Your tax code tells your employer how much income tax to deduct from your pay each month or week. It is based on your Personal Allowance of £12,579 and any adjustments HMRC has made — such as benefits in kind, underpaid tax from previous years, or additional allowances like Marriage Allowance. Getting the right code means you pay the correct amount of tax throughout the year, avoiding both overpayment (where you wait months for a refund) and underpayment (where HMRC collects the shortfall later).[1]
What does the standard tax code 1257L mean?
The standard tax code for 26-27 is 1257L. This means you have a Personal Allowance of £12,579 (the number 1257 in the code multiplied by 10, with the last digit dropped). The “L” suffix means you are entitled to the standard Personal Allowance with no adjustments. The vast majority of employees in England and Wales with a single job and no benefits in kind will have this code.
If your code is 1257L, your employer will not deduct any income tax on the first £12,579 of your annual earnings. Everything above that is taxed at the applicable rates: 20% basic rate on earnings up to £50,270, 40% higher rate above that, and 45% additional rate on income above £125,140. The code ensures the right amount is deducted from each pay packet so you don't owe anything at year end.
If you live in Scotland, your code will be prefixed with “S” (e.g., S1257L), and if you live in Wales, it will be prefixed with “C” (e.g., C1257L). The number and letter after the prefix work the same way.
How do I read a tax code?
Most tax codes have a number followed by a letter. The number represents your tax-free allowance — multiply by 10 to get the actual amount in pounds. The letter indicates your personal circumstances:
| Letter | Meaning |
|---|---|
| L | Standard Personal Allowance (£12,579) |
| M | Marriage Allowance — you received £1,257 from your partner (code becomes 1383M) |
| N | Marriage Allowance — you transferred £1,257 to your partner |
| T | HMRC needs to review your code (other calculations involved) |
| K | Your deductions exceed your allowance — tax is added to your income |
| S | Scottish rate taxpayer (prefix, e.g. S1257L) |
| C | Welsh rate taxpayer (prefix, e.g. C1257L) |
What are the special flat-rate tax codes?
Some codes do not have a number and apply a flat rate to all your income from that particular employment. These are used in specific circumstances where the normal allowance-based approach does not apply:
- BR — all income taxed at 20% (Basic Rate). Used when your Personal Allowance is applied against another job or pension. Common for people with two jobs where the first job uses up the full £12,579 allowance.
- D0 — all income taxed at 40% (Higher Rate). Used for a second income source when you have already used your basic rate band against your primary employment.
- D1 — all income taxed at 45% (Additional Rate). Rare — used when all lower bands are consumed by other income.
- 0T — no Personal Allowance. Tax is calculated using all bands (20%, 40%, 45%) but starting from the first pound. Often used as a temporary emergency code when HMRC does not have enough information about you.
- NT — no tax deducted at all. Extremely rare and used in specific approved circumstances.
What is an emergency tax code and what should I do?
If you start a new job and your employer does not have your P45 or correct tax code from HMRC, they may apply an emergency code — typically 1257L W1 or 1257L M1. The “W1” (week 1) or “M1” (month 1) suffix means the code is applied on a non-cumulative basis: each pay period is treated independently instead of taking into account your year-to-date earnings.[2]
This usually means you overpay tax in the early months because the cumulative unused allowance from months you were not employed is not factored in. For example, if you start a new job in July, under a cumulative code you would receive 4 months of unused Personal Allowance (April–July) in one go. Under a non-cumulative emergency code, you only get 1/12th of £12,579 per month from the start.
The fix is usually automatic: once HMRC issues your correct cumulative code (after receiving your P45 or starter checklist), your employer will refund the overpaid tax through your payslip. If it has not been corrected within 2–3 months, contact HMRC directly. See our emergency tax code guide for detailed steps.
How do K codes work when my allowance is negative?
A K code means HMRC is collecting additional tax through PAYE because your taxable benefits or underpaid tax exceeds your Personal Allowance. Common reasons include a company car, private medical insurance, or tax owed from a previous year being collected through your code. The number after K represents the amount being added to your taxable income (multiplied by 10).
For example, K500 means £5,000 is being added to your taxable income. If you have a company car with a BIK value of £17,570 and your Personal Allowance is £12,579, the excess is £5,000 — hence K500. There is a protection: tax collected via a K code cannot exceed 50% of your gross pay in any pay period, preventing extreme deductions from a single payslip.
If you think your K code is wrong — for example, you have returned a company car but HMRC still shows the BIK — contact HMRC to have it corrected. Your employer cannot change your tax code; only HMRC can issue a new one.
What should I do if my tax code is wrong?
An incorrect tax code means you are either overpaying or underpaying tax throughout the year. Common reasons for errors include:
- A benefit in kind has ended but HMRC still includes it in your code (e.g., you returned a company car months ago).
- HMRC has estimated income from a second source incorrectly — perhaps based on last year's figures when your circumstances have changed.
- Marriage Allowance is still being applied after a separation or divorce.
- Your employer reported incorrect information on a P11D (benefits form).
To fix it: check your code on your payslip or in your HMRC Personal Tax Account online at gov.uk. If it looks wrong, you can update your details online or call HMRC on 0300 200 3300. Your employer cannot change your code directly. Once HMRC issues a corrected code, any overpaid tax will be refunded through your subsequent payslips automatically.
How can I see the effect of my tax code on take-home pay?
Our income tax calculator lets you enter a custom tax code to see exactly how it affects your take-home pay. Try inputting your salary with code 1257L, then compare it against a K code or BR to understand the difference. You can also model what happens if you receive Marriage Allowance (code 1383M) or are put on an emergency code.
For a broader understanding of how your pay is calculated, see our guide to understanding your payslip.
Sources
- HMRC — Tax codes. Official guidance on what tax codes mean and how they are calculated. Accessed July 2026.
- HMRC — Emergency tax codes. When emergency codes are used and how they are resolved. Accessed July 2026.
- HMRC — Income Tax rates and Personal Allowances. Personal Allowance £12,579, basic rate 20%, higher rate 40%, additional rate 45%. Accessed July 2026.