How a tax code is built
A UK tax code is usually a number followed by one or more letters. The number represents your tax-free allowance for the year, divided by 10. So a code of 1257 means 1257 × 10 = £12,570 of tax-free income — the standard Personal Allowance for 2026/27. (HMRC adds a £9 rounding adjustment when constructing the code, which is why the formula is sometimes quoted as "number × 10 + £9".) The letter tells your employer how that allowance should be applied — whether you get the standard allowance, have transferred Marriage Allowance, or should be taxed at a flat rate with no allowance at all.
The letter tells your employer how that allowance should be applied — for example, whether you get the standard allowance, whether you have transferred Marriage Allowance, or whether all your income should be taxed at a flat rate. Some codes have no number at all (like BR or D0), which means no Personal Allowance is applied to that income.
What each letter means
| Letter | Meaning |
|---|---|
| L | Standard Personal Allowance — the most common code |
| M | Marriage Allowance: you have received 10% of your partner's Personal Allowance |
| N | Marriage Allowance: you have transferred 10% of your Personal Allowance to your partner |
| BR | All income taxed at the basic rate (20%) — no Personal Allowance, often a second job or pension |
| D0 | All income taxed at the higher rate (40%) |
| D1 | All income taxed at the additional rate (45%) |
| S | Scottish income tax rates apply |
| NT | No tax to pay on this income |
| K | Tax-free amount is negative — deductions (e.g. benefits in kind) exceed your allowances, so extra tax is collected through your pay |
GOV.UK — Tax codes · 2026/27
The most common tax codes, explained
1257L is the default code for most people in 2026/27. It means you get the full £12,570 Personal Allowance spread across the year, so the first £1,047.50 of your monthly pay is tax-free. If you have one job and no special adjustments, this is the code you should expect.
BR means all of this income is taxed at 20% with no tax-free portion. It is typically used for a second job or a private pension where your Personal Allowance is already being used against your main income. If BR appears on your only job, it is usually wrong and you should contact HMRC.
D0 and D1 work the same way but at 40% and 45% respectively — used when this income falls entirely in the higher or additional rate band. NT means no tax is deducted at all, which is rare and usually applies to specific exempt income or people who have overpaid and are having it refunded through their pay.
K codes are unusual: instead of giving you a tax-free allowance, they add an amount to your taxable pay. This happens when you owe tax from a previous year, or when you receive benefits in kind (like a company car) that exceed your allowances. With a K code, the number × 10 is the amount added to your taxable income, not subtracted.
How to check your tax code
Your tax code appears on your payslip (usually near the tax and National Insurance deductions), your P60 at the end of the tax year, and any P45 from a previous employer. The most reliable place to check is your Personal Tax Account on GOV.UK, which shows your current tax code, how it was calculated, and any changes HMRC has made.
HMRC sends a coding notice (form P2) by post or through your Personal Tax Account whenever your code changes. It is worth reading it — it lists the allowances and deductions HMRC has used, and you can spot errors (like a benefit you no longer receive) before they affect your pay for a full year.
What to do if your tax code is wrong
If your code looks wrong — for example, it shows BR on your only job, or includes a deduction for a benefit you no longer get — you should contact HMRC as soon as possible. You can do this through your Personal Tax Account (the fastest route), by phone, or by post. HMRC will review your code and issue an updated one to your employer, who will apply it from the next payday.
If you have already overpaid tax because of a wrong code, HMRC will usually refund you after the end of the tax year, or adjust your code to collect less in future. If you have underpaid, HMRC will normally adjust your code for the following year to collect the shortfall — as long as it is within the limits for coding out. You can use our income tax calculator to check what your tax should be and compare it to what is being deducted.
Frequently asked questions
What does 1257L mean?
Why am I on a BR tax code?
What is a K tax code?
Can my tax code change mid-year?
How do I find my current tax code?
What happens if I am on the wrong tax code?
Sources
- GOV.UK — Tax codes (letter meanings and how codes work, 2026/27)
- GOV.UK — Income Tax rates and Personal Allowances (£12,570 allowance, 2026/27)
- GOV.UK — Personal Tax Account (how to check and manage your tax code, accessed 2026)