v3.26.1
Provisions - Litigation and other matters - Tax Litigation Narrative (Details)
€ in Millions
Dec. 31, 2025
EUR (€)
Dec. 31, 2024
EUR (€)
Dec. 31, 2023
EUR (€)
Jun. 13, 2023
case
Dec. 31, 2022
EUR (€)
Disclosure of other provisions [line items]          
PROVISIONS € 8,355 € 8,407 € 8,441   € 8,149
Banco Santander (Brasil) S.A.          
Disclosure of other provisions [line items]          
Legal proceedings provision, probable loss fully provisioned 553        
Banco Santander Brasil Sa Subsidiary          
Disclosure of other provisions [line items]          
Legal proceedings provision, possible loss, contingent liabilities 5,040        
Legal Case Relating To Programa de Integraçao Social And Contribuição para Financiamento da Seguridade Social          
Disclosure of other provisions [line items]          
Number of unfavorably cases ruled by federal supreme court | case       2  
Legal case relating to questionable deduction of loan losses in income tax returns | Banco Santander Brazil SA Subsidiary          
Disclosure of other provisions [line items]          
PROVISIONS 0        
Legal Case Relating To Tax Deductibility Of Sale Of Shares | Banco Santander Brazil SA Subsidiary          
Disclosure of other provisions [line items]          
PROVISIONS 0        
Legal case relating to deduction of expenses in income tax | Banco Santander (Brasil) S.A.          
Disclosure of other provisions [line items]          
PROVISIONS 0        
Legal case related to tax deductibility of amortization of goodwill arising on acquisition | Banco Santander Brazil SA Subsidiary | Banco Comercial e de Investimento Sudameris S.A          
Disclosure of other provisions [line items]          
PROVISIONS 0        
Legal case related to tax deductibility of amortization of goodwill arising on acquisition | Banco Santander Brazil SA Subsidiary | Getnet Tecnologia Proces S.A.          
Disclosure of other provisions [line items]          
PROVISIONS 0        
Legal Case Related To Tax Compensation With Credits | Banco Santander Brazil SA Subsidiary          
Disclosure of other provisions [line items]          
PROVISIONS 0        
Legal case related to infringement notices initiated by tax authorities regarding the offsetting of tax losses | Banco Santander Brazil SA Subsidiary          
Disclosure of other provisions [line items]          
PROVISIONS 0        
Legal case related to withholding income tax on payments derived from technology services | Banco Santander (Brasil) S.A.          
Disclosure of other provisions [line items]          
PROVISIONS € 0