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 has special items HMRC needs to review (e.g. high income with allowance reductions).

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 main job already uses the personal allowance.
• D1 — All income taxed at 45% (additional rate).
• 0T — No personal allowance. Often used when HMRC has no information about you yet (new starter without P45).
• NT — No tax taken. Rare; specific cases like merchant seafarers or some non-residents.
• 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 bands apply (e.g. S1257L, SBR).
• C — Welsh income tax bands apply (currently same as the rest of the UK in 2026/27, but separately codified, 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. Sign in to your HMRC personal tax account at gov.uk/personal-tax-account.
2. Check the "Your tax code" page — HMRC shows the breakdown they used.
3. If the code is wrong, use HMRC's "Tell HMRC about a change" service to correct it. Common reasons: a job ended, a benefit-in-kind was removed, or the wrong tax-free allowance was applied.
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.