Monzo has stopped working properly, leaving customers of the app-powered bank stuck at card machines and unable to pay.
Users reported going to pay for things at shops but finding their transactions declined, despite having money in their account and everything being in place.
"We are investigating a problem causing some card transactions to fail," Monzo's status page reads. A similar message appeared in the app to users.
Users reported being left at the tills at shops unable to pay for the items they had bought. Others said they were stuck at cash machines in foreign countries and unable to get cash out.
Some also reported that the associated app had stopped working, either preventing them from logging in entirely or opening up but with missing information.
"HELP!!!!" wrote one. "My joint account has disappeared from the app with all of our money!"
Monzo was founded in 2015 and has quickly gone on to become one of the UK's fastest growing banks. It is one of a variety of companies that tries to combine technology with traditional banking to appeal to customers, offering features like immediate tracking of card payments through its mobile app.
The bank says that more than 2.5 million people use its distinctive cards.
