Every employee and pension recipient in the UK has a tax code. It tells your employer or pension provider how much tax-free income you are entitled to, so they can deduct the right amount of Income Tax from each payment. Your tax code appears on your payslip, your P60, your P45, and your PAYE coding notice from HMRC.
Despite being one of the most important numbers in your financial life, tax codes are widely misunderstood. This guide explains how to read yours, what the most common codes mean, and what to do if you think yours is wrong.
What is a tax code?
A tax code is a combination of numbers and letters that HMRC assigns to you. The number represents your tax-free allowance (usually your Personal Allowance, minus any deductions). The letter tells your employer how to apply that allowance.
To calculate your tax-free allowance from your code, multiply the number by 10. For example, the code 1257L gives you a tax-free allowance of £12,570.
The standard 1257L code
The most common tax code in the UK is 1257L. This means:
- 1257 = a Personal Allowance of £12,570
- L = you are entitled to the standard Personal Allowance
If your only income is a single salary and you have no benefits-in-kind, company car, or other adjustments, your code will almost certainly be 1257L. This code has been in use since the 2021/22 tax year, as the Personal Allowance has been frozen at £12,570 since then.
The Personal Allowance is currently frozen at £12,570 until at least April 2028. This means the 1257L code will remain the standard for several more years — though fiscal drag means more people are being pulled into higher tax brackets as wages rise.
Common tax code letters
The letter suffix on your tax code carries important information about your tax situation. Here are the most common ones:
| Code | Meaning | When it applies |
|---|---|---|
| L | Standard Personal Allowance | Most employees with one job |
| M | Marriage Allowance recipient | Your spouse has transferred 10% of their allowance to you |
| N | Marriage Allowance transferor | You have transferred 10% of your allowance to your spouse |
| BR | Basic Rate — all income taxed at 20% | Usually a second job or pension where your allowance is used elsewhere |
| D0 | Higher Rate — all income taxed at 40% | Second income source for higher-rate taxpayers |
| D1 | Additional Rate — all income taxed at 45% | Second income source for additional-rate taxpayers |
| K | Deductions exceed your allowance | Your tax-free allowance has been reduced to below zero (e.g., large company benefits) |
| 0T | No Personal Allowance | HMRC does not have enough information, or your allowance is fully used |
| NT | No Tax | No tax is deducted (rare — used for specific diplomatic or other exempt situations |
| T | Other calculations | HMRC needs to review your code — usually includes items that need monitoring |
Understanding K codes
A K code is unusual because the number represents tax you owe rather than tax-free income. This happens when your deductions (such as the taxable value of company benefits) exceed your Personal Allowance. For example, a code of K475 means £4,750 is being added to your taxable income.
There is a safety limit on K codes: the additional tax collected through your code cannot exceed 50% of your pay in any pay period.
Scottish and Welsh tax codes
If you live in Scotland, your tax code will begin with S (e.g., S1257L). This tells your employer to apply Scottish Income Tax rates, which differ from the rest of the UK:
| Band | Rate | Income range (2025/26) |
|---|---|---|
| Starter rate | 19% | £12,571 – £14,876 |
| Basic rate | 20% | £14,877 – £26,561 |
| Intermediate rate | 21% | £26,562 – £43,662 |
| Higher rate | 42% | £43,663 – £75,000 |
| Advanced rate | 45% | £75,001 – £125,140 |
| Top rate | 48% | Over £125,140 |
If you live in Wales, your code begins with C (e.g., C1257L). Welsh rates are currently identical to England and Northern Ireland rates, but the prefix exists because the Welsh Government has the power to vary them.
Emergency tax codes (W1/M1)
If you see W1 (weekly paid) or M1 (monthly paid) after your tax code — for example, 1257L W1 or 1257L M1 — this means you are on an emergency tax code. This is also sometimes shown as X on payslips.
An emergency code means your tax is being calculated on a non-cumulative basis. Instead of spreading your annual allowance across the year (so unused allowance from earlier months carries forward), each pay period is treated independently. This can result in you overpaying tax — particularly early in the tax year.
Emergency codes are common when:
- You start a new job and have not provided a P45
- You start receiving a pension
- HMRC has not yet updated your code with your new employer
Getting off an emergency code
Provide your P45 to your new employer as quickly as possible. If you do not have one, complete the Starter Checklist. HMRC should update your code within a few weeks. Any overpaid tax will be refunded automatically through your payroll once the correct code is applied.
What if your tax code is wrong?
Incorrect tax codes are surprisingly common. Signs that your code may be wrong include:
- A sudden change in your take-home pay that you cannot explain
- Still being taxed for a company benefit you no longer receive (e.g., a company car you returned)
- Being taxed as if you have two jobs when you only have one
- Your code reflecting estimated income from previous years instead of actuals
To check and correct your tax code:
- Log in to your HMRC Personal Tax Account at gov.uk
- Check the “Income Tax” section — it shows how your code was calculated
- If anything is wrong, you can update your details online (e.g., remove a company benefit, update your estimated income)
- HMRC will issue a new coding notice to your employer, usually within a few days
- If you have overpaid tax as a result of an incorrect code, the overpayment will usually be refunded through your payroll. In some cases, you may need to file a Self Assessment return or contact HMRC directly for a refund.
Check your coding notice
Every time HMRC changes your tax code, they send you a PAYE coding notice (P2). Always review this carefully. It lists every adjustment applied to your Personal Allowance — benefits-in-kind, estimated untaxed income, underpayments being collected, and more. If any item is wrong, contact HMRC immediately.