How do I check if my tax code is wrong?
Your tax code tells your employer or pension provider how much tax-free income you should get before tax is deducted. If it is wrong, you could be paying too much or too little tax. You can check your code against your circumstances and ask HMRC to correct it if it looks incorrect.
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Check what you're owed →A tax code is a short combination of numbers and a letter that reflects your tax-free allowances and any adjustments. The numbers broadly relate to the amount of income you can receive tax-free, and the letter signals your situation. If your code does not match your circumstances — for example, it omits an allowance you are due, or includes the wrong adjustments — the tax taken from your pay will be off.
Codes can go wrong for many reasons: starting or leaving jobs, having more than one source of income, changes to benefits in kind, or HMRC working from out-of-date information. A code that gives you too little tax-free income means you overpay, while one that gives you too much means you underpay and may face a bill later, so neither is good to ignore.
You can check your code in your online tax account, where you can see how it has been worked out and tell HMRC if something is wrong. Comparing your code against your standard Personal Allowance and your actual circumstances is a sensible regular check, especially after any change in your work or income.
How to check your tax code
- Find your code. Look at your payslip, P45 or P60, or sign in to your online tax account to see your current tax code.
- Compare to your situation. Check the code against your standard Personal Allowance and your actual income and circumstances.
- Spot any errors. Look for missing allowances or wrong adjustments that could mean you are paying too much or too little tax.
- Tell HMRC. Report any mistake through your online tax account or by contacting HMRC so a corrected code is issued.
Key figures (official sources)
- £12,570Standard tax-free Personal AllowanceThe amount you can earn before paying Income Tax; reduced if income is over £100,000.Source: GOV.UK — Income Tax rates and Personal Allowances (checked 2026-06-28)
Frequently asked questions
- What does my tax code mean?
- It reflects your tax-free allowances and any adjustments. The numbers relate to your tax-free income and the letter indicates your situation.
- Why might my code be wrong?
- Causes include changing jobs, having multiple incomes, changes to benefits in kind, or HMRC using out-of-date information about you.
- What if I have underpaid because of my code?
- If your code gave you too much tax-free income, you may owe tax later. It is better to correct the code than to leave it building up.
- How do I get my code corrected?
- Check the details in your online tax account and tell HMRC if anything is wrong so they can issue a corrected code.
MoneyFinder is an independent sign-posting service that helps you find financial support you may be entitled to. We are not a government body and do not provide financial advice. Figures are taken from the official sources cited above and were correct when last checked — always confirm current details on the linked GOV.UK pages.