How to check if you’ve paid too much tax

The short answer: check your tax code first. You can see it on your payslip and in your HMRC online account or the HMRC app. For most people with one job it should be 1257L. If it is something else, or has W1, M1 or X after it, find out why. You can claim back overpaid tax for the last four tax years.

Step 1: check your tax code

Your tax code tells your employer how much tax-free pay to give you. The standard code for 2026/27 is 1257L: £12,570 of tax-free pay a year. Look for these warning signs:

• W1, M1 or X after the code: an emergency basis. Each pay period is taxed on its own, with no catch-up for earlier months.
• 0T: no tax-free allowance at all.
• BR or D0 on your main job: all your pay taxed at 20% or 40%. These belong on a second job, not your main one.
• A lower number than 1257: HMRC is collecting tax on something, such as a company benefit or an old underpayment. Check it is still right.
• A K code: you owe tax on more than your allowance, usually from benefits or untaxed income.

See tax codes explained for what each letter means.

Step 2: compare what you paid with what you owed

Your payslip shows the tax taken this year, and your P60 shows the total for a finished year. Put your total income for the year into the income tax calculator. If you paid noticeably more than it shows, and you have no other income or benefits, you have probably overpaid.

A single month can look wrong without being wrong. A bonus month or a corrected code can make one payslip higher or lower, and it often evens out over the year.

How much an emergency code can cost

On £2,500 a month:

Over three months before it is fixed, that is £628.50.

Common reasons people overpay

Two jobs are a common trap: if your tax-free allowance sits on the smaller job, you can end up overpaying on the bigger one. See why your second job is taxed so much.

Step 3: get the money back

• This tax year: tell HMRC through your online account or the app, for example to update your income or end a benefit. Your code is corrected and the overpayment usually comes back through your pay.
• A finished year with a P800: follow the instructions on it. You can usually claim online and get the money within about 5 working days.
• A finished year without a P800: claim through your HMRC online account, or contact HMRC if you think a calculation is missing.
• Left work part-way through the year and not started again: you can claim a refund for that year without waiting for it to end.
• Work expenses: claim online for up to £2,500 a year. Above that, or if you already file a return, use Self Assessment.
• You file Self Assessment: any overpayment is sorted out through your return.

HMRC usually sends P800s between June and the following spring. If yours says you underpaid, you normally repay it through your tax code over the next year.

Deadlines

You have four years from the end of the tax year you overpaid in. In November 2026 you can claim for 2022/23 onwards. The deadline for 2022/23 is 5 April 2027, after which that year is lost.

Avoid paying for something free

Claiming from HMRC costs nothing. Tax refund companies typically keep 20% to 40% of what you are owed, and some sign you up to keep claiming in future years. Fake "HMRC refund" texts and emails are common: HMRC will not text or email you a link to claim a refund, so go to GOV.UK or the app yourself.

You may also be owed money for reliefs you never claimed, like Marriage Allowance or uniform costs. See tax reliefs people forget to claim and how to read your payslip.

This covers Income Tax paid through PAYE. If you are self-employed or have income from abroad, rental or savings, the steps may differ.