P800 Tax Refund Explained: How to Read the Letter and What to Do Next

A brown envelope arrives, there is a number at the bottom with a plus or a minus in front of it, and most people react to the number and file the rest unread. That is the wrong way round. The number at the bottom is only as good as the four or five figures above it, and those figures came from your employers and pension providers rather than from HMRC's own knowledge of your life.

This guide takes the letter apart line by line, tells you exactly what to do with each outcome, and lists the four failure modes that produce a confident but incorrect P800.

All figures below are estimates based on published 2026/27 rates and thresholds. Confirm your own position with HMRC.

Two letters, not one

HMRC actually sends two different end-of-year letters, and they are not interchangeable. Its guidance on tax overpayments and underpayments says that if you have paid too much or too little tax by 5 April, HMRC will send either "a tax calculation letter (also known as a P800)" or "a Simple Assessment letter".

HMRC issues a Simple Assessment where you "owe tax that cannot be automatically taken out of your income", owe more than £3,000, or have to pay tax on your State Pension.

The rest of this guide is about the P800.

Who gets one, and when

HMRC is precise about eligibility: "You'll only get a letter if you are employed" or "you get a pension". And on timing: "The letters are sent out between June and March of the following tax year."

That range is wide on purpose. HMRC reconciles in batches as employer and pension records settle, so two people with identical circumstances can be nine months apart. If it is October and a friend got theirs in July, nothing has gone wrong.

If you are registered for Self Assessment, HMRC states your bill "will be adjusted automatically if you've underpaid or overpaid tax" and you "will not get a tax calculation letter or a Simple Assessment letter". No letter is ever coming. Your refund route is the return itself.

HMRC also lists the common triggers for a P800. You might get one if you:

• were put on the wrong tax code, for example because HMRC had the wrong information about your income
• finished one job, started a new one and were paid by both in the same month
• started receiving a pension at work
• received Employment and Support Allowance or Jobseeker's Allowance

Notice what those have in common. Every one is a records problem, not a spending problem. That is the whole nature of the letter.

Reading the letter, line by line

Work down in this order and check each line before you look at the total.

1. The tax year. Confirm which year you are holding. People often receive two or three letters at once and they do not arrive in date order.

2. Income, listed per employment and pension. Each employer and pension provider should appear once, with a pay figure matching the P60 or final payslip for that job. This is where most errors live. A job you left still showing income after your leaving date, or a job missing entirely, invalidates everything below it.

3. Allowances and deductions. Your Personal Allowance appears here, normally £12,570 for every year currently claimable since the allowance is frozen. Underneath sit the deductions: company car, fuel, medical insurance, an estimate of untaxed interest, or tax underpaid from an earlier year being collected through your code. Every one of these reduces your tax free income, so every one is worth a second look. A benefit you gave up two years ago is the single most common stale entry.

4. Taxable income and tax due. HMRC applies the rates to whatever survived step 3. For a rest of UK taxpayer in 2026/27 that is 20% up to £50,270, 40% up to £125,140, and 45% above that. Scottish taxpayers have a different band structure entirely, so if your code starts with S the arithmetic on the letter will not match those figures. Our Scottish tax codes guide sets out the bands.

5. Tax you actually paid. Cross check this against the "tax deducted" total on your P60 for the year. A mismatch here is worth querying rather than accepting.

6. The result. A refund figure, or an amount owed.

If you want a second opinion on the tax code that produced the letter, our P800 refund checker estimates what you should have paid for your circumstances across every claimable year, and shows the gap. It is an estimate to sanity-check the letter with, not a substitute for HMRC's figures.

If it says you are owed a refund

Your P800 will tell you which of two things happens next.

If it says you can claim online. Per HMRC's guidance, you claim using the online bank transfer service or request a cheque online, and you need "the reference number from your P800 letter" and "your National Insurance number". You can also claim "through your personal tax account or the HMRC app, if you have a UK bank account", or by contacting HMRC.

The timings HMRC publishes:

If it says HMRC will send a cheque. Then, in HMRC's words, "You do not need to contact HMRC to make a claim - you'll automatically get the cheque by post", and "You'll get your cheque within 14 days of the date on your letter."

One useful detail for anyone owed money across several years: "If you're owed tax from more than one year, you'll get a single cheque for the entire amount." One payment covers the lot, so do not sit waiting for the second and third.

If it says you owe money

Do not assume it is right simply because it came from HMRC. The same input errors that produce refunds produce underpayments, and an inflated income figure or a phantom benefit works against you in exactly the same way.

Check the income lines against your P60s first. If they hold up, an underpayment is usually collected by adjusting your tax code for a future year rather than demanded as a lump sum, which is why an underpayment from 2024/25 can quietly show up as a deduction inside your 2026/27 code. That deduction is legitimate, but it should disappear once the amount is recovered. Ours is one of several reasons to read a coding notice rather than filing it.

If the amounts are wrong, HMRC's instruction is direct: contact them, and "tell HMRC which amounts you think are incorrect and what they should be".

The four ways a P800 goes wrong

1. A leaver record that never landed. You left a job in November, the employer's final submission was late or wrong, and HMRC's records still show income accruing. Your total income for the year is overstated, so the calculation shows an underpayment that does not exist.

2. A benefit in kind that ended. Company cars, fuel and medical insurance are handled as deductions from your allowance. When the benefit stops, the deduction should stop. It frequently does not. A £6,000 car benefit left in place costs a basic rate taxpayer around £1,200 a year.

3. An interest estimate that bears no relation to reality. HMRC estimates untaxed savings interest from prior-year data. A one-off year of higher interest can leave an inflated estimate sitting in your code for years afterwards.

4. The two-jobs allocation. When you hold two jobs, HMRC decides which one carries your Personal Allowance. It should be the higher-paying one. When it lands on the smaller job, part of your allowance goes unused while your main income is taxed flat on a BR code, and that is exactly the pattern that produces both an overpayment and, occasionally, no letter at all.

No P800 arrived. Now what?

This is the most consequential thing on this page, so it gets its own section.

HMRC only reconciles automatically where its records flag a discrepancy. If the wrong figure was in the records from the start, the year reconciles cleanly to the wrong answer and no letter is generated. Nobody will contact you. The overpayment simply sits there.

HMRC's own guidance acknowledges the gap: "If you think you have paid too much tax and HMRC have not sent you a tax calculation letter, find out how to claim a refund."

Your options:

• For the year currently running, correct the code in your Personal Tax Account. The refund comes back through payroll once your employer receives the new code, with no separate claim.
• For a completed year, use Check your Income Tax for previous years, compare HMRC's calculation against your P60, and contact HMRC with the specific figures where they disagree.
• For unclaimed job expenses, that is a separate claim on form P87 rather than anything to do with the P800.

The claim window is four years from the end of the tax year concerned, traced by HMRC's Self Assessment Claims Manual to TMA 1970 s43. As at August 2026, 2022/23 is still open and closes on 5 April 2027.

Our step-by-step guide to reclaiming overpaid tax walks the full four-year recovery, and how to claim a tax refund from HMRC sorts you onto the right claim route in a minute.

What a P800 refund is typically worth

The size of a P800 refund tracks the size of the records error, not your salary. Some rough shapes, all estimates on 2026/27 rest of UK rates:

Losing the whole £12,570 allowance at basic rate is £2,514 every year, at any basic rate salary. That figure recurs constantly in real P800 refunds because the wrong-code failure is so common.

Check what your own code should be, for any year back to 2022/23, with the free tax code checker.