Your tax code is the short string of letters and numbers on your payslip — and it quietly decides how much of your salary reaches your bank account every month. Most UK employees see 1257L and never think about it again. But if your code is wrong, you could be paying hundreds of pounds too much (or too little) without realising. Here's what every common code means under 2025/26 rules, using the same maths as our UK salary calculator.
How a tax code is built
A standard code is number + letter. The number comes from your tax-free personal allowance: it's your allowance with the last digit dropped. With a £12,570 allowance, that becomes 1257 — and the L means you're entitled to the standard allowance. Multiply the number by 10 and you get your tax-free pay for the year: 1257 → £12,570.
The codes you'll actually see
| Code | Meaning | Tax-free pay |
|---|---|---|
| 1257L | Standard employee — full personal allowance | £12,570 |
| BR | Basic rate 20% on everything — usually a second job | £0 |
| D0 | Higher rate 40% on everything | £0 |
| D1 | Additional rate 45% on everything | £0 |
| 0T | No allowance — but normal bands apply (often after BR ends) | £0 |
| K + number | Allowance is negative — e.g. K497 adds £4,970 to your taxable pay | −varies |
| NT | No tax taken at all (rare) | n/a |
Emergency tax: W1, M1 and X
If your payslip code ends in W1 (week 1) or M1 (month 1), you're on a non-cumulative basis: each pay period is taxed on its own, with no memory of what you've earned before. That's why emergency tax usually overcharges people mid-year and only sorts itself out after a refund or year-end reconciliation. The X suffix works the same way for people paid irregularly. When HMRC catches up with your real details, the code drops the suffix and you're back to normal.
Country prefix letters
- C1257L — C is Wales: same allowance, Welsh rates of income tax (currently aligned with England).
- S1257L — S is Scotland: different bands — 19% starter rate, then 20%, 21%, 42% and 45%. A Scottish basic-rate taxpayer pays slightly less; higher earners pay more.
- No prefix — England and Northern Ireland.
Why codes go wrong (and what it costs)
Three classic situations:
- Started a new job and HR used your P45 incorrectly — you land on 0T or BR until HMRC updates. On a £40,000 salary, a month on BR costs about £210 extra.
- Two jobs — your second job has no allowance, so it's taxed at 20%+ from the first pound. Deliberate, but check the split is right if your second job pushes into 40%.
- Company benefits — a £12,000 company car can shrink your code to something like 457L, and the high-income child benefit charge can turn 1257L into a reduced or K code.
A single wrong digit changes your tax by roughly £10 per point of allowance, per month, at basic rate. Over a year that's real money.
How to check and fix your code
Use HMRC's Check your Income Tax service in your Personal Tax Account, or the HMRC app. Your employer can't change the code themselves — only HMRC can. If it's wrong, the online service lets you report it, the corrected code reaches your employer's payroll within days, and any refund is usually paid automatically in the next payslip.
See what your code does to your pay
We have worked take-home examples for common salaries: £30,000, £40,000, £45,000, £50,000 and £55,000 after tax — or enter your exact pay and student-loan status into the UK salary calculator for a full breakdown of income tax, National Insurance and net pay.