Money guide

What does my tax code actually mean?

Updated 3 August 2026 · 5 min read

Your tax code is the short string on your payslip — something like 1257L — that tells your employer how much of your pay to leave untaxed. Get it wrong and you either hand HMRC too much money every month, or quietly build up a bill you'll be asked for later. It's worth five minutes.

The number is your allowance

Take the number and add a zero. That's roughly your tax-free allowance for the year. 1257L means £12,570 of your pay is untaxed — the standard Personal Allowance for 2026/27. Everything above that gets taxed at the normal rates.

So if your number is lower than 1257, HMRC has reduced your allowance for some reason. If it's higher, you've been given extra.

The letter is your situation

L — the standard code. Nothing unusual.
M — you've received part of your partner's allowance through Marriage Allowance.
N — you've given part of yours away to your partner.
S at the start — HMRC has you as a Scottish taxpayer, so Scottish rates apply.
C at the start — Welsh taxpayer.

The codes that usually mean something's up

BR, D0 and D1

These tax all of that income at a single rate — 20%, 40% and 45% respectively — with no tax-free allowance at all. That's completely normal for a second job or a pension, because your allowance is already being used by your main job. It's a problem if it's on your only job: you're likely overpaying, and HMRC won't always spot it.

0T

No allowance either, but usually for a different reason: HMRC doesn't have enough information about you. It's common when you start a job without a P45. It normally sorts itself out once your details catch up.

W1, M1 or X on the end

This is the "emergency" bit. It means your tax is worked out on that pay period alone, rather than your whole year to date — so it can't take account of what you've already earned or paid. Again, common when starting a new job, and it usually resolves itself once HMRC has the full picture.

K codes

A code starting with K works in reverse: instead of tax-free pay, an amount is added to your taxable income. This happens when untaxed income or benefits (a company car, private medical cover, or tax owed from an earlier year) exceed your allowance.

The one to actually check: a number lower than 1257 with no obvious reason. HMRC reduces your allowance when it thinks you're getting taxable benefits. If you no longer have that benefit — you gave the company car back, the health cover stopped — nobody automatically tells them. You just quietly keep paying more.

What to do if it looks wrong

Don't panic, and don't expect a form on a website to fix it — only HMRC can change your code. Check your Personal Tax Account on gov.uk or ring HMRC and ask them to explain the code. If you've overpaid, it's usually corrected through your pay, or refunded after the tax year ends. If you've underpaid, it's much better to find out now than to receive a bill.

Check your tax code against your salary →Our calculator reads your code and flags emergency codes or a reduced allowance.

The short version

Number × 10 = your tax-free pay. Letter = your circumstances. BR, 0T, D0, D1 and anything ending W1/M1/X mean no allowance is being applied to that income — fine for a second job, worth checking on your main one. And if your number dropped without explanation, ask why.

Written in plain English by mytakehome.money. General information, not financial advice — check anything important at gov.uk or with a qualified adviser.