UK Tax Code Checker
Every UK employee has a tax code that determines how much income tax is deducted from their pay. Understanding what your code means can reveal whether you're paying too much, too little, or exactly the right amount of tax.
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HMRC estimates that around one in three tax codes contain errors, often caused by outdated benefits in kind, old underpayments being collected, or incorrect information following a job change. A wrong code could mean you're overpaying by hundreds of pounds each year without realising it.
Enter your tax code below to see an instant breakdown of what it means, how much personal allowance it gives you, and whether it looks correct for your circumstances. If you've recently started a new job and been put on an emergency code, you'll also see how that affects your pay.
Based on 2026/27 tax year rates. Last updated: April 2026.
Enter Your Tax Code
Common Tax Codes
Based on 2026/27 tax year rates. This is a guide only.
Tax Code Breakdown
Personal Allowance
£12,570
Standard tax code. Your tax-free personal allowance is £12,570. This is the most common code for employees with one job and no complications.
Tax Estimate
Income tax only — excludes NI, pension and student loan. Use our Take-Home Pay Calculator for a full breakdown.
Understanding UK Tax Codes
The Number
The number in your tax code represents your tax-free personal allowance, divided by 10. So 1257 means £12,570. HMRC adjusts this number to account for benefits in kind, underpaid tax, or other allowances.
The Letter(s)
Letters tell your employer how to calculate your tax. L is the standard code, M and N relate to Marriage Allowance, T means HMRC needs to review, and K means your deductions exceed your allowance.
Prefixes (S and C)
An S prefix means you pay Scottish income tax rates, which have more bands and generally higher rates above £43,662. A C prefix means you're a Welsh taxpayer. These are determined by your main residence address.
Emergency Codes
W1, M1, or X after your code means you're on a non-cumulative (emergency) basis. Tax is calculated on each pay period alone, often resulting in overpayment. This usually resolves once HMRC updates your records.
Common Tax Code Mistakes
- 1.
Not checking your code when it changes
HMRC sends a P2 coding notice whenever your code changes. Many people ignore these, missing errors that could cost hundreds of pounds over a tax year.
- 2.
Staying on an emergency code too long
Emergency codes should be temporary. If you're still on W1/M1 after a few months, contact HMRC — you're likely overpaying tax.
- 3.
Old benefits in kind still on your code
If you gave up a company car or other benefit but your code still reflects it, you're paying tax on a benefit you no longer receive.
- 4.
Using BR unnecessarily
If your second job earns very little, you might benefit from splitting your personal allowance between jobs rather than using BR on the second.
- 5.
Assuming your employer will fix it
Your employer applies whatever code HMRC instructs. If it's wrong, you need to contact HMRC directly — your employer can't change it.
Frequently Asked Questions
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