HMRC letters • Plain English

P800 tax calculation letter

A P800 is HMRC's tax calculation after the tax year ends. It tells you whether you paid too much tax (a refund) or too little (you owe). It is sent between June and March of the following tax year. If you are registered for Self Assessment you will not get one.

By The HandySums teamLast checked:

Who gets this

Employees and pensioners who have paid too much or too little tax.

How to recognise it

  • It says "Your tax calculation" and shows whether you are owed a refund or owe tax.
  • It explains why, for example a wrong tax code, two jobs paid in one month, or a new pension.
  • If a refund is due, it says whether to claim online or that a cheque will follow.

What to do

  1. Check the figures against your P60, P45 and payslips.
  2. If you owe less than £3,000 and are taxed through a job or pension, HMRC usually collects it by changing your tax code over 12 months from the next 6 April. You can pay sooner if you want.
  3. If you are due a refund, claim on GOV.UK or the HMRC app using the reference on the letter. Claims online are paid within 5 working days; a cheque you ask for takes up to 6 weeks.
  4. If the cheque option is on the letter, it arrives within 14 days of the date on the letter and you do not need to do anything.
  5. If a figure is wrong, tell HMRC which amount and what it should be.

By when

Follow the dates on your letter. Collecting by tax code starts the next 6 April.

What happens if you ignore it

  • A refund is not paid until you claim it (unless the letter says a cheque is coming).
  • Tax you owe may be collected through your tax code, or HMRC will write about another way to pay.

Official GOV.UK pages

P800 refund scams are common. Only claim through GOV.UK or the HMRC app, never from a link in a text or email.

Not sure it is genuine?

Do not use any link or phone number printed in a message you are unsure about. Check the list of genuine HMRC letters, then find HMRC’s contact details on GOV.UK yourself. You never need to upload your letter to HandySums, and we would never ask.

CalculatorWhat has changed for me?Tick your situation and get your own list of every tax change and deadline for 2026/27 and 2027/28, with a £ estimate where we can work one out.CalculatorHow much to set asideHow much to put aside from each invoice, week or month for Income Tax and Class 4 NI, after any CIS.DatesAll HMRC datesEvery HMRC deadline that matters to the self-employed, with a calendar file.

Sources and review

Last checked: 1 November 2026. What this letter is, the deadlines and the penalties described on this page. Written and checked by the HandySums team against the GOV.UK pages below. HandySums is independent and not an accountancy firm — see how we check our sums.

A guide, not tax advice. Results and explanations are a guide and HMRC has the final say. Always follow the dates and instructions on your own letter, and check with HMRC or a qualified accountant if unsure.