How to read a UK tax code
Most UK tax codes consist of a number followed by a letter. The number represents your tax-free income divided by ten, and the letter tells your employer how to apply it. The standard code for 2026/27 is 1257L, which represents the standard personal allowance of £12,570 (1257 multiplied by 10) with the L suffix indicating the standard rate. However, there are many variations.
| Suffix / code | Meaning |
|---|---|
| L | Standard personal allowance (most common) |
| M | Marriage Allowance, you have received 10% of your partner's allowance |
| N | Marriage Allowance, you have transferred 10% of your allowance to your partner |
| T | Your code includes other calculations; HMRC needs to review |
| S prefix | Scottish taxpayer, Scottish income tax rates apply |
| C prefix | Welsh taxpayer, Welsh income tax rates apply |
| K prefix | Negative allowance, you owe more in tax than your allowance covers |
| BR | All income taxed at basic rate (20%), no personal allowance |
| D0 | All income taxed at higher rate (40%), second job or pension |
| D1 | All income taxed at additional rate (45%) |
| NT | No tax to be deducted |
| 0T | No personal allowance, used when allowance is used up elsewhere |
| W1 / M1 | Emergency tax code, tax calculated on a week/month basis only |
K codes: A K code means you have a negative allowance. This happens when deductions from your allowance (for benefits in kind, state pension, or unpaid tax from previous years) exceed your personal allowance. A K code of K100, for example, means HMRC adds £1,000 to your taxable income rather than deducting an allowance.
Frequently asked questions
Not necessarily. Many people have non-standard codes for entirely legitimate reasons. A higher number than 1257 could mean you have the Marriage Allowance added, a professional subscription deducted, or working from home tax relief included. A lower number typically means HMRC is collecting tax on a benefit in kind (company car, private medical) or recovering underpaid tax from a previous year. The key is understanding why your code differs. If you cannot identify a reason, contact HMRC on 0300 200 3300 or check your Personal Tax Account online.
Emergency codes (1257L W1 or 1257L M1, sometimes written as 1257L X) mean your employer is calculating tax on a non-cumulative basis, either weekly or monthly in isolation rather than against your total earnings for the year to date. This is used when you start a new job without providing a P45, or when HMRC cannot confirm your correct code in time. It often results in overpaying tax because it does not account for unused allowance earlier in the year. Once your employer receives your correct code from HMRC, any overpayment should be refunded through payroll automatically.
The fastest way is through your Personal Tax Account at gov.uk/personal-tax-account. You can view all your current tax codes, see what adjustments have been made, and in many cases update the information HMRC holds directly online. Alternatively, call HMRC's income tax helpline on 0300 200 3300 (Monday to Friday, 8am to 6pm). Have your National Insurance number and a recent payslip to hand. If your code is wrong, HMRC will issue a new one and your employer will apply it in the next payroll run.
Your personal allowance can only be used against one income source at a time. HMRC allocates it to your main job or primary pension, which receives your standard code (typically 1257L). Your second job or additional income source receives a BR code (taxed at 20% with no allowance) or D0 (40%) depending on your expected total income for the year. This prevents you benefiting from the personal allowance twice. If your secondary income regularly changes or your main income fluctuates, it is worth checking whether HMRC has the correct job designated as your primary income.
Related calculators
Tax Toolkit UK provides free calculators for guidance purposes only. Results are estimates based on HMRC rates for the 2026/27 tax year. Individual circumstances vary. Always consult a qualified tax adviser before making financial decisions.