P800 Letter Explained: Refund, Underpayment and What to Check

A P800 is the tax calculation letter HMRC sends after the end of a tax year when its PAYE records show you paid too much or too little tax. If it shows a refund you can usually claim it yourself online in a few minutes and keep the whole amount; if it shows an underpayment, HMRC normally collects the tax by adjusting your tax code rather than asking for a cheque.

A P800 is not a bill, a fine or an investigation. It is arithmetic — and like all arithmetic it can be wrong, because it relies on the figures employers, pension payers, banks and the DWP have sent HMRC.

Key points

• P800s are issued after the tax year ends on 5 April, typically over the summer and autumn that follow.
• You never have to pay anyone to claim a P800 refund — the online route on GOV.UK is free and the money goes straight to your bank.
• If you owe tax, HMRC usually spreads it over the next tax year through your tax code.
• HMRC does not text, email or WhatsApp you asking for bank or card details to release a refund. Those messages are scams.
• No P800 does not mean no refund — you can still claim back overpaid tax for up to four earlier tax years.

When HMRC sends P800s

HMRC reconciles PAYE records after the end of each tax year. Where the tax deducted through the year does not match the tax actually due on your total income, it issues a P800 tax calculation. These usually start going out from around June and continue into the autumn , so a calculation for the 2026/27 tax year would normally arrive in the second half of 2027.

The usual triggers are:

• You stopped work part-way through the year, or had a gap between jobs.
• You changed jobs and were briefly taxed on an emergency or BR code.
• You had two jobs or a job plus a pension, and the allowances were split badly.
• Your taxable benefits (company car, medical cover) changed and the code did not keep up.
• You started drawing the State Pension or a private pension mid-year.
• You received taxable benefits such as Jobseeker's Allowance.
• Your bank reported savings interest above your Personal Savings Allowance — £1,000 for basic-rate taxpayers, £500 for higher-rate and nil for additional-rate.

Who does not get a P800

If you are in Self Assessment, you will not get a P800 for that year — your return does the reconciliation instead. And if you owe tax that cannot be collected through a tax code, HMRC may send a Simple Assessment (form PA302) rather than a P800. That is a demand for payment with its own deadline, so it is worth reading our guide to how Simple Assessment works if that is what has landed on your doormat.

What the letter shows

A P800 lists each source of income HMRC holds for the year — employment, pensions, benefits, savings interest — plus your allowances, the tax due, the tax already paid, and the difference. Scottish taxpayers should see Scottish rates applied to non-savings income (starter 19%, basic 20%, intermediate 21%, higher 42%, advanced 45%, top 48%) and a tax code beginning with S. Savings and dividend income is taxed at the same rates across the UK.

Claiming a P800 refund online

If the letter says you are owed money, it will tell you which of two routes applies. Either you claim it yourself, or HMRC posts a cheque automatically.

To claim, sign in to your Personal Tax Account on GOV.UK, open the tax calculation and enter your own bank details. You will need Government Gateway sign-in details and identity documents (a passport, driving licence or recent payslip) the first time.

Refund companies charge a percentage of the money for doing exactly this. A 30% fee on a £1,200 refund is £360 of your own money, and some agreements are drafted so that future refunds are also diverted to the agent. Nothing in the P800 process requires an agent.

P800 saying you owe tax

An underpayment on a P800 is normally collected by reducing your tax code for a later tax year, so the tax comes out of your wages or pension in monthly instalments rather than as a lump sum. HMRC can generally code out up to £3,000, with higher limits for larger incomes . If there is no PAYE income to collect it from, you will be asked to pay directly or be moved onto Simple Assessment.

Worked example: a company car that outgrew its tax code

Daniel earns £55,000 and has a company car. His tax code assumed a benefit of £6,000, but the car he actually drove for the full year had a taxable value of £8,000.

• Understated benefit: £8,000 − £6,000 = £2,000
• Daniel is a higher-rate taxpayer, so the tax due is £2,000 × 40% = £800
• HMRC collects it by reducing next year's code by £2,000, which takes roughly £800 ÷ 12 = £66.67 a month more from his pay

A Scottish taxpayer on the same income would face the 42% higher rate, so £2,000 × 42% = £840.

Do not simply accept an underpayment. Check whether the income HMRC has used is real and whether it has missed reliefs that reduce the bill — higher-rate pension relief and Gift Aid are the two most commonly forgotten. Our underpaid tax check walks through the figures HMRC has used and the reliefs that could shrink the amount.

Is a P800 refund text a scam?

Genuine P800s arrive by post and are also visible in your Personal Tax Account. HMRC does not send texts, emails, WhatsApp messages or social media replies offering a refund, and it never asks for your card number, bank password or a fee to release money.

Signs a "P800 refund" message is fake:

• It arrives by text or email with a link to claim.
• It gives an exact refund figure and a countdown or deadline.
• It asks for card details, a bank login, or a small "processing" payment.
• The web address is not a genuine gov.uk address.

The safe test is to ignore the message entirely and sign in to your Personal Tax Account directly. If a refund exists, it will be there. Suspicious messages can be reported through the GOV.UK page on reporting phishing and scams.

To be clear: the refund process on GOV.UK itself is legitimate. It is the unsolicited messages pretending to be it that are not.

Check it against your P60

Before you bank a refund or accept an underpayment, compare the P800 line by line with your own paperwork: your P60 for each employment, any P45 from a job you left, your P11D for benefits, pension statements, and interest certificates from banks and building societies. Savings interest on a P800 is often an estimate, and estimates go stale.

Worked example: a refund after leaving work

Priya earned £3,000 a month and left her job at the end of September, with no other income for the rest of 2026/27. Her P60/P45 shows gross pay of £18,000 and tax deducted of £2,343.

1. PAYE gave her one twelfth of the £12,570 Personal Allowance each month, so by month six she had received £6,285 of allowance.
2. Taxable pay to that point: £18,000 − £6,285 = £11,715, taxed at 20% = £2,343 deducted.
3. Her actual liability for the whole year: £18,000 − £12,570 = £5,430 at 20% = £1,086.
4. Overpaid: £2,343 − £1,086 = £1,257 refund.

Note that National Insurance is not refunded in the same way. Class 1 NI is worked out pay period by pay period at 8% between £12,570 and £50,270, so stopping work mid-year does not usually produce an NI repayment.

Six things to tick off

• Does the gross pay match each P60 and P45, with no employment listed twice?
• Is every employment and pension present, and none that never existed?
• Is the tax deducted figure the same as your paperwork?
• Is the savings interest an actual figure, or an estimate you can disprove?
• Is the Personal Allowance right — £12,570, tapered only if income is over £100,000?
• Are Scottish rates used if you live in Scotland (code beginning S)?

If something is wrong, contact HMRC with the correct figures and ask for the calculation to be reissued. Cashing a cheque you know to be too large simply creates an underpayment later.

Claiming without a P800

Most overpayments are not picked up automatically, because HMRC cannot see expenses and reliefs you have never told it about. You do not need a P800 to claim:

• Work expenses — uniform and flat-rate expenses (from £60 up to £1,022 depending on occupation), professional subscriptions, tools, and mileage in your own car where your employer paid less than the approved rate.
• Working from home where your job requires it.
• Higher-rate pension relief on personal contributions, which only adds 20% automatically.
• Gift Aid donations if you pay tax above the basic rate.
• Marriage Allowance, worth up to £252 a year and backdatable to £1,260 in total.

The deadline is four years from the end of the tax year concerned, so a claim for 2022/23 must reach HMRC by 5 April 2027. Employment expense claims go on form P87 or through your Personal Tax Account; other claims can be made by letter or, if you file one, on your tax return.

What to do next

If a P800 has arrived, check the income figures against your P60 first, then claim any refund yourself through your Personal Tax Account. If no P800 has arrived and you suspect you are owed money, run the free check to see if HMRC owes you money, which covers the reliefs a P800 will never spot. If your letter shows an underpayment, use the underpaid tax check to test the figures before you accept them, and the income tax calculator to work out what your liability should have been.