NatWest has admitted the outage it suffered on Thursday 26 July was down caused by a hardware failure in one of its datacentres.
The error hit customers around 3pm, leaving them with no access to online banking and unable to use debit cards.
Furious users hit Twitter as fears mounted it could be as bad as the outage faced by NatWest, RBS and Ulster Bank customers last month, which left millions of bank accounts frozen for over a week.
A spokesman from the bank e-mailed Computer Weekly to confirm the fault and say the systems were back up and running.
"We experienced problems yesterday after a hardware failure occurred at one of our technology centres just before 3pm," said the NatWest spokesman.
"The problems, which were not related to the issues experienced last month, affected a number of services, including online banking, debit cards as well as some other payment processing."
"We worked quickly to find a solution and by 7pm the key issues were resolved. All systems are now working as normal. We continue to monitor the situation closely and apologise for any inconvenience caused."
Computer Weekly asked for more information about the specific hardware responsible for the outage, but the spokesman said he didn't have any further details at the time.
The NatWest issue was the second to hit the UK banking sector in the same week. On Tuesday, payments made by Nationwide customers were taken twice after a "human error" at the bank duplicated the payment process.
The building society said it was a one-off, isolated incident and the mistake was fixed the following day.
