Online banking and apps have gone down for customers of NatWest, RBS and First Direct leaving people unable to access their accounts on one of the busiest spending days of the year.
Many have said they are unable to check whether salaries have been paid in on what, for most, is payday.
And others are unsure whether payments are going through or whether they have enough funds as they try to grab Black Friday bargains.
According to website DownDetector - which records website failures - NatWest'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, reports The Mirror .
"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."
Natwest and RBS updated their service status pages to read "We are currently experiencing intermittent issues with our Online Banking service, our Mobile app and Bankline.
"If you need to complete a transaction you can continue to do this using our Telephone Banking service or alternatively you can visit one of our Branches or ATMs.
"We apologise for any inconvenience that this may cause, we are working to resolve this issue as quickly as possible."
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) .
