If you've overpaid income tax, HMRC usually refunds it automatically through an adjusted tax code. If not, claim online through your Personal Tax Account, by calling HMRC, or via form R40 for savings interest tax. Most claims are processed within 2-6 weeks. Common causes of overpayment: emergency tax code on a new job, leaving work mid-year without a P45, having two PAYE income sources simultaneously, or unused pension contribution relief. Claims can generally be backdated four years.
Overpaid tax is more common than most people realise — and HMRC is legally obligated to return it to you. The challenge is that it doesn't always happen automatically, and many people don't realise they've overpaid until something prompts them to check. Here's when overpayment occurs and how to recover what you're owed.
Common Causes of Tax Overpayment
Emergency tax codes
When starting a new job without providing a P45 from your previous employer, HMRC may initially put you on an emergency tax code. This often deducts too much tax because the employer doesn't know how much you've already earned that tax year. HMRC usually corrects this automatically once they have the right information, but it's worth checking.
Leaving work mid-year
Income tax and NI are collected throughout the year on the assumption you'll work for the full year. If you stop working mid-year, you've paid tax on income projected over 12 months but have only earned for part of that period. A refund of the overpaid tax is usually due.
Multiple income sources
If you have two employed jobs simultaneously and both apply the full Personal Allowance to their PAYE calculation, you may underpay tax (tackled through Self Assessment or adjusted tax codes). But some combinations result in overpayment — particularly if one income source uses the wrong code.
Pension contribution relief
Higher-rate taxpayers who contribute to personal pensions automatically receive 20% basic-rate relief added by the pension provider. To claim the additional 20% higher-rate relief, you must submit a Self Assessment return or contact HMRC directly. Many higher-rate taxpayers miss this.
How to Check and Claim
Personal Tax Account
Log into your HMRC Personal Tax Account (gov.uk/personal-tax-account). This shows your income, tax paid, and often highlights any overpayment or underpayment for the current and recent tax years. Many refunds are processed automatically through your tax code.
Online claim
If HMRC hasn't processed a refund automatically, you can claim through your Personal Tax Account. This is usually the fastest route — most claims processed within 2-4 weeks.
Form R40
For overpaid tax on savings interest and investments when you don't complete Self Assessment, complete form R40 and submit to HMRC.
Self Assessment return
If you complete a Self Assessment return, overpaid tax appears as a credit that can either be offset against a future liability or refunded directly.
How Far Back Can You Claim?
Income tax overpayments can generally be claimed back up to four years from the end of the relevant tax year. For the 2026/27 tax year, that means claims back to 2022/23 are still possible (until April 2027).
If you're self-employed and navigating the Self Assessment process, our guide on Self Assessment tax tips covers the common errors and how to avoid them.
Frequently Asked Questions
How long does a refund take?
Online claims processed through the Personal Tax Account: typically 2-4 weeks. Refunds paid by bank transfer (if account details on file) arrive faster than cheques. Call HMRC if you haven't received a refund within 6 weeks of claiming.
Does HMRC automatically check for overpayments?
HMRC runs an annual reconciliation process after the tax year ends and sends P800 or Simple Assessment notices where they identify overpayments or underpayments. However, this doesn't catch everything — particularly higher-rate pension relief and some complex cases. It's worth checking your own position proactively.
Access your HMRC Personal Tax Account at gov.uk/personal-tax-account.
