The bank said euro customers expecting transfers and wages paid into their accounts overnight were affected by a delay, but the issue has been fixed.
“Some files were delayed through our payment system overnight and these payments have now been made. We apologise for this delay and if
any customers have been left out of pocket, we will put this right,” the bank said.
The bank apologised on its Twitter helpdesk service.
It also used the social media network to reassure customers in
Northern Ireland and the Republic that the technical issue would only affect payments for a few hours.
Many angry customers claimed they were unable to access current transactions, wages being paid into accounts and other payments.
It is not known how many customers or payments were affected by the glitch.
It is the latest in a series of embarrassing technical failures at the bank, owned by the Royal Bank of Scotland, which itself suffered a major IT fault last week that left customers unable to use debit or credit cards for a three-hour spell on what was expected to be the busiest online shopping day before Christmas.
An estimated 750,000 RBS, NatWest and Ulster Bank customers were affected. Days later its websites fell victim to a cyber attack which also affected some customers.
RBS, 80% owned by the UK Government, has been beset by system failures, including a major meltdown last summer, and RBS chief Ross McEwan admitted it had not invested properly for decades.