HMRC says you are owed something.
Is that the full amount?

What a P800 actually tells you

A P800 is HMRC's end-of-year reconciliation for PAYE taxpayers. After the tax year closes, HMRC compares the tax your employer actually deducted against what its records say you should have paid, and writes to you when the two do not match. Refund letters go out from around June to November. The letter shows the income and allowances HMRC used, the tax due on them, the tax you paid, and the difference.

The part the letter does not show is whether the tax code that produced those deductions was right in the first place. HMRC is reconciling its own figures, using the code it issued. If that code carried the wrong Personal Allowance, a benefit you stopped getting two jobs ago, or an untaxed-income adjustment that no longer applies, the P800 quietly inherits the mistake - and the refund can come out too small just as easily as too large.

Why one year is rarely the whole story

Tax codes are sticky. A wrong code is usually wrong because of something structural - a benefit in kind HMRC never removed, a second job that split your allowance badly, an emergency code that never got corrected - and those things persist across tax years. When a code is wrong in the year HMRC wrote to you about, it is very often wrong in the years either side.

HMRC allows a claim up to 4 years after the end of a tax year. That means 2022/23 is still claimable until 5 April 2027, after which it drops out of reach permanently. The checker above runs all five claimable years at once and totals them, because the total is the number worth acting on, and because the oldest year is the one on a deadline.

No P800? You can still be owed

A P800 is not a guarantee that HMRC has checked everything, and its absence is not evidence that nothing is wrong. HMRC only writes when its automatic reconciliation spots a difference in the records it holds. An error inside the tax code itself - the code being wrong in a way HMRC does not know about - does not trigger a letter. If you file Self Assessment, you will not receive a P800 at all; any overpaid PAYE is settled through your return instead.

Either way, the route to a refund is the same: establish what your code should have been, then take that to HMRC through your Personal Tax Account or on 0300 200 3300. Doing it yourself is free. Refund firms will do it for a percentage - RIFT charges 36% including VAT - of money that was always yours.

How to claim once you know the number

1. If you have a P800 showing a refund. Claim it online through the link on the letter or in your Personal Tax Account. HMRC says the money usually lands in about 5 working days; leave it 21 days and a cheque follows within 6 weeks instead.
2. If you have no P800, or it looks wrong. Sign in to your Personal Tax Account, check the tax code and the income figures HMRC holds for each year, and correct anything out of date. A corrected code for the current year usually reaches your employer in 2 to 4 weeks.
3. For closed years. Write to HMRC or call 0300 200 3300 with the years you are claiming and why. Have your P60s and details of income, benefits and deductions for each year to hand - that is what the claim is assessed on.