A wrong tax code means wrong pay. HMRC estimates millions of workers are on incorrect codes. Here's how to check yours and fix it fast.
Where to Find Your Tax Code
Your tax code appears on your payslip (usually near the top), your P45 or P60, your HMRC Personal Tax Account (online), and your HMRC app. The standard code for 2025/26 is 1257L.
Common Wrong Tax Codes
BR (20% on everything): You're being taxed with no personal allowance. Common after starting a new job without a P45. 0T (no allowance): HMRC hasn't determined your correct code. You're losing your entire £12,570 allowance. K-code: You owe tax from a previous year being collected through your code. Check this is correct. W1/M1 (emergency): Non-cumulative tax — you're likely overpaying.
How to Fix It
- Check online: Log into your HMRC Personal Tax Account at gov.uk
- Update your details: Make sure your employment information is correct
- Call HMRC: 0300 200 3300 (open Mon-Fri 8am-6pm)
- Wait for correction: A new tax code is usually issued within 2-4 weeks
Getting Your Money Back
If your code was wrong, PAYE automatically adjusts. Once the correct code is applied, your next payslip will include a larger-than-normal payment to refund the overpaid tax. If you were overtaxed in a previous year, you can claim a refund for up to 4 years.
Fixing an Incorrect Tax Code
An incorrect tax code can cost you hundreds or even thousands of pounds per year. The most common errors include emergency tax codes (like 1257L M1 or W1), which stop cumulative adjustments and often result in overpayment. If you have started a new job, changed your circumstances, or received benefits in kind, your tax code may be wrong. Always check your latest payslip — the tax code appears near the top and should typically be 1257L for most employees with one job and no company benefits.
To fix your tax code, contact HMRC directly on 0300 200 3300 or use your Personal Tax Account at gov.uk. You can update your employment details, report untaxed income, and check your coding notice online. HMRC will issue a corrected code to your employer, who will adjust your tax in future payslips. If you have overpaid tax due to a wrong code, HMRC will typically refund you through your pay — you should see a larger net pay for one or two months until the overpayment is cleared. See our tax code guides for detailed explanations of each code.