UK tax codes explained: 1257L, the letters, emergency codes and K codes

What a tax code does

Your employer or pension provider uses the code "to work out how much Income Tax to take from your pay or pension". HMRC tells them which code to use, and you get a separate code for each job or pension.

You can find your code in the Check your Income Tax online service, the HMRC app, on your payslip, or on a "Tax Code Notice" letter if HMRC sends you one.

What the numbers mean

The numbers tell your employer how much tax-free income you get from that job in the tax year. HMRC starts with your Personal Allowance, takes off any income you have not paid tax on (such as untaxed interest or part-time earnings) and any other deductions (such as company benefits), then replaces the final digit with a letter.

For 2026 to 2027 the standard Personal Allowance is £12,570. Drop the last digit and add L and you get 1257L, which GOV.UK calls "the tax code currently used for most people who have one job or pension".

GOV.UK's own example: you get medical insurance from your employer worth £1,570. That company benefit is taken off your £12,570 allowance, leaving £11,000 tax-free, so your code becomes 1100L.

Worked example: the same £35,000 salary on different codes

Here is the Income Tax on a £35,000 salary in England for 2026/27, if each code applied all year. National Insurance is £1,794.40 in every row because the tax code does not affect it.

The move from 1257L to 1100L costs exactly £314 a year: the £1,570 benefit taxed at the 20% basic rate.

What the letters mean

The letter describes your situation. These are the meanings GOV.UK gives:

S and C: Scotland and Wales

A code starting with S means your income is taxed at Scottish rates. GOV.UK says your code will be S1257L if you pay Scottish Income Tax and get the standard £12,570 allowance. Scottish flat-rate codes are SBR (basic), SD0 (intermediate), SD1 (higher), SD2 (advanced) and SD3 (top), plus S0T.

A code starting with C means Welsh rates. HMRC adds the C so you pay the right rates; the Welsh codes include C0T, CBR, CD0 and CD1. For 2026 to 2027 the Welsh rates and bands shown on GOV.UK are the same as England's (20%, 40% and 45%), so C1257L gives the same £4,486 on £35,000 as 1257L. The Scottish Income Tax guide covers how the Scottish bands differ.

Emergency tax codes: W1, M1, X and NONCUM

You are on an emergency code if your code ends in:

• W1 – used when you are paid weekly, for example 1257L W1
• M1 – used when you are paid monthly, for example S875L M1
• X – used when your pay dates vary, for example C663L X

Your payslip may show NONCUM instead, depending on your employer's payroll software. If your code does not end in one of these, you are not on an emergency code.

Normally tax is worked out on your total income so far in the tax year. On an emergency code it is worked out on what you are paid in that week or month only, "as if you're paid that amount every week or month of the year". GOV.UK says this could mean you pay the wrong amount of tax.

The usual trigger is a new job where your employer does not have your previous income details. Giving them the P45 from your last job can help take you off the emergency code. HMRC will usually update your code once it has the details from both employers, which can take up to 35 days from when you start.

K codes

A K code means you have income or deductions that are higher than your tax-free Personal Allowance and are not already being taxed. GOV.UK lists examples:

• paying tax you owe from a previous year through your wages or pension
• getting the State Pension or taxable state benefits
• getting company benefits you need to pay tax on, such as a company car
• getting more interest on your savings than your Personal Savings Allowance

There is a safeguard: employers and pension providers "cannot take more than half of your pre-tax wages or pension when using a K tax code". Because the calculation is different, our take-home pay calculator does not model K codes.

Why your code might change

HMRC changes your code when you need to pay a different amount of tax — for example when you start a new job or a second job or pension, your employer reports a company benefit starting or stopping, you claim Marriage Allowance or job expenses, or you owe tax from being on the wrong code. The Check your Income Tax service shows why a code has changed.

How to check and fix a wrong tax code

GOV.UK says a wrong code is usually caused by HMRC having incorrect or missing information. The steps it gives:

1. Sign in to the Check your Income Tax online service.
2. Check your employment, pension, estimated taxable income, company benefit and expenses details.
3. Update anything that is wrong or missing.
4. Claim tax relief on employment expenses, if you have any.

If you left a job without a P45, ask your old employer for one. If the code needs to change, HMRC updates it and tells you and your employer within 15 working days. If you are paid monthly it should be on your next or the following payslip; if you are paid weekly, on your third payslip. If you have just started a new job, GOV.UK says to wait 35 days before contacting HMRC.

If you paid too much, HMRC usually asks your employer to refund the difference through your pay; if you paid too little, it may adjust your code to collect it over one or more tax years.

Frequently asked questions