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What an HMRC P800 tax calculation means

A P800 is HMRC’s end-of-year tax calculation for many people on PAYE. It compares the tax you paid with the tax HMRC thinks you should have paid — and shows either a refund or an underpayment. Always check the figures on your letter or Personal Tax Account.

General information only — not legal or financial advice, and not a substitute for an accountant. For free help, contact Citizens Advice or read GOV.UK — Tax overpayments and underpayments and use your Personal Tax Account.

In plain English

During the tax year, PAYE tax is estimated through your tax code. After the year ends, HMRC often reconciles what you paid with what you owed. The P800 is that reconciliation letter (you may also see the same calculation online).

• Refund / overpayment: HMRC says you paid too much. You can usually claim online to a bank account, or HMRC may send a cheque — follow the instructions on the letter.
• Underpayment: HMRC says you paid too little. For many people this is collected by adjusting next year’s tax code (“coding out”). If it cannot be coded out, HMRC may send a Simple Assessment (for example a PA302) asking you to pay directly.

A P800 does not automatically mean you are in trouble. Check every figure — employment income, benefits, tax deducted — against your P60 / payslips.

Deadlines and timing

1. Claiming a refund: follow the claim instructions and any time limit shown on the letter or in your Personal Tax Account. Claiming online is often fastest.
2. Underpayment collected via tax code: you usually do not need to send money immediately if HMRC says it will adjust your code — but read the letter carefully.
3. If you disagree: contact HMRC promptly using the details on the letter / GOV.UK. Keep copies of evidence (P60, P45, benefits statements).

What to do next

• Confirm it is a genuine P800 — HMRC does not text or email “claim your refund” links.
• Sign in to your Personal Tax Account and compare the online calculation with the letter.
• Check income and tax-deducted figures against your P60 / employer documents.
• If you are owed a refund, claim via the method HMRC describes (often online).
• If you underpaid, note whether HMRC will collect via your tax code or asks for direct payment.
• If the numbers look wrong, contact HMRC with evidence before the situation escalates.

Common mistakes

• Clicking refund links in texts or emails that look like HMRC (scams).
• Ignoring an underpayment letter because “PAYE already took tax” — the reconciliation can still show a balance.
• Assuming a P800 is the same as a Self Assessment bill — different processes.
• Missing that a Simple Assessment may follow if coding out is not possible.

Free help

• GOV.UK — Tax overpayments and underpayments
• GOV.UK — Personal Tax Account
• GOV.UK — Contact HMRC
• Citizens Advice

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