NatWest customers face further upheaval after technical hitches left angry clients unable to pay bills or access their money.
The bank has taken the unusual step of opening hundreds of branches over the weekend and said it was working "round the clock" to clear a backlog of chaos.
More than 900 branches will be staffed until 6pm and until midday on Sunday. It remains unclear exactly when the issues will be completely resolved.
The repercussions have extended beyond the banks' own clients, with one couple who are not NatWest customers left unable to move into their new home.
Hundreds of customers have vented their frustration over the problems, with some finding payments had gone awry and others observing disappearing wages, or holidays and home purchases disrupted. Account balances were not updated properly overnight, meaning credit and debit payments were not showing up as quickly as they should.
Meanwhile, concerns were raised over penalty charges, amid suggestions that thousands of customers could be hit with fines if their regular household bill payments - including mortgages - are affected.
The issues extend to Royal Bank of Scotland (RBS) and Ulster Bank users. All three banks are part of RBS Group, which is attempting to clear a raft of problems caused by the technical fault which it believes it has fixed.
The group has apologised and moved to quash fears over withdrawals, assuring customers their money is "in the system" and staff will be on hand in branches to help them access their cash. It has pledged no one will be left out of pocket. Anyone who incurs penalties because of the problems has been urged to contact their branch.
Susan Allen, customer services director for RBS-NatWest retail, told ITV News it was difficult to say exactly when all the problems would be resolved.
The problem reportedly arose after staff tried to install a software update on RBS's payment processing system, but ended up corrupting it.
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