Santander UK (STNDF) 6-K12 Aug 242024 Q2 Current report (foreign)Financial data

Company Profile

Cover Page

Cover Page	6 Months Ended
Cover Page	Jun. 30, 2024
Cover [Abstract]
Document Type	6-K
Entity Registrant Name	SANTANDER UK PLC
Amendment Flag	false
Document Period End Date	Jun. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001087711
Current Fiscal Year End Date	--12-31

Condensed Consolidated Income S

Condensed Consolidated Income Statement (Unaudited) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Profit (loss) [abstract]
Interest and similar income	£ 6,279	£ 5,346
Interest expense and similar charges	(4,175)	(2,985)
Net interest income	2,104	2,361
Fee and commission income	370	401
Fee and commission expense	(242)	(251)
Net fee and commission income	128	150
Other operating income	63	83
Total operating income	2,295	2,594
Operating expenses before credit impairment charges, provisions and charges	(1,279)	(1,219)
Credit impairment charges	(61)	(105)
Provisions for other liabilities and charges	(142)	(148)
Total credit impairment charges, provisions and charges	(203)	(253)
Profit before tax	813	1,122
Tax on profit	(213)	(308)
Profit after tax	600	814
Attributable to:
Equity holders of the parent	600	814
Profit after tax	£ 600	£ 814

Condensed Consolidated Statemen

Condensed Consolidated Statement of Comprehensive Income (Unaudited) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Statement of comprehensive income [abstract]
Profit after tax	£ 600	£ 814
Movement in fair value reserve (debt instruments):
- Change in fair value	(29)	(12)
- Income statement transfers	39	8
- Taxation	(3)	1
Other comprehensive income, fair value reserve (debt instruments)	7	(3)
Cash flow hedges:
- Effective portion of changes in fair value	(412)	(1,187)
- Income statement transfers	72	1,112
- Taxation	95	21
Other comprehensive income, cash flow hedges, total	(245)	(54)
Net other comprehensive expense that may be reclassified to profit or loss subsequently	(238)	(57)
Pension remeasurement:
- Change in fair value	(159)	(160)
- Taxation	45	45
Pension remeasurement, total	(114)	(115)
Own credit adjustment:
- Change in fair value	(11)	(7)
- Taxation	3	2
Own credit adjustment, total	(8)	(5)
Net other comprehensive expense that will not be reclassified to profit or loss subsequently	(122)	(120)
Total other comprehensive expense net of tax	(360)	(177)
Total comprehensive income	240	637
Attributable to:
Equity holders of the parent	240	637
Total comprehensive income	£ 240	£ 637

Condensed Consolidated Balance

Condensed Consolidated Balance Sheet (Unaudited) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Assets
Cash and balances at central banks	£ 26,875	£ 38,214
Derivative financial instruments	1,131	1,432
Other financial assets at fair value through profit or loss	249	262
Loans and advances to customers	203,043	207,435
Loans and advances to banks	1,040	1,080
Reverse repurchase agreements - non-trading	15,319	12,468
Other financial assets at amortised cost	1,744	152
Macro hedge of interest rate risk	(1,034)	(632)
Financial assets at fair value through other comprehensive income	8,618	8,481
Interests in other entities	266	245
Intangible assets	1,521	1,548
Property, plant and equipment	1,455	1,494
Current tax assets	557	490
Retirement benefit assets	622	723
Other assets	2,769	2,043
Assets held for sale	13	13
Total assets	264,188	275,448
Liabilities
Derivative financial instruments	741	818
Other financial liabilities at fair value through profit or loss	973	899
Deposits by customers	184,874	190,850
Deposits by banks	16,499	20,332
Repurchase agreements - non-trading	6,623	8,411
Debt securities in issue	34,053	33,910
Subordinated liabilities	2,397	2,386
Macro hedge of interest rate risk	52	86
Other liabilities	3,269	2,479
Provisions	380	402
Deferred tax liabilities	154	186
Retirement benefit obligations	30	66
Total liabilities	250,045	260,825
Equity
Share capital	3,105	3,105
Share premium	5,620	5,620
Other equity instruments	1,860	1,956
Retained earnings	4,149	4,295
Other reserves	(591)	(353)
Total equity	14,143	14,623
Total liabilities and equity	£ 264,188	£ 275,448

Condensed Consolidated Cash Flo

Condensed Consolidated Cash Flow Statement (Unaudited) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities
Profit before tax	£ 813	£ 1,122
Adjustments for:
Non-cash items included in profit	327	1,029
Change in operating assets	4,724	8,032
Change in operating liabilities	(10,898)	(9,355)
Corporation taxes paid	(171)	(295)
Effects of exchange rate differences	154	(437)
Net cash flows from operating activities	(5,051)	96
Cash flows from investing activities
Purchase of property, plant and equipment and intangible assets	(176)	(235)
Proceeds from sale of property, plant and equipment and intangible assets	91	78
Purchase of financial assets at amortised cost and financial assets at FVOCI	(7,017)	(3,417)
Proceeds from sale and redemption of financial assets at amortised cost and financial assets at FVOCI	4,875	2,088
Net cash flows from investing activities	(2,227)	(1,486)
Cash flows from financing activities
Issue of other equity instruments	400	0
Issue of debt securities and subordinated notes	5,135	2,326
Issuance costs of debt securities and subordinated notes	(14)	(10)
Repayment of debt securities and subordinated notes	(4,791)	(1,598)
Repurchase of other equity instruments	(500)	0
Dividends paid on ordinary shares	(554)	(410)
Dividends paid on preference shares and other equity instruments	(66)	(61)
Principal elements of lease payments	(20)	(34)
Net cash flows from financing activities	(410)	213
Change in cash and cash equivalents	(7,688)	(1,177)
Cash and cash equivalents at beginning of the period	42,502	46,484
Effects of exchange rate changes on cash and cash equivalents	(14)	(197)
Cash and cash equivalents at the end of the period	34,800	45,110
Cash and cash equivalents consist of:
Cash and balances at central banks	26,875	39,612
Less: restricted balances	(1,330)	(2,076)
Cash and bank balances at central banks less regulatory minimum cash balances	25,545	37,536
Other cash equivalents: Loans and advances to banks - Non-trading	859	925
Other cash equivalents: Reverse repurchase agreements	8,396	6,649
Cash and cash equivalents at the end of the period	£ 34,800	£ 45,110

Condensed Consolidated Statem_2

Condensed Consolidated Statement of Changes in Equity (Unaudited) - GBP (£) £ in Millions	Total	Share capital	Share premium	Other equity instruments	Fair value	Cash flow hedging	Currency translation	Retained earnings
Beginning balance at Dec. 31, 2022	£ 14,407	£ 3,105	£ 5,620	£ 1,956	£ 5	£ (1,128)	£ 1	£ 4,848
Profit after tax	814							814
Other comprehensive (expense), net of tax:
- Fair value reserve (debt instruments)	(3)				(3)
- Cash flow hedges	(54)					(54)
- Pension remeasurement	(115)							(115)
- Own credit adjustment	(5)							(5)
Total other comprehensive income/(expense)	(177)				(3)	(54)		(120)
Total comprehensive income	637				(3)	(54)		694
Dividends on ordinary shares	(410)							(410)
Dividends on preference shares and other equity instruments	(61)							(61)
Ending balance at Jun. 30, 2023	14,573	3,105	5,620	1,956	2	(1,182)	1	5,071
Beginning balance at Dec. 31, 2023	14,623	3,105	5,620	1,956	(6)	(348)	1	4,295
Profit after tax	600							600
Other comprehensive (expense), net of tax:
- Fair value reserve (debt instruments)	7				7
- Cash flow hedges	(245)					(245)
- Pension remeasurement	(114)							(114)
- Own credit adjustment	(8)							(8)
Total other comprehensive income/(expense)	(360)				7	(245)		(122)
Total comprehensive income	240				7	(245)		478
Issue of other equity instruments	400			400
Repurchase of other equity instruments	(500)			(496)				(4)
Dividends on ordinary shares	(554)							(554)
Dividends on preference shares and other equity instruments	(66)							(66)
Ending balance at Jun. 30, 2024	£ 14,143	£ 3,105	£ 5,620	£ 1,860	£ 1	£ (593)	£ 1	£ 4,149

Accounting Policies

Accounting Policies	6 Months Ended
Accounting Policies	Jun. 30, 2024
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 2023 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 plc (the Company) and its subsidiaries (collectively Santander UK or the Santander UK group) for the year ended 31 December 2023 which were prepared in accordance with UK-adopted International Accounting Standards (IAS). Those consolidated financial statements were also prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the IASB, including interpretations issued by the IFRS Interpretations Committee, as there were no applicable differences from IFRS 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 2023 Annual Report. Future accounting developments The IASB issued the following new/amended accounting standards which are not yet effective and have not been endorsed for use in the UK: – Effective 1 January 2026: ‘Amendments to the Classification and Measurement of Financial Instruments’ (Amendments to IFRS 9 ‘Financial Instruments’ and IFRS 7 ‘Financial Instruments: Disclosures’) - the amendments set out changes to settling financial liabilities using an electronic payment system, assessing contractual cash flow characteristics of financial assets including those with environmental, social and governance (ESG)-linked features and requiring additional disclosures for certain financial instruments. – Effective 1 January 2027: IFRS 18 ‘Presentation and Disclosure in Financial Statements’ – the new standard will replace IAS 1 ‘Presentation of Financial Statements’ and introduces changes to the categories for classifying income and expenses and subtotals presented in the income statement and new or amended disclosures in respect of management-defined performance measures and specified expenses by nature. The Santander UK group is assessing these new/amended accounting standards to determine the potential impacts on the financial statements when they become effective or if they are otherwise earlier adopted when available. 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 Santander UK's condensed consolidated financial statements in accordance with IFRS requires management to make judgements and assumptions in applying the accounting policies that affect the reported amounts of assets, liabilities, income and expenses. Due to the inherent uncertainty in making estimates, actual results reported in future periods may be based on amounts which differ from those estimates. Estimates, judgements and assumptions are continually evaluated and are based on historical experience and other factors, including expectations of future events that are believed to be reasonable under the circumstances. There has been no change in the inherent sensitivity of the areas of judgement in the period. Management have considered the impact of developments in principal risks and uncertainties, as set out in the Risk review, on critical judgements and accounting estimates. The significant judgements, apart from those involving estimation, made by management in applying Santander UK's accounting policies in these financial statements (key judgements) and the key sources of estimation uncertainty that may have a significant risk of causing a material adjustment to the carrying amount of assets and liabilities within the next financial year (key estimates), which together are considered critical to Santander UK's results and financial position, are as follows: a) Credit impairment allowance 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 2023 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 22 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 24 provides disclosure relating to ongoing factual issues and reviews that could impact the timing and amount of any outflows. It includes disclosure relating to an investigation in relation to the historical involvement of Santander UK plc, Santander Financial Services plc and Cater Allen International Limited (all subsidiaries of Santander UK Group Holdings plc) in German dividend tax arbitrage transactions. It also includes disclosure relating to the historical use of discretionary commission arrangements by Santander Consumer (UK) plc. These judgements are based on the specific facts available and often require specialist professional advice. There can be a wide range of possible outcomes and uncertainties, particularly in relation to legal actions, and regulatory and consumer credit matters. As a result, it is often not possible to make reliable estimates of the likelihood and amount of any potential outflows, or to calculate any resulting sensitivities. For more on each of these key judgements and estimates, see Notes 22 and 24 . c) Retirement benefit plans 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 23 . Sensitivity of defined benefit pension scheme estimates For detailed disclosures, see ‘Actuarial assumption sensitivities’ in Note 23 . 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 represent fair value. Given the nature of these investments, we are unable to prepare sensitivities on how their values could vary as market conditions or other variables change. d) Goodwill 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 14 . Sensitivity of goodwill For detailed disclosures, see ‘Sensitivities of key assumptions in calculating VIU’ in Note 20 to the Consolidated Financial Statements in the 2023 Annual Report .

Segments

Segments	6 Months Ended
Segments	Jun. 30, 2024
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 & Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 30 June 2024 £m £m £m £m £m Net interest income/(expense) 1,684 74 383 (37) 2,104 Non-interest income/(expense) 62 83 67 (21) 191 Total operating income/(expense) 1,746 157 450 (58) 2,295 Operating expenses before credit impairment charges, provisions and charges (999) (77) (205) 2 (1,279) Credit impairment charges (49) (8) (3) (1) (61) Provisions for other liabilities and charges (98) (15) (18) (11) (142) Total credit impairment charges, provisions and charges (147) (23) (21) (12) (203) Profit/(loss) before tax 600 57 224 (68) 813 Revenue/(expense) from external customers 1,686 360 264 (15) 2,295 Inter-segment revenue/(expense) 60 (203) 186 (43) — Total operating income/(expense) 1,746 157 450 (58) 2,295 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 212 — 26 — 238 – Insurance, protection and investments 25 — — — 25 – Credit cards 45 — — — 45 – Non-banking and other fees (2) 2 14 37 9 62 Total fee and commission income 284 14 63 9 370 Fee and commission expense (221) (4) (6) (11) (242) Net fee and commission income/(expense) 63 10 57 (2) 128 Customer loans 175,262 4,880 18,084 — 198,226 Customer deposits 150,982 — 25,372 4,794 181,148 30 June 2023 £m £m £m £m £m Net interest income 1,865 79 405 12 2,361 Non-interest income/(expense) 88 100 67 (22) 233 Total operating income 1,953 179 472 (10) 2,594 Operating expenses before credit impairment charges, provisions and charges (912) (73) (170) (64) (1,219) Credit impairment charges (55) (14) (36) — (105) Provisions for other liabilities and charges (106) (3) 4 (43) (148) Total credit impairment charges, provisions and charges (161) (17) (32) (43) (253) Profit/(loss) before tax 880 89 270 (117) 1,122 Revenue from external customers 1,856 313 364 61 2,594 Inter-segment revenue/(expense) 97 (134) 108 (71) — Total operating income/(expense) 1,953 179 472 (10) 2,594 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 4 70 Total fee and commission income 301 12 84 4 401 Fee and commission expense (216) (3) (26) (6) (251) Net fee/(expense) and commission income 85 9 58 (2) 150 31 December 2023 Customer loans 179,887 5,228 17,939 — 203,054 Customer deposits 158,329 — 24,066 5,050 187,445 (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. The table below shows the relationship between Customer assets and Loans and advances to customers as presented in the Condensed Consolidated Balance Sheet. Customer assets exclude Joint ventures, as they carry low credit risk and therefore have an immaterial ECL, and Other items, mainly accrued interest that we have not yet charged to the customer's account and cash collateral. It also shows the relationship between customer liabilities (see above) and Deposits by customers as presented in the Condensed Consolidated Balance Sheet. Net carrying amount Assets Liabilities 30 June 2024 31 December 2023 30 June 2024 31 December 2023 £m £m £m £m Customer balances (gross) 198,226 203,054 181,148 187,445 Loan loss allowance (860) (914) — — Customer balances (net) 197,366 202,140 181,148 187,445 Intercompany balances 4,901 4,544 3,406 2,825 Accrued interest 434 739 1,002 830 Other items 342 12 (682) (250) Loans and advances to customers / Deposits by customers 203,043 207,435 184,874 190,850

Operating Expenses Before Credi

Operating Expenses Before Credit Impairment Charges, Provisions and Charges	6 Months Ended
	Jun. 30, 2024
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 2024 30 June 2023 £m £m Staff costs 641 611 Other administration expenses 488 474 Depreciation, amortisation and impairment 150 134 1,279 1,219

Credit Impairment Charges and P

Credit Impairment Charges and Provisions	6 Months Ended
Credit Impairment Charges and Provisions	Jun. 30, 2024
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 2024 30 June 2023 £m £m Credit impairment charges: Loans and advances to customers 33 98 Recoveries of loans and advances, net of collection costs 8 4 Off-balance sheet credit exposures (See Note 22) 20 3 61 105 Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 22) 141 149 Charge/(release) for residual value and voluntary termination 1 (1) 142 148 203 253 In H124 and H123 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, 2024
Major components of tax expense (income) [abstract]
Taxation	5. TAXATION The Santander UK group’s effective tax rate for H124 was 26.2% ( H123 : 27.5% ). Tax on profit differs from that calculated at the statutory rate as follows: For the half year to 30 June 2024 30 June 2023 £m £m Profit before tax 813 1,122 Tax calculated at the statutory rate of 25% (H123: 23.5%) 203 264 Bank surcharge on profits 23 44 Non-deductible preference dividends paid 4 5 Non-deductible UK Bank Levy 5 8 Non-deductible conduct remediation, fines and penalties — 3 Other non-deductible costs and non-taxable income 2 3 Tax relief on dividends in respect of other equity instruments (20) (19) Adjustment to prior year provisions (4) — Tax on profit 213 308 Interim period corporation tax is accrued based on the estimated average annual effective corporation tax for the year. 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 has consistently applied the UK’s Code of Practice on Taxation for Banks following first adoption in 2010.

Dividends on Ordinary Shares

Dividends on Ordinary Shares	6 Months Ended
Dividends on Ordinary Shares	Jun. 30, 2024
Dividends On Ordinary Shares [Abstract]
Dividends on Ordinary Shares	6. DIVIDENDS ON ORDINARY SHARES An int erim dividend of £554m was declared on the Company’s ordinary shares in issue ( H123 : £410m ).

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
Derivative Financial Instruments	Jun. 30, 2024
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 2024 31 December 2023 Fair value Fair value Notional amount Assets Liabilities Notional amount Assets Liabilities £m £m £m £m £m £m Derivatives held for trading: Exchange rate contracts 13,170 91 97 12,927 92 217 Interest rate contracts (1) 25,892 326 549 28,351 389 583 Equity and credit contracts 727 141 19 765 133 20 Total derivatives held for trading 39,789 558 665 42,043 614 820 Derivatives held for hedging Designated as fair value hedges: Exchange rate contracts 1,398 40 1 1,145 29 2 Interest rate contracts 137,260 1,101 488 107,540 1,275 839 138,658 1,141 489 108,685 1,304 841 Designated as cash flow hedges: Exchange rate contracts 20,544 729 288 21,618 1,008 289 Interest rate contracts (1) 62,615 468 1,064 50,896 553 915 83,159 1,197 1,352 72,514 1,561 1,204 Total derivatives held for hedging 221,817 2,338 1,841 181,199 2,865 2,045 Derivative netting (2) — (1,765) (1,765) — (2,047) (2,047) Total derivatives 261,606 1,131 741 223,242 1,432 818 (1) Interest rate contracts include inflation rate contracts. (2) 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 £682m ( 2023 : £472m ) and the amount of cash collateral paid that had been offset against the gross derivative liabilities was £1m ( 2023 : £12m ). At 30 June 2024 , the fair value of derivative assets included amounts due from Banco Santander group entities of £484m ( 2023 : £762m ) and the fair value of derivative liabilities included amounts due to Banco Santander group entities of £254m ( 2023 : £230m ).

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, 2024
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 2024 31 December 2023 £m £m Loans and advances to customers 44 46 Debt securities 165 167 Other debt instruments 40 49 249 262

Loans and Advances to Customers

Loans and Advances to Customers	6 Months Ended
Loans and Advances to Customers	Jun. 30, 2024
Net Loans And Advances To Customers [Abstract]
Loans and Advances to Customers	9. LOANS AND ADVANCES TO CUSTOMERS 30 June 2024 31 December 2023 £m £m Loans and advances to customers 203,925 208,370 Credit impairment loss allowances on loans and advances to customers (860) (914) Residual value and voluntary termination provisions on finance leases (22) (21) Net loans and advances to customers 203,043 207,435 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, 2024
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. The gross assets securitised, or for the covered bond programme assigned, at 30 June 2024 and 31 December 2023 were: 30 June 2024 31 December 2023 £m £m Mortgage-backed master trust structures: – Holmes 4,669 3,242 – Fosse 2,724 2,048 7,393 5,290 Other asset-backed securitisation structures: – Repton 766 757 766 757 Total securitisation programmes 8,159 6,047 Covered bond programme: – Euro 35bn Global Covered Bond Programme 25,030 21,880 Total securitisation and covered bond programmes 33,189 27,927 The following table sets out the internal and external issuances and redemptions in H124 and H123 for each securitisation and covered bond programme. Internal issuances External issuances Internal redemptions External redemptions H124 H123 H124 H123 H124 H123 H124 H123 £m £m £m £m £m £m £m £m Mortgage-backed master trust structures: – Holmes 106 118 750 750 — 30 — 142 – Fosse 760 — — — — — — — Other asset-backed securitisation structures: – Motor — — — — — — — 7 – Repton — — — 550 — — — — Covered bond programme: – Euro 35bn Global Covered Bond Programme — 1,100 4,099 1,500 41 5 1,962 1,017 866 1,218 4,849 2,800 41 35 1,962 1,166

Reverse Repurchase Agreements -

Reverse Repurchase Agreements - Non Trading	6 Months Ended
Reverse Repurchase Agreements - Non Trading	Jun. 30, 2024
Disclosure Of Reserve Repurchase Agreements Non-Trading [Abstract]
Reverse Repurchase Agreements - Non Trading	11. REVERSE REPURCHASE AGREEMENTS – NON-TRADING 30 June 2024 31 December 2023 £m £m Agreements with banks 1,949 2,397 Agreements with customers 13,370 10,071 15,319 12,468

Other Financial Assets at Amort

Other Financial Assets at Amortised Cost	6 Months Ended
Other Financial Assets at Amortised Cost	Jun. 30, 2024
Financial assets at fair value through profit or loss [abstract]
Other Financial Assets at Amortised Cost	12. OTHER FINANCIAL ASSETS AT AMORTISED COST 30 June 2024 31 December 2023 £m £m Debt securities 1,744 152 1,744 152 A significant portion of the debt securities are held in our eligible liquidity pool and consist mainly of government bonds and covered bonds. In H124, Santander UK increased the allocation of liquid assets to longer-dated, duration-hedged UK Gilts to support ongoing HQLA requirements. Detailed disclosures can be found in the 'Liquidity risk' section of the Risk review.

Interests in Other Entities

Interests in Other Entities	6 Months Ended
Interests in Other Entities	Jun. 30, 2024
Investments accounted for using equity method [abstract]
Interests in Other Entities	13. 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 2023 Annual Report .

Intangible Assets

Intangible Assets	6 Months Ended
Intangible Assets	Jun. 30, 2024
Disclosure of detailed information about intangible assets [abstract]
Intangible Assets	14. INTANGIBLE ASSETS At 30 June 2024 , intangible assets comprised goodwill of £1,199m ( 2023 : £1,199m ) and computer software of £322m ( 2023 : £349m ). At 30 June 2024 , 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. Details of the sensitivity of value in use (VIU) to changes in assumptions, including changes required to achieve nil headroom, are set out in Note 20 to the Consolidated Financial Statements in the 2023 Annual Report .

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
Property, Plant and Equipment	Jun. 30, 2024
Property, plant and equipment [abstract]
Property, Plant and Equipment	15. 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 2024 918 877 67 635 263 2,760 Additions — 21 — 104 16 141 Disposals (3) (16) — (117) (13) (149) At 30 June 2024 915 882 67 622 266 2,752 Accumulated depreciation: At 1 January 2024 226 653 67 147 173 1,266 Charge for the period 11 32 — 37 9 89 Disposals (2) (15) — (41) — (58) At 30 June 2024 235 670 67 143 182 1,297 Carrying amount 680 212 — 479 84 1,455 (1) Property, plant and equipment includes investment properties of £16m ( 2023 : £17m ).

Other Financial Liabilities at

Other Financial Liabilities at Fair Value Through Profit or Loss	6 Months Ended
	Jun. 30, 2024
Disclosure of financial liabilities [abstract]
Other Financial Liabilities at Fair Value Through Profit or Loss	16. OTHER FINANCIAL LIABILITIES AT FAIR VALUE THROUGH PROFIT OR LOSS 30 June 2024 31 December 2023 £m £m Structured Notes Programmes 362 369 Structured deposits 518 426 Zero Amortising Guaranteed Notes 93 104 973 899

Deposits by Customers

Deposits by Customers	6 Months Ended
Deposits by Customers	Jun. 30, 2024
Deposits from customers [abstract]
Deposits by Customers	17. DEPOSITS BY CUSTOMERS 30 June 2024 31 December 2023 £m £m Demand and time deposits (1) 181,468 188,004 Amounts due to other Santander UK Group Holdings plc subsidiaries 123 114 Amounts due to Santander UK Group Holdings plc (2) 1,778 1,772 Amounts due to fellow Banco Santander subsidiaries and joint ventures 1,505 960 184,874 190,850 (1) Includes capital amount guaranteed / protected equity index-linked deposits of £232m ( 2023 : £304m ). (2) Includes downstreamed funding from our immediate parent company Santander UK Group Holdings plc.

Deposits by Banks

Deposits by Banks	6 Months Ended
Deposits by Banks	Jun. 30, 2024
Disclosure Of Deposits From Banks [Abstract]
Deposits by Banks	18. DEPOSITS BY BANKS 30 June 2024 31 December 2023 £m £m Items in the course of transmission 973 732 Deposits held as collateral 578 860 Other deposits (1) 14,944 18,737 Amounts due to Santander UK subsidiaries 4 3 16,499 20,332 (1) Includes balance drawn from the TFSME of £13.0bn ( 2023 : £17.0bn ).

Repurchase Agreements - Non Tra

Repurchase Agreements - Non Trading	6 Months Ended
Repurchase Agreements - Non Trading	Jun. 30, 2024
Disclosure Of Repurchase Agreements [Abstract]
Repurchase Agreements - Non Trading	19. REPURCHASE AGREEMENTS – NON-TRADING 30 June 2024 31 December 2023 £m £m Agreements with banks 616 551 Agreements with customers 6,007 7,860 6,623 8,411

Debt Securities in Issue

Debt Securities in Issue	6 Months Ended
Debt Securities in Issue	Jun. 30, 2024
Debt Securities In Issue [Abstract]
Debt Securities in Issue	20. DEBT SECURITIES IN ISSUE 30 June 2024 31 December 2023 £m £m Medium-term notes 8,879 11,656 Euro €35bn Global Covered Bond Programme 16,896 15,000 US $20bn Commercial Paper Programmes 2,968 2,761 Certificates of deposit 1,397 1,530 Credit linked notes 387 194 Securitisation programmes 3,526 2,769 34,053 33,910

Subordinated Liabilities

Subordinated Liabilities	6 Months Ended
Subordinated Liabilities	Jun. 30, 2024
Subordinated liabilities [abstract]
Subordinated Liabilities	21. SUBORDINATED LIABILITIES 30 June 2024 31 December 2023 £m £m £325m Sterling preference shares 343 343 Undated subordinated liabilities 205 205 Dated subordinated liabilities 1,849 1,838 2,397 2,386 In H124 , no subordinated liabilities were repurchased as part of ongoing liability management exercises. In H123 , certain subordinated liabilities were repurchased, resulting in a profit of £3m .

Provisions

Provisions	6 Months Ended
Provisions	Jun. 30, 2024
Disclosure of other provisions [abstract]
Provisions	22. PROVISIONS Customer remediation Litigation and other regulatory Regulatory levies and fees Bank Levy Property ECL on undrawn facilities and guarantees Restructuring Other Total £m £m £m £m £m £m £m £m £m At 1 January 2024 106 132 — — 47 78 32 7 402 Additional provisions (See Note 4) 6 4 41 — — 20 13 83 167 Provisions released (See Note 4) — (4) — — (1) — — — (5) Utilisation and other (39) (28) (1) — (13) — (27) (76) (184) At 30 June 2024 73 104 40 — 33 98 18 14 380 Net provisions of £6m were recognised in H124 for customer remediations, relating to our mortgage book. The provisions remain subject to change as additional data becomes available and remediation boundaries are finalised. Litigation and other regulatory provisions principally comprised amounts in respect of litigation and other regulatory charges, operational loss and operational risk provisions, and related expenses. A number of uncertainties exist with respect to these provisions given the uncertainties inherent in litigation and other regulatory matters, that affect the amount and timing of any potential outflows with respect to which provisions have been established. These provisions are reviewed at least quarterly. In H124 there were charges of £4m for legal provisions. The balance also includes an amount in respect of our best estimate of liability relating to legal dispute regarding allocation of responsibility for a specific PPI portfolio of complaints, further described in Note 24 . No further information on the best estimate is provided on the basis that it would be seriously prejudicial. Regulatory levies and fees are payable to regulatory bodies such as the FCA, PRA and Bank of England in the ordinary course of business. In H124 there were charges of £37m relating to the new Bank of England levy. In H124 , other provisions included charges for operational risk provisions of £71m ( H123 : £87m ), including fraud losses of £54m ( H123 : £75m ).

Retirement Benefit Plans

Retirement Benefit Plans	6 Months Ended
Retirement Benefit Plans	Jun. 30, 2024
Disclosure of net defined benefit liability (asset) [abstract]
Retirement Benefit Plans	23. RETIREMENT BENEFIT PLANS The amounts recognised in the balance sheet were as follows: 30 June 2024 31 December 2023 £m £m Assets/(liabilities) Funded defined benefit pension scheme - surplus 622 723 Funded defined benefit pension scheme - deficit (6) (41) Unfunded pension and post-retirement medical benefits (24) (25) Total net assets 592 657 a) Defined contribution pension plans An expense of £40m ( H123 : £33m ) 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 charged to the income statement was £6m ( H123 : charge of £16m ). The amounts recognised in other comprehensive income were as follows: For the half year to 30 June 2024 30 June 2023 £m £m Return on plan assets (excluding amounts included in net interest expense) 634 470 Actuarial (gains) arising from changes in demographic assumptions (88) — Actuarial losses arising from experience adjustments 64 89 Actuarial (gains) arising from changes in financial assumptions (451) (399) Pension remeasurement 159 160 The net assets recognised in the balance sheet were determined as follows: 30 June 2024 31 December 2023 £m £m Present value of defined benefit obligations (7,725) (8,201) Fair value of scheme assets 8,317 8,858 Net defined benefit assets 592 657 Actuarial assumptions The principal actuarial assumptions used for the Scheme were: 30 June 2024 31 December 2023 % % To determine benefit obligations (1) : – Discount rate for scheme liabilities 5.2 4.6 – General price inflation 3.1 3.0 – General salary increase 1 1.0 – Expected rate of pension increase 2.9 3.0 Years Years Longevity at 60 for current pensioners, on the valuation date: – Males 27.1 27.0 – Females 29.8 29.8 Longevity at 60 for future pensioners currently aged 40, on the valuation date: – Males 28.7 28.6 – Females 31.4 31.3 (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 H124 was due to increased fixed interest gilt yields. In H124, we adopted a new version of the model that we currently use to set the discount rate. The updated model is based on an expanded data set which improves stability of the model. 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 2024 31 December 2023 Assumption Change in pension obligation at period end from £m £m Discount rate 50 bps increase (460) (507) General price inflation 50 bps increase 348 385 Mortality Each additional year of longevity assumed 201 223

Contingent Liabilities and Comm

Contingent Liabilities and Commitments	6 Months Ended
Contingent Liabilities and Commitments	Jun. 30, 2024
Disclosure of contingent liabilities [abstract]
Contingent Liabilities and Commitments	24. CONTINGENT LIABILITIES AND COMMITMENTS 30 June 2024 31 December 2023 £m £m Guarantees given to third parties 420 452 Formal standby facilities, credit lines and other commitments 36,757 30,976 37,177 31,428 Where the items set out below can be reliably estimated, they are disclosed in the table above. Other legal, regulatory or tax 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, Santander UK is subject to audits, reviews, challenges and tax, regulatory or law enforcement investigations or proceedings by relevant regulators or government agencies in various jurisdictions. All such matters are assessed periodically to determine the likelihood of Santander UK incurring a liability. In those instances where it is concluded that it is not yet probable that a quantifiable payment will be made, for example because the facts are unclear or further time is required to fully assess the merits of the case or to reasonably quantify the expected payment, no provision is made. In addition, where it is not currently practicable to estimate the possible financial effect of these matters, no provision is made. Payment Protection Insurance AXA France IARD and AXA France Vie (former GE Capital Corporation Group entities (GE Capital), known as Financial Insurance Company Ltd (FICL) and Financial Assurance Company Ltd (FACL), acquired by AXA SA in 2015) (together, AXA France) have brought a claim for £552m (plus interest) against (i) Santander Cards UK Limited (former GE Capital entity known as GE Capital Bank Limited (GECB), which was acquired by Banco Santander SA in 2008 and subsequently transferred to Santander UK plc); and (ii) Santander Insurance Services UK Limited (a Banco Santander SA subsidiary) (together the Santander Entities). The claim relates to the allocation of liability for compensation and associated costs in respect of a large number of PPI policies distributed by GECB pre-2005, which were underwritten by FICL and FACL. AXA France reduced their claim from £670m (plus interest) to £552m (plus interest) in their Re-Re- Amended Particulars of Claim dated 29 June 2023. The Santander Entities strongly refute the claim. Trial has been fixed for six weeks, beginning on 3 March 2025. There are ongoing factual issues to be resolved which may have legal consequences including in relation to liability. These issues create uncertainties which mean that it is difficult to reliably predict the outcome or the timing of the resolution of the matter. The litigation and other regulatory provision in Note 22 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 22 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 H124 we continued to cooperate with the German authorities and, with the assistance of external experts, to progress an internal investigation into the matters in question. From Santander UK plc’s perspective, t he investigation is focused principally on the period 2009-2011 and remains on-going. There remain factual issues to be resolved which may have legal consequences including potentially material financial penalties. These issues create uncertainties which mean that it is difficult to predict the resolution of the matter including timing or the significance of the possible impact. These uncertainties mean it is not currently practicable to make a reliable assessment of the size of any related potential liability. Any potential losses, claims or expenses suffered or incurred by Santander Financial Services plc in respect of these matters have been fully indemnified by Santander UK plc, as part of the ring-fencing transfer scheme between Santander UK plc, Santander Financial Services plc and Banco Santander SA. SCUK - Motor Finance Broker Commissions Following the FCA’s Motor Market review in 2019 which resulted in a change in rules in January 2021, Santander Consumer (UK) plc (SCUK) has received a number of county court claims and complaints in respect of its historical use of discretionary commission arrangements (DCAs) prior to the 2021 rule changes. In the context of the complaints made to the Financial Ombudsman Service relating to such commission arrangements, the FCA commenced in January a review of the use of DCAs between lenders and credit brokers (the FCA review). A claim has also 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. In July 2024, the FCA extended the timeline for its review to May 2025 and proposed an extension of the current pause on complaints handling related to discretionary commission arrangements from September 2024 to 4 December 2025. While it is possible that certain charges may be incurred in relation to the FCA’s review or related existing or future county court claims, Financial Ombudsman Service (FOS) complaints and the Competition Appeal Tribunal (CAT) proceedings, it is not considered that a legal or constructive obligation has been incurred in relation to these matters that would require a provision to be recognised at this stage. The resolution of such matters is not possible to predict with any certainty and there remain significant inherent uncertainties regarding the existence, scope and timing of any possible outflow which make it impracticable to disclose the extent of any potential financial impact. Other On 2 November 2015, Visa Europe Ltd agreed to sell 100% of its share capital to Visa Inc. The deal closed on 21 June 2016. As a member and shareholder of Visa Europe Ltd, Santander UK received upfront consideration made up of cash and convertible preferred stock. Conversion of the preferred stock into Class A Common Stock of Visa Inc. depends on the outcome of litigation against Visa involving UK & Ireland multilateral interchange fees (UK&I MIFs). The convertible preferred stock is now held by Santander Equity Investments Limited (SEIL), outside the ring-fenced bank. 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, 2024
Disclosure of classes of share capital [abstract]
Other Equity Instruments	25. OTHER EQUITY INSTRUMENTS Interest rate 30 June 2024 31 December 2023 % Next call date £m £m AT1 securities: - £500m Perpetual Capital Securities 6.75 June 2024 — 496 - £500m Perpetual Capital Securities 6.30 March 2025 500 500 - £210m Perpetual Capital Securities 4.25 March 2026 210 210 - £750m Perpetual Capital Securities 6.50 June 2027 750 750 - £400m Perpetual Capital Securities 8.75 Sept 2029 400 — 1,860 1,956

Assets Charged as Security for

Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets	6 Months Ended
	Jun. 30, 2024
Disclosure Of Assets Pledged As Security [Abstract]
Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets	26. 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 2023 Annual Report , Santander UK plc and certain of its subsidiaries issue securitisations and covered bonds through or involving structured entities. At 30 June 2024 , there were £33,189m ( 2023 : £27,927m ) of gross assets in these secured programmes and £1,637m ( 2023 : £839m ) of these related to internally retained issuances that were available for use as collateral for liquidity purposes in the future. At 30 June 2024 , £3,753m ( 2023 : £2,928m ) 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 2024 ( 2023 : £1,500m ), 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, 2024
Disclosure of transactions between related parties [abstract]
Related Party Disclosures	27. RELATED PARTY DISCLOSURES Related party transactions in the period were similar in nature to those in Note 38 to the Consolidated Financial Statements in the 2023 Annual Report. The financial position and performance of the Santander UK group were not materially affected in H124 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, 2024
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Abstract]
Financial Instruments	28. 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 2023 Annual Report. Valuation, sensitivity methodologies and inputs at 30 June 2024 are consistent with those described in Note 39 to the Consolidated Financial Statements in the 2023 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 2024 and 31 December 2023 . 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 2023 Annual Report. 30 June 2024 31 December 2023 Fair Carrying Fair Carrying value value value value £m £m £m £m Assets Loans and advances to customers 200,648 203,043 205,917 207,435 Loans and advances to banks 1,040 1,040 1,080 1,080 Reverse repurchase agreements - non-trading 15,315 15,319 12,470 12,468 Other financial assets at amortised cost 1,737 1,744 144 152 218,740 221,146 219,611 221,135 Liabilities Deposits by customers 184,436 184,874 190,632 190,850 Deposits by banks 16,524 16,499 20,382 20,332 Repurchase agreements - non-trading 6,626 6,623 8,413 8,411 Debt securities in issue 34,059 34,053 33,621 33,910 Subordinated liabilities 2,613 2,397 2,800 2,386 244,258 244,446 255,848 255,889 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 2024 and 31 December 2023 , analysed by their levels in the fair value hierarchy - Level 1, Level 2 and Level 3. 30 June 2024 31 December 2023 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 — 860 — 860 — 1,129 — 1,129 A Interest rate contracts — 1,895 — 1,895 — 2,216 1 2,217 A & C Equity and credit contracts — 104 37 141 — 98 35 133 B & D Netting — (1,765) — (1,765) — (2,047) — (2,047) — 1,094 37 1,131 — 1,396 36 1,432 Other financial assets at FVTPL Loans and advances to customers — — 44 44 — — 46 46 A Debt securities — 165 40 205 — 167 49 216 A, B & D — 165 84 249 — 167 95 262 Financial assets at FVOCI Debt securities 8,293 325 — 8,618 8,293 188 — 8,481 D 8,293 325 — 8,618 8,293 188 — 8,481 Total assets at fair value 8,293 1,584 121 9,998 8,293 1,751 131 10,175 Liabilities Derivative financial instruments Exchange rate contracts — 386 — 386 — 508 — 508 A Interest rate contracts — 2,101 — 2,101 — 2,336 1 2,337 A & C Equity and credit contracts — 6 13 19 — 11 9 20 B & D Netting — (1,765) — (1,765) — (2,047) — (2,047) — 728 13 741 — 808 10 818 Other financial liabilities at FVTPL Debt securities in issue — 362 — 362 — 369 — 369 A Structured deposits — 518 — 518 — 426 — 426 A Zero Amortising Guaranteed Notes — 93 — 93 — 104 — 104 D — 973 — 973 — 899 — 899 Total liabilities at fair value — 1,701 13 1,714 — 1,707 10 1,717 Transfers between levels of the fair value hierarchy In H124 there were no significant ( H123 : 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 2023 Annual Report . 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 2024 31 December 2023 £m £m Risk-related: - Bid-offer and trade specific adjustments 8 (6) - Uncertainty 5 6 - Credit risk adjustment — 1 - Funding fair value adjustment — 1 13 2 Day One profit 1 1 14 3 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 2023 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 2023 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 H124 : Assets Liabilities Derivatives Other financial assets at FVTPL Total Derivatives Total £m £m £m £m £m At 1 January 2024 36 95 131 (10) (10) Total gains/(losses) recognised: Fair value movements (1) 6 (1) 5 (4) (4) Settlements (5) (10) (15) 1 1 At 30 June 2024 37 84 121 (13) (13) Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period (1) 6 (1) 5 (4) (4) (1) 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 2023 Annual Report .

Assets Held for Sale

Assets Held for Sale	6 Months Ended
Assets Held for Sale	Jun. 30, 2024
Discontinued Operations and Assets and Liabilities Held for Sale [Abstract]
Assets Held for Sale	29. ASSETS HELD FOR SALE Assets held for sale Sale of property Management considered the sale of part of Santander House (Milton Keynes) under a proposed transaction with the developer for the construction of Unity Place and Buckingham House (Bletchley), to be highly probable at the balance sheet date. As such, the Santander UK group classified these properties, which are included in the Corporate Centre segment and carried at their sales prices, as held for sale. Both sales are expected to complete in 2024 with no gain or loss. At 30 June 2024 and 31 December 2023 , assets held for sale comprised: 30 June 2024 31 December 2023 £m £m Assets Property, plant and equipment 13 13 Total assets held for sale 13 13

Events After the Balance Sheet

Events After the Balance Sheet Date	6 Months Ended
Events After the Balance Sheet Date	Jun. 30, 2024
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 2024 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, 2024
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 2023 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 plc (the Company) and its subsidiaries (collectively Santander UK or the Santander UK group) for the year ended 31 December 2023 which were prepared in accordance with UK-adopted International Accounting Standards (IAS). Those consolidated financial statements were also prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the IASB, including interpretations issued by the IFRS Interpretations Committee, as there were no applicable differences from IFRS 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 2023 Annual Report.
Future accounting developments	Future accounting developments The IASB issued the following new/amended accounting standards which are not yet effective and have not been endorsed for use in the UK: – Effective 1 January 2026: ‘Amendments to the Classification and Measurement of Financial Instruments’ (Amendments to IFRS 9 ‘Financial Instruments’ and IFRS 7 ‘Financial Instruments: Disclosures’) - the amendments set out changes to settling financial liabilities using an electronic payment system, assessing contractual cash flow characteristics of financial assets including those with environmental, social and governance (ESG)-linked features and requiring additional disclosures for certain financial instruments. – Effective 1 January 2027: IFRS 18 ‘Presentation and Disclosure in Financial Statements’ – the new standard will replace IAS 1 ‘Presentation of Financial Statements’ and introduces changes to the categories for classifying income and expenses and subtotals presented in the income statement and new or amended disclosures in respect of management-defined performance measures and specified expenses by nature. The Santander UK group is assessing these new/amended accounting standards to determine the potential impacts on the financial statements when they become effective or if they are otherwise earlier adopted when available.
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 Santander UK's condensed consolidated financial statements in accordance with IFRS requires management to make judgements and assumptions in applying the accounting policies that affect the reported amounts of assets, liabilities, income and expenses. Due to the inherent uncertainty in making estimates, actual results reported in future periods may be based on amounts which differ from those estimates. Estimates, judgements and assumptions are continually evaluated and are based on historical experience and other factors, including expectations of future events that are believed to be reasonable under the circumstances. There has been no change in the inherent sensitivity of the areas of judgement in the period. Management have considered the impact of developments in principal risks and uncertainties, as set out in the Risk review, on critical judgements and accounting estimates. The significant judgements, apart from those involving estimation, made by management in applying Santander UK's accounting policies in these financial statements (key judgements) and the key sources of estimation uncertainty that may have a significant risk of causing a material adjustment to the carrying amount of assets and liabilities within the next financial year (key estimates), which together are considered critical to Santander UK's results and financial position, are as follows: a) Credit impairment allowance 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 2023 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 22 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 24 provides disclosure relating to ongoing factual issues and reviews that could impact the timing and amount of any outflows. It includes disclosure relating to an investigation in relation to the historical involvement of Santander UK plc, Santander Financial Services plc and Cater Allen International Limited (all subsidiaries of Santander UK Group Holdings plc) in German dividend tax arbitrage transactions. It also includes disclosure relating to the historical use of discretionary commission arrangements by Santander Consumer (UK) plc. These judgements are based on the specific facts available and often require specialist professional advice. There can be a wide range of possible outcomes and uncertainties, particularly in relation to legal actions, and regulatory and consumer credit matters. As a result, it is often not possible to make reliable estimates of the likelihood and amount of any potential outflows, or to calculate any resulting sensitivities. For more on each of these key judgements and estimates, see Notes 22 and 24 . c) Retirement benefit plans 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 23 . Sensitivity of defined benefit pension scheme estimates For detailed disclosures, see ‘Actuarial assumption sensitivities’ in Note 23 . 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 represent fair value. Given the nature of these investments, we are unable to prepare sensitivities on how their values could vary as market conditions or other variables change. d) Goodwill 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 14 . Sensitivity of goodwill For detailed disclosures, see ‘Sensitivities of key assumptions in calculating VIU’ in Note 20 to the Consolidated Financial Statements in the 2023 Annual Report .

Accounting Policies (Tables)

Accounting Policies (Tables)	6 Months Ended
Accounting Policies (Tables)	Jun. 30, 2024
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, 2024
Disclosure of operating segments [abstract]
Summary of Results by Segment	Results by segment For the half year to Retail & Business Banking Consumer Finance Corporate & Commercial Banking Corporate Centre Total 30 June 2024 £m £m £m £m £m Net interest income/(expense) 1,684 74 383 (37) 2,104 Non-interest income/(expense) 62 83 67 (21) 191 Total operating income/(expense) 1,746 157 450 (58) 2,295 Operating expenses before credit impairment charges, provisions and charges (999) (77) (205) 2 (1,279) Credit impairment charges (49) (8) (3) (1) (61) Provisions for other liabilities and charges (98) (15) (18) (11) (142) Total credit impairment charges, provisions and charges (147) (23) (21) (12) (203) Profit/(loss) before tax 600 57 224 (68) 813 Revenue/(expense) from external customers 1,686 360 264 (15) 2,295 Inter-segment revenue/(expense) 60 (203) 186 (43) — Total operating income/(expense) 1,746 157 450 (58) 2,295 Revenue from external customers includes the following fee and commission income: (1) – Current account and debit card fees 212 — 26 — 238 – Insurance, protection and investments 25 — — — 25 – Credit cards 45 — — — 45 – Non-banking and other fees (2) 2 14 37 9 62 Total fee and commission income 284 14 63 9 370 Fee and commission expense (221) (4) (6) (11) (242) Net fee and commission income/(expense) 63 10 57 (2) 128 Customer loans 175,262 4,880 18,084 — 198,226 Customer deposits 150,982 — 25,372 4,794 181,148 30 June 2023 £m £m £m £m £m Net interest income 1,865 79 405 12 2,361 Non-interest income/(expense) 88 100 67 (22) 233 Total operating income 1,953 179 472 (10) 2,594 Operating expenses before credit impairment charges, provisions and charges (912) (73) (170) (64) (1,219) Credit impairment charges (55) (14) (36) — (105) Provisions for other liabilities and charges (106) (3) 4 (43) (148) Total credit impairment charges, provisions and charges (161) (17) (32) (43) (253) Profit/(loss) before tax 880 89 270 (117) 1,122 Revenue from external customers 1,856 313 364 61 2,594 Inter-segment revenue/(expense) 97 (134) 108 (71) — Total operating income/(expense) 1,953 179 472 (10) 2,594 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 4 70 Total fee and commission income 301 12 84 4 401 Fee and commission expense (216) (3) (26) (6) (251) Net fee/(expense) and commission income 85 9 58 (2) 150 31 December 2023 Customer loans 179,887 5,228 17,939 — 203,054 Customer deposits 158,329 — 24,066 5,050 187,445 (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.
Summary Of Relationship Between Customer Liabilities And Deposits	The table below shows the relationship between Customer assets and Loans and advances to customers as presented in the Condensed Consolidated Balance Sheet. Customer assets exclude Joint ventures, as they carry low credit risk and therefore have an immaterial ECL, and Other items, mainly accrued interest that we have not yet charged to the customer's account and cash collateral. It also shows the relationship between customer liabilities (see above) and Deposits by customers as presented in the Condensed Consolidated Balance Sheet. Net carrying amount Assets Liabilities 30 June 2024 31 December 2023 30 June 2024 31 December 2023 £m £m £m £m Customer balances (gross) 198,226 203,054 181,148 187,445 Loan loss allowance (860) (914) — — Customer balances (net) 197,366 202,140 181,148 187,445 Intercompany balances 4,901 4,544 3,406 2,825 Accrued interest 434 739 1,002 830 Other items 342 12 (682) (250) Loans and advances to customers / Deposits by customers 203,043 207,435 184,874 190,850

Operating Expenses Before Cre_2

Operating Expenses Before Credit Impairment Charges, Provisions and Charges (Tables)	6 Months Ended
	Jun. 30, 2024
Expenses by nature [abstract]
Summary of Operating Expenses Before Credit Impairment Losses, Provisions and Charges	30 June 2024 30 June 2023 £m £m Staff costs 641 611 Other administration expenses 488 474 Depreciation, amortisation and impairment 150 134 1,279 1,219

Credit Impairment Charges and_2

Credit Impairment Charges and Provisions (Tables)	6 Months Ended
Credit Impairment Charges and Provisions (Tables)	Jun. 30, 2024
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Summary of Impairment Losses and Provisions	30 June 2024 30 June 2023 £m £m Credit impairment charges: Loans and advances to customers 33 98 Recoveries of loans and advances, net of collection costs 8 4 Off-balance sheet credit exposures (See Note 22) 20 3 61 105 Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 22) 141 149 Charge/(release) for residual value and voluntary termination 1 (1) 142 148 203 253

Taxation (Tables)

Taxation (Tables)	6 Months Ended
Taxation (Tables)	Jun. 30, 2024
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 Santander UK group’s effective tax rate for H124 was 26.2% ( H123 : 27.5% ). Tax on profit differs from that calculated at the statutory rate as follows: For the half year to 30 June 2024 30 June 2023 £m £m Profit before tax 813 1,122 Tax calculated at the statutory rate of 25% (H123: 23.5%) 203 264 Bank surcharge on profits 23 44 Non-deductible preference dividends paid 4 5 Non-deductible UK Bank Levy 5 8 Non-deductible conduct remediation, fines and penalties — 3 Other non-deductible costs and non-taxable income 2 3 Tax relief on dividends in respect of other equity instruments (20) (19) Adjustment to prior year provisions (4) — Tax on profit 213 308

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	6 Months Ended
Derivative Financial Instruments (Tables)	Jun. 30, 2024
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 2024 31 December 2023 Fair value Fair value Notional amount Assets Liabilities Notional amount Assets Liabilities £m £m £m £m £m £m Derivatives held for trading: Exchange rate contracts 13,170 91 97 12,927 92 217 Interest rate contracts (1) 25,892 326 549 28,351 389 583 Equity and credit contracts 727 141 19 765 133 20 Total derivatives held for trading 39,789 558 665 42,043 614 820 Derivatives held for hedging Designated as fair value hedges: Exchange rate contracts 1,398 40 1 1,145 29 2 Interest rate contracts 137,260 1,101 488 107,540 1,275 839 138,658 1,141 489 108,685 1,304 841 Designated as cash flow hedges: Exchange rate contracts 20,544 729 288 21,618 1,008 289 Interest rate contracts (1) 62,615 468 1,064 50,896 553 915 83,159 1,197 1,352 72,514 1,561 1,204 Total derivatives held for hedging 221,817 2,338 1,841 181,199 2,865 2,045 Derivative netting (2) — (1,765) (1,765) — (2,047) (2,047) Total derivatives 261,606 1,131 741 223,242 1,432 818 (1) Interest rate contracts include inflation rate contracts. (2) 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 £682m ( 2023 : £472m ) and the amount of cash collateral paid that had been offset against the gross derivative liabilities was £1m ( 2023 : £12m ).

Other Financial Assets at Fai_2

Other Financial Assets at Fair Value Through Profit or Loss (Tables)	6 Months Ended
	Jun. 30, 2024
Financial assets at fair value through profit or loss [abstract]
Summary of Other Financial Assets at Fair Value Through Profit or Loss	30 June 2024 31 December 2023 £m £m Loans and advances to customers 44 46 Debt securities 165 167 Other debt instruments 40 49 249 262

Loans and Advances to Custome_2

Loans and Advances to Customers (Tables)	6 Months Ended
Loans and Advances to Customers (Tables)	Jun. 30, 2024
Net Loans And Advances To Customers [Abstract]
Summary of Net Loans and Advances to Customers	30 June 2024 31 December 2023 £m £m Loans and advances to customers 203,925 208,370 Credit impairment loss allowances on loans and advances to customers (860) (914) Residual value and voluntary termination provisions on finance leases (22) (21) Net loans and advances to customers 203,043 207,435

Securitisations and Covered B_2

Securitisations and Covered Bonds (Tables)	6 Months Ended
Securitisations and Covered Bonds (Tables)	Jun. 30, 2024
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 2024 and 31 December 2023 were: 30 June 2024 31 December 2023 £m £m Mortgage-backed master trust structures: – Holmes 4,669 3,242 – Fosse 2,724 2,048 7,393 5,290 Other asset-backed securitisation structures: – Repton 766 757 766 757 Total securitisation programmes 8,159 6,047 Covered bond programme: – Euro 35bn Global Covered Bond Programme 25,030 21,880 Total securitisation and covered bond programmes 33,189 27,927
Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme	The following table sets out the internal and external issuances and redemptions in H124 and H123 for each securitisation and covered bond programme. Internal issuances External issuances Internal redemptions External redemptions H124 H123 H124 H123 H124 H123 H124 H123 £m £m £m £m £m £m £m £m Mortgage-backed master trust structures: – Holmes 106 118 750 750 — 30 — 142 – Fosse 760 — — — — — — — Other asset-backed securitisation structures: – Motor — — — — — — — 7 – Repton — — — 550 — — — — Covered bond programme: – Euro 35bn Global Covered Bond Programme — 1,100 4,099 1,500 41 5 1,962 1,017 866 1,218 4,849 2,800 41 35 1,962 1,166

Reverse Repurchase Agreements_2

Reverse Repurchase Agreements - Non Trading (Tables)	6 Months Ended
Reverse Repurchase Agreements - Non Trading (Tables)	Jun. 30, 2024
Disclosure Of Reserve Repurchase Agreements Non-Trading [Abstract]
Summary of Reverse Repurchase Agreements - Non Trading	30 June 2024 31 December 2023 £m £m Agreements with banks 1,949 2,397 Agreements with customers 13,370 10,071 15,319 12,468 30 June 2024 31 December 2023 £m £m Agreements with banks 616 551 Agreements with customers 6,007 7,860 6,623 8,411

Other Financial Assets at Amo_2

Other Financial Assets at Amortised Cost (Tables)	6 Months Ended
Other Financial Assets at Amortised Cost (Tables)	Jun. 30, 2024
Financial assets at fair value through profit or loss [abstract]
Summary of Other Financial Assets at Amortised Cost	30 June 2024 31 December 2023 £m £m Debt securities 1,744 152 1,744 152

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	6 Months Ended
Property, Plant and Equipment (Tables)	Jun. 30, 2024
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 2024 918 877 67 635 263 2,760 Additions — 21 — 104 16 141 Disposals (3) (16) — (117) (13) (149) At 30 June 2024 915 882 67 622 266 2,752 Accumulated depreciation: At 1 January 2024 226 653 67 147 173 1,266 Charge for the period 11 32 — 37 9 89 Disposals (2) (15) — (41) — (58) At 30 June 2024 235 670 67 143 182 1,297 Carrying amount 680 212 — 479 84 1,455 (1) Property, plant and equipment includes investment properties of £16m ( 2023 : £17m ).

Other Financial Liabilities a_2

Other Financial Liabilities at Fair Value Through Profit or Loss (Tables)	6 Months Ended
	Jun. 30, 2024
Disclosure of financial liabilities [abstract]
Summary of Other Financial Liabilities at Fair Value Through Profit or Loss	30 June 2024 31 December 2023 £m £m Structured Notes Programmes 362 369 Structured deposits 518 426 Zero Amortising Guaranteed Notes 93 104 973 899

Deposits by Customers (Tables)

Deposits by Customers (Tables)	6 Months Ended
Deposits by Customers (Tables)	Jun. 30, 2024
Deposits from customers [abstract]
Schedule of Deposits by Customers	30 June 2024 31 December 2023 £m £m Demand and time deposits (1) 181,468 188,004 Amounts due to other Santander UK Group Holdings plc subsidiaries 123 114 Amounts due to Santander UK Group Holdings plc (2) 1,778 1,772 Amounts due to fellow Banco Santander subsidiaries and joint ventures 1,505 960 184,874 190,850 (1) Includes capital amount guaranteed / protected equity index-linked deposits of £232m ( 2023 : £304m ). (2) Includes downstreamed funding from our immediate parent company Santander UK Group Holdings plc.

Deposits by Banks (Tables)

Deposits by Banks (Tables)	6 Months Ended
Deposits by Banks (Tables)	Jun. 30, 2024
Disclosure Of Deposits From Banks [Abstract]
Schedule of Deposits by Banks	30 June 2024 31 December 2023 £m £m Items in the course of transmission 973 732 Deposits held as collateral 578 860 Other deposits (1) 14,944 18,737 Amounts due to Santander UK subsidiaries 4 3 16,499 20,332 (1) Includes balance drawn from the TFSME of £13.0bn ( 2023 : £17.0bn

Repurchase Agreements - Non T_2

Repurchase Agreements - Non Trading (Tables)	6 Months Ended
Repurchase Agreements - Non Trading (Tables)	Jun. 30, 2024
Disclosure Of Repurchase Agreements [Abstract]
Summary of Reverse Repurchase Agreements - Non Trading	30 June 2024 31 December 2023 £m £m Agreements with banks 1,949 2,397 Agreements with customers 13,370 10,071 15,319 12,468 30 June 2024 31 December 2023 £m £m Agreements with banks 616 551 Agreements with customers 6,007 7,860 6,623 8,411

Debt Securities in Issue (Table

Debt Securities in Issue (Tables)	6 Months Ended
Debt Securities in Issue (Tables)	Jun. 30, 2024
Debt Securities In Issue [Abstract]
Summary of Debt Securities in Issue	30 June 2024 31 December 2023 £m £m Medium-term notes 8,879 11,656 Euro €35bn Global Covered Bond Programme 16,896 15,000 US $20bn Commercial Paper Programmes 2,968 2,761 Certificates of deposit 1,397 1,530 Credit linked notes 387 194 Securitisation programmes 3,526 2,769 34,053 33,910

Subordinated Liabilities (Table

Subordinated Liabilities (Tables)	6 Months Ended
Subordinated Liabilities (Tables)	Jun. 30, 2024
Subordinated liabilities [abstract]
Schedule of Subordinated Liabilities	30 June 2024 31 December 2023 £m £m £325m Sterling preference shares 343 343 Undated subordinated liabilities 205 205 Dated subordinated liabilities 1,849 1,838 2,397 2,386

Provisions (Tables)

Provisions (Tables)	6 Months Ended
Provisions (Tables)	Jun. 30, 2024
Disclosure of other provisions [abstract]
Summary of Provisions Reconciliation	Customer remediation Litigation and other regulatory Regulatory levies and fees Bank Levy Property ECL on undrawn facilities and guarantees Restructuring Other Total £m £m £m £m £m £m £m £m £m At 1 January 2024 106 132 — — 47 78 32 7 402 Additional provisions (See Note 4) 6 4 41 — — 20 13 83 167 Provisions released (See Note 4) — (4) — — (1) — — — (5) Utilisation and other (39) (28) (1) — (13) — (27) (76) (184) At 30 June 2024 73 104 40 — 33 98 18 14 380

Retirement Benefit Plans (Table

Retirement Benefit Plans (Tables)	6 Months Ended
Retirement Benefit Plans (Tables)	Jun. 30, 2024
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 2024 31 December 2023 £m £m Assets/(liabilities) Funded defined benefit pension scheme - surplus 622 723 Funded defined benefit pension scheme - deficit (6) (41) Unfunded pension and post-retirement medical benefits (24) (25) Total net assets 592 657 The amounts recognised in other comprehensive income were as follows: For the half year to 30 June 2024 30 June 2023 £m £m Return on plan assets (excluding amounts included in net interest expense) 634 470 Actuarial (gains) arising from changes in demographic assumptions (88) — Actuarial losses arising from experience adjustments 64 89 Actuarial (gains) arising from changes in financial assumptions (451) (399) Pension remeasurement 159 160 The net assets recognised in the balance sheet were determined as follows: 30 June 2024 31 December 2023 £m £m Present value of defined benefit obligations (7,725) (8,201) Fair value of scheme assets 8,317 8,858 Net defined benefit assets 592 657 The principal actuarial assumptions used for the Scheme were: 30 June 2024 31 December 2023 % % To determine benefit obligations (1) : – Discount rate for scheme liabilities 5.2 4.6 – General price inflation 3.1 3.0 – General salary increase 1 1.0 – Expected rate of pension increase 2.9 3.0 Years Years Longevity at 60 for current pensioners, on the valuation date: – Males 27.1 27.0 – Females 29.8 29.8 Longevity at 60 for future pensioners currently aged 40, on the valuation date: – Males 28.7 28.6 – Females 31.4 31.3 (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 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 2024 31 December 2023 Assumption Change in pension obligation at period end from £m £m Discount rate 50 bps increase (460) (507) General price inflation 50 bps increase 348 385 Mortality Each additional year of longevity assumed 201 223
Summary of Net Assets Recognised	The net assets recognised in the balance sheet were determined as follows: 30 June 2024 31 December 2023 £m £m Present value of defined benefit obligations (7,725) (8,201) Fair value of scheme assets 8,317 8,858 Net defined benefit assets 592 657
Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes	The principal actuarial assumptions used for the Scheme were: 30 June 2024 31 December 2023 % % To determine benefit obligations (1) : – Discount rate for scheme liabilities 5.2 4.6 – General price inflation 3.1 3.0 – General salary increase 1 1.0 – Expected rate of pension increase 2.9 3.0 Years Years Longevity at 60 for current pensioners, on the valuation date: – Males 27.1 27.0 – Females 29.8 29.8 Longevity at 60 for future pensioners currently aged 40, on the valuation date: – Males 28.7 28.6 – Females 31.4 31.3 (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 2024 31 December 2023 Assumption Change in pension obligation at period end from £m £m Discount rate 50 bps increase (460) (507) General price inflation 50 bps increase 348 385 Mortality Each additional year of longevity assumed 201 223

Contingent Liabilities and Co_2

Contingent Liabilities and Commitments (Tables)	6 Months Ended
Contingent Liabilities and Commitments (Tables)	Jun. 30, 2024
Disclosure of contingent liabilities [abstract]
Summary of Contingent Liabilities and Commitments	30 June 2024 31 December 2023 £m £m Guarantees given to third parties 420 452 Formal standby facilities, credit lines and other commitments 36,757 30,976 37,177 31,428

Other Equity Instruments (Table

Other Equity Instruments (Tables)	6 Months Ended
Other Equity Instruments (Tables)	Jun. 30, 2024
Disclosure of classes of share capital [abstract]
Summary of Other Equity Instruments	Interest rate 30 June 2024 31 December 2023 % Next call date £m £m AT1 securities: - £500m Perpetual Capital Securities 6.75 June 2024 — 496 - £500m Perpetual Capital Securities 6.30 March 2025 500 500 - £210m Perpetual Capital Securities 4.25 March 2026 210 210 - £750m Perpetual Capital Securities 6.50 June 2027 750 750 - £400m Perpetual Capital Securities 8.75 Sept 2029 400 — 1,860 1,956

Financial Instruments (Tables)

Financial Instruments (Tables)	6 Months Ended
Financial Instruments (Tables)	Jun. 30, 2024
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 2024 and 31 December 2023 . 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 2023 Annual Report. 30 June 2024 31 December 2023 Fair Carrying Fair Carrying value value value value £m £m £m £m Assets Loans and advances to customers 200,648 203,043 205,917 207,435 Loans and advances to banks 1,040 1,040 1,080 1,080 Reverse repurchase agreements - non-trading 15,315 15,319 12,470 12,468 Other financial assets at amortised cost 1,737 1,744 144 152 218,740 221,146 219,611 221,135 Liabilities Deposits by customers 184,436 184,874 190,632 190,850 Deposits by banks 16,524 16,499 20,382 20,332 Repurchase agreements - non-trading 6,626 6,623 8,413 8,411 Debt securities in issue 34,059 34,053 33,621 33,910 Subordinated liabilities 2,613 2,397 2,800 2,386 244,258 244,446 255,848 255,889
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 2024 and 31 December 2023 , analysed by their levels in the fair value hierarchy - Level 1, Level 2 and Level 3. 30 June 2024 31 December 2023 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 — 860 — 860 — 1,129 — 1,129 A Interest rate contracts — 1,895 — 1,895 — 2,216 1 2,217 A & C Equity and credit contracts — 104 37 141 — 98 35 133 B & D Netting — (1,765) — (1,765) — (2,047) — (2,047) — 1,094 37 1,131 — 1,396 36 1,432 Other financial assets at FVTPL Loans and advances to customers — — 44 44 — — 46 46 A Debt securities — 165 40 205 — 167 49 216 A, B & D — 165 84 249 — 167 95 262 Financial assets at FVOCI Debt securities 8,293 325 — 8,618 8,293 188 — 8,481 D 8,293 325 — 8,618 8,293 188 — 8,481 Total assets at fair value 8,293 1,584 121 9,998 8,293 1,751 131 10,175 Liabilities Derivative financial instruments Exchange rate contracts — 386 — 386 — 508 — 508 A Interest rate contracts — 2,101 — 2,101 — 2,336 1 2,337 A & C Equity and credit contracts — 6 13 19 — 11 9 20 B & D Netting — (1,765) — (1,765) — (2,047) — (2,047) — 728 13 741 — 808 10 818 Other financial liabilities at FVTPL Debt securities in issue — 362 — 362 — 369 — 369 A Structured deposits — 518 — 518 — 426 — 426 A Zero Amortising Guaranteed Notes — 93 — 93 — 104 — 104 D — 973 — 973 — 899 — 899 Total liabilities at fair value — 1,701 13 1,714 — 1,707 10 1,717
Summary of Fair Value Adjustment	The fair value adjustments are set out in the following table: 30 June 2024 31 December 2023 £m £m Risk-related: - Bid-offer and trade specific adjustments 8 (6) - Uncertainty 5 6 - Credit risk adjustment — 1 - Funding fair value adjustment — 1 13 2 Day One profit 1 1 14 3
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 H124 : Assets Liabilities Derivatives Other financial assets at FVTPL Total Derivatives Total £m £m £m £m £m At 1 January 2024 36 95 131 (10) (10) Total gains/(losses) recognised: Fair value movements (1) 6 (1) 5 (4) (4) Settlements (5) (10) (15) 1 1 At 30 June 2024 37 84 121 (13) (13) Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period (1) 6 (1) 5 (4) (4) (1) Fair value movements relating to derivatives and other financial assets at FVTPL are recognised in other operating income in the income statement.

Assets Held for Sale (Tables)

Assets Held for Sale (Tables)	6 Months Ended
Assets Held for Sale (Tables)	Jun. 30, 2024
Discontinued Operations and Assets and Liabilities Held for Sale [Abstract]
Disclosure of Assets Classified as Held for Sale	At 30 June 2024 and 31 December 2023 , assets held for sale comprised: 30 June 2024 31 December 2023 £m £m Assets Property, plant and equipment 13 13 Total assets held for sale 13 13

Segments - Additional Informati

Segments - Additional Information (Details)	Jun. 30, 2024 segment
Disclosure of operating segments [abstract]
Number of segments	4

Segments - Summary of Results b

Segments - Summary of Results by Segment (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Disclosure of operating segments [line items]
Net interest income/(expense)	£ 2,104	£ 2,361
Non-interest income/(expense)	191	233
Total operating income/(expense)	2,295	2,594
Operating expenses before credit impairment charges, provisions and charges	(1,279)	(1,219)
Credit impairment charges	(61)	(105)
Provisions for other liabilities and charges	(142)	(148)
Total credit impairment charges, provisions and charges	(203)	(253)
Profit before tax	813	1,122
Revenue from external customers	2,295	2,594
Inter-segment revenue/(expense)	2,295	2,594
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	238	258
Insurance, protection and investments	25	24
Credit cards	45	49
Non-banking and other fees	62	70
Total fee and commission income	370	401
Fee and commission expense	(242)	(251)
Net fee and commission income	128	150
Customer loans	198,226		£ 203,054
Customer deposits	181,148		187,445
Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	0	0
Retail and Business Banking
Disclosure of operating segments [line items]
Net interest income/(expense)	1,684	1,865
Non-interest income/(expense)	62	88
Total operating income/(expense)	1,746	1,953
Operating expenses before credit impairment charges, provisions and charges	(999)	(912)
Credit impairment charges	(49)	(55)
Provisions for other liabilities and charges	(98)	(106)
Total credit impairment charges, provisions and charges	(147)	(161)
Profit before tax	600	880
Revenue from external customers	1,686	1,856
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	212	227
Insurance, protection and investments	25	24
Credit cards	45	49
Non-banking and other fees	2	1
Total fee and commission income	284	301
Fee and commission expense	(221)	(216)
Net fee and commission income	63	85
Customer loans	175,262		179,887
Customer deposits	150,982		158,329
Retail and Business Banking \| Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	60	97
Consumer Finance
Disclosure of operating segments [line items]
Net interest income/(expense)	74	79
Non-interest income/(expense)	83	100
Total operating income/(expense)	157	179
Operating expenses before credit impairment charges, provisions and charges	(77)	(73)
Credit impairment charges	(8)	(14)
Provisions for other liabilities and charges	(15)	(3)
Total credit impairment charges, provisions and charges	(23)	(17)
Profit before tax	57	89
Revenue from external customers	360	313
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	14	12
Total fee and commission income	14	12
Fee and commission expense	(4)	(3)
Net fee and commission income	10	9
Customer loans	4,880		5,228
Customer deposits	0		0
Consumer Finance \| Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	(203)	(134)
Corporate & Commercial Banking
Disclosure of operating segments [line items]
Net interest income/(expense)	383	405
Non-interest income/(expense)	67	67
Total operating income/(expense)	450	472
Operating expenses before credit impairment charges, provisions and charges	(205)	(170)
Credit impairment charges	(3)	(36)
Provisions for other liabilities and charges	(18)	4
Total credit impairment charges, provisions and charges	(21)	(32)
Profit before tax	224	270
Revenue from external customers	264	364
Revenue from external customers includes the following fee and commission income
Current account and debit card fees	26	31
Insurance, protection and investments	0	0
Credit cards	0	0
Non-banking and other fees	37	53
Total fee and commission income	63	84
Fee and commission expense	(6)	(26)
Net fee and commission income	57	58
Customer loans	18,084		17,939
Customer deposits	25,372		24,066
Corporate & Commercial Banking \| Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	186	108
Corporate Centre
Disclosure of operating segments [line items]
Net interest income/(expense)	(37)	12
Non-interest income/(expense)	(21)	(22)
Total operating income/(expense)	(58)	(10)
Operating expenses before credit impairment charges, provisions and charges	2	(64)
Credit impairment charges	(1)	0
Provisions for other liabilities and charges	(11)	(43)
Total credit impairment charges, provisions and charges	(12)	(43)
Profit before tax	(68)	(117)
Revenue from external customers	(15)	61
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	9	4
Total fee and commission income	9	4
Fee and commission expense	(11)	(6)
Net fee and commission income	(2)	(2)
Customer loans	0		0
Customer deposits	4,794		£ 5,050
Corporate Centre \| Inter-segment revenue/(expense)
Disclosure of operating segments [line items]
Inter-segment revenue/(expense)	£ (43)	£ (71)

Segments - Schedule Of Relation

Segments - Schedule Of Relationship between Customer Assets and Loans and Advances (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Assets
Customer balances (gross)	£ 198,226	£ 203,054
Loan loss allowance	(860)	(914)
Customer balances (net)	197,366	202,140
Accrued interest	434	739
Other items	342	12
Net loans and advances to customers	203,043	207,435
Liabilities
Customer balances (gross)	181,148	187,445
Customer balances (net)	181,148	187,445
Accrued interest	1,002	830
Other items	(682)	(250)
Deposits by customers	184,874	190,850
Intercompany balances
Assets
Intercompany balances	4,901	4,544
Liabilities
Intercompany balances	£ 3,406	£ 2,825

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, 2024	Jun. 30, 2023
Expenses by nature [abstract]
Staff costs	£ 641	£ 611
Other administration expenses	488	474
Depreciation, amortisation and impairment	150	134
Total operating expenses before impairment losses, provisions and charges	£ 1,279	£ 1,219

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, 2024	Jun. 30, 2023
Disclosure Of Credit Impairment Loss And Provisions [Abstract]
Loans and advances to customers	£ 33	£ 98
Recoveries of loans and advances, net of collection costs	8	4
Off-balance sheet credit exposures (See Note 22)	20	3
Credit impairment charges:	61	105
Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 22)	141	149
Charge/(release) for residual value and voluntary termination	1	(1)
Provisions for other liabilities and charges	142	148
Total operating credit impairment (charges)/write-backs, provisions and charges	£ 203	£ 253

Credit Impairment Charges and_4

Credit Impairment Charges and Provisions - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
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, 2024	Jun. 30, 2023
Major components of tax expense (income) [abstract]
Effective tax rate (percentage)	26.20%	27.50%

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, 2024	Jun. 30, 2023
Major components of tax expense (income) [abstract]
Profit before tax	£ 813	£ 1,122
Tax calculated at the statutory rate of 25% (H123: 23.5%)	203	264
Bank surcharge on profits	23	44
Non-deductible preference dividends paid	4	5
Non-deductible UK Bank Levy	5	8
Non-deductible conduct remediation, fines and penalties	0	3
Other non-deductible costs and non-taxable income	2	3
Tax relief on dividends in respect of other equity instruments	(20)	(19)
Adjustment to prior year provisions	(4)	0
Tax on profit	£ 213	£ 308

Dividends on Ordinary Shares (D

Dividends on Ordinary Shares (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Dividends On Ordinary Shares [Abstract]
Dividends declared and paid	£ 554	£ 410

Derivative Financial Instrume_3

Derivative Financial Instruments - Disclosure of Notional Amounts and Fair Values of Derivatives (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure of detailed information about hedges
Notional amount	£ 261,606	£ 223,242
Assets	1,131	1,432
Liabilities	741	818
Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	39,789	42,043
Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	221,817	181,199
Designated as fair value hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	138,658	108,685
Designated as cash flow hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	83,159	72,514
Exchange rate contracts \| Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	13,170	12,927
Exchange rate contracts \| Designated as fair value hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	1,398	1,145
Exchange rate contracts \| Designated as cash flow hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	20,544	21,618
Interest rate contracts \| Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	25,892	28,351
Interest rate contracts \| Designated as fair value hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	137,260	107,540
Interest rate contracts \| Designated as cash flow hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Notional amount	62,615	50,896
Equity and credit contracts \| Derivatives held for trading:
Disclosure of detailed information about hedges
Notional amount	727	765
Derivative assets
Disclosure of detailed information about hedges
Cash collateral received subject to enforceable master netting arrangement or similar agreement set off against financial assets	682	472
Derivative liabilities
Disclosure of detailed information about hedges
Cash collateral pledged subject to enforceable master netting arrangement or similar agreement set off against financial liabilities	1	12
Fair value
Disclosure of detailed information about hedges
Assets	1,131	1,432
Liabilities	741	818
Fair value \| Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	558	614
Liabilities	665	820
Fair value \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	2,338	2,865
Liabilities	1,841	2,045
Fair value \| Designated as fair value hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	1,141	1,304
Liabilities	489	841
Fair value \| Designated as cash flow hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	1,197	1,561
Liabilities	1,352	1,204
Fair value \| Exchange rate contracts \| Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	91	92
Liabilities	97	217
Fair value \| Exchange rate contracts \| Designated as fair value hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	40	29
Liabilities	1	2
Fair value \| Exchange rate contracts \| Designated as cash flow hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	729	1,008
Liabilities	288	289
Fair value \| Interest rate contracts \| Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	326	389
Liabilities	549	583
Fair value \| Interest rate contracts \| Designated as fair value hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	1,101	1,275
Liabilities	488	839
Fair value \| Interest rate contracts \| Designated as cash flow hedges: \| Derivatives held for hedging
Disclosure of detailed information about hedges
Assets	468	553
Liabilities	1,064	915
Fair value \| Equity and credit contracts \| Derivatives held for trading:
Disclosure of detailed information about hedges
Assets	141	133
Liabilities	19	20
Fair value \| Derivative netting
Disclosure of detailed information about hedges
Assets	(1,765)	(2,047)
Liabilities	£ (1,765)	£ (2,047)

Derivative Financial Instrume_4

Derivative Financial Instruments - Additional Information (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Disclosure of detailed information about hedging instruments [line items]
Derivative financial assets	£ 1,131	£ 1,432
Derivative financial liabilities	741	818
Fair value
Disclosure of detailed information about hedging instruments [line items]
Derivative financial assets	1,131	1,432
Derivative financial liabilities	741	£ 818
Fair value \| Group Entities
Disclosure of detailed information about hedging instruments [line items]
Derivative financial assets	484		£ 762
Derivative financial liabilities	£ 254		£ 230

Other Financial Assets at Fai_3

Other Financial Assets at Fair Value Through Profit or Loss (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at fair value through profit or loss	£ 249	£ 262
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	44	46
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	165	167
Other debt instruments
Disclosure Of Other Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at fair value through profit or loss	£ 40	£ 49

Loans and Advances to Custome_3

Loans and Advances to Customers (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Net Loans And Advances To Customers [Abstract]
Loans and advances to customers	£ 203,925	£ 208,370
Credit impairment loss allowances on loans and advances to customers	(860)	(914)
Residual value and voluntary termination provisions on finance leases	(22)	(21)
Net loans and advances to customers	£ 203,043	£ 207,435

Securitisations and Covered B_3

Securitisations and Covered Bonds - Disclosure of Analysis of Securitisations and Covered Bonds (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Securitisations And Covered Bonds [Line Items]
Notional amount	£ 261,606	£ 223,242
Assets recognised in entity's financial statements in relation to structured entities	33,189	27,927
Securitisation programmes
Disclosure Of Securitisations And Covered Bonds [Line Items]
Assets recognised in entity's financial statements in relation to structured entities	8,159	6,047
Securitisation programmes \| Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Assets recognised in entity's financial statements in relation to structured entities	7,393	5,290
Securitisation programmes \| Other asset-backed securitisation structure
Disclosure Of Securitisations And Covered Bonds [Line Items]
Assets recognised in entity's financial statements in relation to structured entities	766	757
Holmes \| Securitisation programmes \| Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Assets recognised in entity's financial statements in relation to structured entities	4,669	3,242
Fosse \| Securitisation programmes \| Mortgage-backed master trust structures
Disclosure Of Securitisations And Covered Bonds [Line Items]
Assets recognised in entity's financial statements in relation to structured entities	2,724	2,048
Repton \| Securitisation programmes \| Other asset-backed securitisation structure
Disclosure Of Securitisations And Covered Bonds [Line Items]
Assets recognised in entity's financial statements in relation to structured entities	766	757
Euro €35bn Global Covered Bond Programme \| Covered bond programme
Disclosure Of Securitisations And Covered Bonds [Line Items]
Assets recognised in entity's financial statements in relation to structured entities	£ 25,030	£ 21,880

Securitisations and Covered B_4

Securitisations and Covered Bonds - Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme (Details) £ in Millions, € in Billions	6 Months Ended
	Jun. 30, 2024 GBP (£)	Jun. 30, 2023 GBP (£)	Jun. 30, 2024 EUR (€)	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 EUR (€)	Jun. 30, 2023 EUR (€)
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Notional amount	£ 261,606			£ 223,242
Euro €35bn Global Covered Bond Programme
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Notional amount \| €			€ 35		€ 35	€ 35
Internal
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	866	£ 1,218
Internal and external redemptions	41	35
External
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	4,849	2,800
Internal and external redemptions	1,962	1,166
Holmes \| Mortgage-backed master trust structures \| Internal
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	106	118
Internal and external redemptions	0	30
Holmes \| Mortgage-backed master trust structures \| External
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	750	750
Internal and external redemptions	0	142
Fosse \| Mortgage-backed master trust structures \| Internal
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	760	0
Internal and external redemptions	0	0
Fosse \| Mortgage-backed master trust structures \| External
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	0
Motor \| Other asset-backed securitisation structure \| Internal
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	0
Motor \| Other asset-backed securitisation structure \| External
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	7
Repton \| Other asset-backed securitisation structure \| Internal
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	0
Internal and external redemptions	0	0
Repton \| Other asset-backed securitisation structure \| External
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	550
Internal and external redemptions	0	0
Euro €35bn Global Covered Bond Programme \| Covered bond programme \| Internal
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	0	1,100
Internal and external redemptions	41	5
Euro €35bn Global Covered Bond Programme \| Covered bond programme \| External
Issuances And Redemptions Of Securitisation And Covered Bond [Line items]
Internal and external issuances	4,099	1,500
Internal and external redemptions	£ 1,962	£ 1,017

Reverse Repurchase Agreements_3

Reverse Repurchase Agreements - Non Trading (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non-trading	£ 15,319	£ 12,468
Agreements with banks
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non-trading	1,949	2,397
Agreements with customers
Disclosure Of Reserve Repurchase Agreements Non-Trading [Line Items]
Reverse repurchase agreements - non-trading	£ 13,370	£ 10,071

Other Financial Assets at Amo_3

Other Financial Assets at Amortised Cost (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at amortised cost	£ 1,744	£ 152
Other financial assets
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at amortised cost	1,744	152
Other financial assets \| Debt securities
Financial Assets At Fair Value Through Profit Or Loss [Line Items]
Financial assets at amortised cost	£ 1,744	£ 152

Intangible Assets (Details)

Intangible Assets (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
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	£ 322	£ 349

Property, Plant and Equipment_2

Property, Plant and Equipment (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	£ 1,494
Property, plant and equipment at end of period	1,455
Investment property	16	£ 17
Cost:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	2,760
Additions	141
Disposals	(149)
Property, plant and equipment at end of period	2,752
Accumulated depreciation:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(1,266)
Charge for the period	89
Disposals	58
Property, plant and equipment at end of period	(1,297)
Property
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	680
Property \| Cost:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	918
Additions	0
Disposals	(3)
Property, plant and equipment at end of period	915
Property \| Accumulated depreciation:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(226)
Charge for the period	11
Disposals	2
Property, plant and equipment at end of period	(235)
Office fixtures and equipment
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	212
Office fixtures and equipment \| Cost:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	877
Additions	21
Disposals	(16)
Property, plant and equipment at end of period	882
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	(653)
Charge for the period	32
Disposals	15
Property, plant and equipment at end of period	(670)
Computer software
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	0
Computer software \| Cost:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	67
Additions	0
Disposals	0
Property, plant and equipment at end of period	67
Computer software \| Accumulated depreciation:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(67)
Charge for the period	0
Disposals	0
Property, plant and equipment at end of period	(67)
Operating lease assets
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	479
Operating lease assets \| Cost:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	635
Additions	104
Disposals	(117)
Property, plant and equipment at end of period	622
Operating lease assets \| Accumulated depreciation:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	(147)
Charge for the period	37
Disposals	41
Property, plant and equipment at end of period	(143)
Right-of-use assets
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at end of period	84
Right-of-use assets \| Cost:
Disclosure of detailed information about property, plant and equipment [line items]
Property, plant and equipment at beginning of period	263
Additions	16
Disposals	(13)
Property, plant and equipment at end of period	266
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	(173)
Charge for the period	9
Disposals	0
Property, plant and equipment at end of period	£ (182)

Other Financial Liabilities a_3

Other Financial Liabilities at Fair Value Through Profit or Loss (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other financial liabilities at fair value through profit or loss	£ 973	£ 899
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	362	369
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	518	426
Zero Amortising Guaranteed Notes
Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [Line Items]
Other financial liabilities at fair value through profit or loss	£ 93	£ 104

Deposits by Customers (Details)

Deposits by Customers (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	£ 184,874	£ 190,850
Demand and time deposits
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	181,468	188,004
Amounts due to other Santander UK Group Holdings plc subsidiaries
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	123	114
Amounts due to Santander UK Group Holdings plc
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	1,778	1,772
Amounts due to fellow Banco Santander subsidiaries and joint ventures
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	1,505	960
Equity index linked deposits
Disclosure Of Deposits From Customers [Line Items]
Deposits by customers	£ 232	£ 304

Deposits by Banks (Details)

Deposits by Banks (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	£ 16,499	£ 20,332
Drawdown from TFSME	13,000	17,000
Items in the course of transmission
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	973	732
Deposits held as collateral
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	578	860
Other deposits
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	14,944	18,737
Amounts due to Santander UK subsidiaries
Disclosure Of Deposits From Banks [Line Items]
Deposits by banks	£ 4	£ 3

Repurchase Agreements - Non T_3

Repurchase Agreements - Non Trading (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non trading	£ 6,623	£ 8,411
Agreements with banks
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non trading	616	551
Agreements with customers
Disclosure Of Repurchase Agreements [Line Items]
Repurchase agreements - non trading	£ 6,007	£ 7,860

Debt Securities in Issue (Detai

Debt Securities in Issue (Details) £ in Millions, € in Billions, $ in Billions	Jun. 30, 2024 GBP (£)	Jun. 30, 2024 EUR (€)	Jun. 30, 2024 USD ($)	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 EUR (€)	Dec. 31, 2023 USD ($)	Jun. 30, 2023 EUR (€)
Debt Securities In Issue [Line Items]
Notional amount	£ 261,606			£ 223,242
Debt securities	34,053			33,910
Medium-term notes
Debt Securities In Issue [Line Items]
Debt securities	8,879			11,656
Euro €35bn Global Covered Bond Programme
Debt Securities In Issue [Line Items]
Notional amount \| €		€ 35			€ 35		€ 35
Debt securities	16,896			15,000
US $20bn Commercial Paper Programmes
Debt Securities In Issue [Line Items]
Notional amount \| $			$ 20			$ 20
Debt securities	2,968			2,761
Certificates of deposit
Debt Securities In Issue [Line Items]
Debt securities	1,397			1,530
Credit linked notes
Debt Securities In Issue [Line Items]
Credit linked notes	387			194
Securitisation programmes
Debt Securities In Issue [Line Items]
Debt securities	£ 3,526			£ 2,769

Subordinated Liabilities - Sche

Subordinated Liabilities - Schedule of Subordinated Liabilities (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Subordinated liabilities [abstract]
£325m Sterling preference shares, notional amount	£ 325	£ 325
£325m Sterling preference shares	343	343
Undated subordinated liabilities	205	205
Dated subordinated liabilities	1,849	1,838
Subordinated liabilities	£ 2,397	£ 2,386

Subordinated Liabilities - Addi

Subordinated Liabilities - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Subordinated liabilities [abstract]
Profit on repurchase of subordinated liabilities	£ 0	£ 3

Provisions - Summary of Provisi

Provisions - Summary of Provisions Reconciliation (Details) £ in Millions	6 Months Ended
	Jun. 30, 2024 GBP (£)
Disclosure of other provisions [line items]
Beginning balance	£ 402
Additional provisions (See Note 4)	167
Provisions released (See Note 4)	(5)
Utilisation and other	(184)
Ending balance	380
Customer remediation
Disclosure of other provisions [line items]
Beginning balance	106
Additional provisions (See Note 4)	6
Provisions released (See Note 4)	0
Utilisation and other	(39)
Ending balance	73
Litigation and other regulatory
Disclosure of other provisions [line items]
Beginning balance	132
Additional provisions (See Note 4)	4
Provisions released (See Note 4)	(4)
Utilisation and other	(28)
Ending balance	104
Regulatory levies and fees
Disclosure of other provisions [line items]
Beginning balance	0
Additional provisions (See Note 4)	41
Provisions released (See Note 4)	0
Utilisation and other	(1)
Ending balance	40
Bank Levy
Disclosure of other provisions [line items]
Beginning balance	0
Additional provisions (See Note 4)	0
Provisions released (See Note 4)	0
Utilisation and other	0
Ending balance	0
Property
Disclosure of other provisions [line items]
Beginning balance	47
Additional provisions (See Note 4)	0
Provisions released (See Note 4)	(1)
Utilisation and other	(13)
Ending balance	33
ECL on undrawn facilities and guarantees
Disclosure of other provisions [line items]
Beginning balance	78
Additional provisions (See Note 4)	20
Provisions released (See Note 4)	0
Utilisation and other	0
Ending balance	98
Restructuring
Disclosure of other provisions [line items]
Beginning balance	32
Additional provisions (See Note 4)	13
Provisions released (See Note 4)	0
Utilisation and other	(27)
Ending balance	18
Other
Disclosure of other provisions [line items]
Beginning balance	7
Additional provisions (See Note 4)	83
Provisions released (See Note 4)	0
Utilisation and other	(76)
Ending balance	£ 14

Provisions - Additional Informa

Provisions - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Disclosure of other provisions [line items]
Additional provisions	£ 167
Customer remediation
Disclosure of other provisions [line items]
Additional provisions	6
Operational risk provisions
Disclosure of other provisions [line items]
Additional provisions	71	£ 87
Fraud losses
Disclosure of other provisions [line items]
Additional provisions	54	£ 75
Litigation and other regulatory
Disclosure of other provisions [line items]
Additional provisions	4
Regulatory levies and fees
Disclosure of other provisions [line items]
Additional provisions	41
Regulatory levies and fees \| Bank of England
Disclosure of other provisions [line items]
Additional provisions	£ 37

Retirement Benefit Plans - Summ

Retirement Benefit Plans - Summary of Retirement Benefit Plans (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Net assets (liabilities) [abstract]
Total net assets	£ 592	£ 657
Unfunded pension and post-retirement medical benefits
Net assets (liabilities) [abstract]
Surplus (deficit) in plan	(24)	(25)
Surplus \| Funded defined benefit pension scheme
Net assets (liabilities) [abstract]
Surplus (deficit) in plan	622	723
Deficit \| Funded defined benefit pension scheme
Net assets (liabilities) [abstract]
Surplus (deficit) in plan	£ (6)	£ (41)

Retirement Benefit Plans - Addi

Retirement Benefit Plans - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Disclosure of net defined benefit liability (asset) [abstract]
Defined contribution expense	£ 40	£ 33
Defined benefit expense	£ 6	£ 16

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, 2024	Jun. 30, 2023
Disclosure of net defined benefit liability (asset) [abstract]
Return on plan assets (excluding amounts included in net interest expense)	£ 634	£ 470
Actuarial (gains) arising from changes in demographic assumptions	(88)	0
Actuarial losses arising from experience adjustments	64	89
Actuarial (gains) arising from changes in financial assumptions	(451)	(399)
Pension remeasurement	£ 159	£ 160

Retirement Benefit Plans - Su_3

Retirement Benefit Plans - Summary of Net Assets Recognised (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure of net defined benefit liability (asset) [abstract]
Present value of defined benefit obligations	£ (7,725)	£ (8,201)
Fair value of scheme assets	8,317	8,858
Net defined benefit assets	£ 592	£ 657

Retirement Benefit Plans - Su_4

Retirement Benefit Plans - Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Disclosure of net defined benefit liability (asset) [abstract]
Discount rate for scheme liabilities	5.20%	4.60%
General price inflation	3.10%	3%
General salary increase	1%	1%
Expected rate of pension increase	2.90%	3%
Longevity at 60 for current pensioners, on the valuation date:
Males	27 years 1 month 6 days	27 years
Females	29 years 9 months 18 days	29 years 9 months 18 days
Longevity at 60 for future pensioners currently aged 40, on the valuation date:
Males	28 years 8 months 12 days	28 years 7 months 6 days
Females	31 years 4 months 24 days	31 years 3 months 18 days

Retirement Benefit Plans - Su_5

Retirement Benefit Plans - Summary of Actuarial Assumption Sensitivities (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Discount rate
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Percentage of reasonably possible increase in actuarial assumption	0.50%	0.50%
Description of changes in methods and assumptions	bps increase	bps increase
Increase (decrease) in defined benefit obligation	£ (460)		£ (507)
General price inflation
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Percentage of reasonably possible increase in actuarial assumption	0.50%	0.50%
Description of changes in methods and assumptions	bps increase	bps increase
Increase (decrease) in defined benefit obligation	£ 348		385
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	£ 201		£ 223

Contingent Liabilities and Co_3

Contingent Liabilities and Commitments - Summary of Contingent Liabilities and Commitments (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Guarantees and formal standby facilities, credit lines and other commitments	£ 37,177	£ 31,428
Contingent liability for guarantees
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Guarantees given to third parties	420	452
Loan commitments
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Formal standby facilities, credit lines and other commitments	£ 36,757	£ 30,976

Contingent Liabilities and Co_4

Contingent Liabilities and Commitments - Additional Information (Details) € in Thousands, £ in Millions		6 Months Ended
	Nov. 02, 2015	Jun. 30, 2024 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
Maximum
Disclosure Of Contingent Liabilities And Commitments [Line Items]
Santander UK liability under indemnity cap		39,850
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) £ in Millions	6 Months Ended	12 Months Ended
Other Equity Instruments (Details) £ in Millions	Jun. 30, 2024 GBP (£)	Dec. 31, 2023 GBP (£)
Disclosure Of Other Equity Instruments [Line Items]
Other equity instruments	£ 1,860	£ 1,956
- £500m Perpetual Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 500	£ 500
Interest rate	0.0675	0.0675
Other equity instruments	£ 0	£ 496
- £500m Perpetual Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 500	£ 500
Interest rate	0.0630	0.0630
Other equity instruments	£ 500	£ 500
- £210m Perpetual Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 210	£ 210
Interest rate	0.0425	0.0425
Other equity instruments	£ 210	£ 210
- £750m Perpetual Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 750	£ 750
Interest rate	0.0650	0.0650
Other equity instruments	£ 750	£ 750
- £400m Perpetual Capital Securities
Disclosure Of Other Equity Instruments [Line Items]
Capital securities	£ 400	£ 400
Interest rate	0.0875	0.0875
Other equity instruments	£ 400	£ 0

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, 2024	Dec. 31, 2023
Disclosure Of Assets Pledged As Security [Line Items]
Gross assets charged as security for liabilities	£ 33,189	£ 27,927
Internally retained \| Securitisations and covered bonds
Disclosure Of Assets Pledged As Security [Line Items]
Notes issued under securitisation and covered bond programmes retained internally	3,753	2,928
Internally retained \| Securitisations and covered bonds \| Santander UK Plc
Disclosure Of Assets Pledged As Security [Line Items]
Internally retained securitisation and covered bond issuances available for creating collateral	1,637	839
Third party bilateral secured funding transactions \| Securitisations and covered bonds
Disclosure Of Assets Pledged As Security [Line Items]
Financial assets pledged as collateral for liabilities or contingent liabilities	£ 1,500	£ 1,500

Financial Instruments - Disclos

Financial Instruments - Disclosure of Analysis of Fair Value of Financial Instruments Carried at Amortised Cost (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Loans and advances to customers	£ 203,043	£ 207,435
Loans and advances to banks	1,040	1,080
Reverse repurchase agreements - non-trading	15,319	12,468
Other financial assets at amortised cost	1,744	152
Deposits by customers	184,874	190,850
Deposits by banks	16,499	20,332
Repurchase agreements - non trading	6,623	8,411
Debt securities in issue	34,053	33,910
Subordinated liabilities	2,397	2,386
Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial liabilities	244,446	255,889
Financial assets at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial assets	221,146	221,135
Deposits by customers \| Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by customers	184,874	190,850
Deposits by banks \| Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Deposits by banks	16,499	20,332
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	6,623	8,411
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	34,053	33,910
Subordinated liabilities \| Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Subordinated liabilities	2,397	2,386
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	203,043	207,435
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	1,040	1,080
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	15,319	12,468
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	1,744	152
Fair value \| Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial liabilities	244,258	255,848
Fair value \| Financial assets at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Total financial assets	218,740	219,611
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	184,436	190,632
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	16,524	20,382
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	6,626	8,413
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	34,059	33,621
Fair value \| Subordinated liabilities \| Financial liabilities at amortised cost
Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [Line Items]
Subordinated liabilities	2,613	2,800
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	200,648	205,917
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	1,040	1,080
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	15,315	12,470
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	£ 1,737	£ 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	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 9,998	£ 10,175
Liabilities at fair value	1,714	1,717
Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	741	818
Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	973	899
Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1,131	1,432
Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	249	262
Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	8,618	8,481
Level 1
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	8,293	8,293
Liabilities at fair value	0	0
Level 1 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Level 1 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Level 1 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Level 1 \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Level 1 \| Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	8,293	8,293
Level 2
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1,584	1,751
Liabilities at fair value	1,701	1,707
Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	728	808
Level 2 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	973	899
Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1,094	1,396
Level 2 \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	165	167
Level 2 \| Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	325	188
Level 3
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	121	131
Liabilities at fair value	13	10
Level 3 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	13	10
Level 3 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Level 3 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	37	36
Level 3 \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	84	95
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	A
Liabilities at fair value	£ 386	£ 508
Exchange rate contracts \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 860	£ 1,129
Valuation technique	A	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	386	508
Exchange rate contracts \| Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	860	1,129
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	A & C
Liabilities at fair value	£ 2,101	£ 2,337
Interest rate contracts \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 1,895	£ 2,217
Valuation technique	A & C	A & C
Interest rate contracts \| Level 1 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	£ 0
Interest rate contracts \| Level 1 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	0	0
Interest rate contracts \| Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	2,101	2,336
Interest rate contracts \| Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	1,895	2,216
Interest rate contracts \| Level 3 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	1
Interest rate contracts \| Level 3 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 0	£ 1
Equity and credit contracts \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Valuation technique	B & D	B & D
Liabilities at fair value	£ 19	£ 20
Equity and credit contracts \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 141	£ 133
Valuation technique	B & D	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	6	11
Equity and credit contracts \| Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	104	98
Equity and credit contracts \| Level 3 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	13	9
Equity and credit contracts \| Level 3 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	37	35
Netting \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	(1,765)	(2,047)
Netting \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	(1,765)	(2,047)
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	(1,765)	(2,047)
Netting \| Level 2 \| Derivative financial instruments
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	(1,765)	(2,047)
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	£ 44	£ 46
Valuation technique	A	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	0	0
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	44	46
Debt securities \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 205	£ 216
Valuation technique	A, B & D	A, B & D
Debt securities \| Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 8,618	£ 8,481
Valuation technique	D	D
Debt securities \| Level 1 \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	£ 0	£ 0
Debt securities \| Level 1 \| Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	8,293	8,293
Debt securities \| Level 2 \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	165	167
Debt securities \| Level 2 \| Financial assets at FVOCI
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	325	188
Debt securities \| Level 3 \| Other financial assets at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Assets at fair value	40	49
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
Debt securities in issue \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Valuation technique	A	A
Liabilities at fair value	£ 362	£ 369
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	362	369
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	£ 0
Structured deposits \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Valuation technique	A	A
Liabilities at fair value	£ 518	£ 426
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	518	426
Structured deposits \| Level 3 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	£ 0
Zero Amortising Guaranteed Notes \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Valuation technique	D	D
Liabilities at fair value	£ 93	£ 104
Zero Amortising Guaranteed Notes \| Level 1 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	0	0
Zero Amortising Guaranteed Notes \| Level 2 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	93	104
Zero Amortising Guaranteed Notes \| Level 3 \| Other financial liabilities at FVTPL
Disclosure Of Fair Value Measurements Of Assets And Liabilities [Line Items]
Liabilities at fair value	£ 0	£ 0

Financial Instruments - Additio

Financial Instruments - Additional Information (Details) - GBP (£) £ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Abstract]
Transfers out of Level 1 into Level 2 of fair value hierarchy, liabilities held at end of reporting period	£ 0	£ 0

Financial Instruments - Summary

Financial Instruments - Summary of Fair Value Adjustment (Details) - GBP (£) £ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Disclosure of financial assets [line items]
Fair value adjustments	£ 14	£ 3
Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	13	2
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	(6)
- Uncertainty \| Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	5	6
- Credit risk adjustment \| Risk-related:
Disclosure of financial assets [line items]
Fair value adjustments	0	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) £ in Millions	6 Months Ended
	Jun. 30, 2024 GBP (£)
Disclosure of fair value measurement of assets [line items]
Beginning balance	£ 275,448
Beginning balance	(260,825)
Ending Balance	264,188
Ending Balance	(250,045)
Level 3 \| Other financial assets at FVTPL
Disclosure of fair value measurement of assets [line items]
Beginning balance	95
Fair value movements	(1)
Settlements	(10)
Ending Balance	84
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 \| Financial assets at fair value
Disclosure of fair value measurement of assets [line items]
Beginning balance	131
Fair value movements	5
Settlements	(15)
Ending Balance	121
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	5
Level 3 \| Derivatives
Disclosure of fair value measurement of assets [line items]
Beginning balance	36
Fair value movements	6
Settlements	(5)
Ending Balance	37
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	6
Derivatives \| Level 3
Disclosure of fair value measurement of assets [line items]
Beginning balance	(10)
Fair value movements	(4)
Settlements	1
Ending Balance	(13)
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	(4)
Financial liabilities at fair value \| Level 3
Disclosure of fair value measurement of assets [line items]
Beginning balance	(10)
Fair value movements	(4)
Settlements	1
Ending Balance	(13)
Gains/(losses) recognised in profit or loss/other comprehensive income relating to assets and liabilities held at the end of the period	£ (4)

Assets Held for Sale (Details)

Assets Held for Sale (Details) - GBP (£) £ in Millions	Jun. 30, 2024	Dec. 31, 2023
Disclosure Of Assets And Liabilities Classified As Held For Sale [Line Items]
Assets held for sale	£ 13	£ 13
Property, plant and equipment
Disclosure Of Assets And Liabilities Classified As Held For Sale [Line Items]
Assets held for sale	£ 13	£ 13