Income Tax Refund Calculator UK
Find out if you are owed a tax refund from HMRC and estimate how much you could claim back
Enter your total income from all jobs, pensions, and other PAYE sources in the selected tax year.
Check your P60 (end of year) or add up tax deducted on all your payslips for the year.
Am I Owed a Tax Refund from HMRC?
Millions of UK taxpayers overpay income tax every year. The most common reasons include being placed on an emergency tax code, leaving a job partway through the tax year, starting work late in the tax year, having multiple jobs with an incorrect split of the personal allowance, or simply not claiming workplace expenses and reliefs you are entitled to.
Unlike many countries where you must actively file a tax return to reclaim overpaid tax, the UK operates a PAYE (Pay As You Earn) system where your employer deducts income tax based on your tax code. HMRC automatically reviews PAYE records after each tax year ends and issues a P800 tax calculation if it identifies an overpayment or underpayment. However, HMRC's automatic review is not infallible, and many taxpayers need to make a proactive claim.
HMRC will never contact you by text message or WhatsApp to tell you that you are owed a refund. Any text or email claiming to be from HMRC with a link to claim a tax refund is a scam. Always check your tax position at gov.uk/check-income-tax or call HMRC directly on 0300 200 3300. Never click links in unsolicited messages about tax refunds.
The P800 Tax Calculation: How HMRC Reviews Your Tax
After each UK tax year ends on 5 April, HMRC conducts an automated reconciliation of PAYE records, comparing the tax collected through payroll against what should have been paid based on actual income and tax code entitlements. If HMRC identifies a discrepancy, it issues a P800 tax calculation letter, typically between June and November following the end of the tax year.
The P800 tells you one of three things:
- You are owed a refund: HMRC will give you an online claim link. If you claim online through the Government Gateway, the refund arrives in your bank within 5 working days. If you do not claim within 45 days, HMRC will post you a cheque (allow 5 weeks).
- You owe HMRC tax: If the underpayment is under £3,000, HMRC will usually collect it by adjusting your tax code in the next year, spreading the debt over 12 months. Larger underpayments may require a direct payment.
- No further action needed: Your tax was correct and no adjustment is necessary.
Not everyone who has overpaid tax receives a P800. If your overpayment arises from unclaimed expenses, pension contributions, or Marriage Allowance, you may need to claim proactively.
Emergency Tax Codes: Why You May Have Overpaid
When you start a new job, your employer needs a tax code to operate PAYE correctly. If you cannot provide a P45 from your previous employer, or if HMRC does not update your code in time, your employer must use an emergency tax code. The most common emergency codes are:
| Emergency Code | What It Means | Effect |
|---|---|---|
| 1257L W1 | Standard allowance, week 1 basis | No cumulative adjustment; may over-deduct early in year |
| 1257L M1 | Standard allowance, month 1 basis | No cumulative adjustment; may over-deduct early in year |
| BR | Basic Rate only — no allowance | Tax deducted at 20% on all earnings; significant overpayment likely |
| 0T | Zero allowance | All income taxed from the first pound; maximum overpayment risk |
To fix an emergency code, provide your new employer with your P45 from your previous job. If you do not have one, complete a Starter Checklist (the online form has replaced the old P46). HMRC will then issue the correct code to your employer and any overpaid tax will be refunded through your payslip once the code is corrected, or through a P800 at year end.
Claiming Back Tax When You Leave Work Mid-Year
The UK tax year runs from 6 April to 5 April. The personal allowance (£12,570 in 2024/25 and 2025/26) is allocated evenly across the 12 months of the tax year. If you only work for part of the year, you will only earn a fraction of the annual income, but HMRC may have assumed a full year of earnings when calculating your tax code.
For example, if you earn £4,000 gross in April and May then stop working, your employer may have projected this to an annual income of £24,000 and deducted tax accordingly. Your actual annual income of £4,000 is well below the £12,570 personal allowance, so you should pay zero income tax. Any tax deducted would be fully refundable.
If you leave employment and do not take on another job immediately, you can claim a refund in-year using form P50 (if you are not claiming jobseeker's allowance) or P50Z (if you have no other income and are not claiming benefits). This allows you to claim your refund before waiting for the P800.
Workplace Expenses You May Have Forgotten to Claim
HMRC allows employees to claim tax relief on certain work-related expenses that are not reimbursed by their employer. These are commonly missed and can generate meaningful refunds:
- Uniforms and specialist clothing: If you must wear a uniform or specialist clothing for work and wash it yourself, you can claim a flat-rate deduction (£60 per year for most occupations, or higher for some trades). Claim up to 4 years back.
- Professional subscriptions and membership fees: If your professional body or trade union subscription is on HMRC's approved list and you paid it from your own pocket, you can claim relief at your marginal rate.
- Mileage for business travel: If you use your own car for work travel (not commuting) and your employer does not reimburse you at the HMRC approved mileage rate (45p per mile for the first 10,000 miles), you can claim the difference.
- Working from home: Since 2020, HMRC has a simplified flat rate of £6 per week (£312 per year) for employees required to work from home, with no receipts needed.
- Tools and equipment: Some trades (construction, engineering) allow claims for tools bought from your own money.
The 4-Year Back-Claiming Rule
A crucial rule that many taxpayers are unaware of: HMRC only allows you to claim tax refunds for the 4 most recent completed tax years. In the 2025/26 tax year, the earliest year you can claim for is 2021/22 (which ended 5 April 2022). Claims for earlier years are permanently time-barred, regardless of how large the overpayment was.
This means if you discover you were on emergency tax three years ago and have never claimed a refund, you should act immediately to ensure you claim before that year falls outside the 4-year window. To claim for older years, you can:
- Log in to the Government Gateway at gov.uk/personal-tax-account
- Call HMRC on 0300 200 3300
- Write to HMRC Pay As You Earn, HM Revenue & Customs, BX9 1AS
- Complete a Self Assessment return if you are registered (even for years you did not submit before)
How Long Does a Tax Refund Take?
| Claim Method | Typical Timescale |
|---|---|
| Online via Government Gateway (after P800) | 5 working days to bank account |
| Cheque (if no action taken within 45 days of P800) | About 5 weeks |
| Self Assessment return (submitted online) | 2–6 weeks |
| Written claim (letter to HMRC) | 6–12 weeks |
| Through tax agent or accountant | 4–10 weeks |
Marriage Allowance: A Commonly Missed Refund
Marriage Allowance (also called the Marriage Tax Allowance) allows a non-taxpayer or low earner (income under £12,570) to transfer up to £1,260 of their personal allowance to a spouse or civil partner who pays basic rate tax (income between £12,571 and £50,270). The benefit is worth up to £252 per year in tax savings (£1,260 × 20%).
You can backdate a Marriage Allowance claim for up to 4 years, meaning you could receive a lump sum of up to £1,008 if you have been eligible since 2021/22 but never claimed. Apply online at gov.uk/marriage-allowance.
Frequently Asked Questions
How do I know if I am owed a tax refund?
You may be owed a refund if you were on an emergency tax code, left a job mid-year, started work late in the year, had multiple jobs with incorrect codes, or did not claim workplace expenses. Use this calculator to compare what you should have paid vs what was deducted. HMRC may also send a P800 after the tax year ends if it detects an overpayment automatically.
How long does a tax refund take from HMRC?
Online claims after receiving a P800 arrive within 5 working days. Cheques sent automatically take about 5 weeks. Self Assessment refunds take 2–6 weeks. Written claims take 6–12 weeks. Processing is slower during peak periods (January and April). HMRC refunds are paid directly to your bank account if you have provided details, otherwise by cheque.
Can I claim a tax refund for previous years?
Yes — you can claim for up to 4 tax years back. In 2025/26, the earliest claimable year is 2021/22 (ended 5 April 2022). Claims for years before that are permanently time-barred. You can claim via your HMRC personal tax account online, by phone (0300 200 3300), or by post. Act promptly to avoid losing the 2021/22 year as it approaches its 4-year deadline.
What is a P800?
A P800 is a tax calculation letter HMRC sends after the tax year ends (usually June to November) to PAYE taxpayers. It shows whether you overpaid or underpaid. If you overpaid, you can claim online for a 5-day bank transfer. If you underpaid, HMRC adjusts your tax code to collect the debt over the following year. Not everyone receives a P800 automatically.
How do I claim emergency tax back?
Provide your new employer with your P45 from your previous job to get the correct tax code. If no P45, complete a Starter Checklist (available from your employer or gov.uk). HMRC will issue the correct code and any overpaid emergency tax will be refunded through your payslip once corrected, or via a P800 at year end. If you've already left that job, contact HMRC directly.
What is the maximum I can claim back in a tax refund?
There is no fixed maximum. The refund equals tax overpaid, which depends on your income and circumstances. Someone put on a BR (basic rate) emergency code with a £40,000 income could overpay several thousand pounds in a year. You can claim refunds for up to 4 previous years simultaneously, so the total could be significant. Use this calculator to estimate your position.