About 600,000 expected payments to RBS customers were not made because of computer problems at the banking group.
Some customers of RBS, NatWest, Ulster Bank and Coutts have not received direct debits they were expecting, including salaries and tax credits.
The group blamed an “overnight process” for the glitch and said the technical difficulties had now been resolved and efforts were being made to ensure that customers’ accounts were credited.
RBS customers, who were also victims of computer software problems in 2012 which left six million people unable to access their accounts, took to Twitter to vent their frustration.
@NatWest_Help no wages have gone in today will these technical issues be sorted today
— andy calvert (@andy_calvert) June 17, 2015
An RBS spokesman said: “We are aware of an issue which has resulted in a delay to payments and direct debits being applied to some customer accounts. We have fixed the underlying issue, we apologise for the inconvenience caused and we are working flat out to get these payments updated for our customers no later than Saturday.
“To any customers concerned about the implications of this issue, we advise them to come into a branch or get in touch with our call centres where our staff will be ready to help. We will ensure no customers are left out of pocket as a result of this issue.”
The group could not confirm how many customers had been affected, but said it was not all accounts.
In June 2012, a software upgrade at an IT centre in Edinburgh, where RBS is headquartered, resulted in customers being unable to access their money or pay bills by direct debit or standing order.
To deal with the chaos, more than 1,000 RBS branches extended their opening hours, with banks serving customers on Sundays for the first time (picture above).
RBS, which is 82 per cent owned by the taxpayer after being bailed out by the government in 2008, promised that customers would not be left out of pocket, with overdraft fees and charges incurred by customers automatically waived.
At the time, the banking group set aside £125m in compensation. In 2014, it was fined £56m by regulators, the Financial Conduct Authority and the Prudential Regulation Authority, for the failure.
RBS says it has invested hundreds of millions of pounds in updating its IT systems.