Customers have been left unable to access their accounts, due to an error related to Natwest's and RBS's 's online banking and apps.
According to website DownDetector - which records website failures - the lender's online banking tool has been having problems since just before 9am.
Emma Smith asked Natwest on Twitter: "Is there an issue with online/mobile banking? I was logged in fine earlier but it’s now saying that it can’t establish a connection. I’ve tried on wifi and 4g but still the same."
The bank responded saying it was looking into the issue.
"We’re currently looking in to reports of issues with some of our services. We are working hard to fix this, thanks for your patience," the bank replied.
Others compained it was ruining their black Friday.
Emma Clarke tweeted: "NatWest ruining everyone's #BlackFriday what a day for your app and online banking to go down."
Emma was not the only person reporting problems.
Steve Gargano asked: "Mobile App and On line banking down - come on... Again?"
"Is online banking down? Can't access online or on the app," Katie asked.
Natwest replied: "The issues are just with Online Banking and the Mobile App at the moment."
A spokesman from NatWest told Mirror Money: "“We are aware that some customers are experiencing intermittent issues accessing our mobile and online banking.
"We apologise to customers for the inconvenience and are working hard to fix the problem.
"There is no impact on debit cards, credit cards, ATMs, telephone and branch banking services – customers can continue to access these as normal.”
You can access NatWest telephone banking on 03457 888 444 (International +44 8705 888 444).
RBS's telephone banking number is 03457 242424 (International +44 (0) 131 549 8888).
