Understanding UK Tax Codes — Complete Guide to 1257L, BR, D0, K, NT and Emergency Codes

Full UK tax code guide for 2026/27 — what 1257L, BR, D0, D1, K, NT, M, N and W1/M1 emergency codes mean, when they're used, and how to fix a wrong code.

Last reviewed · Tax year 2026/27

Your UK tax code is the three-or-four-character string that tells your employer how much Income Tax to deduct from your pay each month. Most people see “1257L” and never think about it — but the code carries a surprising amount of meaning, and getting it wrong is one of the most common reasons UK employees over- or under-pay tax.

This guide walks through every common tax code for 2026/27, what each one means in pounds and pence, when HMRC assigns it, and what to do if you think yours is wrong.

2026 / 27 cycle 6 APR → 5 APR TAX YEAR Q1 · APR–JUN Q2 · JUL–SEP Q3 · OCT–DEC Q4 · JAN–MAR
UK tax year runs 6 April to 5 April. HMRC re-issues tax codes for every new cycle.

What the number means

The first part of your tax code is your Personal Allowance divided by 10.

  • 1257 → Personal Allowance of £12,570 (the standard for 2026/27; frozen since 2021/22).
  • 1383 → Personal Allowance of £13,830 (you received Marriage Allowance).
  • 1131 → Personal Allowance of £11,310 (you transferred Marriage Allowance).

The number is your tax-free headroom for the year. Anything you earn above it is taxed, starting at the basic rate (20%) and climbing through the bands as your income rises.

The Personal Allowance has been frozen at £12,570 since 2021/22 and is set to stay there until at least April 2028 (gov.uk — Income Tax rates).

The letter suffix

The letter after the number modifies the allowance or tells HMRC something special about the taxpayer:

L — Standard

Most common. You get the standard Personal Allowance. No special adjustments. 1257L is what most UK employees see on their payslip.

M — Received Marriage Allowance

Your spouse or civil partner transferred £1,260 of their Personal Allowance to you. You keep your full £12,570 + their £1,260 = £13,830 effective allowance. Code: 1383M.

N — Transferred Marriage Allowance

You transferred £1,260 of your Personal Allowance to your spouse. Your effective allowance drops to £11,310. Code: 1131N.

Marriage Allowance is claimed via gov.uk — Marriage Allowance. The non-taxpayer partner (earning under £12,570) transfers to the basic-rate partner (earning under £50,270). Worth £252 per year in saved tax.

T — Other adjustments

The T suffix is used when HMRC needs to review the tax code — usually because of other income sources, benefits-in-kind, or estate income. Call HMRC if this appears unexpectedly.

BR — Basic Rate

No Personal Allowance; every penny from this job is taxed at 20%. The most common second-job code. If your main job uses 1257L (full PA) and your second job uses BR, HMRC is correctly splitting the allowance between them.

D0 — All at Higher Rate

Every penny from this job is taxed at 40%. Used when your other income already fills the basic-rate band. Common on second jobs for people earning over £50,270 at their main job.

D1 — All at Additional Rate

Every penny taxed at 45%. Applied when you’re already an additional-rate taxpayer (income over £125,140) at your primary employment.

NT — No Tax

Rare. Used for specific scenarios: statutory sick pay during certain certification periods, or some non-residents. If you see NT and aren’t sure why, contact HMRC — you may have under-paid tax by a large amount.

K codes — the negative allowance

A K code means your deductions exceed your Personal Allowance. The number after K, multiplied by 10, is added to your taxable income rather than subtracted.

Example: K500 means £5,000 of extra taxable income will be added to whatever you earn. If you earn £30,000, the tax calculation is on £35,000.

K codes most commonly appear when:

  1. You have a company car or other valuable benefit-in-kind that exceeds your Personal Allowance.
  2. You owe HMRC tax from a previous year (Self Assessment underpayment collected via PAYE).
  3. You’re receiving a state pension that exceeds the Personal Allowance.

HMRC limits K-code deductions to 50% of your gross pay in any pay period — so if your K code would take more than half, only half is actually deducted that month, and the rest carries forward.

W1 / M1 / X — emergency codes

These are “non-cumulative” codes. They tell your employer to tax only the current pay period in isolation, ignoring your year-to-date earnings.

  • W1: week 1 basis (weekly-paid employees).
  • M1: month 1 basis (monthly-paid employees).
  • X: generic emergency code.

They’re usually applied when you:

  • Start a new job without a P45.
  • Complete a Starter Checklist but HMRC hasn’t caught up.
  • Move between jobs mid-year.

Emergency codes almost always resolve themselves once HMRC has enough info. You may get a tax refund (or owe a small amount) at year-end via PAYE adjustment.

Scottish tax codes

Scottish taxpayers have an S prefix: S1257L, S BR, SD0, etc. The Scottish Government sets its own income-tax bands (see our Scottish income tax guide), and the S prefix tells your employer to apply them.

Welsh taxpayers have a C prefix: C1257L, C BR, etc. Welsh rates currently match the rest of the UK, but the separation means Wales can diverge in future without changing HMRC systems.

Pay in practice — a worked example

Let’s say your tax code is 1257L and you earn £30,000 a year, paid monthly (£2,500/month).

  1. Monthly Personal Allowance: £12,570 / 12 = £1,047.50.
  2. Taxable pay per month: £2,500 − £1,047.50 = £1,452.50.
  3. Basic rate (20%) tax: £1,452.50 × 20% = £290.50.
  4. Plus NI (8% of £2,500 − £1,047.50 PT): £116.20.
  5. Net pay: £2,500 − £290.50 − £116.20 = £2,093.30.

That matches our salary calculator output exactly.

How to check and fix your tax code

  1. Log into your Personal Tax Account at gov.uk/personal-tax-account.
  2. You’ll see your current tax code, the breakdown (how HMRC calculated it), and a list of the income sources they’re aware of.
  3. If something looks wrong — missing benefit, wrong employer, old job still listed — you can update it online or call HMRC on 0300 200 3300.
  4. If you’ve over-paid tax this year, HMRC usually refunds it via a larger paycheque in the next few months (adjusted code).
  5. If you’ve under-paid, HMRC normally collects it by reducing next year’s code — spreading the cost.

Common tax code mistakes

  1. Starting a new job and paying emergency tax for months. Usually resolves once HMRC processes your P45 or Starter Checklist. Push back if it drags on.
  2. Old company car still showing. If you returned a company car but the benefit is still on your tax record, you’ll be over-paying. Notify HMRC.
  3. Missing Marriage Allowance. If you or your spouse is a non-taxpayer (earning under £12,570) and the other is a basic-rate taxpayer (under £50,270), claiming Marriage Allowance is £252/year of free money.
  4. BR on the wrong job. If your “main” job is paying you less than your PA and “second” job is the bigger earner, the Personal Allowance is on the wrong employment. Ask HMRC to swap.