What should I do with a P800?

A P800 is a tax calculation and HMRC will issue a P800 once a tax year has passed when they think you have overpaid or underpaid your tax. Only employees or pensioners are likely to receive a P800 because those completing self-assessment tax returns or within Making Tax Digital for income tax should have under or over payments of tax corrected through their self-assessment tax return.

If you receive a P800, you should firstly check all the figures in HMRC’s calculations, by checking:

• your wages against P60s,
• benefits in kind from your employer against form P11D,
• bank interest back to your bank statements and any other income referred to in the P800 against a source document or statement.

If you receive some taxable state benefits, HMRC may add them together so you might need to call them to ask for a break down.

Make sure HMRC haven’t missed any allowances or deductions you’re entitled to, and conversely, that they haven’t given you allowances for items you’re no longer entitled to. You don’t want another tax bill later down the line.

What if I am due a refund?

Once you’re happy the figures are correct, if you’re due a refund, the P800 should tell you how to go about getting your tax rebate. There are time limits for making claims for a tax refund – usually four years from the end of the relevant tax year.

If the P800 says you can claim online, you can do so here. 

What if I owe tax? 

If you have underpaid tax of less than £3,000, HMRC will usually seek to collect it automatically from your employment or pension income by adjusting your tax code. If you earn more than £30,000, HMRC could seek to collect more than £3,000 – but they can not take more than half of your wages.

You can choose to pay the tax as a lump sum instead.  

If you disagree with HMRC’s calculations or you cannot afford to pay HMRC back, you should contact them as soon as possible. You might be able to spread the payments over a longer period.

Last updated 14 Jul 2026 | First published 6 Apr 2018

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This article is intended to inform rather than advise and is based on legislation and practice at the time. Taxpayer’s circumstances do vary and if you feel that the information provided is beneficial it is important that you contact us before implementation. If you take, or do not take action as a result of reading this article, before receiving our written endorsement, we will accept no responsibility for any financial loss incurred.

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