Your tax code is right if the number, multiplied by ten, equals the tax-free allowance you are actually entitled to, and the letter matches your circumstances. For most employees with one job and no company benefits that means 1257L in 2026/27. Anything else needs a reason you can name. Checking takes two minutes with a payslip and the list below, and a wrong code is corrected by HMRC, not by your employer.
What the code is telling payroll
The code has two parts. The numbers tell your employer how much tax-free income to give you across the year; gov.uk puts it as “the numbers in your tax code tell your employer or pension provider how much tax-free income you get from them in that tax year.” Multiply the number by ten to get the pounds: 1257 is £12,570, the standard personal allowance; 1000 is £10,000; 500 is £5,000.
The letter tells payroll how to treat that allowance. From gov.uk’s own definitions:
| Letter | What it means |
|---|---|
| L | You are entitled to the standard tax-free Personal Allowance |
| M | Marriage Allowance: you have received a transfer of 10% of your partner’s Personal Allowance |
| N | Marriage Allowance: you have transferred 10% of your Personal Allowance to your partner |
| T | Your tax code includes other calculations to work out your Personal Allowance |
| 0T | Your Personal Allowance has been used up, or you have started a new job and your employer does not have the details to give you a code |
| BR | All income from this job or pension is taxed at the basic rate, usually a second job or pension |
| D0 | All income from this job or pension is taxed at the higher rate |
| D1 | All income from this job or pension is taxed at the additional rate |
| NT | You are not paying any tax on this income |
| K | You have income you are not paying tax on which is more than your Personal Allowance |
| S or C prefix | Scottish or Welsh rates apply |
| W1, M1 or X suffix | You are on an emergency tax code |
A K code works in reverse: the number is added to your taxable pay rather than taken off it, because deductions such as a company car or an earlier year’s underpayment exceed your allowance. K475 adds £4,750 to the pay you are taxed on. The tax code checker converts any code into pounds and shows the tax it produces.
The two-minute check
- Find the code on your latest payslip, in the HMRC app, or in your personal tax account.
- Convert the number. Multiply by ten. Is that the allowance you expect? With no adjustments, £12,570.
- Read the letter. L if you have the standard allowance; M or N only if you and a partner use the Marriage Allowance; S or C only if you live in Scotland or Wales.
- Look for a suffix. W1, M1 or X means the code is being applied to each payslip on its own. It is normal in the first month or two of a new job and wrong if it persists.
- Check every job and pension. Only one of them should carry your allowance. The others should be BR, D0 or D1, or a split of the allowance that adds up to £12,570.
If all five line up, the code is right. If one does not, the section below usually explains why.
The common reasons a code is wrong
A company benefit that has ended. Medical insurance or a car from a previous job can stay in the code for a year after you leave, lowering the allowance. HMRC removes it when told.
Two jobs both carrying the allowance. Two codes of 1257L mean £25,140 of tax-free pay and an underpayment at the end of the year. The second job should be BR, unless the main job pays under £12,570, in which case a split of the allowance is better. Our second job guide explains the split.
BR on your only job. Everything taxed at 20% with no allowance. Common after a mistake on the starter checklist, and it costs a basic rate taxpayer up to £2,514 a year until it is corrected.
An estimate of other income. HMRC may have put untaxed interest, rental income or a State Pension estimate into the code. If the estimate is wrong, the code is wrong.
An old underpayment. Tax owed from an earlier year is often collected by reducing the code. It is legitimate, but check the amount against the letter HMRC sent.
The wrong nation. An S or C prefix that does not match where you live, or a missing one when it should be there, changes the rates applied.
The emergency basis that never ended. A W1 or M1 code from a job start that HMRC has not replaced with a cumulative code. The emergency tax guide covers how the refund arrives.
What a wrong code costs
Each ten points of code is £100 of allowance, worth £20 a year to a basic rate taxpayer and £40 to a higher rate taxpayer. The table shows the yearly cost of some common errors for someone on £30,000.
| Code applied | Allowance given | Tax paid | Difference from 1257L |
|---|---|---|---|
| 1257L | £12,570 | £3,486 | correct |
| 1100L | £11,000 | £3,800 | £314 too much |
| 1000L | £10,000 | £4,000 | £514 too much |
| BR | £0 | £6,000 | £2,514 too much |
| 1257L on two jobs | £25,140 | too little | underpayment to collect later |
An error that gives you too much allowance feels pleasant until HMRC reconciles the year and collects the shortfall through next year’s code or a P800 demand. It is worth correcting in either direction.
How to get it corrected
The employer applies the code but cannot change it. Corrections come from HMRC through the “check your Income Tax” service in your personal tax account or the HMRC app, where you can add or remove company benefits, correct an estimate of other income, or report that a job has ended. HMRC then sends a new code to your employer, and the next payslip applies it. Because PAYE is cumulative, any tax overpaid earlier in the year comes back in that payslip automatically; you do not need to claim it separately. If the tax year has already ended, HMRC’s reconciliation produces a P800 letter and a refund. Our guide to why you paid more tax this month shows the cumulative arithmetic that makes the refund appear.
A worked check
A payslip shows code 1050L. Multiplying by ten gives £10,500 of allowance, £2,070 less than the standard £12,570. At 20% that is £414 a year of extra tax, £34.50 a month. The HMRC app shows the reason: a £2,070 medical insurance benefit from an employer left eighteen months ago. Removing it in the app produces a new code of 1257L within days; the following payslip applies it cumulatively and refunds the £414 overpaid so far in the year in a single month. The tax code checker shows the pounds behind any code, and the take-home pay calculator shows what the corrected code means for monthly pay.
Common questions
What should my tax code be in 2026/27? 1257L for most people with one job or pension, no company benefits and no Marriage Allowance. It gives the standard £12,570 personal allowance.
Why is my tax code not 1257L? Because something has been added or taken away: a company benefit, an earlier underpayment, an estimate of untaxed income, the Marriage Allowance, a second job, or Scottish or Welsh rates. HMRC’s coding notice or the app lists the adjustments.
What does a K tax code mean? Your deductions exceed your allowance, so the number is added to your taxable pay instead of taken off. Under a K code no more than half of your pay can be taken in tax in any pay period.
Can my employer change my tax code? No. Employers apply the code HMRC issues. You correct it through your personal tax account, the HMRC app or the PAYE helpline, and HMRC sends the new code to payroll.
Will I get a refund if my code was wrong? Yes. Within the tax year the refund arrives through your pay once the corrected code is applied, because PAYE recalculates cumulatively. After the year ends, HMRC issues a P800 and repays the difference.
How long does a corrected code take to reach my employer? HMRC issues the code electronically, and most employers apply it on the next payroll run after they receive it. If a payslip after that still shows the old code, ask payroll whether the notice arrived.
Information, not financial advice. Code definitions are quoted from gov.uk: what your tax code means; tax figures use the 2026/27 rates for England, Wales and Northern Ireland and are estimates to help you understand the rules. Check your own code in your personal tax account before acting on them.