It is arguably the central question in banking – how long depositors will leave their money with an institution. To date, banks have been allowed to answer the question themselves, but the industry is increasingly worried regulators will impose an answer as they try to agree capital rules for interest rate risk in the banking book (IRRBB).

If the maturity that banks can assume is capped – which five industry sources say is one of the options being considered – the fear is that institutions would