Overpaid Tax Calculator UK (2025/26)
Think you paid too much tax? Use our free overpaid tax calculator to estimate whether you are owed a refund, and learn exactly how to claim it from HMRC – free, direct, no agents needed.
Why you may have overpaid tax (6 common reasons)
- 1. Wrong tax code – an outdated code means too much or too little tax is deducted.
- 2. Changing jobs – if your new employer does not get your P45, you may go on an emergency code.
- 3. Multiple jobs – each job gets a share of your personal allowance; a mistake means it is applied twice (under-taxation) or not at all (over-taxation).
- 4. BR code – all income taxed at 20% with no allowance.
- 5. Benefits in kind – company car or medical insurance sometimes taxed twice.
- 6. Student loan over-repayments – common when switching jobs or plans.
Around 700,000 people receive tax refunds from HMRC in a typical year – overpayment is far more common than most people think, and a quick tax refund check can be well worth it.
How to claim your tax refund (free, direct)
- 1. Check your tax code in your HMRC Personal Tax Account.
- 2. Wait for the P800 – HMRC sends this after the tax year ends if you overpaid; the refund is paid automatically into your bank account.
- 3. Non-PAYE income – interest or dividends not taxed at source can be reclaimed using form R40.
- 4. Self-employed – claim through your Self Assessment return.
- 5. Time limit – you can claim a tax refund within 4 years of the end of the tax year. If you owe tax instead, HMRC sends a Simple Assessment notice.
Frequently asked questions
What is a P800?
The tax calculation HMRC sends after the year ends when you paid too much or too little tax. Overpayments are refunded automatically.
What does tax code BR mean?
All income from that job is taxed at 20% with no personal allowance. Common on second jobs or before a P45 is processed – a frequent cause of overpayment.
I changed jobs and got an emergency code – what now?
Update your details in your Personal Tax Account or contact HMRC. Overpaid tax is usually refunded automatically via P800 after the year ends.
How far back can I claim?
Within 4 years of the end of the tax year. 2021/22 overpayments must be claimed by 5 April 2026.
Does it cost money to claim?
No – claiming directly from HMRC is free. Beware fee-charging refund agents and scams.
What is Simple Assessment?
If you owe tax, HMRC may issue a Simple Assessment notice (P800 is the overpayment counterpart). It shows what you owe and how to pay.