NatWest hit by severe technical problems
A large number of NatWest customers, along with RBS and Ulster Bank account holders, have been unable to access online services.
Technical issues also meant that some balances were not updated with overnight payments.
RBS apologised for the "unacceptable inconvenience" and said customers would not be left out of pocket.
The group kept more than 1,000 branches open until 19:00BST on Thursday to assist customers.
Emma Simpson reports.