Written by the TaxTune Editorial Team·Reviewed by our qualified accountants·Updated June 2026

Common reasons you are owed tax

Overpayments happen more often than most people think. The usual causes include being put on an emergency tax code when starting a job, leaving work part way through the year so your allowance was not fully used, having tax taken on savings or a pension when your income was low, or paying through PAYE on expenses you could have claimed.

Two further triggers are worth knowing. If you stop work during a tax year, the personal allowance you have not yet used can mean too much tax was deducted. And if your tax code was wrong for part of the year, the correction may leave you owed money. Our guide to how tax codes work explains how these errors arise.

P800 and Simple Assessment

After the tax year ends, HMRC reviews the income and tax of many PAYE taxpayers. If the figures do not match what you paid, you may receive a P800 calculation or a Simple Assessment. A P800 shows whether you have overpaid or underpaid for the year. If it shows an overpayment, it explains how to claim the refund, often through your personal tax account.

A Simple Assessment is used where HMRC believes you owe tax that cannot be collected through your code. Both documents are worth checking carefully against your own records, because they are based on the information HMRC holds, which is not always complete or up to date.

A worked example

Worked example

A refund after an emergency code

Leila started a new job in May and was placed on an emergency month 1 tax code because her new employer did not have her P45. For three months she was taxed without the benefit of her full personal allowance spread across the year, so more tax was taken than was due. Her code was eventually corrected to 1257L, but the recalculation did not flow fully through her pay. After the year end, HMRC issued a P800 showing she had overpaid 480. She logged in to her personal tax account, checked the figures against her payslips and claimed the refund, which was paid directly to her bank.

If no P800 arrives but you think you have overpaid, you do not have to wait. See our notes on claiming what you are owed and act through your tax account.

Claiming overpaid PAYE and expenses

If you are an employee, you can claim tax relief on certain work costs you have paid yourself and not been reimbursed for, such as professional subscriptions, some travel and the cost of working from home where the rules allow. Relief on these reduces your taxable income and can produce a refund for the current and earlier years. Our guide to allowable expenses sets out what counts.

The main route to claim a PAYE refund or expenses relief is your personal tax account, where you can see your income record, check your code and submit a claim. Refunds are usually paid by bank transfer once HMRC has reviewed the claim. Keep receipts and records, because you may be asked to support what you have claimed.

Refunds through Self Assessment

If you complete a tax return, any overpayment usually comes out in the calculation when you file. Where the return shows you have paid more than you owe, you can ask for the balance to be repaid to your bank account rather than left on your account against the next bill. This is common where payments on account were higher than the final liability.

People who are both employed and self employed often find that tax deducted at source plus expenses relief tips them into a refund position. If you are unsure which route applies to you, our guide to Self Assessment can help, or you can start your quote and we will review whether you are owed anything.

In short

The main reasons you may be owed tax back and how to claim it.

Frequently asked questions

How do I know if I am owed a tax refund?
The clearest sign is a P800 calculation from HMRC after the year end showing an overpayment. You may also suspect a refund if you were on an emergency code, stopped work during the year, or paid for work expenses you never claimed. Checking your personal tax account is the quickest way to confirm your position.
What is a P800?
A P800 is a tax calculation HMRC sends after the tax year to many PAYE taxpayers when the tax paid does not match the tax due. It shows whether you have overpaid or underpaid and, where you have overpaid, explains how to claim the refund. It is based on the information HMRC holds, so it is worth checking against your own records.
How long do I have to claim a refund?
There is a time limit for claiming overpaid income tax, so it is best not to leave it. You can usually claim for the current year and several earlier years. If you think an older year is affected, check your records and your tax account promptly rather than assuming the chance has passed.
How will my refund be paid?
Refunds are most often paid by bank transfer once you have claimed through your personal tax account and HMRC has reviewed the claim. In some cases a refund may come through an adjustment to your tax code or your pay, particularly when a wrong code is corrected during the same tax year.
Can I claim tax back on work expenses?
Yes, employees can claim tax relief on certain costs paid for work and not reimbursed, such as professional subscriptions, some travel and working from home in qualifying cases. The relief reduces your taxable income and can lead to a refund. Keep receipts and records, as HMRC may ask you to support the claim.
Do I need to file a tax return to get a refund?
Not always. Many PAYE refunds are handled through a P800 and your personal tax account without a return. But if you already complete Self Assessment, the refund usually falls out of the calculation when you file, and you can ask for it to be repaid to your bank rather than carried forward.