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Wrong Tax Code or Owed a Tax Refund
If you paid too much tax, for example because you were on the wrong tax code, HMRC usually sends a P800 tax calculation or a Simple Assessment letter between June and March after the tax year ends. The letter tells you how to get your refund. You can also claim through GOV.UK.
At a Glance
Your Rights
What the rules say, with a link to the official source for each.
Getting Tax Back
HMRC Letters
HMRC sends a P800 tax calculation or a Simple Assessment letter between June and March of the following tax year if you paid too much or too little. Reasons include being on the wrong tax code, for example if HMRC had incorrect information about your income. You get a Simple Assessment letter if you owe more than £3,000 or tax cannot be taken automatically. source
What You Can Claim
You may get a refund if you paid too much tax on pay from a job, job expenses (working from home, fuel, work clothing, tools), Self Assessment, a redundancy payment, savings or PPI interest, a life annuity, or foreign income. Use the GOV.UK tool; pensions have a separate process. source
Time Limits to Know
Miss a deadline and you can lose a right. Check the dates on your own paperwork.
- June to MarchHMRC sends tax calculation lettersAfter the tax year ends
Steps to Take
Step 1 of 5
Check your tax code on your payslip or HMRC account.
Step 2 of 5
Tell HMRC if your income or job has changed.
Step 3 of 5
Wait for your P800, or claim using the GOV.UK tool.
Step 4 of 5
If HMRC gets it wrong, complain.
Step 5 of 5
Never give bank details in reply to a refund text or email.
(Tap the numbers to reveal steps)
Where to Go If It Is Not Put Right
Your options, in order, and when each one applies.
Claim a Tax Refund (GOV.UK)
Free, direct from HMRC.
HMRC Complaints
If something has gone wrong.
Good to Know
Small things that make your complaint stronger.
Refund companies can take a large share: claiming direct from HMRC is free.
Want Help?
If you would like one of our team to look at your problem, our initial case review is free. We cannot guarantee any outcome and we do not give legal advice.
Lead reviewer
Luke Marley
Founder and Lead Reviewer
Luke founded CPUK in 2026 after seeing how hard it is for ordinary people to get problems with companies put right. He oversees our guides and checks them against official sources.
Research by Katie Burt, Co-founder and Operations Lead (17 years in the care sector, including managing services for vulnerable adults), and the CPUK Research Team. Researched with AI-assisted research tools, then checked and corrected by our team.
Last checked: 13 October 2026. We are not paid by the companies we write about. Adverts never affect our guidance. Read our editorial policy.
Sources and official links
- gov.uk/tax-overpayments-and-underpayments Checked 13 October 2026
- gov.uk/claim-tax-refund Checked 13 October 2026
- gov.uk/complain-to-hm-revenue-and-customs Checked 13 October 2026