HMRC P800 Tax Calculation 2026/27: What It Means and How to Claim a Refund
What an HMRC P800 tax calculation means, why you might receive one in 2026/27, and how to claim a refund online, by cheque, or through your tax code — with a worked example.
What triggers a P800
HMRC runs an automatic reconciliation after each tax year ends, comparing the tax actually deducted through PAYE against what should have been due based on the income (and any other data, such as benefits-in-kind or savings interest) it holds for you. Where there's a mismatch, it issues a P800 tax calculation — either as a letter or through your online personal tax account.
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Open Tax Code Checker calculatorCommon reasons for a refund
The most frequent causes of an overpayment showing up on a P800 are:
- An outdated or incorrect tax code being used for part of the year — for example, still on an emergency tax code after starting a new job, or a code that hadn't caught up with a change in circumstances
- Changing jobs partway through the tax year, where PAYE's cumulative calculation temporarily over-collects before catching up
- Having more than one job or pension taxed under separate PAYE records that don't automatically account for each other's Personal Allowance usage
- A period of unemployment, reduced hours, or unpaid leave during the year that wasn't smoothly reflected in real time
Worked example: mid-year job change refund
Someone is made redundant in July, is unemployed for two months, then starts a new job in October on an emergency tax code that doesn't initially recognise the Personal Allowance already used earlier in the year.
- Total Personal Allowance for the year: £12,570
- Because of the gap and emergency coding, more tax was deducted across the two jobs combined than the annual calculation says was actually due
- HMRC's year-end reconciliation calculates the true total tax due against total tax actually paid
- The difference — say £340 — is issued as a P800 refund
Claiming a refund
If a P800 shows a refund is due, HMRC typically gives the option to claim it online through your personal tax account, which usually results in the money arriving by bank transfer within a matter of days. If the refund isn't claimed online within the window given, HMRC generally issues a cheque automatically instead, though this can take noticeably longer to arrive.
If the P800 shows you owe tax
Where the calculation shows tax was underpaid, HMRC usually recovers it automatically by adjusting your tax code for a future tax year — reducing your Personal Allowance slightly so the shortfall is collected gradually through your ongoing PAYE deductions, provided you're still employed or receiving a pension through PAYE and the amount is below the threshold HMRC applies for this automatic-recovery approach. Larger underpayments, or cases where automatic coding-out isn't possible, may require direct payment instead.
self-employed-tax-ukBottom line
A P800 is simply HMRC catching up on your PAYE tax position after the fact — most commonly triggered by a job change, emergency tax code, or multiple sources of PAYE income during the year. Refunds are usually straightforward to claim online, while underpayments are typically spread out through a tax code adjustment rather than demanded as a lump sum.
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Frequently asked questions
What is a P800?
A P800 is a tax calculation letter (or online notification) HMRC sends after the end of a tax year to PAYE taxpayers whose tax has not been quite right — either too much or too little was deducted through their tax code over the year, based on the income data HMRC has processed.
Why would I get a P800 showing I'm owed a refund?
Common reasons include an incorrect or outdated tax code being used for part of the year, changing jobs partway through the year, having more than one job or pension taxed separately, or a period of unemployment or reduced hours that wasn't fully accounted for by PAYE's cumulative calculation.
How do I claim a refund shown on a P800?
If HMRC issues a P800 showing you're owed money, you can usually claim it online through your personal tax account for a fast bank transfer, or wait for a cheque to be sent automatically if you don't claim online within a set period — the letter or online notification explains the specific options for your case.
What if my P800 shows I owe tax instead?
If the P800 shows underpaid tax, HMRC usually collects it automatically by adjusting your tax code for a future year (spreading the repayment over time) if the amount is below a certain limit and you're still employed or receiving a pension through PAYE, rather than requiring an immediate lump-sum payment.
Does everyone get a P800 every year?
No — most PAYE taxpayers whose tax code has been accurate all year never receive one, because their tax was already correct. A P800 is only sent when HMRC's end-of-year reconciliation identifies a discrepancy between what was deducted and what was actually due.
Is a P800 the same as a Self Assessment tax bill?
No. A P800 relates to PAYE income only and is generated automatically by HMRC's reconciliation process. If you complete Self Assessment, your tax position is calculated through your tax return instead, and you would not normally receive a separate P800 for the same income.
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Related reading
How to Check Your Tax Code in 2026 (and Reclaim Overpaid Tax)
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