UK Tax Codes Explained: What 1257L, BR, K and Emergency Codes Mean

Your tax code is a short instruction from HMRC to your employer or pension provider. It tells payroll how much of your pay is tax-free in each pay period. Get it wrong and you can pay hundreds of pounds too much or too little tax over a year, so it’s worth knowing how to read it.

The anatomy of a tax code

Most codes are a number followed by a letter, for example 1257L.

• The number is your tax-free allowance divided by 10. 1257 means £12,570 of tax-free income in the year.
• The letter describes your situation. L is the standard letter for someone entitled to the basic Personal Allowance.

Payroll spreads the allowance across the year. On a monthly payroll, 1257L gives you £1,047.50 of tax-free pay each month, and everything above is taxed at your rates.

Common letters and codes

Code	Meaning
L	Standard Personal Allowance
M	You receive 10% of your partner’s allowance through Marriage Allowance
N	You’ve transferred 10% of your allowance to your partner
T	Your allowance includes items HMRC needs to review, for example after the £100k taper
S prefix	You’re a Scottish taxpayer, taxed on Scottish bands
C prefix	You’re a Welsh taxpayer (Welsh rates currently match England’s)
BR	All income taxed at the basic rate, 20%. Common for a second job
D0	All income taxed at the higher rate, 40%
D1	All income taxed at the additional rate, 45% (Scottish advanced rate for SD1)
NT	No tax deducted
0T	No tax-free allowance: tax starts from the first pound
K	Negative allowance. See below

K codes: when you owe more than your allowance

A K code means the deductions in your code are bigger than your allowances. That usually happens because of taxable benefits, such as a company car or medical insurance, or tax HMRC is collecting from an earlier year. The number is added to your taxable pay rather than taken off.

For example, K475 adds £4,750 to your taxable income for the year. To stop K codes taking too much in one go, the tax deducted in any pay period can’t be more than 50% of your pay for that period.

Emergency codes: W1, M1 and X

Codes ending W1 (week 1), M1 (month 1) or X are non-cumulative. Payroll treats every payday as if it were the first of the tax year, ignoring what you’ve already earned and paid. You’ll usually see one when you start a new job without a P45, or when HMRC doesn’t yet have your details.

Emergency codes often mean you pay the wrong amount. You might not get the benefit of allowance you didn’t use earlier in the year. Once HMRC has your information, it issues a normal cumulative code and payroll corrects the difference over the remaining paydays.

Cumulative tax: why your tax goes up and down

With a normal code, PAYE is cumulative. Each payday, payroll works out the tax due on your total pay so far this tax year, compares it with the tax already deducted, and takes the difference. So:

• if you start a job part-way through the year, your first payslips may show very little tax, because you’re catching up on unused allowance;
• a bonus month is taxed at your marginal rate, but tax isn’t “overcharged” for the year as a whole.

National Insurance is different. It’s worked out separately for each pay period and doesn’t catch up. Our take-home pay calculator models both.

Why your tax code might change

HMRC can change your code during the year when:

• you start receiving a taxable benefit, or it changes;
• you start or stop claiming Marriage Allowance;
• your income goes over £100,000 and your allowance tapers;
• you have untaxed income, such as savings interest above your allowance or rental profit, that HMRC collects through PAYE;
• you’ve underpaid tax in a previous year (up to £3,000 can usually be collected through your code);
• you start a second job or a pension.

You’ll get a P2 coding notice, or see it in your HMRC app or personal tax account.

How to check your tax code is right

1. Find it on your payslip, P60, HMRC app or personal tax account.
2. Check the number. If you only have one job, no benefits and earn under £100,000, it should almost always be 1257L (or S1257L in Scotland) for 2026/27.
3. Check for an emergency suffix. W1, M1 or X after a few months in a job usually means something’s missing.
4. Check the letter against your circumstances, for example whether you claim Marriage Allowance.
5. Read the coding notice to see which adjustments HMRC has made and why.

If something’s wrong, update your details in the HMRC app or call HMRC. Your employer can’t change your code without HMRC’s instruction. Overpaid tax is refunded through your pay, or after the tax year ends.

Two jobs and BR codes

With two jobs, your full allowance normally goes to the main one, so the second job uses BR. If your main job pays less than £12,570 a year, part of your allowance is wasted. You can ask HMRC to split it, for example 900L for the main job and 357L for the second. The pay rise calculator’s Add a second job mode shows the effect.

If you have more than one job, the pay rise calculator has a two-jobs mode. For what each payslip line means, see how to read your payslip.

Try it with your own code

Enter your code in the take-home pay calculator under Tax code & other options. We support L, M, N and T codes, Scottish and Welsh prefixes, K codes, BR, D0, D1, D2, NT, 0T and emergency suffixes. If a code isn’t recognised, we tell you, and fall back to the standard allowance rather than guessing.