Royal Bank of Scotland 'sincerely sorry' for technical fault
3 December 2013 Last updated at 09:52 GMT
Royal Bank of Scotland (RBS) has apologised and promised to compensate those left "out of pocket" after customers were unable to pay for purchases.
RBS, NatWest and Ulster Bank customers making online and card payments were affected between 18:30 and 21:30 GMT on Monday.
The group said all systems were now back to normal.
"We are sincerely sorry for the inconvenience," said Susan Allen, Director of Customer Solutions at the RBS Group.