The Co-operative Bank has apologised to customers after a glitch caused payments to be taken twice from some small business accounts.
The issue appears to have started on Tuesday, with the bank saying it was working to resolve the problem.
It is unclear how many accounts have been affected, although a spokesperson for the bank said that it was a “small number”.
Co-op Bank has roughly 96,000 small business customers, according to its website.
A company spokesperson commented: “We are aware there are a small number of SME account holders who have duplicated payments showing in their balances and are in the process of correcting this issue.
“We apologise for any inconvenience caused and are supporting customers during this period.”
Customers took to X, formerly known as Twitter, to complain. One person said that were “almost £5k down thanks to this with no resolution in sight”.
Another user claimed that they had “loads of duplicated transactions from months ago”, while one person said they had “been in overdraft all day and still waiting to hear from you”.
“Utter shambles regarding duplicate historical transactions being taken from customer accounts without any notification from you this has happened,” another said.
“Thousands of £ out peoples accounts without even notifying customers. Tell us how this will be resolved?”
“Our business team are aware of duplicate transactions showing and they’re working to resolve this as quickly as possible,” the bank said in reply to one user. “We’re sorry for the concern and inconvenience this has caused.”
Co-op Bank is set to return to mutual ownership as part of a £780m takeover by Coventry Building Society that was confirmed last month.
The 152-year-old lender was rescued from a potential taxpayer bailout in 2013 after it secured a lifeline from American hedge funds to plug a £1.5bn hole in its balance sheet, revealed after an aborted attempt to buy 632 branches from Lloyds.
Co-op Bank agreed a further £700m rescue package with investors in 2017, resulting in the bank becoming fully owned by private equity rather than The Co-operative Group.