More than 5.5 million workers paid too much tax to HM Revenue and Customs (HMRC) last year, receiving payments of £661 (on average) back as a result. 

A total of £3.57 billion in overpaid tax was rebated to more than 5.5 million workers across the UK last year, according to a Freedom of Information (FOI) request put to HMRC by The Sun.

The main reason for these repayments, according to the news outlet, was these employees were in the wrong tax code.

The Sun explains: "Anyone employed or paid via PAYE is given a tax code by their employer via HMRC and it is shown on your payslip.

"This code dictates how much income tax you pay on your earnings - so it's important to check if you're on the right one."

Are you owed £661 by HMRC? - how to check

If you want to check your tax code to make sure it is correct, you can do so via:

  • The HMRC app
  • Your payslip

A HMRC spokesperson, speaking to The Mirror, said: “Tax codes are based on information provided by employers or pension providers.

"People can quickly and easily check their code on our free HMRC app and online.

"If they think they’re on the wrong tax code, they should tell us by using their online personal tax account.”

If you’ve paid too much tax by the end of the tax year (April 5), HMRC will send you a tax calculation letter, also known as a P800.

This will tell you how to get a refund or pay tax you owe, the UK Government website explains.

The website adds: "If your tax calculation letter says you can claim online, you can claim using the online bank transfer service or request a cheque online."

For these options you'll need:

  • The reference number from your P800 letter
  • Your National Insurance number

To begin your tax back claim online visit the UK Government website here.

There are also several other ways to claim a tax refund:

  • Through your personal tax account
  • Through the HMRC app
  • By contacting HMRC and asking them to send you a cheque

There is also a tax refund tool on the Government website that can help you check if you are owed anything and what to do.

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When you'll get your refund

You will be sent your refund within five working days if you've claimed online, or six weeks if you've asked HMRC to send a cheque.

You can claim back overpaid tax for up to four years.