P800 tax refunds explained — and how to check first

A P800 is HMRC doing its sums at the end of your tax year: a calculation — by post or in your online account — that says you paid too much or too little income tax. Millions go out every year between June and November. Understanding one takes about ten minutes; this guide covers what triggers them, how to check the direction before the letter lands, what to do about underpayments, and how to refuse the scam versions.

What a P800 actually is (and isn't)

PAYE collects tax as a rolling estimate across the year. When the year ends, HMRC compares what you paid against what its records say your total income should have produced. If the two disagree beyond a small tolerance, it issues the P800 tax calculation showing:

• your total income from every employer and pension it knows about
• the tax deducted from each source
• your tax-free allowance and any adjustments (benefits in kind, Marriage Allowance, job expenses)
• the bottom line: overpaid or underpaid, and by how much

A P800 isn't a bill and it isn't a fine — it's a reconciliation. It also isn't the whole truth about your tax: it only contains what HMRC's systems know. Rentals, self-employment and foreign income live elsewhere (usually Self Assessment).

The triggers: why you got one (or will)

In order of how often we see them:

1. Job changes. Overlapping P45s, a starter checklist ticked wrongly, or an emergency code that overstayed — the single biggest cause.
2. Company benefits. A car or medical insurance coded late, coded twice, or left in the code after you lost the benefit.
3. Multiple incomes. Two jobs, or a job plus a pension, each given a full Personal Allowance by mistake — leads to underpayments that surface later.
4. State benefits. The taxable state pension or Carer's Allowance sitting alongside a workplace code that didn't account for them.
5. Starting or stopping work mid-year. The system assumed twelve months; reality delivered seven.

Checking the direction before the letter arrives

You don't have to wait for HMRC to write. The arithmetic is deterministic: take total pay and total tax from your P60, apply the year's rates, and compare. That's exactly what the P800 checker on this site does, privately, on your device — the same comparison HMRC runs months later. Your Personal Tax Account usually shows the reconciled figure online before any paper arrives, too.

If your P800 says you owe HMRC money

Read it twice before paying anything:

• Check the inputs. Is every income figure yours? A duplicated employer record or a benefit you never received inflates the bill. HMRC corrects these readily when you phone with your P60s.
• Small underpayments go into your code. Amounts under £3,000 are usually collected by shrinking next year's tax-free code over twelve months — not demanded in one go. You feel it as slightly less take-home pay, not a letter demanding cash.
• Bigger amounts can have payment plans. HMRC's Time to Pay arrangements spread them further if paying hurts.
• ESC A19 can wipe old debts. If HMRC had the right information, failed to use it within a year, and you reasonably believed your tax was right, the Extra-Statutory Concession A19 sometimes writes the underpayment off. It only works if HMRC genuinely sat on usable data.

P800 scams: the anatomy

Refund season is phishing season, and the fake versions are polished:

• Texts and emails claiming you've a refund waiting, with a link to a cloned GOV.UK page asking for card details. HMRC never sends refund links by text, and never asks for card details to pay you.
• Pressure deadlines — "claim within 48 hours". Real refunds don't expire next Tuesday.
• Release fees or "solicitor" deductions — no genuine UK tax refund has a cost to receive.

P800 vs Simple Assessment vs Self Assessment

Three different machines, often confused: the P800 reconciles standard PAYE years. A Simple Assessment (PA302) is HMRC's bill when you owe tax that can't be coded out — common for state pensioners with untaxed pensions. Self Assessment is the full annual return for the self-employed, landlords, higher earners and complex affairs. Mixing them up causes panic where none is needed; each document names itself clearly at the top.

If your P800 never arrives

No letter by December doesn't mean no refund — HMRC reconciles in bulk and misses edge cases. That's exactly why checking your own P60 against the year's rates is worth five minutes: if your maths shows a clear overpayment and HMRC's account doesn't, the online refund service or the helpline settles it without waiting for the system to notice.