The HMRC letter that can mean you paid too much tax last year

Most people who pay tax through their wages or a workplace pension never deal with HMRC directly. The system is meant to get it right through the tax code. When it does not, the correction arrives in a letter called a P800.

A P800 is a tax calculation. It compares the Income Tax you should have paid for a tax year with the tax that was actually taken through Pay As You Earn (PAYE), and it tells you which way the difference goes. HMRC sends these letters between June and March of the following tax year, so calculations for 2025/26, the year that ended on 5 April 2026, are going out now. Here is what the letter means and what, if anything, you need to do.

Who gets a P800, and who does not

You only receive a P800 if you are employed or receive a pension and paid too much or too little tax by the end of the tax year. If you already send a Self Assessment tax return, your position is settled through the return instead and no P800 is sent. If HMRC cannot collect what you owe automatically, or you owe more than £3,000, or the tax is on the State Pension, you may receive a Simple Assessment letter instead, which works differently.

The usual reasons the sums do not add up

HMRC lists several common causes. You may have been on the wrong tax code, for example because HMRC held the wrong figure for your income or benefits. You may have finished one job and started another and been paid by both in the same month. You may have started receiving a workplace pension, or received Employment and Support Allowance or Jobseeker's Allowance during the year. Each of these can leave PAYE slightly out of step with the tax that was actually due.

Taxable savings interest is another frequent reason. If interest pushes past your Personal Savings Allowance, HMRC may collect the extra tax through your code. With thresholds frozen, as we explain in our article on fiscal drag, more people's total income now crosses a band without them noticing.

Reading the letter

A P800 sets out the income HMRC has on record for the year, the allowances it has given you, the tax that should have been paid and the tax that was deducted. Read the income figures first. If a job, a pension or a benefit is missing or wrong, the result will be wrong too. The calculation is also shown in your personal tax account and the HMRC app.

If the P800 says you are due a refund

There are two ways the money reaches you, and the letter tells you which applies.

• You claim it. Use HMRC's online service to have the refund paid by bank transfer, or ask for a cheque online. You need the reference number from the P800 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. HMRC says a bank transfer arrives within 5 working days of an online claim, and a cheque within 6 weeks.
• A cheque is sent automatically. Some letters say a cheque is on its way. You do not need to contact HMRC; it should arrive within 14 days of the date on the letter. If you are owed money for more than one year, you get a single cheque for the total.

Claiming through HMRC costs nothing. Firms that offer to reclaim tax for a fee are not part of the process, and a P800 refund does not need a middleman.

If it says you owe tax

HMRC will usually collect an underpayment by changing your tax code, normally in equal instalments over 12 months from the start of the next tax year, provided you owe less than £3,000. You do not need to send a payment unless the letter asks for one. If paying this way would cause hardship, or you would rather pay at once, contact HMRC; its guidance also covers what to do if you cannot pay on time.

When the calculation looks wrong

Contact HMRC and say which figures you think are incorrect and what they should be. Common slips are a job that ended but is still shown, a benefit counted twice or untaxed income HMRC has estimated. Keep payslips, P60s and P45s, because the numbers on them are what you will be checking against.

How to tell a real P800 from a scam

Tax refunds are a favourite subject for fraudsters, and their messages often look official. HMRC's own guidance is clear on a few points:

• HMRC will never notify you of a tax rebate by text message.
• It only emails about a tax rebate from an address ending in hmrc.gov.uk, and it does not use social media to offer rebates.
• Suspicious emails can be forwarded to phishing@hmrc.gov.uk, and texts to 60599.

If a message urges you to click a link and enter card or bank details to receive a refund, do not respond. Go to GOV.UK yourself, or sign in to the HMRC app, and check there.

Who this matters for, and what to check

People who changed jobs, had two jobs at once, started a workplace pension, received a taxable benefit or had more savings interest than usual during 2025/26 are the most likely to see a P800 this winter. Carers who also work should note that Carer's Allowance is taxable, as we explain in our Carer's Allowance guide. If you also have income from a side business or property, check whether you should be in Self Assessment instead; our guide to the £1,000 allowances sets out the tests.

The takeaway

A P800 is a routine correction, not a penalty. Check that the income on it is right, follow the instructions for a refund or let HMRC adjust your code, and treat any message that asks for bank details out of the blue as suspect. Everything you need is available free from HMRC.