Guides › Public Services › P800 Tax Calculation Letter: Refunds and What to Do
P800 Tax Calculation Letter: Refunds and What to Do
A P800 is a tax calculation letter from HMRC showing whether you paid too much or too little tax. If you are due a refund, you can usually claim it online with the reference number from the letter and your National Insurance number, and it usually arrives within 5 working days. If the letter says you will get a cheque, you do not need to claim. If you think it is wrong, contact HMRC with the amounts you think are incorrect.
At A Glance
Your Rights
What the rules say, with a link to the official source for each.
Your P800
Claiming a Refund
Claim online using the reference number from your letter and your National Insurance number; you usually get the money within 5 working days. You can also claim through your personal tax account or the HMRC app. source
Cheques
If your letter says you will get a cheque, you do not need to claim: it arrives within 14 days of the date on the letter. If you ask HMRC for a cheque, allow up to 6 weeks. source
If It Says You Owe Tax
HMRC usually changes your tax code to collect it over 12 months from the next tax year if you pay tax through PAYE and owe less than £3,000. Otherwise HMRC writes to tell you how to pay. You can pay early. source
If It Is Wrong
Contact HMRC and say which amounts are wrong and what they should be. If HMRC agrees, you will get a new calculation. source
Time Limits to Know
Miss a deadline and you can lose a right. Check the dates on your own paperwork.
- 5 working daysOnline refund usually paidAfter you claim
- 12 monthsUnderpayment usually collectedThrough your tax code
Steps to Take
Step 1 of 5
Check the income figures against your P60 and payslips.
Step 2 of 5
Claim a refund online if due.
Step 3 of 5
Beware texts and emails offering refunds: HMRC does not send refund links that way.
Step 4 of 5
If it says you owe tax, check how it will be collected.
Step 5 of 5
Contact HMRC if any amount is wrong.
(Tap the numbers to reveal steps)
Where to Go If It Is Not Put Right
Your options, in order, and when each one applies.
HMRC
Contact HMRC through your personal tax account, the HMRC app or the phone and post details on GOV.UK.
Your Personal Tax Account
Sign in on GOV.UK to check your tax code, income and letters.
Free Tax Help
TaxAid and Tax Help for Older People give free advice if your income is low.
Good to Know
Small things that make your complaint stronger.
Scam texts copy P800 wording. Claim only through GOV.UK, your personal tax account or the HMRC app.
Scotland has its own Income Tax rates and bands. The rules on returns, penalties and HMRC complaints apply across the UK.
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Lead reviewer
Luke Marley
Founder and Lead Reviewer
Luke founded CPUK in 2026 after seeing how hard it is for ordinary people to get problems with companies put right. He oversees our guides and checks them against official sources.
Research by Katie Burt, Co-founder and Operations Lead (17 years in the care sector, including managing services for vulnerable adults), and the CPUK Research Team. Researched with AI-assisted research tools, then checked and corrected by our team.
Last checked: 15 October 2026. We are not paid by the companies we write about. Adverts never affect our guidance. Read our editorial policy.
Sources and official links
- gov.uk/p800refund Checked 15 October 2026
- gov.uk/tax-overpayments-and-underpayments/if-you-owe-tax Checked 15 October 2026