UK tax codes explained

A tax code is the instruction HMRC gives your employer or pension provider so they can work out how much Income Tax to take from that pay or pension. You can have a different code for each employment or pension. GOV.UK is the official place to look up your current code, and HMRC may also write to you when it changes. This guide explains the common patterns in official wording, and our tax code decoder will parse a code you type. Neither the guide nor the decoder can confirm that a particular code is the correct one for you.

The numbers, and the most common code

The official “what your tax code means” page says the numbers tell your employer or pension provider how much tax-free income you get from them in that tax year. HMRC starts with your tax-free Personal Allowance and takes off income you have not paid tax on, and other deductions in the code such as company benefits or the High Income Child Benefit Charge, then replaces the final digit with a letter. In an official example, a £12,570 allowance minus a £1,570 medical-insurance benefit leaves £11,000, and the code is 1100L.

For most people with one job or pension, GOV.UK says 1257L is the tax code currently used. That matches the standard Personal Allowance of £12,570, which is the official figure for both 2025/26 and 2026/27. Seeing 1257L on a payslip is therefore common, and still not proof that nothing else should have been adjusted in your case. If you have two jobs, untaxed interest, a company car or a High Income Child Benefit Charge collected through PAYE, the numbers will often be different.

Letters you will see often

L means you are entitled to the standard tax-free Personal Allowance. M means you have received a transfer of 10% of your partner’s Personal Allowance under Marriage Allowance; N means you have transferred 10% of yours to your partner. T means the code includes other calculations to work out the allowance. BR taxes all income from that job or pension at the basic rate, D0 at the higher rate, and D1 at the additional rate; the official table notes that these are usually used if you have more than one job or pension. NT means you are not paying any tax on that income. 0T means the Personal Allowance has been used up, or you have started a new job and the employer does not have the details needed to give you a fuller code.

K is the letter that reverses the usual logic. The official K-code page is the place to read the detail; in short, you have income you are not paying tax on which is more than your Personal Allowance, and the number in a K code, multiplied by ten, is added to taxable pay from that employment rather than being a tax-free amount. Our decoder accepts both K497 and 497K and will describe that addition rather than calling it a tax-free allowance.

Scotland, Wales, and emergency suffixes

An S at the start of a code means the income or pension is taxed using the rates in Scotland. A C means the rates in Wales. There is a matching family of letter-only codes: SBR, S0T, SD0 (intermediate), SD1 (higher), SD2 (advanced), SD3 (top) in Scotland, and CBR, C0T, CD0 and CD1 in Wales. Those official labels matter, because “D0” in England is the higher rate, while “SD0” in Scotland is the intermediate rate, not the higher rate. Mixing them up will misread a payslip.

You are on an emergency tax code if the code ends in W1, M1 or X, or if a payslip shows NONCUM. W1 is used when you are paid weekly, M1 when you are paid monthly, and X when pay dates vary. Official employer pages state that the emergency tax codes from 6 April 2025, and again from 6 April 2026, are 1257L W1, 1257L M1 and 1257L X. Emergency tax is worked out on that week or month only, as if you were paid the same amount every period of the year, which can mean too much or too little tax until HMRC updates the code. A suffix M1 is not the Marriage Allowance letter M. 1257L M1 is an emergency monthly code; a code such as 1383M is a Marriage Allowance letter with a £13,830 tax-free amount.

Official emergency-code guidance says a new employer who does not have your previous income and tax details will often start you on an emergency code, usually temporarily, and that giving them a P45 helps. HMRC will usually update the code when it has details from the new and previous employers, which can take up to 35 days from when you start. If you have not paid enough tax you may stay on the emergency code until the year’s tax is caught up; if you have paid too much you can get a refund. Starting company benefits or the State Pension can also put you on an emergency code until the end of the tax year.

If you think the code is wrong

It is your responsibility, official starting-a-job guidance says, to make sure you are paying the right amount of tax, and a wrong code is a common reason a payslip looks off. Check the code in your Personal Tax Account or the HMRC app, compare it with the payslip, and use the official service to update details if something is missing. Our decoder will only explain the characters. It will not tell HMRC to change anything, and it will not calculate the tax on your pay. For a planning view of a whole year’s Income Tax, use the tax calculator as an estimate, then rely on HMRC for the code itself.

Several jobs, pensions, and keeping a record

Official guidance is that you will get a tax code for each employment or pension you have. One job can be on 1257L while a second is on BR, which usually means the Personal Allowance has been given to the first job and the second is taxed at the basic rate in full. That arrangement can be correct, and it can also collect too much if the first job never uses the whole allowance. The settlement then happens through a repayment, a code change, or a return if you already file one.

A pension provider uses a tax code in the same way an employer does. People who start drawing a private pension while still working often see a new code land on the pension slips, sometimes an emergency one, while the job stays on a different code. Check both. The official tax-code service and the HMRC app can show codes for the current year and, official wording says, for previous tax years, and they can let you sign up for paperless notifications when a code changes.

Keep payslips for a full tax year if you can. They are the practical record of which code was applied in which month, which is useful if you query a deduction or if you later complete a return. Our decoder will read a single code you type today; it will not reconstruct a year of payroll history.