v3.25.4
Tax - Narrative (Details) - GBP (£)
£ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Effective tax rate 21.60% 21.00% 15.70%
UK Corporation tax rate 25.00% 25.00% 23.50%
Additional taxes related to Pillar Two £ 22    
Tax relating to items credited directly to equity 189 £ 94  
Deferred tax assets 2,936 4,133  
Unused tax credits for which no deferred tax asset recognised 336 359  
Deferred tax liabilities 1 2  
Temporary differences associated with investments in related entities for which deferred tax liabilities have not been recognised 868 873  
Within five years      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Unused tax credits for which no deferred tax asset recognised 13 13  
Within six to ten years      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Unused tax credits for which no deferred tax asset recognised 2,216 6  
Within eleven to twenty years      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Unused tax credits for which no deferred tax asset recognised 9,747 11,789  
Indefinitely      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Unused tax credits for which no deferred tax asset recognised 9,040 9,213  
After more than 12 months      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 3,590 4,662  
Deferred tax liabilities 1,023 1,021  
Unused tax losses      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deductible temporary differences for which no deferred tax asset is recognised 21,016 21,021  
Temporary differences      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deductible temporary differences for which no deferred tax asset is recognised 288 373  
Capital losses      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deductible temporary differences for which no deferred tax asset is recognised 3,719 3,629  
UK Tax Group      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 1,712 2,638  
Deferred tax liabilities 1 2  
UK Tax Group | UK      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 1,433 2,315  
UK Tax Group | Unused tax losses | UK      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 846 1,066  
US Intermediate Holding Company Tax Group ("IHC Tax Group")      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 1,005 1,162  
US Intermediate Holding Company Tax Group ("IHC Tax Group") | Unused tax losses      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 12 38  
US Intermediate Holding Company Tax Group ("IHC Tax Group") | Loss in current or prior year      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 307 365  
Barclays Bank PLC's US Branch Tax Group      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 255 270  
Other subsidiaries      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 243 386  
Other subsidiaries | Unused tax losses      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets 54 111  
Other subsidiaries | Loss in current or prior year      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Deferred tax assets £ 12 £ 4