How Much Tax Am I Overpaying?

Use the tax overpayment checker above

Enter your income, the tax you have paid (it is on your payslip, P60 or P45) and your current tax code. The tool works out the tax you should have paid under the 2026/27 rules, subtracts it from what came out of your pay, and shows whether you are owed money — and roughly how much. Treat the result as a strong indicator, not a formal HMRC assessment, then follow the claim steps below.

How the overpayment checker works

Most people overpay not because the maths is complicated, but because the wrong figures were fed into the PAYE system in the first place. The check itself is simple. In plain terms:

Tax you should pay = (income above your Personal Allowance) taxed at the correct bands. Overpayment = tax actually deducted − tax you should pay.

Everyone with a normal tax code gets a Personal Allowance of £12,570 you can earn before income tax starts. Income above that is taxed at 20% up to £37,700 of taxable income, then 40% up to £125,140, then 45% above that. PAYE is supposed to spread your allowance evenly across the year. When something disrupts that — a duplicate code, an emergency code, a job change — the system over-deducts, and you are left out of pocket until it is corrected or you claim.

You can see exactly what HMRC currently thinks your income and code are by signing in to the free check your Income Tax service on gov.uk. If the income or code shown there is wrong, that is very often where your overpayment is coming from.

The usual reasons people overpay tax

• A wrong or emergency tax code. Codes like BR, 0T, D0 or anything ending W1/M1 stop you getting your full allowance and can tax you far too heavily.
• Changing jobs or having two at once. Overlapping codes can mean two employers both withhold tax as if it were your only income, or neither applies your allowance correctly.
• Emergency tax on a pension lump sum. The first flexible withdrawal from a pension is often taxed on a "month 1" basis, over-deducting hundreds or thousands.
• Unclaimed reliefs. Higher-rate pension relief, Marriage Allowance, work expenses, professional fees and uniform laundry are all routinely missed.
• Stopping work mid-year. If you leave a job in, say, July, you have only used part of your allowance, so tax paid earlier in the year may be refundable.

Not sure your code is right? Our tax code checker decodes what your code means and whether it matches your circumstances, and the emergency tax calculator shows how much extra an emergency code is costing you.

Worked example: a wrong tax code

Take Daniel, a warehouse supervisor on £30,000. After starting a new job without handing over his P45, his employer put him on a BR (basic rate) code, which taxes every pound at 20% with no Personal Allowance.

• What he should pay: £30,000 − £12,570 allowance = £17,430 taxable × 20% = £3,486.
• What BR actually takes: £30,000 × 20% = £6,000.
• Overpayment: £6,000 − £3,486 = £2,514 too much over a full year.

Once his code is corrected to 1257L, the system usually repays the excess through his next payslips, or HMRC issues a P800 refund after the tax year ends. You can sanity-check the "correct" figure with our income tax calculator.

Worked example: unclaimed higher-rate pension relief

Now take Sarah, a project manager earning £60,000 who pays £4,000 a year into a personal pension from her own pocket. The pension provider automatically adds 20% basic-rate relief, turning her £4,000 into a £5,000 gross contribution. But as a higher-rate taxpayer she is entitled to another 20% — and that part is not automatic.

• Gross contribution: £4,000 ÷ 0.8 = £5,000.
• Extra higher-rate relief due: £5,000 × 20% = £1,000.

If Sarah never claims it through Self Assessment or by contacting HMRC, she overpays £1,000 of tax every single year. Workplace pensions taken under "net pay" or salary sacrifice already give full relief, so this mainly bites people paying into a private pension or SIPP. The pension tax relief calculator shows what you can reclaim.

Worked example: Marriage Allowance left on the table

If one partner earns under the £12,570 Personal Allowance and the other is a basic-rate taxpayer, the lower earner can transfer £1,260 of unused allowance. That cuts the higher earner's tax by £1,260 × 20% = £252 a year. Crucially, you can backdate a claim up to four tax years, so a first-time claim can be worth over £1,000 in one go. Check your eligibility with the Marriage Allowance calculator.

2026/27 income tax rates and thresholds

These are the England, Wales and Northern Ireland figures the checker uses. Scotland sets its own bands (see below).

The allowance shrinks by £1 for every £2 you earn over £100,000, vanishing entirely at £125,140 — the so-called 60% tax trap. Figures are from gov.uk Income Tax rates and checked for the 2026/27 tax year. The Personal Savings Allowance (£1,000 for basic-rate, £500 for higher-rate taxpayers) means many people also overpay on bank interest that should be tax-free.

How to claim tax back from HMRC

If the checker suggests you have overpaid, here is what to do, depending on the cause:

• Wrong tax code: contact HMRC (online or by phone) to correct it. Once fixed, an in-year overpayment is usually refunded through your pay. After the tax year, HMRC sends a P800 calculation and you claim the refund online.
• Emergency tax on a pension: reclaim it during the year using HMRC form P55, P53Z or P50Z, rather than waiting for the automatic year-end reconciliation.
• Work expenses, fees or uniform: claim online for the current year and up to four previous years through gov.uk.
• Missed pension or Marriage Allowance relief: apply through your Personal Tax Account or Self Assessment.

The official route is set out at gov.uk's claim a tax refund guide. For impartial help understanding a letter or calculation, MoneyHelper is a free, non-commercial source. You can also see whether HMRC is sitting on money owed to you with our checker for money HMRC owes you.

If you live in Scotland

Scottish taxpayers keep the same UK-wide £12,570 Personal Allowance, but income tax is charged on different bands and rates — starter, basic, intermediate, higher, advanced and top — with the higher rate kicking in at 42% rather than 40%. That means an English overpayment estimate will not match a Scottish one, and a wrong residency flag on your record can itself cause an over- or under-deduction. Always check the result against your actual code and nation.

Common mistakes when checking for a refund

• Assuming PAYE is always right. It is automated and only as good as the codes and income figures HMRC holds. Errors are common, especially after a job change.
• Ignoring a W1/M1 code. These "non-cumulative" codes are a classic overpayment signal and often need a quick call to fix.
• Forgetting to backdate. Most reliefs can be claimed for the current year plus four previous years — people leave hundreds behind by claiming only this year.
• Confusing a refund with a scam. HMRC never texts or emails a link to "claim your refund". Always go through gov.uk directly.
• Double-counting reliefs already given. If your pension is salary sacrifice or net pay, the relief is already in your code — claiming again will not work.

These estimates are for guidance only and are not personal tax or financial advice; check your own figures with HMRC or a qualified adviser before acting.

Related tools to dig deeper

Once you have a number, line up the rest of the picture: confirm what your code should be with the tax code checker, see the full effect of an emergency code with the emergency tax calculator, and reclaim missed pension relief using the pension tax relief calculator.

Who should use this calculator

Starts from the suspicion rather than the paperwork: something looks wrong and you want to know whether it is. Rather than asking you to decode a P60, it works from what you earned and what was deducted, and shows what should have been taken.

Over-deduction is common and has predictable causes: leaving a job mid-year so an annual allowance was only partly used, an emergency code on a new job, or benefits still on your code after they ended. None of these correct themselves unless HMRC is told.

What this calculator assumes

• Tax due is recalculated on the annual figures you provide and compared against what was deducted.
• The Personal Allowance is an annual entitlement, so a part-year almost always means over-deduction.
• Only Income Tax is assessed.
• Scottish rates apply where selected.

Limitations — what it does not cover

• Benefits in kind, which legitimately increase tax through your code and explain many apparent overpayments.
• Other income collected through the code — savings, dividends, rent.
• Underpayments from previous years being recovered.
• National Insurance, assessed per pay period and not refundable this way.
• Multiple employments, where allowance is split.
• The four-year claim limit, after which a refund is lost.