How to Claim Back Overpaid Tax UK: P800, R40 and HMRC Refunds

Quick answer

If HMRC has taken too much tax from you (wrong tax code, emergency tax, mid-year job change, ended a job partway through the year, or other PAYE adjustments needed), you can claim back the overpayment through:

1. Personal Tax Account at gov.uk — fastest, most flexible.
2. HMRC app — same data, mobile-friendly.
3. P800 tax calculation — issued automatically June-November after each tax year.
4. R40 form — for refunds on bank interest tax.
5. Self Assessment — if you file annually anyway.

Time limit: 4 years from the end of the tax year. So 2022/23 refunds must be claimed by 5 April 2027.

Common reasons HMRC overcharges

1. Emergency / non-cumulative tax code (W1, M1, X)

When you start a new job without a P45, your employer applies an emergency tax code (usually 1257L W1/M1). This treats each pay period in isolation rather than cumulatively — leading to overtaxation.

The cumulative PAYE system normally self-corrects once HMRC reconciles, but the W1/M1 flag breaks this. Refund typically comes via P800 after tax-year-end.

2. Wrong personal allowance

Your tax code might not reflect your full Personal Allowance:

• Old company-car BIK in the code that you no longer have.
• Outdated estimates of investment income.
• Marriage Allowance not applied.
• Tax code from a previous employer's payroll.

Fix it via Personal Tax Account by updating the relevant items — usually within 48 hours.

3. BR / D0 / D1 codes on a primary job

These codes apply 20% / 40% / 45% on the entire income — no Personal Allowance applied. Often used on second jobs but sometimes mistakenly applied to a primary job.

If your only job has a BR code, you've been overcharged by the full Personal Allowance × 20% = up to £2,514/year of tax.

4. Mid-year job change / gap

Leaving one job mid-year and starting another (or not working between) frequently leaves you in a position where you've paid more PAYE than you'd owe over the full year.

Same problem if you finish a fixed-term contract or are self-employed for part of the year then PAYE for another part.

5. Pension and PAYE coordination issues

When you start drawing a pension while still employed, the State Pension reduces your tax code at PAYE jobs. If HMRC's adjustment lags reality, refunds become due.

6. Bank interest taxed at 20% historically

For UK savings accounts opened before April 2016, banks deducted 20% interest tax automatically. Many savers under the Personal Savings Allowance (£1,000 basic / £500 higher) overpaid on this and never claimed.

R40 form is the standard route for this.

P800 — the automatic reconciliation

After each tax year ends (5 April), HMRC matches your PAYE deductions against your full taxable income and works out whether you've overpaid or underpaid.

If a difference exists, HMRC sends a P800 tax calculation between June and November of the following tax year. The P800 either:

• States you've overpaid and offers a refund (BACS or cheque), OR
• States you've underpaid and offers options to repay (typically reduced tax code next year).

P800s are automatic for most PAYE-only workers. You don't have to ask for one. But if you think you're owed a refund and haven't received a P800 by November:

1. Sign in to gov.uk Personal Tax Account.
2. View your tax calculation for the relevant year.
3. Request a refund if owed.

Claiming via Personal Tax Account (fastest)

For PAYE workers, the Personal Tax Account is the simplest route:

1. Sign in at gov.uk/personal-tax-account.
2. Click "Check your Income Tax".
3. View your tax record for the current and previous 4 years.
4. Update any incorrect items (BIK, MA, etc.).
5. Request a refund if owed.

Most updates process within 48-72 hours. Refunds clear within 5-10 working days via BACS.

You'll need a Government Gateway login. If you don't have one yet, you can register with passport or driving licence verification.

R40 — for bank interest refunds

If a UK bank or building society deducted 20% income tax from your savings interest (historical accounts, deceased estate accounts, trust accounts) and you have unused Personal Savings Allowance, use the R40 form.

Process:

1. Download the R40 from gov.uk/government/publications/income-tax-claim-for-repayment-of-tax-deducted-from-savings-and-investments.
2. Fill in the relevant tax year details.
3. Include the bank's tax certificate (sent at end of tax year).
4. Post to HMRC.

Process time: typically 4-8 weeks. R40 refunds normally come as cheques.

Most modern UK savings accounts pay interest without automatic tax deduction since April 2016, so R40 is now less common — but still relevant for trust / estate accounts and some specific products.

Self Assessment route

If you file Self Assessment annually (self-employed, landlord, side-income earner), refunds are handled automatically as part of your tax return:

1. File your annual return.
2. HMRC's tax calculation shows any refund or balance due.
3. Refund issued to your bank account (BACS) within 5-10 working days of return processing.

Self Assessment refunds can include:

• Overpaid PAYE.
• Excess payments on account.
• Marriage Allowance backdated claims.
• Higher-rate pension contribution relief.
• Gift Aid higher-rate reclaim.
• Capital losses set against gains.

Higher-rate pension relief — often missed

This is the single most-missed refund opportunity for UK higher-rate taxpayers.

If your workplace pension uses relief at source (you contribute from net pay, HMRC adds 20% basic-rate), higher-rate (40%) and additional-rate (45%) taxpayers can claim the extra 20% or 25% via Self Assessment.

Example: £5,000 personal pension contribution from a 40% taxpayer.

• £4,000 of your net pay goes in.
• HMRC adds £1,000 basic-rate top-up → £5,000 in pension.
• Claim extra £1,000 of higher-rate relief via Self Assessment.
• This is paid as a refund or applied to your following year's tax.

People often miss this for years. You can backdate 4 years. A consistent £5,000/year pension contributor who's never claimed higher-rate relief could be owed £4,000-£5,000 in backdated refunds.

If you're not in Self Assessment, you can register and claim a single back-year refund, or write to HMRC directly with pension contribution evidence.

Marriage Allowance — backdate up to 4 years

Marriage Allowance is worth £252/year for eligible basic-rate couples. You can apply now and backdate 4 years, getting an immediate refund of up to £1,260 plus £252/year going forward.

Apply free at gov.uk/apply-marriage-allowance. See our Marriage Allowance post for details.

Working from home tax relief

If you were required to work from home (especially during 2020/21 and 2021/22 lockdown periods) you may be entitled to £6/week tax relief (£312/year):

• Basic-rate taxpayer: £62.40/year (£6 × 52 × 20%).
• Higher-rate: £124.80/year.

The rules tightened from April 2022 — you now need to be required to work from home, not just choosing to. But pre-2022 claims can still be backdated.

Claim at gov.uk/tax-relief-for-employees/working-at-home.

Uniform and professional fees relief

Tax relief is available on:

• Cleaning / maintaining a uniform required for work (£60/year flat rate for most uniformed workers).
• Professional body subscriptions on HMRC's approved list (chartered bodies, royal colleges, etc.).
• Tools and equipment required for your job.

Worth £12-£25/year of refund for basic-rate; £24-£50/year for higher-rate. Backdate 4 years.

Common scams to avoid

There's a flourishing industry of tax refund agents advertising "you may be owed £X" via Facebook ads, text messages and post.

These companies:

• Fill in HMRC's free forms on your behalf.
• Take 30-50% of the refund as fee.
• Sometimes lock you into ongoing commission on future refunds.
• Occasionally submit incorrect claims, leading to HMRC penalties for you.

There is never a reason to pay one. All HMRC refund forms are free, take 5-15 minutes, and the help guides at gov.uk are clear.

HMRC does not:

• Text you offering refunds (always a scam).
• Email asking for bank details (scam).
• Charge fees for refunds.

Real HMRC communications start at gov.uk/sign-in and arrive in your Personal Tax Account.

When refunds are held up

Common reasons HMRC delays a refund:

• Identity verification triggered — typically a one-off check.
• Bank account name mismatch — name on HMRC record doesn't match bank.
• Other debts owed to government (council tax, Child Maintenance via DWP) — HMRC offsets.
• Open compliance check — HMRC holding pending review.

If your refund's been pending for over 6 weeks, phone the HMRC Income Tax helpline (0300 200 3300).

Try the numbers

For income tax modelling:

Sources

• gov.uk: Claim a tax refund
• gov.uk: Tax overpayments and underpayments (P800)
• HMRC: R40 form
• gov.uk: Personal Tax Account
• HMRC: Tax relief for employees