Customers have been left unable to access their accounts, after seeing errors on Natwest's online banking systems.
According to website DownDetector - which records website failures - the lender's online banking tool has been having problems since around 9am.
The bank's service status page says things are running normally, and at 10am it has said "there are no reported issues with online banking at the moment".
But that hasn't stopped people reporting problems.
Customers on social media have also complained that they've been left unable to access online banking.
"Hi NatWest_Help having issue logging on to online banking," Lucy Doyle wrote on Twitter.
The bank initially responded saying they weren't aware of any issues with online banking - but also said there were some problems with Bankline.
"We’re aware that some customers may be experiencing issues logging in to Bankline," the bank tweeted.
"This is currently under investigation however we would advise that you try reconnecting at regular intervals. Apologies for any inconvenience."
Mirror Money has contacted Natwest for comment.
In the past Natwest has advised people having problems to try the nwolb.com address.
ClearScore chief executive Justin Basini said: "When banks suffer IT meltdowns consumers don’t just suffer the immediate inconvenience of not being able to access their account; there can also be lasting damage if payments are missed.
"It might take several weeks for a missed payment to show up on your credit report so many only found out they’ve been a victim when they’re turned down for a financial product like a mobile phone contract or a mortgage.
"I’d urge everyone to check their credit report when they hear about major IT outages at UK banks so that you can clear your name if anything is missed and it wasn’t your fault.”
