Customers of have been locked out of the mobile banking app and Internet banking services for over 24 hours following a major IT outage.
This means thousands of customers were unable to pay bills, check if their salaries were paid, or even pay their tax return to before the deadline for .
A Barclays spokesperson told it will ensure customers are not penalised because of the outage.
They said: "We're incredibly sorry for the ongoing technical issues that are impacting our customers' accounts. Some may see an outdated balance, and payments made or received may not show.
"We're working hard to fix this issue, and customers should not try to make the payment again.
"Customers can use their cards and withdraw cash, and as soon as these remaining issues are resolved, we'll let our customers know. We will ensure that no impacted customer is left out of pocket."
DownDetector, a website that monitors outages, appeared to show a slowing in hourly complaints, down from a peak of nearly 5,000 an hour to around 500.
Some customers posted on DownDetector that things appeared to be easing on Saturday afternoon.
Rob25 added: "Just managed to pay for the road tax on the van which couldn't do yesterday. Also used debit card twice for contactless payment. Slowly getting things in order it would seem."A newlywed couple said they had been locked out of their Barclays bank accounts while on their honeymoon.
David Marsh and his wife, from Cumbria, told Sky News they've been experiencing problems accessing their money while on holiday in Australia to celebrate their marriage.
"I'm unable to receive money for my honeymoon into my current account or use my current account to clear my credit card before departing," he said.
"My message to Barclays is: I've been a current account holder with Barclays since 1986. The day I return to the UK, I will be moving my current account to another provider and leaving them."
Can I claim compensation from my bank?While banks do not legally have to pay compensation if there is a service outage, you may be able to put in a claim if you have been charged because you were unable to make a payment or access your cash.
In the first instance, speak to your bank, but if you are not happy with any compensation offered, you can contact the
