What a P800 letter from HMRC means
A P800 is the tax calculation HMRC sends when you paid the wrong amount of tax through your job or your pension. It says whether you paid too much or too little, and by how much.
Who gets one
People whose tax is taken from their pay or pension by the employer or pension provider, the system called PAYE. HMRC sends the letters between June and March after the tax year ends. A tax year runs from 6 April to 5 April.
If you are registered for Self Assessment, you do not get a P800. HMRC adjusts your Self Assessment bill instead.
The terms, in plain words
- Tax calculation
- HMRC’s name for the P800 itself.
- Overpaid
- You paid more tax than you owed for that year, and HMRC owes you the difference.
- Underpaid
- You paid less tax than you owed for that year, and you owe HMRC the difference.
- Tax code
- The code your employer or pension provider uses to work out how much Income Tax to take from your pay or pension. HMRC changes it to collect an underpayment.
- Personal Allowance
- The amount of income you do not pay tax on. The standard Personal Allowance is £12,570 for the tax year 6 April 2026 to 5 April 2027.
- Simple Assessment
- A separate tax bill HMRC sends when it cannot collect what you owe through your tax code.
If you paid too much
The letter says how the money comes back. If it says you can claim online, HMRC offers a bank transfer, which it says takes 5 working days, or a cheque you request online, which takes 6 weeks. You can also claim through your personal tax account or the HMRC app if you have a UK bank account.
If the letter says a cheque will be sent to you, HMRC says it arrives within 14 days of the date on the letter.
If you paid too little
If you owe less than £3,000 and still have pay or a pension taxed through PAYE, HMRC collects it by changing your tax code. The amount usually comes out in equal parts over the 12 months from the start of the next tax year.
If you owe more than £3,000, or it cannot be taken through your tax code, HMRC sends a Simple Assessment letter instead. That letter gives the date to pay by, and HMRC gives 60 days to contact it if you think the bill is wrong.
If a figure looks wrong
HMRC asks you to tell it which amounts you think are wrong and what the right figures are. If it agrees, it sends a new calculation.
Checking it is from HMRC
HMRC sometimes writes first and follows up by email, phone call or text. It keeps a list of its genuine contacts on gov.uk.
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Sources
- GOV.UK: Tax overpayments and underpayments
- GOV.UK: If you’re due a refund
- GOV.UK: If you owe tax
- GOV.UK: Simple Assessment
- GOV.UK: If you do not agree with your Simple Assessment bill
- GOV.UK: Tax codes
- GOV.UK: Income Tax rates and Personal Allowances
- GOV.UK: Check a list of genuine HMRC contacts
Checked against these pages on 28 September 2026. This page explains the letter. It is not tax advice, and it does not say whether the figures on yours are right.