Audience: All PAYE employees
If you have ever glanced at your payslip and wondered what the combination of numbers and letters in the 'tax code' box actually means, you are not alone. For most employees, their tax code is something they vaguely recognise but rarely understand. Yet your tax code has a direct and significant impact on how much income tax is deducted from your pay every month. Getting it wrong — or failing to notice when it is wrong — can mean overpaying hundreds or even thousands of pounds in tax each year.
This guide explains every element of UK tax codes in plain English, so you can check yours with confidence and act if something looks amiss.
Your tax code is a short combination of numbers and letters issued by HMRC and used by your employer to work out how much income tax to deduct from your wages. It essentially tells your employer how much of your income you can receive tax-free — that is, your personal allowance — and whether any adjustments need to be made to account for benefits, other income, or amounts owed.
For most people in the UK, the standard tax code for 2024/25 is 1257L. This code tells your employer that you are entitled to the standard personal allowance of £12,570 and that no other adjustments are needed. But there are dozens of variations, and understanding them can save you money.
The number in your tax code represents your tax-free amount, but with the last digit removed. So a code of 1257 means you have a tax-free allowance of £12,570. A code of 1100 would mean a tax-free allowance of £11,000. The number can be higher than 1257 if you are entitled to additional allowances — for example, if you are claiming the Marriage Allowance transfer from your spouse.
Conversely, the number can be lower than 1257 if there are deductions to your personal allowance. This might happen if you have untaxed income (such as rental income or a state pension), a company benefit (such as a company car or private medical insurance), or if you owe tax from a previous year that HMRC is collecting gradually through your code.
The letter at the end of your tax code is equally important and tells your employer additional information about your tax situation. Here is what the most common letters mean.
L is the most common letter and simply means that you are entitled to the standard personal allowance. Most employed workers in the UK will have an L in their tax code.
M means that you have received a transfer of 10% of your partner's personal allowance under the Marriage Allowance scheme. This increases your tax-free amount.
N is the mirror image of M — it means you have transferred 10% of your personal allowance to your partner, reducing your own tax-free amount slightly.
T means that HMRC needs to review your tax code and that there are items that require special consideration. You may see this if your tax affairs are more complex than usual.
0T means that you are receiving no personal allowance at all. This might be because you have already used your personal allowance against another source of income, or because HMRC does not have enough information about you.
BR stands for Basic Rate and means that all of your income from this employment is taxed at 20%. This is often applied to a second job where your personal allowance has already been used against your main job.
D0 means that all of your income is taxed at the higher rate of 40%, and D1 means all income is taxed at 45% (the additional rate).
NT means No Tax — no income tax will be deducted at all. This is rare but can apply in certain specific circumstances.
W1 or M1 at the end of your tax code means it is operating on a week-by-week or month-by-month basis, rather than cumulatively. This is known as a non-cumulative or emergency code and often arises when you start a new job without a P45.
Your tax code appears in several places. You will find it on your payslip, usually in a box labelled 'tax code'. You will also find it on your P60 at the end of the tax year, and on any P45 you receive when leaving employment. HMRC also sends out a PAYE coding notice (form P2) when your tax code changes, and you can view your current tax code at any time through your Personal Tax Account on the gov.uk website.
If you are not sure how to access your Personal Tax Account, you can register using your National Insurance number and a form of identity verification. Once set up, it gives you a clear view of your tax code, your estimated income, and any adjustments HMRC has made.
Tax codes go wrong more often than most people realise. Common reasons include starting a new job and being placed on an emergency code because your previous employer's records were not transferred; HMRC applying an out-of-date adjustment for a benefit in kind that you no longer receive; or income estimates being incorrect, leading to adjustments that do not reflect your actual situation.
If you believe your tax code is incorrect, you should contact HMRC directly. You can do this through your Personal Tax Account, by phone on 0300 200 3300, or by post. Your employer cannot change your tax code — only HMRC can issue a new one.
Once HMRC issues a corrected code, your employer will update their payroll system and any overpaid tax from earlier in the tax year should be automatically refunded through your pay in subsequent months. If you have overpaid tax for a previous year, you may need to claim a refund separately.
Emergency tax codes deserve special mention because they catch so many people out. If your employer does not have enough information to work out your correct tax code — most commonly when you start a new job without providing a P45 — they will apply an emergency code.
The emergency code for 2024/25 is 1257L W1 or 1257L M1. The W1 or M1 suffix means your employer taxes each pay period in isolation, rather than calculating your tax cumulatively. This can result in overpayments, particularly if you started the job partway through the tax year, since the cumulative system would take into account any unused personal allowance from earlier months.
The solution is straightforward: provide your P45 from your previous employer as soon as possible, or contact HMRC to let them know your situation. They will issue a corrected tax code to your new employer.
One of the most practical ways to check whether your tax code is delivering the right results is to use an online PAYE tax calculator. By entering your gross salary and your current tax code, a good calculator will show you exactly how much income tax and National Insurance should be deducted each month or week. You can then compare this to your payslip to see whether the figures match.
If there is a discrepancy, it is a strong indication that something is wrong — either with your tax code or with your employer's payroll calculation. Either way, it is worth investigating promptly, since errors have a habit of compounding over time.
**Disclaimer: ***This article is for general information purposes only and does not constitute tax advice. Tax rules can change and individual circumstances vary. Always consult a qualified tax adviser or contact HMRC directly for advice specific to your situation.*