Royal Bank of Scotland has been fined £56m by regulators after IT failures left millions of the bank's customers unable to access their accounts.
The Financial Conduct Authority fined RBS, as well as NatWest and Ulster Bank, £42 million for software failures which occurred in June 2012.
The failings meant the banks' customers were unable to access their money or make transactions.
RBS, in which the UK government has an 81% stake, was also hit with an additional £14m fine from the Prudential Regulation Authority.
The fines levied could have been higher had the banks not agreed to settle at an early stage of the investigation.
Tracey McDermott, director of enforcement and financial crime at the FCA said: "Modern banking depends on effective, reliable and resilient IT systems. The banks' failures meant millions of customers were unable to carry out the banking transactions which keep businesses and people's everyday lives moving.
"The problems arose due to failures at many levels within the RBS Group to identify and manage the risks which can flow from disruptive IT incidents and the result was that RBS customers were left exposed to these risks.
"We expect all firms to focus on how they ensure that they can meet the requirements of their customers when looking at their IT strategies and policies."