HM Revenue and Customs has begun issuing P800 letters to around four million UK households who have overpaid income tax.

"HMRC will send a tax calculation letter and tell you if you have a tax overpayment or underpayment. Your bank or building society will tell HMRC how much interest you received at the end of the year.

A P800, formally known as a tax calculation letter, ... If you do not understand your calculation, you can get advice from HMRC or a professional, for example a tax advisor or accountant.

HMRC responded to first ask if the letter was a P800 tax calculation letter or a notice of coding letter. The person responded to say they had actually received both of these letters.

The taxpayer reached out via Twitter, now X, to discuss "a mistake" in their tax calculation with a 20-year cut-off for adjusting the code, as they sought to have it rectified.

P800 letters (tax calculation letter) ... Article continues below. were put on the wrong tax code, for example because HMRC had the wrong information about your income; ...

The letters, known as Simple Assessment Letters or Tax Calculation Letters, are typically sent out between March and June. HMRC uses simple assessment as a way of collecting tax they think you owe ...

HMRC said in response: "The 20-year window relates to how far back HMRC can go back to review a self-assessment calculation, and this is if we suspect deliberate tax evasion." ...

Pensioners and employees who have issues with their tax could be at risk of receiving a letter from HM Revenue and Customs (HMRC). The government department is in the process of issuing both tax ...