,060,000,000	7,060,000,000
Issued capital	£ 7,060	£ 7,060	£ 7,060

Other Equity Instruments - Summ

Other Equity Instruments - Summary of Other Equity Instruments (Details)	12 Months Ended
	Dec. 31, 2023 GBP (£)	Dec. 31, 2022 GBP (£)
Disclosure Of Other Equity Instruments [Line Items]
Other equity instruments	£ 2,196,000,000	£ 2,196,000,000
£500m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 500,000,000
Interest rate	0.0675
Other equity interest maturity period	2024-06
Other equity instruments	£ 496,000,000	496,000,000
£750m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 750,000,000
Interest rate	0.0650
- £500m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 500,000,000
Interest rate	0.0630
Other equity interest maturity period	2025-03
Other equity instruments	£ 500,000,000	500,000,000
- £450m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 450,000,000
Interest rate	0.0425
Other equity interest maturity period	2026-03
Other equity instruments	£ 450,000,000	450,000,000
- £750m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 750,000,000
Interest rate	0.0650
Other equity interest maturity period	2027-06
Other equity instruments	£ 750,000,000	£ 750,000,000

Other Equity Instruments - Addi

Other Equity Instruments - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 GBP (£)
AT1 securities
Disclosure Of Other Equity Instruments [Line Items]
Distribution rate reset, period	5 years
Common equity tier 1 capital ratio minimum	7%
- £450m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities issued	£ 450,000,000
Interest rate	0.0425
- £500m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities issued	£ 500,000,000
Interest rate	0.0630
£750m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities issued	£ 750,000,000
Interest rate	0.0650

Notes to Cash Flows - Summary o

Notes to Cash Flows - Summary of Changes in Liabilities Arising from Financing Activities (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	£ 41,077	£ 36,133	£ 48,576
Proceeds from issue of debt securities	5,347	8,667	2,847
Repayment of debt securities	(5,438)	(4,482)	(13,724)
Proceeds from issue of subordinated liabilities	1,050
Repayment of subordinated liabilities	(971)	(40)	(4)
Issue of other equity instruments		750	450
Repurchase of other equity instruments		(750)	(500)
Principal elements of lease payments	(48)	(26)	(25)
Dividends paid	(1,671)	(1,173)	(1,506)
Liability-related other changes	(101)	(1,254)	(418)
Non-cash changes:
– Unrealised foreign exchange	(804)	2,083	(916)
– Other changes	2,033	1,169	1,353
Ending balance	40,474	41,077	36,133
Debt securities in issue
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	36,420	31,580	43,679
Proceeds from issue of debt securities	5,347	8,667	2,847
Repayment of debt securities	(5,438)	(4,482)	(13,724)
Liability-related other changes	(159)	(1,282)	(473)
Non-cash changes:
– Unrealised foreign exchange	(750)	1,893	(930)
– Other changes	358	44	181
Ending balance	35,778	36,420	31,580
Subordinated liabilities
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	2,332	2,228	2,556
Proceeds from issue of subordinated liabilities	1,050
Repayment of subordinated liabilities	(971)	(40)	(4)
Liability-related other changes	25	2	(4)
Non-cash changes:
– Unrealised foreign exchange	(54)	190	14
– Other changes	4	(47)	(334)
Ending balance	2,386	2,332	2,228
Other equity instruments
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	2,196	2,191	2,241
Issue of other equity instruments		750	450
Repurchase of other equity instruments		(750)	(500)
Liability-related other changes	0	5
Non-cash changes:
Ending balance	2,196	2,196	2,191
Lease liabilities
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	129	134	100
Principal elements of lease payments	(48)	(26)	(25)
Liability-related other changes	33	21	59
Non-cash changes:
Ending balance	114	129	134
Dividends paid
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	0	0	0
Dividends paid	(1,671)	(1,173)	(1,506)
Non-cash changes:
– Other changes	1,671	1,173	1,506
Ending balance	£ 0	£ 0	£ 0

Notes to Cash Flows - Additiona

Notes to Cash Flows - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Cash Flows Explanatory Notes [Line Items]
Interest received	£ 11,627	£ 6,618	£ 4,873
Interest paid	6,496	2,107	1,085
Dividends received	0	0	0
Cash outflow for leases	£ 50	£ 28	28
Disposal of non-controlling interests			£ (181)

Assets Charged as Security fo_3

Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets - Financial Assets Charged as Security Under On-Balance Sheet and Off-Balance (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	£ 1,682	£ 1,541
On-balance sheet:
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	54,792	62,135
On-balance sheet: | Cash and balances at central banks
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	1,480	1,330
On-balance sheet: | Loans and advances to banks
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	254	163
On-balance sheet: | Total loans and advances to customers | Securitisations and covered bonds
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	27,088	24,155
On-balance sheet: | Total loans and advances to customers | Other
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	20,703	32,011
On-balance sheet: | Other financial assets at amortised cost
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	14	35
On-balance sheet: | Financial assets at fair value through other comprehensive income
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	5,253	4,441
Off-balance sheet
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	£ 10,184	£ 9,184

Assets Charged as Security fo_4

Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets - Additional Information (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	£ 1,682	£ 1,541
Gross assets charged as security for liabilities	27,927	24,984
Notes issued under securitisation and covered bond programmes retained internally	17,769	16,102
Purchase and resale agreements
Disclosure Of Assets Pledged As Security [Line Items]
Collateral accepted as security for assets	12,983	8,628
Securitisations and covered bonds | Internally retained
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued under securitisation and covered bond programmes retained internally	2,928	1,725
Securitisations and covered bonds | Third party bilateral secured funding transactions
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	1,500	500
Securities lending
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	23,713	34,963
Collateral accepted as security for assets	2,669	1,767
Derivatives | Cash
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	1,793	1,548
Collateral accepted as security for assets	888	1,758
Subsidiaries | Sale and repurchase agreements
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	13,291	11,553
Subsidiaries | Loans and advances to customers securitisations and covered bonds
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued as collateral	909	900
Santander UK plc | Securitisations and covered bonds | Internally retained
Disclosure Of Assets Pledged As Security [Line Items]
Internally retained securitisation and covered bond issuances available for creating collateral	£ 839	£ 829

Assets Charged as Security fo_5

Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets - Schedule of Collateral Held as Security for Assets (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
On-balance sheet:
Disclosure Of Assets Pledged As Security [Line Items]
Total on-balance sheet/ off-balance sheet	£ 888	£ 1,758
On-balance sheet: | Deposits by banks
Disclosure Of Assets Pledged As Security [Line Items]
Total on-balance sheet/ off-balance sheet	888	1,758
Off-balance sheet
Disclosure Of Assets Pledged As Security [Line Items]
Total on-balance sheet/ off-balance sheet	£ 15,652	£ 10,395

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details)	12 Months Ended		180 Months Ended
	Dec. 31, 2023 GBP (£) £ / shares shares	Dec. 31, 2022 GBP (£) £ / shares shares	Dec. 31, 2022 GBP (£) invitation
Disclosure of terms and conditions of share-based payment arrangement [line items]
Liabilities arising from share-based payment transactions	£ 14,700,000	£ 6,600,000	£ 6,600,000
Liabilities arising from share-based payment transactions, vested liabilities	1,100,000	£ 100,000	£ 100,000
Number of sharesave schemes launched | invitation			16
Employee saving on share based compensation	£ 500,000
Price determination period for options	3 days
Maximum discount applicable	20%
Actual discount applied	10%
Expiration term of vested options	6 months
Weighted average share price (GBP per share) | £ / shares	£ 3.22	£ 2.34
Weighted average grant-date fair value (GBP per share)	£ 0.33	£ 0.23	£ 0.23
Number of shares outstanding | shares	3,937,473	3,974,698
Material Risk Takers
Disclosure of terms and conditions of share-based payment arrangement [line items]
Additional retention period for deferred bonus awards	1 year
Share Incentive Plans
Disclosure of terms and conditions of share-based payment arrangement [line items]
Maximum investment value per tax year	£ 1,800
Percentage of maximum salary that can be invested	10%
Transformation Incentive Plan
Disclosure of terms and conditions of share-based payment arrangement [line items]
Liabilities arising from share-based payment transactions	£ 3,800,000	£ 1,800,000	£ 1,800,000
Value of awards granted	£ 1,300,000	£ 1,000,000
Shares | Material Risk Takers Option 1
Disclosure of terms and conditions of share-based payment arrangement [line items]
Annual bonus percentage	50%
Cash | Material Risk Takers Option 1
Disclosure of terms and conditions of share-based payment arrangement [line items]
Annual bonus percentage	50%
Minimum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Employee saving on share based compensation	£ 5
Terms of options	3 years
Minimum | Share Incentive Plans
Disclosure of terms and conditions of share-based payment arrangement [line items]
Minimum retention period to sell shares free of income tax	5 years
Maximum
Disclosure of terms and conditions of share-based payment arrangement [line items]
Employee saving on share based compensation	£ 500
Terms of options	5 years
Variable pay of less than 500,000 | Material Risk Takers
Disclosure of terms and conditions of share-based payment arrangement [line items]
Percentage of defer annual bonus	40%
Variable pay at or above 500,000 | Material Risk Takers
Disclosure of terms and conditions of share-based payment arrangement [line items]
Percentage of defer annual bonus	60%
Period one | Material Risk Takers
Disclosure of terms and conditions of share-based payment arrangement [line items]
Deferral period from anniversary of initial award	4 years
Period two | Material Risk Takers
Disclosure of terms and conditions of share-based payment arrangement [line items]
Deferral period from anniversary of initial award	5 years
Period three | Material Risk Takers
Disclosure of terms and conditions of share-based payment arrangement [line items]
Deferral period from anniversary of initial award	7 years

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Movement in Share Options (Details) - Sharesave Schemes number in Thousands	12 Months Ended
	Dec. 31, 2023 £ / shares	Dec. 31, 2022 £ / shares
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options outstanding, beginning balance (in shares)	29,988	25,993
Number of options granted (in shares)	7,175	13,068
Number of options exercised (in shares)	(5,980)	(242)
Number of options forfeited/expired (in shares)	(4,044)	(8,831)
Number of options outstanding, ending balance (in shares)	27,139	29,988
Number of options exercisable (in shares)	868	3,439
Weighted average exercise price outstanding, beginning balance	£ 2	£ 2.25
Weighted average exercise price granted	2.78	1.89
Weighted average exercise price exercised	1.70	1.69
Weighted average exercise price forfeited/expired	2.53	2.59
Weighted average exercise price outstanding, ending balance	2.19	2
Weighted average exercise price exercisable	£ 1.84	£ 3.22

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Range of Exercise Prices and Weighted Average Remaining Contractual Life of the Options Outstanding (Details) - Sharesave Schemes - £ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Weighted average exercise price (in GBP per share)	£ 2.19	£ 2	£ 2.25
£1 to £2
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Weighted average remaining contractual life	3 years	3 years
Weighted average exercise price (in GBP per share)	£ 1.84	£ 1.79
£2 to £3
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Weighted average remaining contractual life	3 years	2 years
Weighted average exercise price (in GBP per share)	£ 2.65	£ 2.56
£3 to £4
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Weighted average remaining contractual life	0 years	1 year
Weighted average exercise price (in GBP per share)	£ 3.46	£ 3.46
£4 to £5
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Weighted average remaining contractual life	0 years	0 years
Weighted average exercise price (in GBP per share)	£ 0	£ 4.02
Minimum | £1 to £2
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Range of exercise prices	1
Minimum | £2 to £3
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Range of exercise prices	2
Minimum | £3 to £4
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Range of exercise prices	3
Minimum | £4 to £5
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Range of exercise prices	4
Maximum | £1 to £2
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Range of exercise prices	2
Maximum | £2 to £3
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Range of exercise prices	3
Maximum | £3 to £4
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Range of exercise prices	4
Maximum | £4 to £5
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]
Range of exercise prices	£ 5

Transactions with Directors a_4

Transactions with Directors and Other Key Management Personnel - Summary of Remuneration of the Directors and Other Key Management Personnel (Details)	12 Months Ended
	Dec. 31, 2023 GBP (£) individual	Dec. 31, 2022 GBP (£) individual	Dec. 31, 2021 GBP (£)
Disclosure Of Directors And Key Management Remuneration [Line Items]
Salaries and fees	£ 4,008,772	£ 4,037,116	£ 3,828,333
Performance-related payments	1,002,607	3,701,569	3,431,294
Other fixed remuneration (pension and other allowances & non-cash benefits)	222,538	906,201	806,103
Expenses	0	13,004	3,705
Total remuneration	5,233,917	8,657,890	8,069,435
Short-term employee benefits	13,235,757	15,641,669	18,831,380
Post-employment benefits	611,769	740,333	913,842
Compensation for loss of office	0	1,540,400	0
Total compensation	£ 13,847,526	£ 17,922,402	£ 19,745,222
Number key management persons who receives termination benefit | individual	0	3

Transactions with Directors a_5

Transactions with Directors and Other Key Management Personnel - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 GBP (£) director transaction	Dec. 31, 2022 GBP (£) director transaction	Dec. 31, 2021 GBP (£)
Disclosure Of Directors And Key Management Remuneration [Line Items]
Remuneration excluding pension contribution | £	£ 2,640,491	£ 3,510,441	£ 3,740,810
Remuneration excluding pension contribution performance | £	1,002,607	1,900,506	1,864,320
Accrued defined benefit pension related to the highest paid director | £	£ 0	0	22,119
Directors with a deferred pension benefit accruing under a defined benefit scheme	0
Ex gratia pensions paid to former Directors | £	£ 327,462	£ 379,945	£ 370,668
Directors who held any interest in the shares	0	0
Directors who exercised or were granted any rights to subscribe for shares	0	0
Directors who exercised share options over shares in Banco Santander	0	0
Number of loan made to directors	1	4
Loans made to directors | £	£ 312,846	£ 332,426
Number of other transactions, arrangements or agreements with material interest | transaction	0	0
Number of Directors having material interest in contract of significance	0	0
Other key management personnel
Disclosure Of Directors And Key Management Remuneration [Line Items]
Number of loan made to key management personnel	5	2
Loans made to key management personnel | £	£ 578,568	£ 314,667

Transactions with Directors a_6

Transactions with Directors and Other Key Management Personnel - Summary of Transactions with Directors, Other Key Management Personnel (Details) - Key Management Personnel £ in Thousands	12 Months Ended
	Dec. 31, 2023 GBP (£) deposits loans	Dec. 31, 2022 GBP (£) deposits loans
Disclosure Of Directors And Key Management Remuneration [Line Items]
Number of secured loans, unsecured loans and overdrafts, beginning balance | loans	6	4
Number of secured loans, unsecured loans and overdrafts, net movements | loans	0	2
Number of secured loans, unsecured loans and overdrafts, ending balance | loans	6	6
Beginning balance	£ 647	£ 27
Net movements	244	620
Ending balance	£ 891	£ 647
Number of deposit, bank and instant access accounts and investments, beginning balance | deposits	16	16
Number of deposit, bank and instant access accounts and investments, net movements | deposits	(3)	0
Number of deposit, bank and instant access accounts and investments, ending balance | deposits	13	16
Beginning balance	£ 2,995	£ 6,427
Net movements	(1,819)	(3,432)
Ending balance	£ 1,176	£ 2,995

Related Party Disclosures - Sum

Related Party Disclosures - Summary of Transactions With Related Parties (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	£ (223)	£ (1,000)	£ (291)
Interest, fees and other expenses paid	724	235	189
Amounts owed by related parties	5,415	5,605
Amounts owed to related parties	(3,282)	(2,983)
Ultimate parent
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	(12)	(863)	(210)
Interest, fees and other expenses paid	475	47	34
Amounts owed by related parties	903	1,423
Amounts owed to related parties	(2,250)	(1,732)
Subsidiaries
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	(28)	(60)	(47)
Interest, fees and other expenses paid	194	171	151
Amounts owed by related parties	26	31
Amounts owed to related parties	(251)	(278)
Joint ventures
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	(183)	(77)	(34)
Interest, fees and other expenses paid	55	17	£ 4
Amounts owed by related parties	4,486	4,151
Amounts owed to related parties	£ (781)	£ (973)

Related Party Disclosures - Add

Related Party Disclosures - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Nov. 30, 2022	Dec. 31, 2021
Unsecured Committed Liquidity Facility
Disclosure of transactions between related parties [line items]
Borrowings			£ 600
Santander UK Investments
Disclosure of transactions between related parties [line items]
Rental expense	£ 9	£ 6
Santander Consumer (UK) | PSA Finance UK Limited [Member]
Disclosure of transactions between related parties [line items]
Proportion of ownership interest in subsidiary sold				50%

Financial Instruments - Disclos

Financial Instruments - Disclosure of Analysis of Fair Value of Financial Instruments Carried at Amortised Cost (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to customers	£ 211,222	£ 223,840
Loans and advances to banks	1,216	1,105
Reverse repurchase agreements - non trading	12,468	7,348
Other financial assets at amortised cost	152	156
Deposits by customers	195,149	197,313
Deposits by banks	20,357	28,543
Repurchase agreements - non trading	8,411	7,982
Debt securities in issue	35,778	36,420
Subordinated liabilities	2,386	2,332
Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Financial liabilities	262,081	272,590
Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial assets	225,058	232,449
Deposits by customers | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by customers	195,149	197,313
Deposits by banks | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by banks	20,357	28,543
Repurchase agreements - non trading | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Repurchase agreements - non trading	8,411	7,982
Debt securities in issue | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Debt securities in issue	35,778	36,420
Subordinated liabilities | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Subordinated liabilities	2,386	2,332
Total loans and advances to customers | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to customers	211,222	223,840
Loans and advances to banks | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to banks	1,216	1,105
Reverse repurchase agreements – non trading | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Reverse repurchase agreements - non trading	12,468	7,348
Other financial assets at amortised cost | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Other financial assets at amortised cost	152	156
Level 1 | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Financial liabilities	12,382	5,007
Level 1 | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial assets	144	144
Level 1 | Deposits by customers | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by customers	0	0
Level 1 | Deposits by banks | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by banks	0	0
Level 1 | Repurchase agreements - non trading | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Repurchase agreements - non trading	0	0
Level 1 | Debt securities in issue | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Debt securities in issue	11,511	4,988
Level 1 | Subordinated liabilities | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Subordinated liabilities	871	19
Level 1 | Total loans and advances to customers | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to customers	0	0
Level 1 | Loans and advances to banks | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to banks	0	0
Level 1 | Reverse repurchase agreements – non trading | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Reverse repurchase agreements - non trading	0	0
Level 1 | Other financial assets at amortised cost | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Other financial assets at amortised cost	144	144
Level 2 | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Financial liabilities	53,239	66,984
Level 2 | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial assets	13,686	8,446
Level 2 | Deposits by customers | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by customers	76	52
Level 2 | Deposits by banks | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by banks	20,371	27,997
Level 2 | Repurchase agreements - non trading | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Repurchase agreements - non trading	8,413	7,982
Level 2 | Debt securities in issue | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Debt securities in issue	22,710	28,685
Level 2 | Subordinated liabilities | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Subordinated liabilities	1,669	2,268
Level 2 | Total loans and advances to customers | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to customers	0	0
Level 2 | Loans and advances to banks | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to banks	1,216	1,105
Level 2 | Reverse repurchase agreements – non trading | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Reverse repurchase agreements - non trading	12,470	7,341
Level 2 | Other financial assets at amortised cost | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Other financial assets at amortised cost	0	0
Level 3 | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Financial liabilities	196,231	199,088
Level 3 | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial assets	209,641	216,451
Level 3 | Deposits by customers | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by customers	194,831	197,228
Level 3 | Deposits by banks | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by banks	37	54
Level 3 | Repurchase agreements - non trading | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Repurchase agreements - non trading	0	0
Level 3 | Debt securities in issue | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Debt securities in issue	1,154	1,582
Level 3 | Subordinated liabilities | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Subordinated liabilities	209	224
Level 3 | Total loans and advances to customers | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to customers	209,641	216,451
Level 3 | Loans and advances to banks | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to banks	0	0
Level 3 | Reverse repurchase agreements – non trading | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Reverse repurchase agreements - non trading	0	0
Level 3 | Other financial assets at amortised cost | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Other financial assets at amortised cost	0	0
Fair value | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Financial liabilities	261,852	271,079
Fair value | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial assets	223,471	225,041
Fair value | Deposits by customers | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by customers	194,907	197,280
Fair value | Deposits by banks | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by banks	20,408	28,051
Fair value | Repurchase agreements - non trading | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Repurchase agreements - non trading	8,413	7,982
Fair value | Debt securities in issue | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Debt securities in issue	35,375	35,255
Fair value | Subordinated liabilities | Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Subordinated liabilities	2,749	2,511
Fair value | Total loans and advances to customers | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to customers	209,641	216,451
Fair value | Loans and advances to banks | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to banks	1,216	1,105
Fair value | Reverse repurchase agreements – non trading | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Reverse repurchase agreements - non trading	12,470	7,341
Fair value | Other financial assets at amortised cost | Financial assets at amortised cost:
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Other financial assets at amortised cost	£ 144	£ 144

Financial Instruments - Discl_2

Financial Instruments - Disclosure of Analysis of Fair Value of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 10,555	£ 8,897
Liabilities at fair value	1,790	1,811
Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	891	1,008
Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	899	803
Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1,472	2,439
Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	602	434
Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	8,481	6,024
Level 1
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	8,293	5,996
Liabilities at fair value	0	0
Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Level 1 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Level 1 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Level 1 | Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	8,293	5,996
Level 2
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	2,101	2,720
Liabilities at fair value	1,780	1,796
Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	881	996
Level 2 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	899	800
Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1,436	2,385
Level 2 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	477	307
Level 2 | Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	188	28
Level 3
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	161	181
Liabilities at fair value	10	15
Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	10	12
Level 3 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	3
Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	36	54
Level 3 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	125	127
Level 3 | Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Exchange rate contracts | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 533	489
Valuation technique	A
Exchange rate contracts | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 1,129	2,049
Valuation technique	A
Exchange rate contracts | Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	0
Exchange rate contracts | Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Exchange rate contracts | Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	533	489
Exchange rate contracts | Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1,129	2,049
Exchange rate contracts | Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Exchange rate contracts | Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Interest rate contracts | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 2,380	2,666
Valuation technique	A & C
Interest rate contracts | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 2,228	2,413
Valuation technique	A & C
Interest rate contracts | Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	0
Interest rate contracts | Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Interest rate contracts | Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	2,379	2,662
Interest rate contracts | Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	2,227	2,406
Interest rate contracts | Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	1	4
Interest rate contracts | Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1	7
Equity and credit contracts
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	35	30
Equity and credit contracts | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 25	26
Valuation technique	B & D
Equity and credit contracts | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 162	150
Valuation technique	B & D
Equity and credit contracts | Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	0
Equity and credit contracts | Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Equity and credit contracts | Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	16	18
Equity and credit contracts | Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	127	103
Equity and credit contracts | Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	9	8
Equity and credit contracts | Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	35	47
Netting | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	(2,047)	(2,173)
Netting | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	(2,047)	(2,173)
Netting | Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Netting | Level 1 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Netting | Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	(2,047)	(2,173)
Netting | Level 2 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	(2,047)	(2,173)
Netting | Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Netting | Level 3 | Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Total loans and advances to customers | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 355	339
Valuation technique	A
Total loans and advances to customers | Level 1 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 0	0
Total loans and advances to customers | Level 2 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	309	294
Total loans and advances to customers | Level 3 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	46	45
Debt securities | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 217	85
Valuation technique	A, B & D
Debt securities | Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 8,481	6,024
Valuation technique	D
Debt securities | Level 1 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 0	0
Debt securities | Level 1 | Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	8,293	5,996
Debt securities | Level 2 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	168	13
Debt securities | Level 2 | Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	188	28
Debt securities | Level 3 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	49	72
Debt securities | Level 3 | Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Equity securities | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 30	10
Valuation technique	B
Equity securities | Level 1 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 0	0
Equity securities | Level 2 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Equity securities | Level 3 | Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	30	10
Debt securities in issue | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 369	375
Valuation technique	A
Debt securities in issue | Level 1 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	0
Debt securities in issue | Level 2 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	369	372
Debt securities in issue | Level 3 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	3
Structured deposits | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 426	321
Valuation technique	A
Structured deposits | Level 1 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	0
Structured deposits | Level 2 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	426	321
Structured deposits | Level 3 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Zero Amortising Guaranteed Notes | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 104	107
Valuation technique	D
Zero Amortising Guaranteed Notes | Level 1 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	0
Zero Amortising Guaranteed Notes | Level 2 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	104	107
Zero Amortising Guaranteed Notes | Level 3 | Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	£ 0

Financial Instruments - Additio

Financial Instruments - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Assets
Transfers out of Level 1 into Level 2 of fair value hierarchy, assets held at end of reporting period	£ 22	£ 0
Transfers out of Level 2 into Level 1 of fair value hierarchy, assets held at end of reporting period	22	0
Transfers into Level 3 of fair value hierarchy, assets	22	0
Transfers out of Level 3 of fair value hierarchy, assets	22	0
Liabilities
Transfers out of Level 1 into Level 2 of fair value hierarchy, liabilities held at end of reporting period	22	0
Transfers out of Level 2 into Level 1 of fair value hierarchy, liabilities held at end of reporting period	22	0
Transfers into Level 3 of fair value hierarchy, liabilities	22	0
Transfers out	£ 22	£ 0

Financial Instruments - Summary

Financial Instruments - Summary of Fair Value Adjustment (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of financial assets [line items]
Fair value adjustments	£ 21	£ 14
Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	22	15
Day One profit
Disclosure of financial assets [line items]
Fair value adjustments	(1)	(1)
- Bid-offer and trade specific adjustments | Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	(6)	(12)
- Uncertainty | Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	29	27
- Credit risk adjustment | Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	(2)	(1)
- Funding fair value adjustment | Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	£ 1	£ 1

Financial Instruments - Discl_3

Financial Instruments - Disclosure of Analysis of Financial Instruments Valued Using Internal Models Based on Information Other than Market Data (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Financial Assets And Liabilities [Line Items]
FVTPL assets	£ 602	£ 434
Financial assets at fair value through other comprehensive income	8,481	6,024
Total net assets	151	166
Total income/(expense)	44	(21)	£ (1)
Level 3
Disclosure Of Financial Assets And Liabilities [Line Items]
Financial assets and liabilities	160	155
Financial asset liabilities	38	(40)	(1)
Other Level 3 | Level 3
Disclosure Of Financial Assets And Liabilities [Line Items]
Other Level 3 assets	1	26
Other Level 3 liabilities	(10)	(15)
Derivative assets and other Level 3 assets, fair value movements recognised in profit/(loss)	7	17	(6)
Derivative liabilities and other Level 3 liabilities, fair value movements recognised in profit/(loss)	(1)	2	6
Reversionary property interests | Equity and credit contracts
Disclosure Of Financial Assets And Liabilities [Line Items]
Derivative assets	35	30
Derivative assets and other Level 3 assets, fair value movements recognised in profit/(loss)	12	(8)	0
Reversionary property interests | Debt securities in issue
Disclosure Of Financial Assets And Liabilities [Line Items]
FVTPL assets	49	70
Derivative assets and other Level 3 assets, fair value movements recognised in profit/(loss)	(3)	0	5
Roll-up mortgage portfolio | Total loans and advances to customers
Disclosure Of Financial Assets And Liabilities [Line Items]
FVTPL assets	24	28
Derivative assets and other Level 3 assets, fair value movements recognised in profit/(loss)	(2)	(18)	(5)
Other loans | Total loans and advances to customers
Disclosure Of Financial Assets And Liabilities [Line Items]
FVTPL assets	22	17
Derivative assets and other Level 3 assets, fair value movements recognised in profit/(loss)	4	(4)	(2)
Unlisted equity shares | Equity securities
Disclosure Of Financial Assets And Liabilities [Line Items]
FVTPL assets	30	10
Derivative assets and other Level 3 assets, fair value movements recognised in profit/(loss)	£ 27	£ (10)	£ 1

Financial Instruments - Summa_2

Financial Instruments - Summary of Reconciliation of Fair Value Measurement in Level 3 of the Fair Value Hierarchy (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of fair value measurement of assets [line items]
Beginning balance	£ 292,243
Beginning balance	(277,532)
Transfers out	22	£ 0
Transfers in	(22)	0
Transfers out	(22)	0
Transfers out	22	0
Ending Balance	282,083	292,243
Ending Balance	(267,117)	(277,532)
Level 3 | Other financial assets at FVTPL
Disclosure of fair value measurement of assets [line items]
Beginning balance	127	235
Fair value movements	27	(28)
Foreign exchange and other movements	(7)	(2)
Purchases	1
Transfers out		0
Transfers out	0	(28)
Netting	(3)	(8)
Sales		(5)
Settlements	(20)	(37)
Ending Balance	125	127
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	20	(30)
Level 3 | Financial assets at FVOCI
Disclosure of fair value measurement of assets [line items]
Beginning balance	0	18
Fair value movements	0	0
Foreign exchange and other movements	0	0
Purchases	0
Transfers out		0
Transfers out	0	0
Netting	0	0
Sales		0
Settlements	0	(18)
Ending Balance	0	0
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	0	0
Level 3 | Financial assets at fair value
Disclosure of fair value measurement of assets [line items]
Beginning balance	181	309
Fair value movements	45	(23)
Foreign exchange and other movements	(7)	(2)
Purchases	1
Transfers out		0
Transfers out	(22)	(28)
Netting	(3)	(8)
Sales		(5)
Settlements	(34)	(62)
Ending Balance	161	181
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	38	(25)
Level 3 | Derivatives
Disclosure of fair value measurement of assets [line items]
Beginning balance	54	56
Fair value movements	18	5
Foreign exchange and other movements	0	0
Purchases	0
Transfers out		0
Transfers out	(22)	0
Netting	0	0
Sales		0
Settlements	(14)	(7)
Ending Balance	36	54
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	18	5
Derivatives | Level 3
Disclosure of fair value measurement of assets [line items]
Beginning balance	(12)	(32)
Fair value movements	(1)	2
Foreign exchange and other movements	0	0
Purchases	0
Transfers in		(2)
Transfers out	0	0
Netting	0	0
Sales		0
Settlements	3	20
Ending Balance	(10)	(12)
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	(1)	2
Other financial liabilities at FVTPL | Level 3
Disclosure of fair value measurement of assets [line items]
Beginning balance	(3)	(6)
Fair value movements	0	0
Foreign exchange and other movements	0	1
Purchases	0
Transfers in		0
Transfers out	0	0
Netting	0	0
Sales		0
Settlements	3	2
Ending Balance	0	(3)
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	0	1
Financial liabilities at fair value | Level 3
Disclosure of fair value measurement of assets [line items]
Beginning balance	(15)	(38)
Fair value movements	(1)	2
Foreign exchange and other movements	0	1
Purchases	0
Transfers in		(2)
Transfers out	0	0
Netting	0	0
Sales		0
Settlements	6	22
Ending Balance	(10)	(15)
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	£ (1)	£ 3

Financial Instruments - Discl_4

Financial Instruments - Disclosure of Effects of Changes in Significant Unobservable Assumptions to Reasonably Possible Alternatives Level Three (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£) index	Dec. 31, 2022 GBP (£) index
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assets at fair value	£ 10,555	£ 8,897
Liabilities at fair value	(1,790)	(1,811)
Equity and credit contracts
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assets at fair value	£ 35	£ 30
Assumption description	HPI Forward growth rate	HPI Forward growth rate
Shift	1%	1%
Favourable changes	£ 2	£ 4
Unfavourable changes	£ (2)	£ (4)
Equity and credit contracts | Reversionary property derivatives
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Shift	10%	10%
Favourable changes	£ 2	£ 4
Unfavourable changes	£ (4)	£ (4)
Equity and credit contracts | Minimum
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	(5.00%)	(5.00%)
Equity and credit contracts | Maximum
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	5%	5%
Equity and credit contracts | Weighted average
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	(0.20%)	0.53%
Equity and credit contracts | Weighted average | Reversionary property derivatives
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
HPI spot rate index level | index	513	513
Total loans and advances to customers | Roll-up mortgage portfolio | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assets at fair value	£ 24	£ 28
Assumption description	HPI Forward growth rate	HPI Forward growth rate
Shift	1%	1%
Favourable changes	£ 0	£ 1
Unfavourable changes	0	(1)
Total loans and advances to customers | Other loans | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assets at fair value	£ 22	£ 17
Assumption description	Credit spreads	Credit spreads
Shift	20%	20%
Favourable changes	£ 0	£ 0
Unfavourable changes	£ 0	£ 0
Total loans and advances to customers | Minimum | Roll-up mortgage portfolio | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	(5.00%)	(5.00%)
Total loans and advances to customers | Minimum | Other loans | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	0.13%	0.19%
Total loans and advances to customers | Maximum | Roll-up mortgage portfolio | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	5%	5%
Total loans and advances to customers | Maximum | Other loans | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	2.54%	2.04%
Total loans and advances to customers | Weighted average | Roll-up mortgage portfolio | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	1.31%	1.39%
Total loans and advances to customers | Weighted average | Other loans | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	0.97%	0.98%
Debt securities in issue | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assets at fair value	£ 49	£ 70
Assumption description	HPI Forward growth rate	HPI Forward growth rate
Shift	1%	1%
Favourable changes	£ 0	£ 1
Unfavourable changes	£ 0	£ (1)
Debt securities in issue | Reversionary property securities | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Shift	10%	10%
Favourable changes	£ 2	£ 3
Unfavourable changes	£ (2)	£ (3)
Debt securities in issue | Minimum | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	(5.00%)	(5.00%)
Debt securities in issue | Maximum | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	5%	5%
Debt securities in issue | Weighted average | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	(0.20%)	0.53%
Debt securities in issue | Weighted average | Reversionary property securities | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
HPI spot rate index level | index	513	513
Equity securities
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Liabilities at fair value		£ (8)
Assumption description		HPI Forward growth rate
Shift		1%
Favourable changes		£ 1
Unfavourable changes		£ (1)
Equity securities | Property related options and forwards
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Shift		10%
Favourable changes		£ 2
Unfavourable changes		(3)
Equity securities | Unlisted equity shares | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assets at fair value	£ 30	£ 10
Assumption description	Contingent litigation risk	Contingent litigation risk
Shift	20%	20%
Favourable changes	£ 3	£ 7
Unfavourable changes	£ (3)	£ (7)
Equity securities | Minimum | Property related options and forwards
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value		(5.00%)
Equity securities | Minimum | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	0%	0%
Equity securities | Maximum | Property related options and forwards
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value		5%
Equity securities | Maximum | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	100%	100%
Equity securities | Weighted average
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value		(0.92%)
Equity securities | Weighted average | Property related options and forwards
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
HPI spot rate index level | index		491
Equity securities | Weighted average | Unlisted equity shares | Other financial assets at FVTPL
Effect Of Changes In Significant Unobservable Assumptions To Reasonably Possible Alternatives - Level 3 [Line Items]
Assumption value	39%	0.95%

Financial Instruments - Discl_5

Financial Instruments - Disclosure of Maturity Analysis of Undiscounted Cash Flows for Financial Liabilities and Off Balance Sheet Commitments (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Maturity Analysis For Financial Liabilities [Line Items]
Other financial liabilities at fair value through profit or loss	£ 899	£ 803
Deposits by customers	195,149	197,313
Deposits by banks	20,357	28,543
Repurchase agreements - non trading	8,411	7,982
Debt securities in issue	35,778	36,420
Subordinated liabilities	2,386	2,332
Lease liabilities	114	129
Undiscounted Cash Flow
Disclosure Of Maturity Analysis For Financial Liabilities [Line Items]
Derivative financial instruments	991	1,147
Other financial liabilities at fair value through profit or loss	1,073	978
Deposits by customers	195,537	197,443
Deposits by banks	21,890	29,814
Repurchase agreements - non trading	8,426	7,987
Debt securities in issue	41,640	38,685
Subordinated liabilities	3,456	3,275
Lease liabilities	128	142
Total financial liabilities	273,141	279,471
Off-balance sheet commitments given	31,439	31,858
Undiscounted Cash Flow | On demand
Disclosure Of Maturity Analysis For Financial Liabilities [Line Items]
Derivative financial instruments	1	0
Other financial liabilities at fair value through profit or loss	0	0
Deposits by customers	181,492	181,744
Deposits by banks	1,479	2,067
Repurchase agreements - non trading	0	0
Debt securities in issue	0	0
Subordinated liabilities	0	0
Lease liabilities	0	0
Total financial liabilities	182,972	183,811
Off-balance sheet commitments given	3,805	19,111
Undiscounted Cash Flow | Not later than 3 months
Disclosure Of Maturity Analysis For Financial Liabilities [Line Items]
Derivative financial instruments	221	224
Other financial liabilities at fair value through profit or loss	8	0
Deposits by customers	4,826	4,969
Deposits by banks	806	948
Repurchase agreements - non trading	8,418	7,984
Debt securities in issue	7,500	6,678
Subordinated liabilities	27	35
Lease liabilities	0	0
Total financial liabilities	21,806	20,838
Off-balance sheet commitments given	15,205	787
Undiscounted Cash Flow | Later than 3 months and not later than 1 year
Disclosure Of Maturity Analysis For Financial Liabilities [Line Items]
Derivative financial instruments	53	120
Other financial liabilities at fair value through profit or loss	7	98
Deposits by customers	5,987	7,927
Deposits by banks	1,518	659
Repurchase agreements - non trading	8	3
Debt securities in issue	3,835	2,101
Subordinated liabilities	83	691
Lease liabilities	30	32
Total financial liabilities	11,521	11,631
Off-balance sheet commitments given	1,408	898
Undiscounted Cash Flow | Later than 1 year and not later than 5 years
Disclosure Of Maturity Analysis For Financial Liabilities [Line Items]
Derivative financial instruments	480	501
Other financial liabilities at fair value through profit or loss	538	443
Deposits by customers	2,946	2,471
Deposits by banks	18,087	26,140
Repurchase agreements - non trading	0	0
Debt securities in issue	21,708	23,076
Subordinated liabilities	876	1,149
Lease liabilities	73	82
Total financial liabilities	44,708	53,862
Off-balance sheet commitments given	7,399	7,508
Undiscounted Cash Flow | Later than five years
Disclosure Of Maturity Analysis For Financial Liabilities [Line Items]
Derivative financial instruments	236	302
Other financial liabilities at fair value through profit or loss	520	437
Deposits by customers	286	332
Deposits by banks	0	0
Repurchase agreements - non trading	0	0
Debt securities in issue	8,597	6,830
Subordinated liabilities	2,470	1,400
Lease liabilities	25	28
Total financial liabilities	12,134	9,329
Off-balance sheet commitments given	£ 3,622	£ 3,554

Offsetting Financial Assets a_3

Offsetting Financial Assets and Liabilities (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Offsetting Of Financial Assets And Liabilities [Line Items]
Gross amounts, Assets	£ 24,659	£ 18,527
Amounts offset, Assets	(6,009)	(4,559)
Net amounts reported on the balance sheet, Assets	18,650	13,968
Financial instruments, Assets	(597)	(535)
Financial collateral, Assets	(13,353)	(9,059)
Net amount, Assets	4,700	4,374
Assets not subject to enforceable netting arrangements, Assets	207,728	220,764
Balance sheet total, Assets	226,378	234,732
Gross amounts, Liabilities	16,849	15,867
Amounts offset, Liabilities	(6,009)	(4,559)
Net amounts reported on the balance sheet, Liabilities	10,840	11,308
Financial instruments, Liabilities	(597)	(535)
Financial collateral, Liabilities	(8,519)	(8,131)
Net amount, Liabilities	1,724	2,642
Assets not subject to enforceable netting arrangements, Liabilities	213,968	223,538
Balance sheet total, Liabilities	224,808	234,846
Derivative financial assets
Disclosure Of Offsetting Of Financial Assets And Liabilities [Line Items]
Gross amounts, Assets	3,469	4,557
Amounts offset, Assets	(2,047)	(2,173)
Net amounts reported on the balance sheet, Assets	1,422	2,384
Financial instruments, Assets	(479)	(526)
Financial collateral, Assets	(823)	(1,720)
Net amount, Assets	120	138
Assets not subject to enforceable netting arrangements, Assets	50	55
Balance sheet total, Assets	1,472	2,439
Amortised cost
Disclosure Of Offsetting Of Financial Assets And Liabilities [Line Items]
Gross amounts, Assets	15,625	8,826
Amounts offset, Assets	(3,157)	(1,478)
Net amounts reported on the balance sheet, Assets	12,468	7,348
Financial instruments, Assets	(118)	(9)
Financial collateral, Assets	(12,350)	(7,339)
Net amount, Assets	0	0
Assets not subject to enforceable netting arrangements, Assets	0	0
Balance sheet total, Assets	12,468	7,348
Gross amounts, Liabilities	11,568	9,460
Amounts offset, Liabilities	(3,157)	(1,478)
Net amounts reported on the balance sheet, Liabilities	8,411	7,982
Financial instruments, Liabilities	(118)	(9)
Financial collateral, Liabilities	(8,293)	(7,973)
Net amount, Liabilities	0	0
Assets not subject to enforceable netting arrangements, Liabilities	0	0
Balance sheet total, Liabilities	8,411	7,982
Total loans and advances to customers
Disclosure Of Offsetting Of Financial Assets And Liabilities [Line Items]
Gross amounts, Assets	5,565	5,144
Amounts offset, Assets	(805)	(908)
Net amounts reported on the balance sheet, Assets	4,760	4,236
Financial instruments, Assets	0	0
Financial collateral, Assets	(180)	0
Net amount, Assets	4,580	4,236
Assets not subject to enforceable netting arrangements, Assets	207,678	220,709
Balance sheet total, Assets	212,438	224,945
Derivative financial liabilities
Disclosure Of Offsetting Of Financial Assets And Liabilities [Line Items]
Gross amounts, Liabilities	2,911	3,142
Amounts offset, Liabilities	(2,047)	(2,173)
Net amounts reported on the balance sheet, Liabilities	864	969
Financial instruments, Liabilities	(479)	(526)
Financial collateral, Liabilities	(226)	(158)
Net amount, Liabilities	159	285
Assets not subject to enforceable netting arrangements, Liabilities	27	39
Balance sheet total, Liabilities	891	1,008
Deposits by customers and banks
Disclosure Of Offsetting Of Financial Assets And Liabilities [Line Items]
Gross amounts, Liabilities	2,370	3,265
Amounts offset, Liabilities	(805)	(908)
Net amounts reported on the balance sheet, Liabilities	1,565	2,357
Financial instruments, Liabilities	0	0
Financial collateral, Liabilities	0	0
Net amount, Liabilities	1,565	2,357
Assets not subject to enforceable netting arrangements, Liabilities	213,941	223,499
Balance sheet total, Liabilities	£ 215,506	£ 225,856

Interest Rate Benchmark Refor_3

Interest Rate Benchmark Reform - Schedule of Amounts Affected by IBOR Reform (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets
Derivative financial instruments	£ 1,472	£ 2,439
Total assets	282,083	292,243
Liabilities
Derivative financial instruments	891	1,008
Total liabilities	267,117	277,532
Total
Assets
Derivative financial instruments		1,665
Financial assets at amortised cost	6	321
Total assets	6	1,986
Liabilities
Derivative financial instruments		1,912
Financial liabilities at amortised cost		2,491
Total liabilities		4,403
Off-balance sheet commitments given		2
GBP LIBOR
Assets
Derivative financial instruments		0
Financial assets at amortised cost	6	76
Total assets	6	76
Liabilities
Derivative financial instruments		66
Financial liabilities at amortised cost		0
Total liabilities		66
Off-balance sheet commitments given		2
USD LIBOR
Assets
Derivative financial instruments		1,665
Financial assets at amortised cost	0	245
Total assets	£ 0	1,910
Liabilities
Derivative financial instruments		1,846
Financial liabilities at amortised cost		2,491
Total liabilities		4,337
Off-balance sheet commitments given		£ 0

Discontinued Operations and A_3

Discontinued Operations and Assets Held for Sale - Disclosure of Financial Performance Relating to Discontinued Operations (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of analysis of single amount of discontinued operations [line items]
Net interest income	£ 4,667	£ 4,472	£ 3,997
Net fee and commission income	296	324	280
Other operating income	213	210	267
Total operating income	5,176	5,006	4,544
Operating expenses before credit impairment charges, provisions and charges	(2,485)	(2,370)	(2,540)
Credit impairment charges	(206)
Provisions for other liabilities and charges	(336)	(421)	(379)
Total operating credit impairment charges, provisions and charges	(542)	(742)	(146)
Profit from discontinued operations before tax	0	0	44
Tax on profit from discontinued operations	0	0	(12)
Profit from discontinued operations after tax	0	0	32
Discontinued operations
Disclosure of analysis of single amount of discontinued operations [line items]
Net interest income	0	0	33
Net fee and commission income	0	0	34
Other operating income	0	0	2
Total operating income	0	0	69
Operating expenses before credit impairment charges, provisions and charges	0	0	(32)
Credit impairment charges	0	0	11
Provisions for other liabilities and charges	0	0	(4)
Total operating credit impairment charges, provisions and charges	£ 0	£ 0	£ 7

Discontinued Operations and A_4

Discontinued Operations and Assets Held for Sale - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Discontinued Operations and Assets and Liabilities Held for Sale [Abstract]
Gain (loss) recognised on measurement to fair value less costs to sell or on disposal of assets or disposal groups constituting discontinued operation	£ 0	£ 0
Cash flows from (used in) operating activities, discontinued operations	£ 0	£ 0	£ 3,612

Discontinued Operations and A_5

Discontinued Operations and Assets Held for Sale - Disclosure of Assets and Liabilities Held for Sale (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Assets And Liabilities Classified As Held For Sale [Line Items]
Assets held for sale	£ 13	£ 49
Property, plant and equipment
Disclosure Of Assets And Liabilities Classified As Held For Sale [Line Items]
Assets held for sale	£ 13	£ 49

Events After the Balance Shee_3

Events After the Balance Sheet Date (Details)	12 Months Ended
	Dec. 31, 2023
Disclosure of non-adjusting events after reporting period [abstract]
Description of nature of non-adjusting event after reporting period	There have been no significant events between 31 December 2023 and the date of approval of these financial statements which would require a change to or additional disclosure in the financial statements.

Notes to the Balance Sheet (Det

Notes to the Balance Sheet (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of reclassifications or changes in presentation [line items]
Other assets	£ (2,029)	£ (2,004)
Other liabilities	(2,501)	(2,601)
Macro hedge of interest rate risk	(630)	(2,654)
Macro hedge of interest rate risk	£ 86	£ 95

Non-Controlling Interests - Sch

Non-Controlling Interests - Schedule of Amounts Attributable to Non-Controlling Interests (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Noncontrolling Interests [Line Items]
Notional amount	£ 225,608	£ 177,802

Non-Controlling Interests - Add

Non-Controlling Interests - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 GBP (£)
£750m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Noncontrolling Interests [Line Items]
Interest rate	0.0650
Capital securities issued	£ 750,000,000
- £750m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Noncontrolling Interests [Line Items]
Interest rate	0.0650
Capital securities issued	£ 750,000,000

Operating Expenses Before Cre_8

Operating Expenses Before Credit Impairment Charges, Provisions and Charges - Parent (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£) employee	Dec. 31, 2022 GBP (£) employee	Dec. 31, 2021 GBP (£)
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Wages and salaries	£ 854	£ 761	£ 759
Santander UK Group Holdings plc
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Wages and salaries	£ 7	£ 6
Number of full-time staff | employee	0	0

Other Financial Assets at Fai_7

Other Financial Assets at Fair Value Through Profit or Loss - Parent - Summary of Other Financial Assets at Fair Value Through Profit or Loss (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Debt securities	£ 602	£ 434
Debt securities
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Debt securities	168	16
Santander UK Group Holdings plc
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Debt securities	9,591	7,888
Santander UK Group Holdings plc | Debt securities
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Debt securities	£ 9,591	£ 7,888

Other Financial Assets at Fai_8

Other Financial Assets at Fair Value Through Profit or Loss - Parent - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Financial assets designated at FVTPL	£ 317	£ 312
Santander UK Group Holdings plc
Disclosure Of Financial Assets Designated As Measured At Fair Value Through Profit Or Loss [Line Items]
Financial assets designated at FVTPL	9,591	7,888
Debt securities issued during period for MREL requirements	£ 1,481	£ 3,991

Loans and Advances to Banks -_2

Loans and Advances to Banks - Parent (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Loans And Advances To Banks [Line Items]
Impairment losses on loans and advances to banks	£ 0	£ 0	£ 0
Santander UK Group Holdings plc
Net Loans And Advances To Banks [Line Items]
Impairment losses on loans and advances to banks	£ 0	£ 0

Other Financial Assets at Amo_5

Other Financial Assets at Amortised Cost - Parent (Details)	12 Months Ended
	Dec. 31, 2023
Santander UK Group Holdings plc | Later than ten years
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Investments maturity period	10 years

Interests in Other Entities -_3

Interests in Other Entities - Parent - Summary of Interest in Other Entities - Parent (Details) - Santander UK Group Holdings plc - GBP (£)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of subsidiaries [line items]
Interests in other entities	£ 13,640,000,000	£ 13,640,000,000
£500m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure of subsidiaries [line items]
Capital securities issued	500,000,000	500,000,000
Interests in other entities	495,000,000	495,000,000
£750m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure of subsidiaries [line items]
Capital securities issued	750,000,000	750,000,000
Interests in other entities	750,000,000	750,000,000
£500m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure of subsidiaries [line items]
Capital securities issued	500,000,000	500,000,000
Interests in other entities	210,000,000	210,000,000
£500m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure of subsidiaries [line items]
Capital securities issued	500,000,000	500,000,000
Interests in other entities	500,000,000	500,000,000
£450m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure of subsidiaries [line items]
Capital securities issued	450,000,000	450,000,000
Interests in other entities	50,000,000	50,000,000
Interests in ordinary shares of subsidiaries | Interests in ordinary shares of subsidiaries
Disclosure of subsidiaries [line items]
Interests in other entities	£ 11,635,000,000	£ 11,635,000,000

Interests in Other Entities -_4

Interests in Other Entities - Parent - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of subsidiaries [line items]
Ownership interest in share capital	100%
Impairment loss on investment	£ 206
Santander UK plc
Disclosure of subsidiaries [line items]
Impairment loss on investment	0	£ 0
Santander Financial Services plc
Disclosure of subsidiaries [line items]
Impairment loss on investment	£ 0	£ 0
Santander UK Group Holdings plc
Disclosure of subsidiaries [line items]
Ownership interest in share capital	100%

Interests in Other Entities -_5

Interests in Other Entities - Parent - Disclosure of Movements in Company's Interests in Subsidiaries - Parent (Details) - Santander UK Group Holdings plc £ in Millions, $ in Millions	Dec. 31, 2023 GBP (£)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 USD ($)
Disclosure of subsidiaries [line items]
Investments in subsidiaries	£ 11,635	£ 11,635
Cost
Disclosure of subsidiaries [line items]
Investments in subsidiaries	11,645		$ 11,645
Accumulated impairment
Disclosure of subsidiaries [line items]
Investments in subsidiaries	£ (10)	£ (10)

Interests in Other Entities - D

Interests in Other Entities - Disclosure of Key Assumptions in VIU Calculation (Details) - Santander UK Group Holdings plc - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of subsidiaries [line items]
Carrying value	£ 11,635	£ 11,635
Santander UK plc
Disclosure of subsidiaries [line items]
Carrying value	£ 11,268	£ 11,268
Discount rate	16.70%	16.90%
Growth rate beyond initial cash flow projections	1.60%	1.60%
Santander Financial Services plc
Disclosure of subsidiaries [line items]
Carrying value	£ 337	£ 337
Discount rate	17.90%	16.70%
Growth rate beyond initial cash flow projections	1.60%	1.60%
Other
Disclosure of subsidiaries [line items]
Carrying value	£ 30	£ 30

Interests in Other Entities -_6

Interests in Other Entities - Disclosure of Key Assumptions in Calculating VIU for Investments (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of subsidiaries [line items]
Value in use estimate, impairment increase sensitivity for GDP growth rate adjustment	£ (19)	£ (31)
Santander UK Group Holdings plc | Santander UK plc
Disclosure of subsidiaries [line items]
Decrease in cash flows projections	10%	5%
Increase in discount rate	1%	1%
Decrease in GDP growth rate	0.10%	0.10%
Value in use estimate, impairment increase sensitivity for cash flows adjustment	£ (1,261)	£ (773)
Value in use estimate, impairment increase sensitivity for discount rate adjustment	(1,026)	(1,212)
Value in use estimate, impairment increase sensitivity for GDP growth rate adjustment	£ (24)	£ (42)
Santander UK Group Holdings plc | Santander Financial Services plc
Disclosure of subsidiaries [line items]
Decrease in cash flows projections	10%	5%
Increase in discount rate	1%	1%
Value in use estimate, impairment increase sensitivity for cash flows adjustment	£ (50)	£ (18)
Value in use estimate, impairment increase sensitivity for discount rate adjustment	£ (34)	£ (29)

Interests in Other Entities -_7

Interests in Other Entities - Disclosure of Sensitivity of VIU Changes to Current Assumptions to Achieve Nil Headroom (Details) - Santander UK Group Holdings plc - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure of subsidiaries [line items]
Carrying value	£ 11,635	£ 11,635
Santander UK plc
Disclosure of subsidiaries [line items]
Carrying value	11,268	11,268
Value in use	12,610	15,461
Headroom	£ 1,342	£ 4,193
Increase in discount rate	1.35%	4.50%
Decrease in cash flows	11%	27%
Santander Financial Services plc
Disclosure of subsidiaries [line items]
Carrying value	£ 337	£ 337
Value in use	497	359
Headroom	£ 160	£ 22
Increase in discount rate	7.20%	0.75%
Decrease in cash flows	32%	6%

Other Financial Liabilities a_7

Other Financial Liabilities at Fair Value Through Profit or Loss - Parent - Summary of Other Financial Liabilities at Fair Value Through Profit or Loss (Details) - Santander UK Group Holdings plc - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Financial liabilities designated at fair value	£ 9,591	£ 7,888
Medium-term notes
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Financial liabilities designated at fair value	£ 9,591	£ 7,888

Other Financial Liabilities a_8

Other Financial Liabilities at Fair Value Through Profit or Loss - Parent - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Accumulated increase (decrease) in fair value of financial liability, attributable to changes in credit risk of liability	£ (6)	£ 15	£ (10)
Difference between carrying amount of financial liability and amount contractually required to pay at maturity to holder of obligation	97	(138)
Santander UK Group Holdings plc
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Financial liabilities designated at fair value	9,591	7,888
Debt securities issued during period for MREL requirements	1,481	3,991
Accumulated increase (decrease) in fair value of financial liability, attributable to changes in credit risk of liability	0	0
Difference between carrying amount of financial liability and amount contractually required to pay at maturity to holder of obligation	£ 197	£ 755

Debt Securities in Issue - Pa_3

Debt Securities in Issue - Parent (Details) £ in Millions	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 EUR (€)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)
Debt Securities In Issue [Line Items]
Notional amount	£ 225,608		£ 177,802
Debt securities in issue	35,778		36,420
Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities in issue	13,524		15,533
– Euro 30bn Euro Medium Term Note Programme | Medium-term notes
Debt Securities In Issue [Line Items]
Notional amount | €		€ 30,000,000,000		€ 30,000,000,000
Debt securities in issue	5,619		6,435
– US SEC-registered Debt Programme - Santander UK Group Holdings plc | Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities in issue	6,130		7,083
Santander UK Group Holdings plc
Debt Securities In Issue [Line Items]
Debt securities in issue	1,911		4,898
Santander UK Group Holdings plc | Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities in issue	1,911		4,898
Santander UK Group Holdings plc | – Euro 30bn Euro Medium Term Note Programme | Medium-term notes
Debt Securities In Issue [Line Items]
Notional amount | €		€ 30,000,000,000		€ 30,000,000,000
Debt securities in issue	1,123		2,387
Santander UK Group Holdings plc | – US SEC-registered Debt Programme - Santander UK Group Holdings plc | Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities in issue	£ 788		£ 2,511

Subordinated Liabilities - Pa_3

Subordinated Liabilities - Parent (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Subordinated Liabilities [Line Items]
Subordinated liabilities	£ 2,386	£ 2,332
Santander UK Group Holdings plc
Disclosure Of Subordinated Liabilities [Line Items]
Subordinated liabilities	£ 1,633	£ 942
Santander UK Group Holdings plc | 4.75% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	4.75%	4.75%
Maturity	2025	2025
Subordinated liabilities	£ 326	£ 608
Santander UK Group Holdings plc | 5.625% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	5.625%	5.625%
Maturity	2045	2045
Subordinated liabilities	£ 222	£ 334
Santander UK Group Holdings plc | 8.296% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	8.296%	8.296%
Maturity	2033	2033
Subordinated liabilities	£ 767	£ 0
Santander UK Group Holdings plc | 7.869% Subordinated notes
Disclosure Of Subordinated Liabilities [Line Items]
Borrowings, interest rate	7.869%	7.869%
Maturity	2033	2033
Subordinated liabilities	£ 318	£ 0

Notes to Cash Flows - Parent -

Notes to Cash Flows - Parent - Summary of Changes in Liabilities Arising from Financing Activities (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	£ 41,077	£ 36,133	£ 48,576
Proceeds from issue of debt securities	5,347	8,667	2,847
Repayment of debt securities	(5,438)	(4,482)	(13,724)
Proceeds from issue of subordinated liabilities	1,050
Repayment of subordinated liabilities	(971)	(40)	(4)
Issue of other equity instruments		750	450
Repurchase of other equity instruments		(750)	(500)
Dividends paid	(1,671)	(1,173)	(1,506)
Liability-related other changes	(101)	(1,254)	(418)
Non-cash changes:
– Unrealised foreign exchange	(804)	2,083	(916)
– Other changes	2,033	1,169	1,353
Ending balance	40,474	41,077	36,133
Debt securities in issue
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	36,420	31,580	43,679
Proceeds from issue of debt securities	5,347	8,667	2,847
Repayment of debt securities	(5,438)	(4,482)	(13,724)
Liability-related other changes	(159)	(1,282)	(473)
Non-cash changes:
– Unrealised foreign exchange	(750)	1,893	(930)
– Other changes	358	44	181
Ending balance	35,778	36,420	31,580
Subordinated liabilities
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	2,332	2,228	2,556
Proceeds from issue of subordinated liabilities	1,050
Repayment of subordinated liabilities	(971)	(40)	(4)
Liability-related other changes	25	2	(4)
Non-cash changes:
– Unrealised foreign exchange	(54)	190	14
– Other changes	4	(47)	(334)
Ending balance	2,386	2,332	2,228
Other equity instruments
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	2,196	2,191	2,241
Issue of other equity instruments		750	450
Repurchase of other equity instruments		(750)	(500)
Liability-related other changes	0	5
Non-cash changes:
Ending balance	2,196	2,196	2,191
Dividends paid
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	0	0	0
Dividends paid	(1,671)	(1,173)	(1,506)
Non-cash changes:
– Other changes	1,671	1,173	1,506
Ending balance	0	0	0
Santander UK Group Holdings plc
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	15,924	13,232
Proceeds from issue of debt securities	1,528	3,889
Repayment of debt securities	(2,870)	(1,446)
Proceeds from issue of subordinated liabilities	1,050	0
Repayment of subordinated liabilities	(360)	0
Issue of other equity instruments	0	750
Repurchase of other equity instruments	0	(750)
Dividends paid	(1,671)	(1,156)
Liability-related other changes	565	(199)
Non-cash changes:
– Unrealised foreign exchange	(514)	442
– Other changes	1,679	1,162
Ending balance	15,331	15,924	13,232
Santander UK Group Holdings plc | Debt securities in issue
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	4,898	6,013
Repayment of debt securities	(2,870)	(1,446)
Liability-related other changes	(23)	(14)
Non-cash changes:
– Unrealised foreign exchange	(99)	339
– Other changes	5	6
Ending balance	1,911	4,898	6,013
Santander UK Group Holdings plc | Other liabilities at FVTPL
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	7,888	4,190
Proceeds from issue of debt securities	1,528	3,889
Liability-related other changes	558	(191)
Non-cash changes:
– Unrealised foreign exchange	(383)
Ending balance	9,591	7,888	4,190
Santander UK Group Holdings plc | Subordinated liabilities
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	942	838
Proceeds from issue of subordinated liabilities	1,050
Repayment of subordinated liabilities	(360)
Liability-related other changes	30	1
Non-cash changes:
– Unrealised foreign exchange	(32)	103
– Other changes	3
Ending balance	1,633	942	838
Santander UK Group Holdings plc | Other equity instruments
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	2,196	2,191
Issue of other equity instruments	0	750
Repurchase of other equity instruments	0	(750)
Liability-related other changes	0	5
Non-cash changes:
Ending balance	2,196	2,196	2,191
Santander UK Group Holdings plc | Dividends paid
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	0	0
Dividends paid	(1,671)	(1,156)
Non-cash changes:
– Other changes	1,671	1,156
Ending balance	£ 0	£ 0	£ 0

Notes to Cash Flows - Parent _2

Notes to Cash Flows - Parent - Additional Information (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Cash Flows Explanatory Notes [Line Items]
Interest received	£ 11,627	£ 6,618	£ 4,873
Interest paid	6,496	2,107	1,085
Dividends received	0	0	£ 0
Santander UK Group Holdings plc
Disclosure Of Cash Flows Explanatory Notes [Line Items]
Interest received	197	202
Interest paid	130	159
Dividends received	£ 1,685	£ 1,212

Related Party Transactions - _2

Related Party Transactions - Parent (Details) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	£ (223)	£ (1,000)	£ (291)
Interest, fees and other expenses paid	724	235	189
Amounts owed by related parties	5,415	5,605
Amounts payable, related party transactions	(3,282)	(2,983)
Loans and advances to banks	1,216	1,105
Santander UK Group Holdings plc
Disclosure of transactions between related parties [line items]
Dividend income	1,685	1,212	1,497
Loans and advances to banks	1,816	4,800
Ultimate parent
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	(12)	(863)	(210)
Interest, fees and other expenses paid	475	47	34
Amounts owed by related parties	903	1,423
Amounts payable, related party transactions	(2,250)	(1,732)
Subsidiaries
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	(28)	(60)	(47)
Interest, fees and other expenses paid	194	171	151
Amounts owed by related parties	26	31
Amounts payable, related party transactions	(251)	(278)
Santander UK Group Undertakings | Santander UK Group Holdings plc
Disclosure of transactions between related parties [line items]
Loans and advances to banks	1,772
Santander UK Group Holdings plc
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	(990)	(192)	0
Interest, fees and other expenses paid	43	656	0
Amounts owed by related parties	15,004	15,597
Amounts payable, related party transactions	(1,092)	(3)
Santander UK Group Holdings plc | Ultimate parent
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	0	0	0
Interest, fees and other expenses paid	36	0	0
Amounts owed by related parties	0	0
Amounts payable, related party transactions	(1,092)	0
Santander UK Group Holdings plc | Subsidiaries
Disclosure of transactions between related parties [line items]
Interest, fees and other income received	(990)	(192)	0
Interest, fees and other expenses paid	7	656	£ 0
Amounts owed by related parties	15,004	15,597
Amounts payable, related party transactions	£ 0	£ (3)

Interest Rate Benchmark Refor_4

Interest Rate Benchmark Reform - Parent (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of expected impact of initial application of new standards or interpretations [line items]
Total liabilities	£ 267,117	£ 277,532
USD LIBOR
Disclosure of expected impact of initial application of new standards or interpretations [line items]
Total liabilities		4,337
Santander UK Group Holdings plc
Disclosure of expected impact of initial application of new standards or interpretations [line items]
Total liabilities	£ 13,135	13,728
Santander UK Group Holdings plc | USD LIBOR
Disclosure of expected impact of initial application of new standards or interpretations [line items]
Total liabilities		£ 2,491