Santander Uk 6-K14 Aug 232023 Q2 Current report (foreign)Financial data

Company Profile

Cover Page

Cover Page	6 Months Ended
Cover Page	Jun. 30, 2023
Cover [Abstract]
Document Type	6-K
Entity Registrant Name	SANTANDER UK GROUP HOLDINGS PLC
Amendment Flag	false
Document Period End Date	Jun. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001649373
Current Fiscal Year End Date	--12-31

Condensed Consolidated Income S

Condensed Consolidated Income Statement - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Profit (loss) [abstract]
Interest and similar income	£ 5,454	£ 2,786
Interest expense and similar charges	(3,093)	(638)
Net interest income	2,361	2,148
Fee and commission income	400	376
Fee and commission expense	(252)	(210)
Net fee and commission income	148	166
Other operating income	149	101
Total operating income	2,658	2,415
Operating expenses before credit impairment charges, provisions and charges	(1,232)	(1,186)
Credit impairment charges	(105)	(118)
Provisions for other liabilities and charges	(148)	(118)
Total operating credit impairment charges, provisions and charges	(253)	(236)
Profit before tax	1,173	993
Tax on profit	(315)	(233)
Profit after tax	858	760
Attributable to:
Equity holders of the parent	858	743
Non-controlling interests	0	17
Profit after tax	£ 858	£ 760

Condensed Consolidated Statemen

Condensed Consolidated Statement of Comprehensive Income - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Statement of comprehensive income [abstract]
Profit after tax	£ 858	£ 760
Movement in fair value reserve (debt instruments):
- Change in fair value	(12)	(171)
- Income statement transfers	8	162
- Taxation	1	4
Other comprehensive income, fair value reserve (debt instruments)	(3)	(5)
Cash flow hedges:
- Effective portion of changes in fair value	(1,262)	729
- Income statement transfers	1,190	(1,807)
- Taxation	20	299
Other comprehensive income, cash flow hedges, total	(52)	(779)
Net other comprehensive expense that may be reclassified to profit or loss subsequently	(55)	(784)
Pension remeasurement:
- Change in fair value	(160)	326
- Taxation	45	(26)
Pension remeasurement, total	(115)	300
Own credit adjustment:
- Change in fair value	(7)	29
- Taxation	2	(9)
Own credit adjustment, total	(5)	20
Net other comprehensive (expense)/income that will not be reclassified to profit or loss subsequently	(120)	320
Total other comprehensive expense net of tax	(175)	(464)
Total comprehensive income	683	296
Attributable to:
Equity holders of the parent	683	279
Non-controlling interests	0	17
Total comprehensive income	£ 683	£ 296

Condensed Consolidated Balance

Condensed Consolidated Balance Sheet - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Assets
Cash and balances at central banks	£ 42,523	£ 46,635
Derivative financial instruments	2,592	2,439
Other financial assets at fair value through profit or loss	614	434
Loans and advances to customers	215,010	223,840
Loans and advances to banks	1,276	1,105
Reverse repurchase agreements - non trading	12,024	7,348
Other financial assets at amortised cost	152	156
Macro hedge of interest rate risk	(3,517)	(2,654)
Financial assets at fair value through other comprehensive income	7,072	6,024
Interests in other entities	222	252
Intangible assets	1,549	1,550
Property, plant and equipment	1,512	1,526
Current tax assets	548	484
Retirement benefit assets	999	1,051
Other assets	1,716	2,004
Assets held for sale	49	49
Total assets	284,341	292,243
Liabilities
Derivative financial instruments	1,570	1,008
Other financial liabilities at fair value through profit or loss	864	803
Deposits by customers	191,638	197,313
Deposits by banks	25,602	28,543
Repurchase agreements - non trading	9,853	7,982
Debt securities in issue	35,083	36,420
Subordinated liabilities	2,150	2,332
Macro hedge of interest rate risk	(67)	95
Other liabilities	2,267	2,601
Provisions	397	380
Deferred tax liabilities	46	30
Retirement benefit obligations	25	25
Total liabilities	269,428	277,532
Equity
Share capital	7,060	7,060
Other equity instruments	2,196	2,196
Retained earnings	6,820	6,563
Other reserves	(1,163)	(1,108)
Total equity	14,913	14,711
Total liabilities and equity	£ 284,341	£ 292,243

Condensed Consolidated Cash Flo

Condensed Consolidated Cash Flow Statement - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities
Profit before tax	£ 1,173	£ 993
Adjustments for:
Non-cash items included in profit:	1,407	698
Change in operating assets	8,163	(4,748)
Change in operating liabilities	(8,074)	(8,081)
Corporation taxes paid	(296)	(222)
Effects of exchange rate differences	(1,340)	1,703
Net cash flows from operating activities	1,033	(9,657)
Cash flows from investing activities
Purchase of property, plant and equipment and intangible assets	(241)	(264)
Proceeds from sale of property, plant and equipment and intangible assets	78	103
Purchase of financial assets at amortised cost and financial assets at FVOCI	(3,417)	(1,146)
Proceeds from sale and redemption of financial assets at amortised cost and financial assets at FVOCI	2,088	2,421
Net cash flows from investing activities	(1,492)	1,114
Cash flows from financing activities
Issue of other equity instruments	0	750
Issue of debt securities and subordinated notes	3,353	5,352
Issuance costs of debt securities and subordinated notes	(10)	(10)
Repayment of debt securities and subordinated notes	(3,097)	(3,138)
Disposal of non-controlling interests	0	(235)
Repurchase of other equity instruments	0	(750)
Dividends paid on ordinary shares	(414)	(397)
Dividends paid on other equity instruments	(67)	(76)
Dividends paid on non-controlling interests	0	(17)
Principal elements of lease payments	(35)	(33)
Net cash flows from financing activities	(270)	1,446
Change in cash and cash equivalents	(729)	(7,097)
Cash and cash equivalents at beginning of the period	48,945	51,787
Effects of exchange rate changes on cash and cash equivalents	(199)	38
Cash and cash equivalents at the end of the period	48,017	44,728
Cash and cash equivalents consist of:
Cash and balances at central banks	42,523	45,172
Less: restricted balances	(2,095)	(2,154)
Cash and bank balances at central banks less regulatory minimum cash balances	40,428	43,018
Other cash equivalents: Loans and advances to banks - Non trading	940	829
Other cash equivalents: Reverse repurchase agreements	6,649	881
Cash and cash equivalents at the end of the period	£ 48,017	£ 44,728

Condensed Consolidated Statem_2

Condensed 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, 2021	£ 16,378	£ 16,143	£ 7,060	£ 2,191	£ 26	£ 110	£ 2	£ 6,754	£ 235
Profit after tax	760	743						743	17
Other comprehensive (expense), net of tax:
- Fair value reserve (debt instruments)	(5)	(5)			(5)
- Cash flow hedges	(779)	(779)				(779)
- Pension remeasurement	300	300						300
- Own credit adjustment	20	20						20
Total comprehensive income	296	279			(5)	(779)		1,063	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	(397)	(397)						(397)
Dividends on other equity instruments	(76)	(76)						(76)
Dividends on non-controlling interests	(17)								(17)
Ending balance at Jun. 30, 2022	15,949	15,949	7,060	2,196	21	(669)	2	7,339	0
Beginning balance at Dec. 31, 2022	14,711	14,711	7,060	2,196	6	(1,116)	2	6,563	0
Profit after tax	858	858						858
Other comprehensive (expense), net of tax:
- Fair value reserve (debt instruments)	(3)	(3)			(3)
- Cash flow hedges	(52)	(52)				(52)
- Pension remeasurement	(115)	(115)						(115)
- Own credit adjustment	(5)	(5)						(5)
Total comprehensive income	683	683			(3)	(52)		738	0
Dividends on ordinary shares	(414)	(414)						(414)
Dividends on other equity instruments	(67)	(67)						(67)
Ending balance at Jun. 30, 2023	£ 14,913	£ 14,913	£ 7,060	£ 2,196	£ 3	£ (1,168)	£ 2	£ 6,820	£ 0

Accounting Policies

Accounting Policies	6 Months Ended
Accounting Policies	Jun. 30, 2023
Disclosure Of Significant Accounting Policies [Abstract]
Accounting Policies	1. ACCOUNTING POLICIES The financial information in these Condensed Consolidated Interim Financial Statements is unaudited and does not constitute statutory accounts as defined in section 434 of the UK Companies Act 2006. Statutory accounts for the year ended 31 December 2022 have been delivered to the Registrar of Companies. The Condensed Consolidated Interim Financial Statements reflect all adjustments that, in the opinion of management, are necessary for a fair statement of the results of operations for the interim period. All such adjustments to the financial information are of a normal, recurring nature. Because the results from common banking activities are so closely related and responsive to changes in market conditions, the results for any interim period are not necessarily indicative of the results that can be expected for the year. The Condensed Consolidated Interim Financial Statements have been prepared in accordance with International Accounting Standard IAS 34 ‘Interim Financial Reporting', as issued by the International Accounting Standards Board (IASB) and adopted in the UK, and the Disclosure Guidance and Transparency Rules sourcebook of the UK's Financial Conduct Authority (FCA). They do not include all the information and disclosures normally required for full annual financial statements and should be read in conjunction with the Consolidated Financial Statements of Santander UK Group Holdings plc (the Company) and its subsidiaries (collectively Santander UK or the Santander UK group) for the year ended 31 December 2022 which were prepared in accordance with UK-adopted International Accounting Standards (IAS). Those consolidated financial statements were also prepared in accordance with IFRSs as issued by the IASB, including interpretations issued by the IFRS Interpretations Committee, as there were no applicable differences from IFRSs as issued by the IASB for the periods presented. The same accounting policies, presentation and methods of computation are followed in these Condensed Consolidated Interim Financial Statements as were applied in the presentation of the Santander UK group’s 2022 Annual Report. Going concern In light of geopolitical and economic uncertainty, the Directors updated their going concern assessment in preparing these Condensed Consolidated Interim Financial Statements. In making their going concern assessment, the Directors considered a wide range of information that included Santander UK's long term business and strategic plans, forecasts and projections, estimated capital, funding and liquidity requirements, contingent liabilities and the reasonably possible changes in trading performance arising from potential economic, market and product developments. After making enquiries, the Directors have a reasonable expectation that Santander UK has adequate resources to continue in operational existence for at least twelve months from the date of this report and, therefore, having reassessed the principal risks and uncertainties, the Directors consider it appropriate for the Condensed Consolidated Interim Financial Statements to be prepared on a going concern basis. Critical judgements and accounting estimates The preparation of the Condensed Consolidated Interim 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. 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 in the 2022 Annual Report. 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 21 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, and Plevin related litigation. Note 23 provides disclosure relating to ongoing factual issues and reviews that could impact the timing and amount of any outflows. Note 23 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. 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 21 and 23. 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 22. Sensitivity of defined benefit pension scheme estimates For detailed disclosures, see ‘Actuarial assumption sensitivities’ in Note 22. 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. Key judgements: – Determining the basis of goodwill impairment testing methodology, including the need for planning assumptions and internal capital allocations – Identifying the indicators of potential impairment 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 For more on each of these key judgements and estimates, see Note 13. Sensitivity of goodwill

Segments

Segments	6 Months Ended
Segments	Jun. 30, 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. Results by segment For the Half Year to Retail Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 30 June 2023 £m £m £m £m £m Net interest income 1,873 79 405 4 2,361 Non-interest income 85 100 67 45 297 Total operating income 1,958 179 472 49 2,658 Operating expenses before credit impairment charges, provisions and charges (912) (73) (170) (77) (1,232) Credit impairment charges (55) (14) (36) — (105) Provisions for other liabilities and charges (106) (3) 4 (43) (148) Total operating credit impairment charges, provisions and charges (161) (17) (32) (43) (253) Profit/(loss) before tax 885 89 270 (71) 1,173 Revenue from external customers 1,884 313 364 97 2,658 Inter-segment revenue/(expense) 74 (134) 108 (48) — Total operating income 1,958 179 472 49 2,658 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 227 — 31 — 258 – Insurance, protection and investments 24 — — — 24 – Credit cards 49 — — — 49 – Non-banking and other fees (2) 1 12 53 3 69 Total fee and commission income 301 12 84 3 400 Fee and commission expense (218) (3) (26) (5) (252) Net fee and commission income/(expense) 83 9 58 (2) 148 Customer loans 185,904 5,319 18,367 1,209 210,799 Total assets (3) 193,145 10,541 18,367 62,288 284,341 Of which assets held for sale — — — 49 49 Customer deposits 155,692 — 23,525 11,520 190,737 Total liabilities 155,799 1,683 23,562 88,384 269,428 (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) Includes customer loans, net of credit impairment charge allowances. Retail Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 30 June 2022 £m £m £m £m £m Net interest income 1,792 92 241 23 2,148 Non-interest income/(expense) 107 101 70 (11) 267 Total operating income 1,899 193 311 12 2,415 Operating expenses before credit impairment (charges)/write-backs, provisions and charges (832) (73) (181) (100) (1,186) Credit impairment (charges)/write-backs (126) (13) 20 1 (118) Provisions for other liabilities and charges (101) — (2) (15) (118) Total operating credit impairment (charges)/write-backs, provisions and charges (227) (13) 18 (14) (236) Profit/(loss) before tax 840 107 148 (102) 993 Revenue/(expense) from external customers 2,049 243 345 (222) 2,415 Inter-segment revenue/(expense) (150) (50) (34) 234 — Total operating income/(expense) 1,899 193 311 12 2,415 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 218 — 29 — 247 – Insurance, protection and investments 31 — — — 31 – Credit cards 46 — — — 46 – Non-banking and other fees (2) 4 8 36 4 52 Total fee and commission income 299 8 65 4 376 Fee and commission expense (193) — (11) (6) (210) Net fee/(expense) and commission income 106 8 54 (2) 166 31 December 2022 Customer loans 194,661 5,384 18,518 1,141 219,704 Total assets (3) 203,697 10,371 18,518 59,657 292,243 Of which assets held for sale — — — 49 49 Customer deposits 161,748 — 24,798 9,930 196,476 Total liabilities 161,821 1,223 24,473 90,015 277,532 (2) Non-banking and other fees include mortgages (except mortgage account fees), consumer finance, commitment commission, asset finance, invoice finance and trade finance. (3) Includes customer loans, net of credit impairment charge allowances..

Operating Expenses Before Credi

Operating Expenses Before Credit Impairment Charges, Provisions and Charges	6 Months Ended
	Jun. 30, 2023
Expenses by nature [abstract]
Operating Expenses Before Credit Impairment Charges, Provisions and Charges	3. OPERATING EXPENSES BEFORE CREDIT IMPAIRMENT CHARGES, PROVISIONS AND CHARGES For the Half Year to 30 June 2023 30 June 2022 £m £m Staff costs 621 567 Other administration expenses 476 461 Depreciation, amortisation and impairment 135 158 1,232 1,186 In H123, 'Depreciation, amortisation and impairment' included an impairment charge of £2m ( H122 : £10m) associated with branch and head office site closures as part of the transformation programme. For more, see Note 14.

Credit Impairment Charges and P

Credit Impairment Charges and Provisions	6 Months Ended
Credit Impairment Charges and Provisions	Jun. 30, 2023
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Credit Impairment Charges and Provisions	4. CREDIT IMPAIRMENT CHARGES AND PROVISIONS For the Half Year to 30 June 2023 30 June 2022 £m £m Credit impairment charges/(write-backs): Loans and advances to customers 98 114 Recoveries of loans and advances, net of collection costs 4 (6) Off-balance sheet credit exposures (See Note 21) 3 10 105 118 Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 21) 149 121 Releases for residual value and voluntary termination (1) (3) 148 118 253 236 In H123 and H122 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	6 Months Ended
Taxation	Jun. 30, 2023
Major components of tax expense (income) [abstract]
Taxation	5. TAXATION The Santander UK group’s effective tax rate for H123 was 26.9% (H122: 23.5%). The tax on profit before tax differs from the theoretical amount that would arise using the basic corporation tax rate as follows: For the Half Year to 30 June 2023 30 June 2022 £m £m Profit before tax 1,173 993 Tax calculated at a tax rate of 23.5% (H122:19%) 276 189 Bank surcharge on profits 45 70 Non-deductible preference dividends paid 5 5 Non-deductible UK Bank Levy 9 8 Non-deductible conduct remediation, fines and penalties 4 (1) Other non-deductible costs and non-taxable income (4) 6 Effect of change in tax rate on deferred tax provision — (22) Tax relief on dividends in respect of other equity instruments (20) (22) Tax charge 315 233 Interim period corporation tax is accrued based on the estimated average annual effective corporation tax for the year of 26.9% (H122: 25.7% before including the impact of the reduction in the bank surcharge substantively enacted in Q1 2022). See Note 9 to the Consolidated Financial Statements in the 2022 Annual Report for further details of changes in tax rates. On 20 June 2023, Finance (No.2) Act 2023 was substantively enacted in the UK, introducing a global minimum effective tax rate of 15%. The legislation implements a domestic top-up tax and a multinational top-up tax, effective for accounting periods starting on or after 31 December 2023.

Dividends on Ordinary Shares

Dividends on Ordinary Shares	6 Months Ended
Dividends on Ordinary Shares	Jun. 30, 2023
Dividends On Ordinary Shares [Abstract]
Dividends on Ordinary Shares	6. DIVIDENDS ON ORDINARY SHARES An int erim dividend of £414m was declared on the Company’s ordinary shares in issue (H122: £397m).

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
Derivative Financial Instruments	Jun. 30, 2023
Disclosure of nature and extent of risks arising from financial instruments [abstract]
Derivative Financial Instruments	7. DERIVATIVE FINANCIAL INSTRUMENTS The table below includes the notional amounts of transactions outstanding at the balance sheet date; they do not represent actual exposures. 30 June 2023 31 December 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 10,100 125 141 14,769 320 299 Interest rate contracts 29,513 697 842 31,599 473 792 Equity and credit contracts 910 145 21 954 142 25 Total derivatives held for trading 40,523 967 1,004 47,322 935 1,116 Derivatives held for hedging Designated as fair value hedges: Exchange rate contracts 742 4 7 538 12 4 Interest rate contracts 102,684 2,379 593 77,885 1,776 411 103,426 2,383 600 78,423 1,788 415 Designated as cash flow hedges: Exchange rate contracts 27,400 1,317 298 26,035 1,717 186 Interest rate contracts 38,821 168 1,930 25,971 164 1,463 Equity derivative contracts 52 19 — 51 8 1 66,273 1,504 2,228 52,057 1,889 1,650 Total derivatives held for hedging 169,699 3,887 2,828 130,480 3,677 2,065 Derivative netting (1) — (2,262) (2,262) — (2,173) (2,173) Total derivatives 210,222 2,592 1,570 177,802 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 £1,607m (2022: £1,368m) and the amount of cash collateral paid that had been offset against the gross derivative liabilities was £54m (2022: £70m). At 30 June 2023, the fair value of derivative assets included amounts due from Banco Santander group entities of £1,281m (2022: £1,346m) and the fair value of derivative liabilities included amounts due to Banco Santander group entities of £241m (2022: £246m). IBOR Reform Note 28 includes details of the notional value of hedging instruments by benchmark interest rate impacted by IBOR reform and the notional amounts of assets, liabilities and off-balance sheet commitments affected by IBOR reform that have yet to transition to an alternative benchmark interest rate.

Other Financial Assets at Fair

Other Financial Assets at Fair Value Through Profit or Loss	6 Months Ended
Other Financial Assets at Fair Value Through Profit or Loss	Jun. 30, 2023
Financial assets at fair value through profit or loss [abstract]
Other Financial Assets at Fair Value Through Profit or Loss	8. OTHER FINANCIAL ASSETS AT FAIR VALUE THROUGH PROFIT OR LOSS 30 June 2023 31 December 2022 £m £m Loans and advances to customers 322 339 Debt securities 219 85 Equity securities 73 10 614 434 In June 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.

Loans and Advances to Customers

Loans and Advances to Customers	6 Months Ended
Loans and Advances to Customers	Jun. 30, 2023
Net Loans And Advances To Customers [Abstract]
Loans and Advances to Customers	9. LOANS AND ADVANCES TO CUSTOMERS 30 June 2023 31 December 2022 £m £m Loans and advances to customers 215,973 224,795 Credit impairment loss allowances on loans and advances to customers (942) (933) Residual value and voluntary termination provisions on finance leases (21) (22) Net loans and advances to customers 215,010 223,840 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.

Securitisations and Covered Bon

Securitisations and Covered Bonds	6 Months Ended
Securitisations and Covered Bonds	Jun. 30, 2023
Disclosure Of Securitisations And Covered Bonds [Abstract]
Securitisations and Covered Bonds	10. 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. 30 June 2023 31 December 2022 £m £m Mortgage-backed master trust structures: – Holmes 2,214 1,646 – Fosse 1,892 2,028 4,106 3,674 Other asset-backed securitisation structures: – Motor — 6 – Repton 750 — 750 6 Total securitisation programmes 4,856 3,680 Covered bond programme: – Euro 35bn Global Covered Bond Programme 20,790 21,304 Total securitisation and covered bond programmes 25,646 24,984 The following table sets out the internal and external issuances and redemptions in H123 and H122 for each securitisation and covered bond programme. Internal issuances External issuances Internal redemptions External redemptions H123 H122 H123 H122 H123 H122 H123 H122 £m £m £m £m £m £m £m £m Mortgage-backed master trust structures: – Holmes 118 — 750 — 30 42 142 114 – Fosse — — — — — 34 — 185 Other asset-backed securitisation structures: – Motor — — — — — — 7 21 – Repton — — 550 — — — — — Covered bond programme: – Euro 35bn Global Covered Bond Programme 1,100 — 1,500 4,182 5 — 1,017 827 1,218 — 2,800 4,182 35 76 1,166 1,147 During H123, the remaining asset-backed notes from the Motor securitisation structure were redeemed. In H123 Repton 2023-1 Limited borrowed £550m through an asset-backed variable funding note facility. Repayment of this will begin in 2025.

Reverse Repurchase Agreements -

Reverse Repurchase Agreements - Non Trading	6 Months Ended
Reverse Repurchase Agreements - Non Trading	Jun. 30, 2023
Disclosure Of Reserve Repurchase Agreements Non-Trading [Abstract]
Reverse Repurchase Agreements - Non Trading	11. REVERSE REPURCHASE AGREEMENTS – NON TRADING 30 June 2023 31 December 2022 £m £m Agreements with banks 1,253 885 Agreements with customers 10,771 6,463 12,024 7,348

Interests in Other Entities

Interests in Other Entities	6 Months Ended
Interests in Other Entities	Jun. 30, 2023
Investments accounted for using equity method [abstract]
Interests in Other Entities	12. INTERESTS IN OTHER ENTITIES There have been no significant changes to the Santander UK group's interests in subsidiaries, joint ventures and unconsolidated structured entities, as set out in Note 19 to the Consolidated Financial Statements in the 2022 Annual Report.

Intangible Assets

Intangible Assets	6 Months Ended
Intangible Assets	Jun. 30, 2023
Disclosure of detailed information about intangible assets [abstract]
Intangible Assets	13. INTANGIBLE ASSETS At 30 June 2023, intangible assets comprised goodwill of £1,199m (2022: £1,199m ) and computer software of £350m (2022: £351m). At 30 June 2023, a review was performed to identify any potential impairment indicators for goodwill. No indicators of impairment were identified and so a full impairment test was not performed for the half year. At 30 June 2023, there were no significant changes in key assumptions that gave rise to an indicator of impairment. Details of the sensitivity of value in use (VIU) changes to assumptions to achieve nil headroom are set out in Note 20 to the Consolidated Financial Statements in the 2022 Annual Report.

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
Property, Plant and Equipment	Jun. 30, 2023
Property, plant and equipment [abstract]
Property, Plant and Equipment	14. PROPERTY, PLANT AND EQUIPMENT 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 31 48 1 41 23 144 Disposals (63) (9) — (81) (22) (175) At 30 June 2023 861 870 80 682 273 2,766 Accumulated depreciation: At 1 January 2023 271 625 73 145 157 1,271 Charge for the period 9 32 — 33 10 84 Disposals (63) (8) — (30) — (101) At 30 June 2023 217 649 73 148 167 1,254 Carrying amount 644 221 7 534 106 1,512

Other Financial Liabilities at

Other Financial Liabilities at Fair Value Through Profit or Loss	6 Months Ended
	Jun. 30, 2023
Disclosure of financial liabilities [abstract]
Other Financial Liabilities at Fair Value Through Profit or Loss	15. OTHER FINANCIAL LIABILITIES AT FAIR VALUE THROUGH PROFIT OR LOSS 30 June 2023 31 December 2022 £m £m Structured Notes Programmes 370 375 Eurobonds 93 102 Structured deposits 401 321 Other — 5 864 803

Deposits by Customers

Deposits by Customers	6 Months Ended
Deposits by Customers	Jun. 30, 2023
Deposits from customers [abstract]
Deposits by Customers	16. DEPOSITS BY CUSTOMERS 30 June 2023 31 December 2022 £m £m Demand and time deposits (1) 190,534 196,160 Amounts due to fellow Banco Santander subsidiaries and joint ventures 1,104 1,153 191,638 197,313 (1) Includes capital amount guaranteed / protected equity index-linked deposits of £364m (2022: £408m).

Deposits by Banks

Deposits by Banks	6 Months Ended
Deposits by Banks	Jun. 30, 2023
Disclosure Of Deposits From Banks [Abstract]
Deposits by Banks	17. DEPOSITS BY BANKS 30 June 2023 31 December 2022 £m £m Items in the course of transmission 531 701 Deposits held as collateral 1,631 1,758 Other deposits (1) 23,440 26,084 25,602 28,543 (1) Includes drawdown from the TFSME of £21.0bn (2022: £25.0bn).

Repurchase Agreements - Non Tra

Repurchase Agreements - Non Trading	6 Months Ended
Repurchase Agreements - Non Trading	Jun. 30, 2023
Disclosure Of Repurchase Agreements [Abstract]
Repurchase Agreements - Non Trading	18. REPURCHASE AGREEMENTS – NON TRADING 30 June 2023 31 December 2022 £m £m Agreements with banks 406 50 Agreements with customers 9,447 7,932 9,853 7,982

Debt Securities in Issue

Debt Securities in Issue	6 Months Ended
Debt Securities in Issue	Jun. 30, 2023
Debt Securities In Issue [Abstract]
Debt Securities in Issue	19. DEBT SECURITIES IN ISSUE 30 June 2023 31 December 2022 £m £m Medium-term notes 14,182 15,533 Euro 35bn Global Covered Bond Programme 15,247 15,205 US$20bn Commercial Paper Programmes 1,591 1,851 Certificates of deposit 1,975 2,874 Credit linked notes — 60 Securitisation programmes 2,088 897 35,083 36,420

Subordinated Liabilities

Subordinated Liabilities	6 Months Ended
Subordinated Liabilities	Jun. 30, 2023
Subordinated liabilities [abstract]
Subordinated Liabilities	20. SUBORDINATED LIABILITIES 30 June 2023 31 December 2022 £m £m £325m Sterling preference shares 344 344 Undated subordinated liabilities 205 219 Dated subordinated liabilities 1,601 1,769 2,150 2,332 In H123, certain subordinated liabilities were repurchased as part of ongoing liability management exercises, resulting in a profit of £3m (H122: a loss of £1m).

Provisions

Provisions	6 Months Ended
Provisions	Jun. 30, 2023
Disclosure of other provisions [abstract]
Provisions	21. PROVISIONS 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 4) 30 14 — 4 3 34 90 175 Provisions released (See Note 4) (20) — — (1) — — (2) (23) Utilisation and other (10) (12) (4) (2) — (17) (90) (135) At 30 June 2023 90 138 — 48 77 39 5 397 An additional provision of £30m was recognised in H123, for a customer remediation exercise relating to our mortgage book. This remediation relates to the proposed refund of interest inconsistently charged on mortgage products for customers in Financial Support. A £30m provision was recognised in H123, relating to restructuring announced to employees in January 2023. In H123, other provisions included charges for operational risk provisions of £87m (H122: £78m), including fraud losses of £75m (H122: £63m).

Retirement Benefit Plans

Retirement Benefit Plans	6 Months Ended
Retirement Benefit Plans	Jun. 30, 2023
Disclosure of net defined benefit liability (asset) [abstract]
Retirement Benefit Plans	22. RETIREMENT BENEFIT PLANS The amounts recognised in the balance sheet were as follows: 30 June 2023 31 December 2022 £m £m Assets/(liabilities) Funded defined benefit pension scheme - surplus 999 1,051 Unfunded pension and post-retirement medical benefits (25) (25) Total net assets 974 1,026 An expense of £33m (H122: £30m) was recognised for defined contribution plans in the period and is included in staff costs within operating expenses (see Note 3). b) Defined benefit pension schemes The total amount released to the income statement was £16m (H122: charge of £4m ). The amounts recognised in other comprehensive income were as follows: 30 June 2023 30 June 2022 £m £m Return on plan assets (excluding amounts included in net interest expense) 470 3,352 Actuarial losses arising from experience adjustments 89 296 Actuarial gains arising from changes in financial assumptions (399) (3,974) Pension remeasurement 160 (326) The net assets recognised in the balance sheet were determined as follows: 30 June 2023 31 December 2022 £m £m Present value of defined benefit obligations (7,639) (7,937) Fair value of scheme assets 8,613 8,963 Net defined benefit assets 974 1,026 Actuarial assumptions The principal actuarial assumptions used for the Scheme were: 30 June 2023 31 December 2022 % % To determine benefit obligations (1) : – Discount rate for scheme liabilities 5.3 4.9 – General price inflation 3.1 3.1 – General salary increase 1.0 1.0 – Expected rate of pension increase 3.0 3.0 Years Years Longevity at 60 for current pensioners, on the valuation date: – Males 27.4 27.4 – Females 30.1 30.1 Longevity at 60 for future pensioners currently aged 40, on the valuation date: – Males 28.9 28.9 – Females 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 H123 was due to increased long-term index-linked gilt yields. 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. (Decrease)/increase 30 June 2023 31 December 2022 Assumption Change in pension obligation at period end from £m £m Discount rate 50bps increase (466) (501) General price inflation 50bps increase 341 374 Mortality Each additional year of longevity assumed 185 203

Contingent Liabilities and Comm

Contingent Liabilities and Commitments	6 Months Ended
Contingent Liabilities and Commitments	Jun. 30, 2023
Disclosure of contingent liabilities [abstract]
Contingent Liabilities and Commitments	23. CONTINGENT LIABILITIES AND COMMITMENTS 30 June 2023 31 December 2022 £m £m Guarantees given to third parties 436 448 Formal standby facilities, credit lines and other commitments 33,289 31,410 33,725 31,858 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 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 21 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 21 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 H123 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, the 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 possible to make a reliable assessment of the size of any related potential liability. Motor Finance Broker Commissions Following the FCA’s Motor Market review, Santander Consumer (UK) plc (SCUK) has received a number of county court claims and complaints in respect of its historical commission arrangements and is monitoring industry developments for potential liabilities for claims related to the use of discretionary commission models prior to the Motor Market review. It is possible that further claims and complaints may be received. 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 costs will be incurred in relation to existing or future county court claims, complaints and the CAT proceedings, the resolution of such matters is not possible to predict with any certainty. It is also not considered that a legal or constructive obligation has been incurred in relation to such matters that would require a provision to be recognised at this stage. In view of the inherent uncertainties, it is therefore also not possible to estimate the extent of any financial impact. Taxation The Santander UK group engages in discussion, and co-operates, with HM Revenue & Customs (HMRC) in their oversight of the Santander UK group’s tax matters. The Santander UK group adopted the UK’s Code of Practice on Taxation for Banks in 2010. 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. Following ring-fencing, the convertible preferred stock is now held by Santander Equity Investments Limited (SEIL), outside the ring-fenced bank. Conversion of the preferred stock into Class A Common Stock of Visa Inc. depends on the outcome of litigation against Visa involving UK & Ireland (UK&I) multilateral interchange fees (MIFs). In June 2020, the Supreme Court issued a judgement finding that MIFs restricted competition. 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.

Other Equity Instruments

Other Equity Instruments	6 Months Ended
Other Equity Instruments	Jun. 30, 2023
Disclosure of classes of share capital [abstract]
Other Equity Instruments	24. OTHER EQUITY INSTRUMENTS Interest rate 30 June 2023 31 December 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

Assets Charged as Security for

Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets	6 Months Ended
	Jun. 30, 2023
Disclosure Of Assets Pledged As Security [Abstract]
Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets	25. ASSETS CHARGED AS SECURITY FOR LIABILITIES AND COLLATERAL ACCEPTED AS SECURITY FOR ASSETS Securitisations and covered bonds As described in Note 14, to the Consolidated Financial Statements in the 2022 Annual Report and Note 10, Santander UK plc and certain of its subsidiaries issue securitisations and covered bonds. At 30 June 2023, there were £25,646m (2022: £24,984m) of gross assets in these secured programmes and £775m (2022: £829m) of these related to internally retained issuances that were available for use as collateral for liquidity purposes in the future. At 30 June 2023, £2,875m (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 30 June 2023 (2022: £500m), or for use as collateral for liquidity purposes in the future.

Related Party Disclosures

Related Party Disclosures	6 Months Ended
Related Party Disclosures	Jun. 30, 2023
Disclosure of transactions between related parties [abstract]
Related Party Disclosures	26. RELATED PARTY DISCLOSURES The financial position and performance of the Santander UK group were not materially affected in H123 by any related party transactions, or changes to related party transactions, other than as disclosed herein.

Financial Instruments

Financial Instruments	6 Months Ended
Financial Instruments	Jun. 30, 2023
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Abstract]
Financial Instruments	27. FINANCIAL INSTRUMENTS a) Measurement basis of financial assets and liabilities Disclosures relating to fair value measurement and hierarchy, valuation techniques and the control framework and related aspects pertaining to financial instruments at fair value are included in the 2022 Annual Report. Valuation, sensitivity methodologies and inputs at 30 June 2023 are consistent with those described in Note 39 to the Consolidated Financial Statements in the 2022 Annual Report. Details regarding fair value measurement under a valuation technique of groups of financial assets and liabilities with offsetting positions in market risks or credit risks, on the basis of net exposure using the exception under IFRS 13, can be found in Note 39(a) to the Consolidated Financial Statements in the 2022 Annual Report. b) 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 30 June 2023 and 31 December 2022. 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. Details of the valuation methodology of the financial assets and financial liabilities carried at amortised cost can be found in Note 39(d) to the Consolidated Financial Statements in the 2022 Annual Report. 30 June 2023 31 December 2022 Fair Carrying Fair Carrying value value value value £m £m £m £m Assets Loans and advances to customers 207,690 215,010 216,451 223,840 Loans and advances to banks 1,276 1,276 1,105 1,105 Reverse repurchase agreements - non trading 12,007 12,024 7,341 7,348 Other financial assets at amortised cost 138 152 144 156 221,111 228,462 225,041 232,449 Liabilities Deposits by customers 191,581 191,638 197,280 197,313 Deposits by banks 25,659 25,602 28,051 28,543 Repurchase agreements - non trading 9,853 9,853 7,982 7,982 Debt securities in issue 34,322 35,083 35,255 36,420 Subordinated liabilities 2,409 2,150 2,511 2,332 263,824 264,326 271,079 272,590 c) 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 30 June 2023 and 31 December 2022, analysed by their levels in the fair value hierarchy - Level 1, Level 2 and Level 3. 30 June 2023 31 December 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 — 1,446 — 1,446 — 2,049 — 2,049 A Interest rate contracts — 3,241 3 3,244 — 2,406 7 2,413 A & C Equity and credit contracts — 107 57 164 — 103 47 150 B & D Netting — (2,262) — (2,262) — (2,173) — (2,173) — 2,532 60 2,592 — 2,385 54 2,439 Other financial assets at FVTPL Loans and advances to customers — 280 42 322 — 294 45 339 A Debt securities — 159 60 219 — 13 72 85 A, B & D Equity securities — 46 27 73 — — 10 10 B — 485 129 614 — 307 127 434 Financial assets at FVOCI Debt securities 6,968 104 — 7,072 5,996 28 — 6,024 D 6,968 104 — 7,072 5,996 28 — 6,024 Total assets at fair value 6,968 3,121 189 10,278 5,996 2,720 181 8,897 Liabilities Derivative financial instruments Exchange rate contracts — 446 — 446 — 489 — 489 A Interest rate contracts — 3,365 — 3,365 — 2,662 4 2,666 A & C Equity and credit contracts — 12 9 21 — 18 8 26 B & D Netting — (2,262) — (2,262) — (2,173) — (2,173) — 1,561 9 1,570 — 996 12 1,008 Other financial liabilities at FVTPL Debt securities in issue — 463 — 463 — 477 3 480 A Structured deposits — 401 — 401 — 321 — 321 A Collateral and associated financial guarantees — — — — — 2 — 2 D — 864 — 864 — 800 3 803 Total liabilities at fair value — 2,425 9 2,434 — 1,796 15 1,811 Transfers between levels of the fair value hierarchy In H123 there were no significant (H122: no significant) transfers of financial instruments between levels of the fair value hierarchy. d) Valuation techniques The main valuation techniques employed in internal models to measure the fair value of the financial instruments are disclosed in Note 39(b) to the Consolidated Financial Statements in the 2022 Annual Report. Santander UK made a material change to the valuation of unlisted equity holdings in H123. For more details, see Note 8. e) 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: 30 June 2023 31 December 2022 £m £m Risk-related: - Bid-offer and trade specific adjustments (8) (12) - Uncertainty 21 27 - Credit risk adjustment (3) (1) - Funding fair value adjustment — 1 10 15 Day One profit (1) (1) 9 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. For more details, see ‘Risk-related adjustments’ in Note 39(f) to the Consolidated Financial Statements in the 2022 Annual Report. f) Internal models based on information other than market data (Level 3) Valuation techniques There have been no significant changes to the valuation techniques as set out in Note 39(g) to the Consolidated Financial Statements in the 2022 Annual Report. 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 H123: Assets Liabilities Derivatives Other financial assets at FVTPL Total Derivatives Other financial liabilities at FVTPL Total £m £m £m £m £m £m At 1 January 2023 54 127 181 (12) (3) (15) Total (losses)/gains recognised: Fair value movements (2) 14 62 76 (1) — (1) Foreign exchange and other movements — (6) (6) — — — Purchases — 1 1 — — — Transfers out — (46) (46) — — — Netting (1) — (2) (2) — — — Settlements (8) (7) (15) 4 3 7 At 30 June 2023 60 129 189 (9) — (9) Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period(2) 14 56 70 (1) — (1) (1) 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 to the Consolidated Financial Statements in the 2022 Annual Report (2) Fair value movements relating to derivatives and other financial assets at FVTPL are recognised in other operating income in the income statement. Effect of changes in significant unobservable assumptions to reasonably possible alternatives (Level 3) There has been no significant change to the unobservable inputs and sensitivities used in Level 3 fair values as set out in Note 39(g) to the Consolidated Financial Statements in the 2022 Annual Report.

Interest Rate Benchmark Reform

Interest Rate Benchmark Reform	6 Months Ended
Interest Rate Benchmark Reform	Jun. 30, 2023
Interest Rate Benchmark Reform [Abstract]
Interest Rate Benchmark Reform	28. INTEREST RATE BENCHMARK REFORM The following tables show the notional amounts of assets, liabilities and off-balance sheet commitments at 30 June 2023 and 31 December 2022 affected by IBOR reform that have yet to transition to an alternative benchmark interest rate as provided internally to key management personnel. 30 June 2023 GBP (2) LIBOR USD (2) LIBOR Total £m £m £m Assets Financial assets at amortised cost 7 1 8 7 1 8 Liabilities Derivatives (1) — 49 49 — 49 49 31 December 2022 Assets Derivatives (1) — 1,665 1,665 Financial assets at amortised cost 76 245 321 76 1,910 1,986 Liabilities Derivatives (1) 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 (1) Many of the Santander UK group's derivatives subject to IBOR reform are standard ISDA contracts and are subject to supplementary ISDA fallback provisions which became effective on 25 January 2021. (2) Settings for GBP, JPY & NOK LIBOR & 1-week and 2-month USD LIBOR ceased on 31 December 2021 and for EONIA on 3 January 2022. For certain legacy contracts, while 1-month, 3-month and 6-month settings for JPY LIBOR ceased on 31 December 2022 and 1-month and 6-month synthetic GBP LIBOR settings ceased on 31 March 2023, the 3-month synthetic GBP LIBOR setting has been extended until the end of March 2024. Overnight, and 12-month USD LIBOR settings ceased on 30 June 2023. For certain legacy contracts, 1-month, 3-month and 6-month synthetic USD LIBOR settings will cease on 30 September 2024. IBOR Reform The table below shows the notional amount of derivatives in hedging relationships directly affected by uncertainties related to IBOR reform. 30 June 2023 31 December 2022 USD Total USD Total £m £m £m £m Total notional value of hedging instruments – Cash flow hedges — — 2,906 2,906 – Fair value hedges — — 178 178 — — 3,084 3,084 Maturing after cessation date (1) – Cash flow hedges — — 2,906 2,906 – Fair value hedges — — 178 178 — — 3,084 3,084 (1) Overnight and 12-month USD LIBOR settings ceased on 30 June 2023. For certain legacy contracts, 1-month, 3-month and 6-month synthetic USD LIBOR settings will cease at the end of September 2024. For more details on interest rate benchmark reform and the Santander UK group’s transition from IBORs to alternative benchmark rates, see Note 41 to the Consolidated Financial Statements in the 2022 Annual Report.

Assets Held for Sale

Assets Held for Sale	6 Months Ended
Assets Held for Sale	Jun. 30, 2023
Discontinued Operations and Assets and Liabilities Held for Sale [Abstract]
Assets Held for Sale	29. ASSETS HELD FOR SALE Sale of property Management considered the sale of Santander House and Shenley Wood freehold land and buildings, part of an agreement with the developer for the construction of Unity Place, 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 H2 2023 with no gain or loss. At 30 June 2023, assets held for sale comprised: 30 June 2023 31 December 2022 £m £m Assets Property, plant and equipment 49 49 Total assets held for sale 49 49

Events After the Balance Sheet

Events After the Balance Sheet Date	6 Months Ended
Events After the Balance Sheet Date	Jun. 30, 2023
Disclosure of non-adjusting events after reporting period [abstract]
Events After the Balance Sheet Date	30. EVENTS AFTER THE BALANCE SHEET DATE There have been no significant events between 30 June 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 (Policies)

Accounting Policies (Policies)	6 Months Ended
Accounting Policies (Policies)	Jun. 30, 2023
Disclosure Of Significant Accounting Policies [Abstract]
Basis of preparation and accounting developments	The financial information in these Condensed Consolidated Interim Financial Statements is unaudited and does not constitute statutory accounts as defined in section 434 of the UK Companies Act 2006. Statutory accounts for the year ended 31 December 2022 have been delivered to the Registrar of Companies. The Condensed Consolidated Interim Financial Statements reflect all adjustments that, in the opinion of management, are necessary for a fair statement of the results of operations for the interim period. All such adjustments to the financial information are of a normal, recurring nature. Because the results from common banking activities are so closely related and responsive to changes in market conditions, the results for any interim period are not necessarily indicative of the results that can be expected for the year. The Condensed Consolidated Interim Financial Statements have been prepared in accordance with International Accounting Standard IAS 34 ‘Interim Financial Reporting', as issued by the International Accounting Standards Board (IASB) and adopted in the UK, and the Disclosure Guidance and Transparency Rules sourcebook of the UK's Financial Conduct Authority (FCA). They do not include all the information and disclosures normally required for full annual financial statements and should be read in conjunction with the Consolidated Financial Statements of Santander UK Group Holdings plc (the Company) and its subsidiaries (collectively Santander UK or the Santander UK group) for the year ended 31 December 2022 which were prepared in accordance with UK-adopted International Accounting Standards (IAS). Those consolidated financial statements were also prepared in accordance with IFRSs as issued by the IASB, including interpretations issued by the IFRS Interpretations Committee, as there were no applicable differences from IFRSs as issued by the IASB for the periods presented. The same accounting policies, presentation and methods of computation are followed in these Condensed Consolidated Interim Financial Statements as were applied in the presentation of the Santander UK group’s 2022 Annual Report.
Going concern	Going concern In light of geopolitical and economic uncertainty, the Directors updated their going concern assessment in preparing these Condensed Consolidated Interim Financial Statements. In making their going concern assessment, the Directors considered a wide range of information that included Santander UK's long term business and strategic plans, forecasts and projections, estimated capital, funding and liquidity requirements, contingent liabilities and the reasonably possible changes in trading performance arising from potential economic, market and product developments. After making enquiries, the Directors have a reasonable expectation that Santander UK has adequate resources to continue in operational existence for at least twelve months from the date of this report and, therefore, having reassessed the principal risks and uncertainties, the Directors consider it appropriate for the Condensed Consolidated Interim Financial Statements to be prepared on a going concern basis.
Critical judgements and accounting estimates	Critical judgements and accounting estimates The preparation of the Condensed Consolidated Interim 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. 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 in the 2022 Annual Report. 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 21 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, and Plevin related litigation. Note 23 provides disclosure relating to ongoing factual issues and reviews that could impact the timing and amount of any outflows. Note 23 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. 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 21 and 23. 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 22. Sensitivity of defined benefit pension scheme estimates For detailed disclosures, see ‘Actuarial assumption sensitivities’ in Note 22. 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. Key judgements: – Determining the basis of goodwill impairment testing methodology, including the need for planning assumptions and internal capital allocations – Identifying the indicators of potential impairment 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 For more on each of these key judgements and estimates, see Note 13. Sensitivity of goodwill

Accounting Policies (Tables)

Accounting Policies (Tables)	6 Months Ended
Accounting Policies (Tables)	Jun. 30, 2023
Disclosure Of Significant Accounting Policies [Abstract]
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 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 methodology, including the need for planning assumptions and internal capital allocations – Identifying the indicators of potential impairment 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)	6 Months Ended
Segments (Tables)	Jun. 30, 2023
Disclosure of operating segments [abstract]
Summary of Results by Segment	Results by segment For the Half Year to Retail Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 30 June 2023 £m £m £m £m £m Net interest income 1,873 79 405 4 2,361 Non-interest income 85 100 67 45 297 Total operating income 1,958 179 472 49 2,658 Operating expenses before credit impairment charges, provisions and charges (912) (73) (170) (77) (1,232) Credit impairment charges (55) (14) (36) — (105) Provisions for other liabilities and charges (106) (3) 4 (43) (148) Total operating credit impairment charges, provisions and charges (161) (17) (32) (43) (253) Profit/(loss) before tax 885 89 270 (71) 1,173 Revenue from external customers 1,884 313 364 97 2,658 Inter-segment revenue/(expense) 74 (134) 108 (48) — Total operating income 1,958 179 472 49 2,658 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 227 — 31 — 258 – Insurance, protection and investments 24 — — — 24 – Credit cards 49 — — — 49 – Non-banking and other fees (2) 1 12 53 3 69 Total fee and commission income 301 12 84 3 400 Fee and commission expense (218) (3) (26) (5) (252) Net fee and commission income/(expense) 83 9 58 (2) 148 Customer loans 185,904 5,319 18,367 1,209 210,799 Total assets (3) 193,145 10,541 18,367 62,288 284,341 Of which assets held for sale — — — 49 49 Customer deposits 155,692 — 23,525 11,520 190,737 Total liabilities 155,799 1,683 23,562 88,384 269,428 (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) Includes customer loans, net of credit impairment charge allowances. Retail Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 30 June 2022 £m £m £m £m £m Net interest income 1,792 92 241 23 2,148 Non-interest income/(expense) 107 101 70 (11) 267 Total operating income 1,899 193 311 12 2,415 Operating expenses before credit impairment (charges)/write-backs, provisions and charges (832) (73) (181) (100) (1,186) Credit impairment (charges)/write-backs (126) (13) 20 1 (118) Provisions for other liabilities and charges (101) — (2) (15) (118) Total operating credit impairment (charges)/write-backs, provisions and charges (227) (13) 18 (14) (236) Profit/(loss) before tax 840 107 148 (102) 993 Revenue/(expense) from external customers 2,049 243 345 (222) 2,415 Inter-segment revenue/(expense) (150) (50) (34) 234 — Total operating income/(expense) 1,899 193 311 12 2,415 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 218 — 29 — 247 – Insurance, protection and investments 31 — — — 31 – Credit cards 46 — — — 46 – Non-banking and other fees (2) 4 8 36 4 52 Total fee and commission income 299 8 65 4 376 Fee and commission expense (193) — (11) (6) (210) Net fee/(expense) and commission income 106 8 54 (2) 166 31 December 2022 Customer loans 194,661 5,384 18,518 1,141 219,704 Total assets (3) 203,697 10,371 18,518 59,657 292,243 Of which assets held for sale — — — 49 49 Customer deposits 161,748 — 24,798 9,930 196,476 Total liabilities 161,821 1,223 24,473 90,015 277,532 (2) Non-banking and other fees include mortgages (except mortgage account fees), consumer finance, commitment commission, asset finance, invoice finance and trade finance. (3) Includes customer loans, net of credit impairment charge allowances..

Operating Expenses Before Cre_2

Operating Expenses Before Credit Impairment Charges, Provisions and Charges (Tables)	6 Months Ended
	Jun. 30, 2023
Expenses by nature [abstract]
Summary of Operating Expenses Before Credit Impairment Losses, Provisions and Charges	For the Half Year to 30 June 2023 30 June 2022 £m £m Staff costs 621 567 Other administration expenses 476 461 Depreciation, amortisation and impairment 135 158 1,232 1,186

Credit Impairment Charges and_2

Credit Impairment Charges and Provisions (Tables)	6 Months Ended
Credit Impairment Charges and Provisions (Tables)	Jun. 30, 2023
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Summary of Impairment Losses and Provisions	30 June 2023 30 June 2022 £m £m Credit impairment charges/(write-backs): Loans and advances to customers 98 114 Recoveries of loans and advances, net of collection costs 4 (6) Off-balance sheet credit exposures (See Note 21) 3 10 105 118 Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 21) 149 121 Releases for residual value and voluntary termination (1) (3) 148 118 253 236

Taxation (Tables)

Taxation (Tables)	6 Months Ended
Taxation (Tables)	Jun. 30, 2023
Major components of tax expense (income) [abstract]
Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate	). The tax on profit before tax differs from the theoretical amount that would arise using the basic corporation tax rate as follows: For the Half Year to 30 June 2023 30 June 2022 £m £m Profit before tax 1,173 993 Tax calculated at a tax rate of 23.5% (H122:19%) 276 189 Bank surcharge on profits 45 70 Non-deductible preference dividends paid 5 5 Non-deductible UK Bank Levy 9 8 Non-deductible conduct remediation, fines and penalties 4 (1) Other non-deductible costs and non-taxable income (4) 6 Effect of change in tax rate on deferred tax provision — (22) Tax relief on dividends in respect of other equity instruments (20) (22) Tax charge 315 233

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	6 Months Ended
Derivative Financial Instruments (Tables)	Jun. 30, 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. 30 June 2023 31 December 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 10,100 125 141 14,769 320 299 Interest rate contracts 29,513 697 842 31,599 473 792 Equity and credit contracts 910 145 21 954 142 25 Total derivatives held for trading 40,523 967 1,004 47,322 935 1,116 Derivatives held for hedging Designated as fair value hedges: Exchange rate contracts 742 4 7 538 12 4 Interest rate contracts 102,684 2,379 593 77,885 1,776 411 103,426 2,383 600 78,423 1,788 415 Designated as cash flow hedges: Exchange rate contracts 27,400 1,317 298 26,035 1,717 186 Interest rate contracts 38,821 168 1,930 25,971 164 1,463 Equity derivative contracts 52 19 — 51 8 1 66,273 1,504 2,228 52,057 1,889 1,650 Total derivatives held for hedging 169,699 3,887 2,828 130,480 3,677 2,065 Derivative netting (1) — (2,262) (2,262) — (2,173) (2,173) Total derivatives 210,222 2,592 1,570 177,802 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 £1,607m (2022: £1,368m) and the amount of cash collateral paid that had been offset against the gross derivative liabilities was £54m (2022: £70m).

Other Financial Assets at Fai_2

Other Financial Assets at Fair Value Through Profit or Loss (Tables)	6 Months Ended
	Jun. 30, 2023
Financial assets at fair value through profit or loss [abstract]
Summary of Other Financial Assets at Fair Value Through Profit or Loss	30 June 2023 31 December 2022 £m £m Loans and advances to customers 322 339 Debt securities 219 85 Equity securities 73 10 614 434

Loans and Advances to Custome_2

Loans and Advances to Customers (Tables)	6 Months Ended
Loans and Advances to Customers (Tables)	Jun. 30, 2023
Net Loans And Advances To Customers [Abstract]
Summary of Net Loans and Advances to Customers	30 June 2023 31 December 2022 £m £m Loans and advances to customers 215,973 224,795 Credit impairment loss allowances on loans and advances to customers (942) (933) Residual value and voluntary termination provisions on finance leases (21) (22) Net loans and advances to customers 215,010 223,840

Securitisations and Covered B_2

Securitisations and Covered Bonds (Tables)	6 Months Ended
Securitisations and Covered Bonds (Tables)	Jun. 30, 2023
Disclosure Of Securitisations And Covered Bonds [Abstract]
Disclosure of Analysis of Securitisations and Covered Bonds	The gross assets securitised, or for the covered bond programme assigned at 30 June 2023 and 31 December 2022 were: 30 June 2023 31 December 2022 £m £m Mortgage-backed master trust structures: – Holmes 2,214 1,646 – Fosse 1,892 2,028 4,106 3,674 Other asset-backed securitisation structures: – Motor — 6 – Repton 750 — 750 6 Total securitisation programmes 4,856 3,680 Covered bond programme: – Euro 35bn Global Covered Bond Programme 20,790 21,304 Total securitisation and covered bond programmes 25,646 24,984
Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme	The following table sets out the internal and external issuances and redemptions in H123 and H122 for each securitisation and covered bond programme. Internal issuances External issuances Internal redemptions External redemptions H123 H122 H123 H122 H123 H122 H123 H122 £m £m £m £m £m £m £m £m Mortgage-backed master trust structures: – Holmes 118 — 750 — 30 42 142 114 – Fosse — — — — — 34 — 185 Other asset-backed securitisation structures: – Motor — — — — — — 7 21 – Repton — — 550 — — — — — Covered bond programme: – Euro 35bn Global Covered Bond Programme 1,100 — 1,500 4,182 5 — 1,017 827 1,218 — 2,800 4,182 35 76 1,166 1,147

Reverse Repurchase Agreements_2

Reverse Repurchase Agreements - Non Trading (Tables)	6 Months Ended
Reverse Repurchase Agreements - Non Trading (Tables)	Jun. 30, 2023
Disclosure Of Reserve Repurchase Agreements Non-Trading [Abstract]
Summary of Reverse Repurchase Agreements - Non Trading	30 June 2023 31 December 2022 £m £m Agreements with banks 1,253 885 Agreements with customers 10,771 6,463 12,024 7,348

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	6 Months Ended
Property, Plant and Equipment (Tables)	Jun. 30, 2023
Property, plant and equipment [abstract]
Disclosure of Detailed Information about Property, Plant and Equipment	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 31 48 1 41 23 144 Disposals (63) (9) — (81) (22) (175) At 30 June 2023 861 870 80 682 273 2,766 Accumulated depreciation: At 1 January 2023 271 625 73 145 157 1,271 Charge for the period 9 32 — 33 10 84 Disposals (63) (8) — (30) — (101) At 30 June 2023 217 649 73 148 167 1,254 Carrying amount 644 221 7 534 106 1,512

Other Financial Liabilities a_2

Other Financial Liabilities at Fair Value Through Profit or Loss (Tables)	6 Months Ended
	Jun. 30, 2023
Disclosure of financial liabilities [abstract]
Summary of Other Financial Liabilities at Fair Value Through Profit or Loss	30 June 2023 31 December 2022 £m £m Structured Notes Programmes 370 375 Eurobonds 93 102 Structured deposits 401 321 Other — 5 864 803

Deposits by Customers (Tables)

Deposits by Customers (Tables)	6 Months Ended
Deposits by Customers (Tables)	Jun. 30, 2023
Deposits from customers [abstract]
Schedule of Deposits by Customers	30 June 2023 31 December 2022 £m £m Demand and time deposits (1) 190,534 196,160 Amounts due to fellow Banco Santander subsidiaries and joint ventures 1,104 1,153 191,638 197,313 (1) Includes capital amount guaranteed / protected equity index-linked deposits of £364m (2022: £408m).

Deposits by Banks (Tables)

Deposits by Banks (Tables)	6 Months Ended
Deposits by Banks (Tables)	Jun. 30, 2023
Disclosure Of Deposits From Banks [Abstract]
Schedule of Deposits by Banks	30 June 2023 31 December 2022 £m £m Items in the course of transmission 531 701 Deposits held as collateral 1,631 1,758 Other deposits (1) 23,440 26,084 25,602 28,543 (1) Includes drawdown from the TFSME of £21.0bn (2022: £25.0bn).

Repurchase Agreements - Non T_2

Repurchase Agreements - Non Trading (Tables)	6 Months Ended
Repurchase Agreements - Non Trading (Tables)	Jun. 30, 2023
Disclosure Of Repurchase Agreements [Abstract]
Summary of Repurchase Agreements - Non Trading	30 June 2023 31 December 2022 £m £m Agreements with banks 406 50 Agreements with customers 9,447 7,932 9,853 7,982

Debt Securities in Issue (Table

Debt Securities in Issue (Tables)	6 Months Ended
Debt Securities in Issue (Tables)	Jun. 30, 2023
Debt Securities In Issue [Abstract]
Summary of Debt Securities in Issue	30 June 2023 31 December 2022 £m £m Medium-term notes 14,182 15,533 Euro 35bn Global Covered Bond Programme 15,247 15,205 US$20bn Commercial Paper Programmes 1,591 1,851 Certificates of deposit 1,975 2,874 Credit linked notes — 60 Securitisation programmes 2,088 897 35,083 36,420

Subordinated Liabilities (Table

Subordinated Liabilities (Tables)	6 Months Ended
Subordinated Liabilities (Tables)	Jun. 30, 2023
Subordinated liabilities [abstract]
Schedule of Subordinated Liabilities	30 June 2023 31 December 2022 £m £m £325m Sterling preference shares 344 344 Undated subordinated liabilities 205 219 Dated subordinated liabilities 1,601 1,769 2,150 2,332

Provisions (Tables)

Provisions (Tables)	6 Months Ended
Provisions (Tables)	Jun. 30, 2023
Disclosure of other provisions [abstract]
Summary of Provisions Reconciliation	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 4) 30 14 — 4 3 34 90 175 Provisions released (See Note 4) (20) — — (1) — — (2) (23) Utilisation and other (10) (12) (4) (2) — (17) (90) (135) At 30 June 2023 90 138 — 48 77 39 5 397

Retirement Benefit Plans (Table

Retirement Benefit Plans (Tables)	6 Months Ended
Retirement Benefit Plans (Tables)	Jun. 30, 2023
Disclosure of net defined benefit liability (asset) [abstract]
Summary of Retirement Benefit Plans	The amounts recognised in the balance sheet were as follows: 30 June 2023 31 December 2022 £m £m Assets/(liabilities) Funded defined benefit pension scheme - surplus 999 1,051 Unfunded pension and post-retirement medical benefits (25) (25) Total net assets 974 1,026
Summary of Amounts Recognised in Other Comprehensive Income	The amounts recognised in other comprehensive income were as follows: 30 June 2023 30 June 2022 £m £m Return on plan assets (excluding amounts included in net interest expense) 470 3,352 Actuarial losses arising from experience adjustments 89 296 Actuarial gains arising from changes in financial assumptions (399) (3,974) Pension remeasurement 160 (326)
Summary of Net Assets Recognised	The net assets recognised in the balance sheet were determined as follows: 30 June 2023 31 December 2022 £m £m Present value of defined benefit obligations (7,639) (7,937) Fair value of scheme assets 8,613 8,963 Net defined benefit assets 974 1,026
Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes	The principal actuarial assumptions used for the Scheme were: 30 June 2023 31 December 2022 % % To determine benefit obligations (1) : – Discount rate for scheme liabilities 5.3 4.9 – General price inflation 3.1 3.1 – General salary increase 1.0 1.0 – Expected rate of pension increase 3.0 3.0 Years Years Longevity at 60 for current pensioners, on the valuation date: – Males 27.4 27.4 – Females 30.1 30.1 Longevity at 60 for future pensioners currently aged 40, on the valuation date: – Males 28.9 28.9 – Females 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. (Decrease)/increase 30 June 2023 31 December 2022 Assumption Change in pension obligation at period end from £m £m Discount rate 50bps increase (466) (501) General price inflation 50bps increase 341 374 Mortality Each additional year of longevity assumed 185 203

Contingent Liabilities and Co_2

Contingent Liabilities and Commitments (Tables)	6 Months Ended
Contingent Liabilities and Commitments (Tables)	Jun. 30, 2023
Disclosure of contingent liabilities [abstract]
Summary of Contingent Liabilities and Commitments	30 June 2023 31 December 2022 £m £m Guarantees given to third parties 436 448 Formal standby facilities, credit lines and other commitments 33,289 31,410 33,725 31,858

Other Equity Instruments (Table

Other Equity Instruments (Tables)	6 Months Ended
Other Equity Instruments (Tables)	Jun. 30, 2023
Disclosure of classes of share capital [abstract]
Summary of Other Equity Instruments	Interest rate 30 June 2023 31 December 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

Financial Instruments (Tables)

Financial Instruments (Tables)	6 Months Ended
Financial Instruments (Tables)	Jun. 30, 2023
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Abstract]
Disclosure of Analysis of Fair Value of Financial Instruments Carried at Amortised Cost	The following tables analyse the fair value of the financial instruments carried at amortised cost at 30 June 2023 and 31 December 2022. 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. Details of the valuation methodology of the financial assets and financial liabilities carried at amortised cost can be found in Note 39(d) to the Consolidated Financial Statements in the 2022 Annual Report. 30 June 2023 31 December 2022 Fair Carrying Fair Carrying value value value value £m £m £m £m Assets Loans and advances to customers 207,690 215,010 216,451 223,840 Loans and advances to banks 1,276 1,276 1,105 1,105 Reverse repurchase agreements - non trading 12,007 12,024 7,341 7,348 Other financial assets at amortised cost 138 152 144 156 221,111 228,462 225,041 232,449 Liabilities Deposits by customers 191,581 191,638 197,280 197,313 Deposits by banks 25,659 25,602 28,051 28,543 Repurchase agreements - non trading 9,853 9,853 7,982 7,982 Debt securities in issue 34,322 35,083 35,255 36,420 Subordinated liabilities 2,409 2,150 2,511 2,332 263,824 264,326 271,079 272,590
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 30 June 2023 and 31 December 2022, analysed by their levels in the fair value hierarchy - Level 1, Level 2 and Level 3. 30 June 2023 31 December 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 — 1,446 — 1,446 — 2,049 — 2,049 A Interest rate contracts — 3,241 3 3,244 — 2,406 7 2,413 A & C Equity and credit contracts — 107 57 164 — 103 47 150 B & D Netting — (2,262) — (2,262) — (2,173) — (2,173) — 2,532 60 2,592 — 2,385 54 2,439 Other financial assets at FVTPL Loans and advances to customers — 280 42 322 — 294 45 339 A Debt securities — 159 60 219 — 13 72 85 A, B & D Equity securities — 46 27 73 — — 10 10 B — 485 129 614 — 307 127 434 Financial assets at FVOCI Debt securities 6,968 104 — 7,072 5,996 28 — 6,024 D 6,968 104 — 7,072 5,996 28 — 6,024 Total assets at fair value 6,968 3,121 189 10,278 5,996 2,720 181 8,897 Liabilities Derivative financial instruments Exchange rate contracts — 446 — 446 — 489 — 489 A Interest rate contracts — 3,365 — 3,365 — 2,662 4 2,666 A & C Equity and credit contracts — 12 9 21 — 18 8 26 B & D Netting — (2,262) — (2,262) — (2,173) — (2,173) — 1,561 9 1,570 — 996 12 1,008 Other financial liabilities at FVTPL Debt securities in issue — 463 — 463 — 477 3 480 A Structured deposits — 401 — 401 — 321 — 321 A Collateral and associated financial guarantees — — — — — 2 — 2 D — 864 — 864 — 800 3 803 Total liabilities at fair value — 2,425 9 2,434 — 1,796 15 1,811
Summary of Fair Value Adjustment	The fair value adjustments are set out in the following table: 30 June 2023 31 December 2022 £m £m Risk-related: - Bid-offer and trade specific adjustments (8) (12) - Uncertainty 21 27 - Credit risk adjustment (3) (1) - Funding fair value adjustment — 1 10 15 Day One profit (1) (1) 9 14
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 H123: Assets Liabilities Derivatives Other financial assets at FVTPL Total Derivatives Other financial liabilities at FVTPL Total £m £m £m £m £m £m At 1 January 2023 54 127 181 (12) (3) (15) Total (losses)/gains recognised: Fair value movements (2) 14 62 76 (1) — (1) Foreign exchange and other movements — (6) (6) — — — Purchases — 1 1 — — — Transfers out — (46) (46) — — — Netting (1) — (2) (2) — — — Settlements (8) (7) (15) 4 3 7 At 30 June 2023 60 129 189 (9) — (9) Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period(2) 14 56 70 (1) — (1) (1) 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 to the Consolidated Financial Statements in the 2022 Annual Report (2) Fair value movements relating to derivatives and other financial assets at FVTPL are recognised in other operating income in the income statement.

Interest Rate Benchmark Reform

Interest Rate Benchmark Reform (Tables)	6 Months Ended
Interest Rate Benchmark Reform (Tables)	Jun. 30, 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 30 June 2023 and 31 December 2022 affected by IBOR reform that have yet to transition to an alternative benchmark interest rate as provided internally to key management personnel. 30 June 2023 GBP (2) LIBOR USD (2) LIBOR Total £m £m £m Assets Financial assets at amortised cost 7 1 8 7 1 8 Liabilities Derivatives (1) — 49 49 — 49 49 31 December 2022 Assets Derivatives (1) — 1,665 1,665 Financial assets at amortised cost 76 245 321 76 1,910 1,986 Liabilities Derivatives (1) 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 (1) Many of the Santander UK group's derivatives subject to IBOR reform are standard ISDA contracts and are subject to supplementary ISDA fallback provisions which became effective on 25 January 2021. (2) Settings for GBP, JPY & NOK LIBOR & 1-week and 2-month USD LIBOR ceased on 31 December 2021 and for EONIA on 3 January 2022. For certain legacy contracts, while 1-month, 3-month and 6-month settings for JPY LIBOR ceased on 31 December 2022 and 1-month and 6-month synthetic GBP LIBOR settings ceased on 31 March 2023, the 3-month synthetic GBP LIBOR setting has been extended until the end of March 2024. Overnight, and 12-month USD LIBOR settings ceased on 30 June 2023. For certain legacy contracts, 1-month, 3-month and 6-month synthetic USD LIBOR settings will cease on 30 September 2024.
Schedule of Derivatives Directly Affected by IBOR Reform Uncertainties	The table below shows the notional amount of derivatives in hedging relationships directly affected by uncertainties related to IBOR reform. 30 June 2023 31 December 2022 USD Total USD Total £m £m £m £m Total notional value of hedging instruments – Cash flow hedges — — 2,906 2,906 – Fair value hedges — — 178 178 — — 3,084 3,084 Maturing after cessation date (1) – Cash flow hedges — — 2,906 2,906 – Fair value hedges — — 178 178 — — 3,084 3,084 (1) Overnight and 12-month USD LIBOR settings ceased on 30 June 2023. For certain legacy contracts, 1-month, 3-month and 6-month synthetic USD LIBOR settings will cease at the end of September 2024.

Assets Held for Sale (Tables)

Assets Held for Sale (Tables)	6 Months Ended
Assets Held for Sale (Tables)	Jun. 30, 2023
Discontinued Operations and Assets and Liabilities Held for Sale [Abstract]
Disclosure of Assets Classified as Held for Sale	At 30 June 2023, assets held for sale comprised: 30 June 2023 31 December 2022 £m £m Assets Property, plant and equipment 49 49 Total assets held for sale 49 49

Segments - Additional Informati

Segments - Additional Information (Details) £ in Millions	6 Months Ended
Segments - Additional Information (Details) £ in Millions	Jun. 30, 2023 GBP (£) segment	Jun. 30, 2022 GBP (£)
Disclosure of operating segments [line items]
Number of segments \| segment	4
Profit before tax	£ 1,173	£ 993
Corporate & Commercial Banking
Disclosure of operating segments [line items]
Profit before tax	270	148
Corporate Centre
Disclosure of operating segments [line items]
Profit before tax	£ (71)	(102)
Reclassified amounts \| Corporate & Commercial Banking
Disclosure of operating segments [line items]
Profit before tax		1
Reclassified amounts \| Corporate Centre
Disclosure of operating segments [line items]
Profit before tax		£ (1)

Segments - Summary of Results b

Segments - Summary of Results by Segment (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Disclosure of operating segments [line items]
Net interest income	£ 2,361	£ 2,148
Non-interest income/(expense)	297	267
Total operating income/(expense)	2,658	2,415
Operating expenses before credit impairment (charges)/write-backs, provisions and charges	(1,232)	(1,186)
Credit impairment (charges)/write-backs	(105)	(118)
Provisions for other liabilities and charges	(148)	(118)
Total operating credit impairment charges, provisions and charges	(253)	(236)
Profit before tax	1,173	993
Revenue/(expense) from external customers	2,658	2,415
Inter-segment revenue/(expense)	2,658	2,415
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	258	247
Insurance, protection and investments	24	31
Credit cards	49	46
Non-banking and other fees	69	52
Total fee and commission income	400	376
Fee and commission expense	(252)	(210)
Net fee and commission income	148	166
Customer loans	210,799		£ 219,704
Total assets	284,341		292,243
Assets held for sale	49		49
Customer deposits	190,737		196,476
Total liabilities	269,428		277,532
Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	0	0
Retail Banking
Disclosure of operating segments [line items]
Net interest income	1,873	1,792
Non-interest income/(expense)	85	107
Total operating income/(expense)	1,958	1,899
Operating expenses before credit impairment (charges)/write-backs, provisions and charges	(912)	(832)
Credit impairment (charges)/write-backs	(55)	(126)
Provisions for other liabilities and charges	(106)	(101)
Total operating credit impairment charges, provisions and charges	(161)	(227)
Profit before tax	885	840
Revenue/(expense) from external customers	1,884	2,049
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	227	218
Insurance, protection and investments	24	31
Credit cards	49	46
Non-banking and other fees	1	4
Total fee and commission income	301	299
Fee and commission expense	(218)	(193)
Net fee and commission income	83	106
Customer loans	185,904		194,661
Total assets	193,145		203,697
Assets held for sale	0		0
Customer deposits	155,692		161,748
Total liabilities	155,799		161,821
Retail Banking \| Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	74	(150)
Consumer Finance
Disclosure of operating segments [line items]
Net interest income	79	92
Non-interest income/(expense)	100	101
Total operating income/(expense)	179	193
Operating expenses before credit impairment (charges)/write-backs, provisions and charges	(73)	(73)
Credit impairment (charges)/write-backs	(14)	(13)
Provisions for other liabilities and charges	(3)	0
Total operating credit impairment charges, provisions and charges	(17)	(13)
Profit before tax	89	107
Revenue/(expense) from external customers	313	243
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	0	0
Insurance, protection and investments	0	0
Credit cards	0	0
Non-banking and other fees	12	8
Total fee and commission income	12	8
Fee and commission expense	(3)	0
Net fee and commission income	9	8
Customer loans	5,319		5,384
Total assets	10,541		10,371
Assets held for sale	0		0
Customer deposits	0		0
Total liabilities	1,683		1,223
Consumer Finance \| Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	(134)	(50)
Corporate & Commercial Banking
Disclosure of operating segments [line items]
Net interest income	405	241
Non-interest income/(expense)	67	70
Total operating income/(expense)	472	311
Operating expenses before credit impairment (charges)/write-backs, provisions and charges	(170)	(181)
Credit impairment (charges)/write-backs	(36)	20
Provisions for other liabilities and charges	4	(2)
Total operating credit impairment charges, provisions and charges	(32)	18
Profit before tax	270	148
Revenue/(expense) from external customers	364	345
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	31	29
Insurance, protection and investments	0	0
Credit cards	0	0
Non-banking and other fees	53	36
Total fee and commission income	84	65
Fee and commission expense	(26)	(11)
Net fee and commission income	58	54
Customer loans	18,367		18,518
Total assets	18,367		18,518
Assets held for sale	0		0
Customer deposits	23,525		24,798
Total liabilities	23,562		24,473
Corporate & Commercial Banking \| Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	108	(34)
Corporate Centre
Disclosure of operating segments [line items]
Net interest income	4	23
Non-interest income/(expense)	45	(11)
Total operating income/(expense)	49	12
Operating expenses before credit impairment (charges)/write-backs, provisions and charges	(77)	(100)
Credit impairment (charges)/write-backs	0	1
Provisions for other liabilities and charges	(43)	(15)
Total operating credit impairment charges, provisions and charges	(43)	(14)
Profit before tax	(71)	(102)
Revenue/(expense) from external customers	97	(222)
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	0	0
Insurance, protection and investments	0	0
Credit cards	0	0
Non-banking and other fees	3	4
Total fee and commission income	3	4
Fee and commission expense	(5)	(6)
Net fee and commission income	(2)	(2)
Customer loans	1,209		1,141
Total assets	62,288		59,657
Assets held for sale	49		49
Customer deposits	11,520		9,930
Total liabilities	88,384		£ 90,015
Corporate Centre \| Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	£ (48)	£ 234

Operating Expenses Before Cre_3

Operating Expenses Before Credit Impairment Charges, Provisions and Charges - Summary of Operating Expenses Before Credit Impairment Losses, Provisions and Charges (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Expenses by nature [abstract]
Staff costs	£ 621	£ 567
Other administration expenses	476	461
Depreciation, amortisation and impairment	135	158
Total operating expenses before impairment losses, provisions and charges	£ 1,232	£ 1,186

Operating Expenses Before Cre_4

Operating Expenses Before Credit Impairment Charges, Provisions and Charges - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Accumulated depreciation \| Branch and head office site closures
Operating Expenses Before Credit Impairment Losses Provision And Charges [Line Items]
Impairment during the period	£ 2	£ 10

Credit Impairment Charges and_3

Credit Impairment Charges and Provisions - Summary of Impairment Losses and Provisions (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Credit impairment charges/(write-backs):
Loans and advances to customers	£ 98	£ 114
Recoveries of loans and advances, net of collection costs	4	(6)
Off-balance sheet credit exposures (See Note 21)	3	10
Impairment loss on financial assets	105	118
Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 21)	149	121
Releases for residual value and voluntary termination	(1)	(3)
Provisions for other liabilities and charges	148	118
Total operating credit impairment (charges)/write-backs, provisions and charges	£ 253	£ 236

Credit Impairment Charges and_4

Credit Impairment Charges and Provisions - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Impairment losses on loans and advances to banks	£ 0	£ 0
Impairment losses on non-trading reverse repurchase agreements	0	0
Impairment losses on other financial assets at amortised cost	0	0
Impairment losses on financial assets at FVOCI	£ 0	£ 0

Taxation - Additional Informati

Taxation - Additional Information (Details)	6 Months Ended
Taxation - Additional Information (Details)	Jun. 30, 2023	Jun. 30, 2022
Income Tax Expense Benefits [Line Items]
Effective tax rate (percentage)	26.90%	23.50%
Forecast
Income Tax Expense Benefits [Line Items]
Effective tax rate (percentage)	26.90%	25.70%

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	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Major components of tax expense (income) [abstract]
Profit before tax	£ 1,173	£ 993
Tax calculated at a tax rate of 23.5% (H122:19%)	276	189
Bank surcharge on profits	45	70
Non-deductible preference dividends paid	5	5
Non-deductible UK Bank Levy	9	8
Non-deductible conduct remediation, fines and penalties	4	(1)
Other non-deductible costs and non-taxable income	(4)	6
Effect of change in tax rate on deferred tax provision	0	(22)
Tax relief on dividends in respect of other equity instruments	(20)	(22)
Tax on profit	£ 315	£ 233

Dividends on Ordinary Shares (D

Dividends on Ordinary Shares (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Dividends On Ordinary Shares [Abstract]
Dividends declared and paid	£ 414	£ 397

Derivative Financial Instrume_3

Derivative Financial Instruments - Disclosure of Notional Amounts and Fair Values of Derivatives (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure of detailed information about hedges
Notional amount	£ 210,222	£ 177,802
Assets	2,592	2,439
Liabilities	1,570	1,008
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	1,607	1,368
Derivative liabilities
Disclosure of detailed information about hedges
Collateral cash	54	70
Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	40,523	47,322
Derivatives held for trading: \| Exchange rate contracts
Disclosure of detailed information about hedges
Notional amount	10,100	14,769
Derivatives held for trading: \| Interest rate contracts
Disclosure of detailed information about hedges
Notional amount	29,513	31,599
Derivatives held for trading: \| Equity and credit contracts
Disclosure of detailed information about hedges
Notional amount	910	954
Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	169,699	130,480
Fair value hedges \| Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	103,426	78,423
Fair value hedges \| Derivatives held for hedging \| Exchange rate contracts
Disclosure of detailed information about hedges
Notional amount	742	538
Fair value hedges \| Derivatives held for hedging \| Interest rate contracts
Disclosure of detailed information about hedges
Notional amount	102,684	77,885
Cash flow hedges \| Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	66,273	52,057
Cash flow hedges \| Derivatives held for hedging \| Exchange rate contracts
Disclosure of detailed information about hedges
Notional amount	27,400	26,035
Cash flow hedges \| Derivatives held for hedging \| Interest rate contracts
Disclosure of detailed information about hedges
Notional amount	38,821	25,971
Cash flow hedges \| Derivatives held for hedging \| Equity derivative contracts
Disclosure of detailed information about hedges
Notional amount	52	51
Fair value
Disclosure of detailed information about hedges
Assets	2,592	2,439
Liabilities	1,570	1,008
Fair value \| Derivative netting
Disclosure of detailed information about hedges
Assets	(2,262)	(2,173)
Liabilities	(2,262)	(2,173)
Fair value \| Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	967	935
Liabilities	1,004	1,116
Fair value \| Derivatives held for trading: \| Exchange rate contracts
Disclosure of detailed information about hedges
Assets	125	320
Liabilities	141	299
Fair value \| Derivatives held for trading: \| Interest rate contracts
Disclosure of detailed information about hedges
Assets	697	473
Liabilities	842	792
Fair value \| Derivatives held for trading: \| Equity and credit contracts
Disclosure of detailed information about hedges
Assets	145	142
Liabilities	21	25
Fair value \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	3,887	3,677
Liabilities	2,828	2,065
Fair value \| Fair value hedges \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	2,383	1,788
Liabilities	600	415
Fair value \| Fair value hedges \| Derivatives held for hedging \| Exchange rate contracts
Disclosure of detailed information about hedges
Assets	4	12
Liabilities	7	4
Fair value \| Fair value hedges \| Derivatives held for hedging \| Interest rate contracts
Disclosure of detailed information about hedges
Assets	2,379	1,776
Liabilities	593	411
Fair value \| Cash flow hedges \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	1,504	1,889
Liabilities	2,228	1,650
Fair value \| Cash flow hedges \| Derivatives held for hedging \| Exchange rate contracts
Disclosure of detailed information about hedges
Assets	1,317	1,717
Liabilities	298	186
Fair value \| Cash flow hedges \| Derivatives held for hedging \| Interest rate contracts
Disclosure of detailed information about hedges
Assets	168	164
Liabilities	1,930	1,463
Fair value \| Cash flow hedges \| Derivatives held for hedging \| Equity derivative contracts
Disclosure of detailed information about hedges
Assets	19	8
Liabilities	£ 0	£ 1

Derivative Financial Instrume_4

Derivative Financial Instruments - Additional Information (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022
Disclosure of detailed information about hedges
Derivative financial assets	£ 2,592	£ 2,439
Derivative financial liabilities	1,570	1,008
Fair value
Disclosure of detailed information about hedges
Derivative financial assets	2,592	2,439
Derivative financial liabilities	1,570	£ 1,008
Group entities \| Fair value
Disclosure of detailed information about hedges
Derivative financial assets	1,281		£ 1,346
Derivative financial liabilities	£ 241		£ 246

Other Financial Assets at Fai_3

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	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at fair value through profit or loss	£ 614	£ 434
Loans and advances to customers
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at fair value through profit or loss	322	339
Debt securities
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at fair value through profit or loss	219	85
Equity securities
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at fair value through profit or loss	£ 73	£ 10

Other Financial Assets at Fai_4

Other Financial Assets at Fair Value Through Profit or Loss - Additional Information (Details) £ in Millions	1 Months Ended
	Jun. 30, 2023 GBP (£)
Santander Equity Investments Limited (SEIL) \| Equity securities
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

Loans and Advances to Custome_3

Loans and Advances to Customers (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Net Loans And Advances To Customers [Abstract]
Loans and advances to customers	£ 215,973	£ 224,795
Credit impairment loss allowances on loans and advances to customers	(942)	(933)
Residual value and voluntary termination provisions on finance leases	(21)	(22)
Net loans and advances to customers	£ 215,010	£ 223,840

Securitisations and Covered B_3

Securitisations and Covered Bonds - Disclosure of Analysis of Securitisations and Covered Bonds (Details) £ in Millions	Jun. 30, 2023 GBP (£)	Jun. 30, 2023 EUR (€)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Jun. 30, 2022 EUR (€)
Disclosure Of Securitisations And Covered Bonds [Line Items]
Notional amount	£ 210,222		£ 177,802
Gross assets	25,646		24,984
Euro 35bn Global Covered Bond Programme
Disclosure Of Securitisations And Covered Bonds [Line Items]
Notional amount \| €		€ 35,000,000,000		€ 35,000,000,000	€ 35,000,000,000
Securitisation programmes
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	4,856		3,680
Securitisation programmes \| Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	4,106		3,674
Securitisation programmes \| Other asset-backed securitisation structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	750		6
Holmes \| Securitisation programmes \| Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	2,214		1,646
Fosse \| Securitisation programmes \| Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	1,892		2,028
Motor \| Securitisation programmes \| Other asset-backed securitisation structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	0		6
Repton \| Securitisation programmes \| Other asset-backed securitisation structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	750		0
Euro 35bn Global Covered Bond Programme \| Covered bond programme
Disclosure Of Securitisations And Covered Bonds [Line Items]
Gross assets	£ 20,790		£ 21,304

Securitisations and Covered B_4

Securitisations and Covered Bonds - Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme (Details) £ in Millions	6 Months Ended
	Jun. 30, 2023 GBP (£)	Jun. 30, 2022 GBP (£)	Jun. 30, 2023 EUR (€)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Jun. 30, 2022 EUR (€)
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Notional amount	£ 210,222			£ 177,802
Euro 35bn Global Covered Bond Programme
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Notional amount \| €			€ 35,000,000,000		€ 35,000,000,000	€ 35,000,000,000
Internal
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	1,218	£ 0
Internal and external redemptions	35	76
External
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	2,800	4,182
Internal and external redemptions	1,166	1,147
Holmes \| Internal \| Mortgage-backed master trust structures
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	118	0
Internal and external redemptions	30	42
Holmes \| External \| Mortgage-backed master trust structures
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	750	0
Internal and external redemptions	142	114
Fosse \| Internal \| Mortgage-backed master trust structures
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	34
Fosse \| External \| Mortgage-backed master trust structures
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	185
Motor \| Internal \| Other asset-backed securitisation structures
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	0
Motor \| External \| Other asset-backed securitisation structures
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	7	21
Repton \| Internal \| Other asset-backed securitisation structures
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	0
Repton \| External \| Other asset-backed securitisation structures
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	550	0
Internal and external redemptions	0	0
Euro 35bn Global Covered Bond Programme \| Internal \| Covered bond programme
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	1,100	0
Internal and external redemptions	5	0
Euro 35bn Global Covered Bond Programme \| External \| Covered bond programme
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	1,500	4,182
Internal and external redemptions	£ 1,017	£ 827

Securitisations and Covered B_5

Securitisations and Covered Bonds - Additional Information (Details) - External - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure Of Securitisations And Covered Bonds [Line Items]
Internal and external issuances	£ 2,800	£ 4,182
Repton \| Other asset-backed securitisation structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Internal and external issuances	£ 550	£ 0

Reverse Repurchase Agreements_3

Reverse Repurchase Agreements - Non Trading (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non trading	£ 12,024	£ 7,348
Agreements with banks
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non trading	1,253	885
Agreements with customers
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non trading	£ 10,771	£ 6,463

Intangible Assets (Details)

Intangible Assets (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure of detailed information about intangible assets [line items]
Goodwill	£ 1,199	£ 1,199
Computer software
Disclosure of detailed information about intangible assets [line items]
Intangible assets other than goodwill	£ 350	£ 351

Property, Plant and Equipment_2

Property, Plant and Equipment (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	£ 1,526
Property, plant and equipment at end of period	1,512
Construction in progress	259	£ 204
Investment property	17	£ 17
Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	2,797
Additions	144
Disposals	(175)
Property, plant and equipment at end of period	2,766
Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(1,271)
Additions	(84)
Disposals	101
Property, plant and equipment at end of period	(1,254)
Property
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	644
Property \| Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	893
Additions	31
Disposals	(63)
Property, plant and equipment at end of period	861
Property \| Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(271)
Additions	(9)
Disposals	63
Property, plant and equipment at end of period	(217)
Office fixtures and equipment
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	221
Office fixtures and equipment \| Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	831
Additions	48
Disposals	(9)
Property, plant and equipment at end of period	870
Office fixtures and equipment \| Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(625)
Additions	(32)
Disposals	8
Property, plant and equipment at end of period	(649)
Computer software
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	7
Computer software \| Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	79
Additions	1
Disposals	0
Property, plant and equipment at end of period	80
Computer software \| Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(73)
Additions	0
Disposals	0
Property, plant and equipment at end of period	(73)
Operating lease assets
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	534
Operating lease assets \| Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	722
Additions	41
Disposals	(81)
Property, plant and equipment at end of period	682
Operating lease assets \| Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(145)
Additions	(33)
Disposals	30
Property, plant and equipment at end of period	(148)
Right-of-use assets
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	106
Right-of-use assets \| Cost
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	272
Additions	23
Disposals	(22)
Property, plant and equipment at end of period	273
Right-of-use assets \| Accumulated depreciation
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(157)
Additions	(10)
Disposals	0
Property, plant and equipment at end of period	£ (167)

Other Financial Liabilities a_3

Other Financial Liabilities at Fair Value Through Profit or Loss (Details) - GBP (£) £ in Millions	Jun. 30, 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	£ 864	£ 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	370	375
Eurobonds
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other financial liabilities at fair value through profit or loss	93	102
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	401	321
Other
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other financial liabilities at fair value through profit or loss	£ 0	£ 5

Deposits by Customers (Details)

Deposits by Customers (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	£ 191,638	£ 197,313
Demand and time deposits
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	190,534	196,160
Amounts due to fellow Banco Santander subsidiaries and joint ventures
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	1,104	1,153
Equity index linked deposits
Disclosure Of Deposits From Customers [Line Items]
Capital amount guaranteed or protected	£ 364	£ 408

Deposits by Banks (Details)

Deposits by Banks (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	£ 25,602	£ 28,543
Drawdown from TFSME	21,000	25,000
Items in the course of transmission
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	531	701
Deposits held as collateral
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	1,631	1,758
Other deposits
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	£ 23,440	£ 26,084

Repurchase Agreements - Non T_3

Repurchase Agreements - Non Trading (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non trading	£ 9,853	£ 7,982
Agreements with banks
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non trading	406	50
Agreements with customers
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non trading	£ 9,447	£ 7,932

Debt Securities in Issue (Detai

Debt Securities in Issue (Details) £ in Millions	Jun. 30, 2023 GBP (£)	Jun. 30, 2023 EUR (€)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Dec. 31, 2022 USD ($)	Jun. 30, 2022 EUR (€)
Debt Securities In Issue [Line Items]
Debt securities	£ 35,083			£ 36,420
Notional amount	210,222			177,802
Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities	14,182			15,533
Euro 35bn Global Covered Bond Programme
Debt Securities In Issue [Line Items]
Debt securities	15,247			15,205
Notional amount \| €		€ 35,000,000,000			€ 35,000,000,000		€ 35,000,000,000
US$20bn Commercial Paper Programmes
Debt Securities In Issue [Line Items]
Debt securities	1,591			1,851
Notional amount \| $			$ 20,000,000,000			$ 20,000,000,000
Certificates of deposit
Debt Securities In Issue [Line Items]
Debt securities	1,975			2,874
Credit linked notes
Debt Securities In Issue [Line Items]
Credit linked notes	0			60
Securitisation programmes
Debt Securities In Issue [Line Items]
Debt securities	£ 2,088			£ 897

Subordinated Liabilities - Sche

Subordinated Liabilities - Schedule of Subordinated Liabilities (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Subordinated liabilities [abstract]
£325m Sterling preference shares	£ 344	£ 344
Undated subordinated liabilities	205	219
Dated subordinated liabilities	1,601	1,769
Subordinated liabilities	2,150	2,332
£325m Sterling preference shares, notional amount	£ 325	£ 325

Subordinated Liabilities - Addi

Subordinated Liabilities - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Subordinated liabilities [abstract]
Loss on repurchase of subordinated liabilities	£ 3	£ (1)

Provisions - Summary of Provisi

Provisions - Summary of Provisions Reconciliation (Details) £ in Millions	6 Months Ended
	Jun. 30, 2023 GBP (£)
Disclosure of other provisions [line items]
Beginning balance	£ 380
Additional provisions (See Note 4)	175
Provisions released (See Note 4)	(23)
Utilisation and other	(135)
Ending balance	397
Customer remediation
Disclosure of other provisions [line items]
Beginning balance	90
Additional provisions (See Note 4)	30
Provisions released (See Note 4)	(20)
Utilisation and other	(10)
Ending balance	90
Litigation and other regulatory
Disclosure of other provisions [line items]
Beginning balance	136
Additional provisions (See Note 4)	14
Provisions released (See Note 4)	0
Utilisation and other	(12)
Ending balance	138
Bank Levy
Disclosure of other provisions [line items]
Beginning balance	4
Additional provisions (See Note 4)	0
Provisions released (See Note 4)	0
Utilisation and other	(4)
Ending balance	0
Property
Disclosure of other provisions [line items]
Beginning balance	47
Additional provisions (See Note 4)	4
Provisions released (See Note 4)	(1)
Utilisation and other	(2)
Ending balance	48
ECL on undrawn facilities and guarantees
Disclosure of other provisions [line items]
Beginning balance	74
Additional provisions (See Note 4)	3
Provisions released (See Note 4)	0
Utilisation and other	0
Ending balance	77
Restructuring
Disclosure of other provisions [line items]
Beginning balance	22
Additional provisions (See Note 4)	34
Provisions released (See Note 4)	0
Utilisation and other	(17)
Ending balance	39
Other
Disclosure of other provisions [line items]
Beginning balance	7
Additional provisions (See Note 4)	90
Provisions released (See Note 4)	(2)
Utilisation and other	(90)
Ending balance	£ 5

Provisions - Additional Informa

Provisions - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure of other provisions [line items]
Additional provisions	£ 175
Customer remediation
Disclosure of other provisions [line items]
Additional provisions	30
Restructuring provision, January 2023
Disclosure of other provisions [line items]
Additional provisions	30
Operational risk provisions
Disclosure of other provisions [line items]
Additional provisions	87	£ 78
Fraud losses
Disclosure of other provisions [line items]
Additional provisions	£ 75	£ 63

Retirement Benefit Plans - Summ

Retirement Benefit Plans - Summary of Retirement Benefit Plans (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Net change in operating assets and liabilities:
Total net assets	£ 974	£ 1,026
Unfunded pension and post-retirement medical benefits
Net change in operating assets and liabilities:
Surplus (deficit) in plan	(25)	(25)
Surplus \| Funded defined benefit pension scheme
Net change in operating assets and liabilities:
Surplus (deficit) in plan	£ 999	£ 1,051

Retirement Benefit Plans - Addi

Retirement Benefit Plans - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure of net defined benefit liability (asset) [abstract]
Defined contribution expense	£ 33	£ 30
Defined benefit expense	£ (16)	£ 4

Retirement Benefit Plans - Su_2

Retirement Benefit Plans - Summary of Amounts Recognised in Other Comprehensive Income (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure of net defined benefit liability (asset) [abstract]
Return on plan assets (excluding amounts included in net interest expense)	£ 470	£ 3,352
Actuarial losses arising from experience adjustments	89	296
Actuarial gains arising from changes in financial assumptions	(399)	(3,974)
Pension remeasurement	£ 160	£ (326)

Retirement Benefit Plans - Su_3

Retirement Benefit Plans - Summary of Net Assets Recognised (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure of net defined benefit liability (asset) [abstract]
Present value of defined benefit obligations	£ (7,639)	£ (7,937)
Fair value of scheme assets	8,613	8,963
Net defined benefit assets	£ 974	£ 1,026

Retirement Benefit Plans - Su_4

Retirement Benefit Plans - Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes (Details)	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Disclosure of net defined benefit liability (asset) [abstract]
– Discount rate for scheme liabilities	530%		4.90%
– General price inflation	310%		3.10%
– General salary increase	100%		1%
– Expected rate of pension increase	300%		3%
Longevity at 60 for current pensioners, on the valuation date:
– Males	27 years 4 months 24 days	27 years 4 months 24 days
– Females	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 10 months 24 days	28 years 10 months 24 days
– Females	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	6 Months Ended
	Jun. 30, 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	£ (466)	£ (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	£ 341	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	£ 185	£ 203

Contingent Liabilities and Co_3

Contingent Liabilities and Commitments - Summary of Contingent Liabilities and Commitments (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Guarantees and formal standby facilities, credit lines and other commitments	£ 33,725	£ 31,858
Contingent liability for guarantees
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Guarantees given to third parties	436	448
Loan commitments
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Formal standby facilities, credit lines and other commitments	£ 33,289	£ 31,410

Contingent Liabilities and Co_4

Contingent Liabilities and Commitments - Additional Information (Details) £ in Millions		6 Months Ended
	Nov. 02, 2015	Jun. 30, 2023 EUR (€)	Jun. 29, 2023 GBP (£)	Oct. 21, 2022 GBP (£)
Minimum
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Losses on litigation settlements		€ 1,000,000,000
Maximum
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Santander UK liability under indemnity cap		39,850,000
AXA France
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Amount claimed by other party \| £			£ 552	£ 670
UK&I Banks
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Preferred stock issued, threshold value		€ 0
Visa Europe Ltd
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Visa Europe Ltd sale to Visa Inc	100%

Other Equity Instruments (Detai

Other Equity Instruments (Details)	6 Months Ended	12 Months Ended
Other Equity Instruments (Details)	Jun. 30, 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 issued	£ 500,000,000	£ 500,000,000
Interest rate	0.0675	0.0675
Other equity interest maturity period	2024-06	2024-06
Other equity instruments	£ 496,000,000	£ 496,000,000
- £500m Fixed Rate Reset Perpetual AT1 Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities issued	£ 500,000,000	£ 500,000,000
Interest rate	0.0630	0.0630
Other equity interest maturity period	2025-03	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 issued	£ 450,000,000	£ 450,000,000
Interest rate	0.0425	0.0425
Other equity interest maturity period	2026-03	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 issued	£ 750,000,000	£ 750,000,000
Interest rate	0.0650	0.0650
Other equity interest maturity period	2027-06	2027-06
Other equity instruments	£ 750,000,000	£ 750,000,000

Assets Charged as Security fo_2

Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Assets Pledged As Security [Line Items]
Gross assets charged as security for liabilities	£ 25,646	£ 24,984
Securitisations and covered bonds \| Internally retained
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued under securitisation and covered bond programmes retained internally	2,875	1,725
Securitisations and covered bonds \| Third party bilateral secured funding transactions
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued to Santander UK plc/subsidiaries as collateral	1,500	500
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	£ 775	£ 829

Financial Instruments - Disclos

Financial Instruments - Disclosure of Analysis of Fair Value of Financial Instruments Carried at Amortised Cost (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to customers	£ 215,010	£ 223,840
Loans and advances to banks	1,276	1,105
Reverse repurchase agreements - non trading	12,024	7,348
Other financial assets at amortised cost	152	156
Deposits by customers	191,638	197,313
Deposits by banks	25,602	28,543
Repurchase agreements - non trading	9,853	7,982
Debt securities in issue	35,083	36,420
Subordinated liabilities	2,150	2,332
Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial liabilities	264,326	272,590
Financial assets at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial assets	228,462	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	191,638	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	25,602	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	9,853	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	35,083	36,420
Subordinated liabilities \| Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Subordinated liabilities	2,150	2,332
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	215,010	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	1,276	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	12,024	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
Fair value \| Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial liabilities	263,824	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	221,111	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	191,581	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	25,659	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	9,853	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	34,322	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	2,409	2,511
Fair value \| 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	207,690	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	1,276	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	12,007	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	£ 138	£ 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	6 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 10,278	£ 8,897
Liabilities at fair value	2,434	1,811
Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	1,570	1,008
Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	864	803
Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	2,592	2,439
Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	614	434
Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	7,072	6,024
Level 1
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	6,968	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	6,968	5,996
Level 2
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	3,121	2,720
Liabilities at fair value	2,425	1,796
Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	1,561	996
Level 2 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	864	800
Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	2,532	2,385
Level 2 \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	485	307
Level 2 \| Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	104	28
Level 3
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	189	181
Liabilities at fair value	9	15
Level 3 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	9	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	60	54
Level 3 \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	129	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]
Valuation technique	A
Liabilities at fair value	£ 446	489
Exchange rate contracts \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 1,446	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	446	489
Exchange rate contracts \| Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1,446	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]
Valuation technique	A & C
Liabilities at fair value	£ 3,365	2,666
Interest rate contracts \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 3,244	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	3,365	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	3,241	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	0	4
Interest rate contracts \| Level 3 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 3	7
Equity and credit contracts \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Valuation technique	B & D
Liabilities at fair value	£ 21	26
Equity and credit contracts \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 164	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	12	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	107	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	57	47
Netting \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	(2,262)	(2,173)
Netting \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	(2,262)	(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	(2,262)	(2,173)
Netting \| Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	(2,262)	(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
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	£ 322	339
Valuation technique	A
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
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	280	294
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	42	45
Debt securities \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 219	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	£ 7,072	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	6,968	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	159	13
Debt securities \| Level 2 \| Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	104	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	60	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	£ 73	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	46	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	£ 27	10
Debt securities in issue \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Valuation technique	A
Liabilities at fair value	£ 463	480
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	463	477
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]
Valuation technique	A
Liabilities at fair value	£ 401	321
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	401	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
Other \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Valuation technique	D
Liabilities at fair value	£ 0	2
Other \| Level 1 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Other \| Level 2 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	2
Other \| 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	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Abstract]
Transfers out of Level 1 into Level 2 of fair value hierarchy, assets held at end of reporting period	£ 0	£ 0
Transfers out of Level 2 into Level 1 of fair value hierarchy, assets held at end of reporting period	0	0
Transfers into Level 3 of fair value hierarchy, assets	0	0
Transfers out of Level 3 of fair value hierarchy, assets	0	0
Transfers out of Level 1 into Level 2 of fair value hierarchy, liabilities held at end of reporting period	0	0
Transfers out of Level 2 into Level 1 of fair value hierarchy, liabilities held at end of reporting period	0	0
Transfers into Level 3 of fair value hierarchy, liabilities	0	0
Transfers out	£ 0	£ 0

Financial Instruments - Summary

Financial Instruments - Summary of Fair Value Adjustment (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure of financial assets [line items]
Fair value adjustments	£ 9	£ 14
Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	10	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	(8)	(12)
- Uncertainty \| Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	21	27
- Credit risk adjustment \| Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	(3)	(1)
- Funding fair value adjustment \| Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	£ 0	£ 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	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Disclosure of fair value measurement of assets [line items]
Beginning balance	£ 292,243
Beginning balance	(277,532)
Transfers out	0	£ 0
Transfers out	0	£ 0
Ending Balance	284,341
Ending Balance	(269,428)
Level 3 \| Other financial liabilities at FVTPL
Disclosure of fair value measurement of assets [line items]
Beginning balance	(3)
Fair value movements	0
Foreign exchange and other movements	0
Purchases	0
Transfers out	0
Netting	0
Settlements	3
Ending Balance	0
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	0
Level 3 \| Financial liabilities at fair value
Disclosure of fair value measurement of assets [line items]
Beginning balance	(15)
Fair value movements	(1)
Foreign exchange and other movements	0
Purchases	0
Transfers out	0
Netting	0
Settlements	7
Ending Balance	(9)
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	(1)
Level 3 \| Derivatives
Disclosure of fair value measurement of assets [line items]
Beginning balance	(12)
Fair value movements	(1)
Foreign exchange and other movements	0
Purchases	0
Transfers out	0
Netting	0
Settlements	4
Ending Balance	(9)
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	(1)
Level 3 \| Other financial assets at FVTPL
Disclosure of fair value measurement of assets [line items]
Beginning balance	127
Fair value movements	62
Foreign exchange and other movements	(6)
Purchases	1
Transfers out	(46)
Netting	(2)
Settlements	(7)
Ending Balance	129
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	56
Level 3 \| Financial assets at fair value
Disclosure of fair value measurement of assets [line items]
Beginning balance	181
Fair value movements	76
Foreign exchange and other movements	(6)
Purchases	1
Transfers out	(46)
Netting	(2)
Settlements	(15)
Ending Balance	189
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	70
Level 3 \| Derivatives
Disclosure of fair value measurement of assets [line items]
Beginning balance	54
Fair value movements	14
Foreign exchange and other movements	0
Purchases	0
Transfers out	0
Netting	0
Settlements	(8)
Ending Balance	60
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	£ 14

Interest Rate Benchmark Refor_2

Interest Rate Benchmark Reform - Schedule of Amounts Affected by IBOR Reform (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Assets
Derivative financial instruments	£ 2,592	£ 2,439
Total assets	284,341	292,243
Liabilities
Derivative financial instruments	1,570	1,008
Total liabilities	269,428	277,532
Total
Assets
Derivative financial instruments		1,665
Financial assets at amortised cost	8	321
Total assets	8	1,986
Liabilities
Derivative financial instruments	49	1,912
Financial liabilities at amortised cost		2,491
Total liabilities	49	4,403
Off-balance sheet commitments given		2
GBP LIBOR
Assets
Derivative financial instruments		0
Financial assets at amortised cost	7	76
Total assets	7	76
Liabilities
Derivative financial instruments	0	66
Financial liabilities at amortised cost		0
Total liabilities	0	66
Off-balance sheet commitments given		2
USD LIBOR
Assets
Derivative financial instruments		1,665
Financial assets at amortised cost	1	245
Total assets	1	1,910
Liabilities
Derivative financial instruments	49	1,846
Financial liabilities at amortised cost		2,491
Total liabilities	£ 49	4,337
Off-balance sheet commitments given		£ 0

Interest Rate Benchmark Refor_3

Interest Rate Benchmark Reform - Schedule of Derivatives Directly Affected by IBOR Reform Uncertainties (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Total
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	3,084
Total \| Maturing after cessation date
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	3,084
USD LIBOR
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	3,084
USD LIBOR \| Maturing after cessation date
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	3,084
Cash flow hedges \| Total
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	2,906
Cash flow hedges \| Total \| Maturing after cessation date
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	2,906
Cash flow hedges \| USD LIBOR
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	2,906
Cash flow hedges \| USD LIBOR \| Maturing after cessation date
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	2,906
Fair value hedges \| Total
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	178
Fair value hedges \| Total \| Maturing after cessation date
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	178
Fair value hedges \| USD LIBOR
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	178
Fair value hedges \| USD LIBOR \| Maturing after cessation date
Disclosure Of Analysis Of Notional And Fair Values Of Derivatives By Trading And Settlement Method [Line Items]
Notional value of hedging instruments	0	178

Assets Held for Sale (Details)

Assets Held for Sale (Details) - GBP (£) £ in Millions	Jun. 30, 2023	Dec. 31, 2022
Disclosure Of Assets And Liabilities Classified As Held For Sale [Line Items]
Assets held for sale	£ 49	£ 49
Property, plant and equipment
Disclosure Of Assets And Liabilities Classified As Held For Sale [Line Items]
Assets held for sale	£ 49	£ 49

Events After the Balance Shee_2

Events After the Balance Sheet Date (Details)	6 Months Ended
Events After the Balance Sheet Date (Details)	Jun. 30, 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 30 June 2023 and the date of approval of these financial statements which would require a change to or additional disclosure in the financial statements.