Barclays bank is experiencing serious IT problems which are affecting its app and online banking, as well as payments in and out of accounts.

The bank says it is also unable to provide help via telephone or its “Message us” service.

It says cards and cash machines can be used as normal – though some customers have said this is not the case..

The outage is occurring on what is pay day for many people in the UK, and the deadline for self-assessment tax returns.

Barclays has not explained the cause of the IT problems, or how many people are affected.

It has apologised and says it is “working hard to fix the issue”.

Customers replying to Barclays’ announcement about the outage on social media are reporting a series of problems.

One said their card had been declined despite them having funds, while others have reported money going missing during transactions.

One customer said that that her January wages “had disappeared”.

Many have expressed anger at the bank for failing to resolve the situation.

Friday is the deadline for self-assessment tax returns, and some customers have said the outage has left them unable to make payments to HMRC.

Earlier, HMRC warned that millions of people have still not filed their self-assessment tax returns and those who miss the deadline of midnight could be fined £100.

Customers have asked on social media whether the bank will cover any fines resulting from late tax payments.

Website downdetector, which monitors outages, says thousands of people have flagged problems at the bank.

Barclays is one of the UK’s largest banks, with over 20 million UK retail customers. It says it processes over 40% of the UK’s credit and debit card transactions.

A Barclays spokesperson told BBC News: “We’re aware that some of our customers are experiencing technical issues using some features in our app, online banking and with payments in and out of their accounts.

“We’re sorry for this and are working hard to fix the problem. As soon as it’s resolved, we’ll let our customers know.”

BBC News has contacted HMRC for comment.

It is not the first time banking app customers have been left unable to access funds or make payments.

PayPal suffered a brief but notable outage in November that impacted customers globally across a number of its products, including its cryptocurrency services and popular US peer-to-peer payment app, Venmo.

Thousands of UK bank customers were affected by payment problems with some of the biggest lenders in June last year, with banks including HSBC, Nationwide, Barclays and Virgin Money all impacted by issues with a system that facilitates payments between individuals and companies.

Some cash-strapped customers continued to feel the effects of the issue for days afterwards.

During last July’s major global IT outage, several UK retailers were unable to take card payments and IT services were unable to access payroll after an erroneous update by antivirus company CrowdStrike affected systems worldwide.

Additional reporting by Liv McMahon