Understanding your tax code
Your tax code is one of the most important numbers in your life that almost nobody understands. It tells your employer or pension provider exactly how much tax to take off your pay — so if it’s wrong, every payslip is wrong, and you could be handing over hundreds of pounds too much (or storing up a bill for later). The good news: once you can read it, checking it takes two minutes.
This is information, not financial advice. It explains how UK tax codes work for 2026/27. If your code looks wrong, contact HMRC or your payroll team.
What the number means
For most people in 2026/27, the tax code is 1257L. The number is the key part: multiply it by 10 and you get your tax-free Personal Allowance. So 1257 means you can earn £12,570 a year before paying any income tax — the standard allowance, frozen until 2030/31.
If your number is higher than 1257, you have more tax-free pay than usual (perhaps job expenses you can claim). If it’s lower, something is reducing your allowance — a taxable work benefit like a company car, or tax owed from a previous year being collected gradually.
What the letters mean
The letter adds context about your situation. The common ones:
- L — the standard tax-free Personal Allowance. Most people have this.
- M — you’ve received 10% of your partner’s allowance through Marriage Allowance.
- N — you’ve given away 10% of your allowance to your partner.
- T — your code includes other calculations HMRC reviews individually.
- 0T — no tax-free allowance is being applied. Often temporary, when you start a job without a P45.
- BR — all of this income is taxed at the basic 20% rate, with no allowance. Correct for some second jobs; a mistake if it’s on your main one.
- D0 / D1 — all taxed at the higher (40%) or additional (45%) rate. Usually for a second income.
- NT — no tax is taken at all.
- K — a special case where deductions (like a big benefit or past underpayment) are more than your allowance, so tax is added rather than allowance given.
Two prefixes depend on where you live: S at the start means Scottish rates apply; C means Welsh rates.
The emergency codes to watch for
If your code ends in W1, M1, or X, that’s an emergency (non-cumulative) code. It taxes each pay period on its own, ignoring what you’ve earned or paid so far this year. It’s common when you start a new job, and it often means you overpay until HMRC gets the full picture and issues a proper cumulative code. It usually corrects itself — but it’s worth keeping an eye on, because the sooner it’s fixed, the sooner any overpayment comes back.
Why wrong codes happen
Tax codes drift out of date for ordinary reasons: you change jobs, start or stop a second job, get a pay rise into a new tax band, gain or lose a company benefit, or your Marriage Allowance changes. HMRC updates codes automatically most of the time, but it works from the information it has — which isn’t always complete or current. That’s why a quick check now and then pays off.
How to check — and fix — yours
The single best tool is your free HMRC Personal Tax Account online. It shows your current code, spells out exactly why it’s set that way (what’s been added or deducted), and lets you correct details — for example, telling HMRC you no longer have a company car.
A simple sense-check: put your salary into our calculator, which assumes the standard code, and compare the take-home to your payslip. If they’re close, your code is probably fine. If they’re far apart, your code is the first thing to investigate.
Check your expected take-home →
If you’ve overpaid, HMRC often refunds it automatically at year end, but you can prompt it through your account. If you’ve underpaid, it’s usually collected by adjusting next year’s code — better to know now than be surprised later.
One easy win: Marriage Allowance
If you’re married or in a civil partnership and one of you earns under £12,570 while the other is a basic-rate taxpayer, the lower earner can transfer 10% of their allowance to the other — worth a few hundred pounds a year, and you can often backdate it. You’ll see it reflected in M and N codes.
Last checked 30 July 2026 for the 2026/27 tax year. The standard code is 1257L; your correct code depends on your circumstances.
Sources
Just so you know: this guide is information and journalism, not financial advice, and we don't recommend specific financial products. Your circumstances are your own — if you need personal advice, speak to a suitably qualified adviser. Information was correct at the "last updated" date above but things change; always check the linked primary sources.