UK Tax Code Decoder

What every part of a UK tax code means

A standard UK tax code is a number followed by a letter. The number is your tax-free amount divided by 10 (so 1257L means £12,570 personal allowance). The letter and any prefix change how that allowance is applied.

Common suffix letters

• L — standard personal allowance applies (the typical code).
• M — you have received 10% of your spouse's personal allowance via Marriage Allowance.
• N — you have given 10% of your personal allowance to your spouse via Marriage Allowance.
• T — your tax code includes other calculations to work out your personal allowance, for example a reduction because your income is over £100,000.

Special codes

• BR — Basic Rate. All income from this source taxed at 20% with no personal allowance. Common for second jobs.
• D0 — All income taxed at 40% (higher rate). Used when your other income already uses your personal allowance and basic-rate band.
• D1 — All income taxed at 45% (additional rate).
• SD0, SD1, SD2, SD3 — the Scottish versions: all income taxed at 21% (intermediate), 42% (higher), 45% (advanced) or 48% (top) respectively.
• 0T — No personal allowance on this job or pension. Used when your allowance has been used up, or you have started a new job and your employer does not have the details it needs.
• NT — No tax is taken from this income. Rare on a normal payslip.
• K codes (e.g. K500) — your taxable income is being increased by £5,000 to recover untaxed amounts (e.g. company benefits, unpaid tax). Tax taken cannot exceed 50% of pay in any period.

Prefix letters

• S — Scottish income tax rates apply (e.g. S1257L, SBR). For 2026/27 those are 19% starter (£12,571 to £16,537), 20% basic, 21% intermediate, 42% higher, 45% advanced and 48% top rate above £125,140.
• C — Welsh rates apply (the same as the rest of the UK in 2026/27, but shown separately, e.g. C1257L).

Emergency markers

• W1 / M1 / X — non-cumulative ("emergency") basis. Each pay period treated in isolation rather than year-to-date. Common for new starters and after job changes. Often results in over- or under-paying tax until the code is updated.

Found a wrong code? What to do next

1. Check your tax code online in your HMRC personal tax account (gov.uk/personal-tax-account) or the HMRC app, which also show earlier years' codes.
2. Look at how HMRC worked the code out: the allowances it started from and anything it took off, such as company benefits or untaxed income.
3. If something is wrong — a job that has ended, a benefit you no longer get, or an estimate of income that is out of date — update the details in your account or app, or contact HMRC, so it can issue a new code to your employer or pension provider.
4. Once HMRC issues a corrected code, your employer applies it on the next pay run. Any over-paid tax is usually refunded automatically over the rest of the tax year.
5. If you've over-paid tax for a previous tax year, you can claim a refund through HMRC; see also our emergency tax refund checker.

Sources

The letters, prefixes and rates used by the decoder were checked on 3 October 2026 against:

• GOV.UK, What your tax code means (letters including BR, D0, D1, SD0 to SD3, K, M, N, NT, T and the W1, M1 and X emergency markers).
• GOV.UK, Emergency tax codes (1257L W1, M1 or X for 2026/27).
• GOV.UK, Income Tax rates and Personal Allowances and Scottish Income Tax (2026/27 bands).
• HMRC PAYE Manual, PAYE11095 (K codes) and PAYE76055 (the 50% limit) (updated 2 October 2026).