The Royal Bank of Scotland group will compensate customers left "out of pocket" after they were unable to pay for purchases last night.
Customers of RBS, Natwest and Ulster Bank making online and card payments were affected from 6pm on what was one of the busiest shopping days of 2013.
A spokeswoman for RBS said the group was "very sorry for the system issues" but would not reveal the cause of the problem.
"If customers have been left out of pocket as a result of these system problems, we will put this right," she said.
"If any customer is unable to resolve an issue caused by the disruption, they should get in touch with our call centres or come into a branch in the morning where our staff will be ready to help."
The bank, which is still 80%-owned by the UK government, said it had improved its services since the problems occurred in June and July of 2012.
They have released the following numbers for customers experiencing problems.
Customers can contact us free phone on 08001510404 (NatWest) or 08001510405 (RBS). otherwise 03457888444 (NatWest) or 03457242424 (RBS).
— RBS Group (@RBSGroup) December 3, 2013