The computer error that has affected thousands of NatWest customers has been fixed, a spokeswoman has said.
But the company, owned by the RBS group, is still working through a long backlog of accounts, she said.
The technical fault has disrupted payments to and from NatWest, RBS and Ulster Bank accounts since Thursday.
Branches at these banks are opening longer this weekend to help customers, who have reported unpaid salaries and rent payments not being processed.
More than 1,300 branches will stay open until 16:00 or 18:00 on Saturday and some will also open on Sunday.
Susan Allen, director of customer services at the RBS Group, said the underlying computer failure had been resolved but there was still a lot of accounts to update through the day.
"We've made it very clear that nobody would be out of pocket as a result of this error.
"So we deeply regret the inconvenience caused to our customers and customers of other banks, and if people can get in touch we will make sure that we fix this for them."
Staff had worked through the night and there would be double the number of people staffing the phones, she said.
"For those customers affected, please call us, please come into our branches. We can help you, we can get money to you.
"Yesterday I organised to have some money go in a cab to one of our customers. We know this is terrible and we want to make sure we get money to as many people as possible."
Some customers have had to delay completing purchases of homes and others reported concerns about getting money for the weekend, with overnight payments still not appearing on balances on Friday.
Debbie Morphus, in Mansfield, Nottinghamshire, said her daughter was on holiday in Majorca with two children but unable to withdraw any cash from her NatWest account.
"I can't help her with any funds, as I also bank with NatWest and am in the same boat," said Ms Morphus.
"They fly back on Tuesday but I don't know what they'll do until then. I think the customer service I got was disgusting and my daughter is quite upset."
The computer problem is understood to have arisen after staff tried to install a software update on RBS's payment processing system, but ended up corrupting it.
NatWest and Ulster Bank are part of the RBS group, but the problem has not been confined to customers of these banks, because other people whose transactions involve banks in this group have also been affected.
The Financial Ombudsman Service has said that anyone affected should keep a record of how they were financially disadvantaged.
Anyone unhappy with how their bank was responding to their concerns could make a complaint to them, a spokesman said.
Banks are obliged to return affected customers to the position they should have been in had the problem not occurred.
NatWest has 7.5 million personal banking customers and said a large number had been affected. Ulster Bank said earlier that 100,000 of its customers had been affected.