Tax Codes Explained: What 1257L Actually Means

The number in your tax code is your tax-free pay for the year with the last digit dropped. 1257L means £12,570 before income tax starts, and on the wrong code you can hand over £2,514 a year you don't owe. Here's how to read your code, which letters cost you money, and how to get a refund if it's wrong.

Last updated: 1 August 2026

How to read your tax code

A tax code is the instruction HMRC sends your employer telling them how much of your pay to leave untaxed. Multiply the number by 10 and you have your tax-free pay for the year. 1257L gives you £12,570, the standard Personal Allowance for 2026/27, which is the amount you can earn before income tax starts. That allowance has been frozen at £12,570 since 2021 and is set to stay there until April 2031.

Payroll spreads the allowance evenly across the year. On 1257L paid monthly, you get £1,047.50 tax-free each month, and anything above that is taxed. The letter on the end tells payroll something about your circumstances. L is the standard allowance. M and N mean you've received or given away part of your allowance through Marriage Allowance. T means HMRC wants to review the code, and K means your allowance has gone negative.

Your code appears on your payslip, your P45, your P60, and in the coding notice HMRC posts or emails you when it changes. Your employer doesn't choose it. They apply whatever HMRC sends, which is why a wrong code can sit there for months with nobody noticing.

The difference between codes is not small. Here's what the same £30,000 salary pays in income tax under each of the common codes, using 2026/27 rates for England, Wales and Northern Ireland.

Code	What it tells payroll	Tax on £30,000	vs 1257L
1257L	Standard £12,570 allowance	£3,486	Baseline
BR	Everything at 20%, no allowance	£6,000	+£2,514
0T	No allowance, normal bands	£6,000	+£2,514
K500	Adds £5,000 to your taxable pay	£7,000	+£3,514
D0	Everything at 40%	£12,000	+£8,514

Income tax only, 2026/27 rates for England, Wales and Northern Ireland. BR and 0T cost the same at £30,000 because both fall inside the basic rate band. Above about £50,000 they separate, because 0T pushes you into the 40% band while BR stays at 20%.

One thing your code doesn't touch is National Insurance. That's worked out separately against its own thresholds on every pay period, so a wrong code moves the income tax line on your payslip and leaves National Insurance alone.

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The codes that quietly cost you money

Some codes are correct and simply look alarming. Others are a sign something has gone wrong. These are the ones worth recognising.

BR, D0 and D1

These tax every pound at one rate with no allowance at all: 20% for BR, 40% for D0, 45% for D1. They're the right codes for a second job or a second pension when your main income already uses your full allowance. They're wrong when they land on your only job, and on a £30,000 salary a stray BR code costs you £2,514 over the year.

0T

No allowance, but the normal bands still apply, so higher earnings still reach 40% and 45%. It usually turns up when you start a job without a P45 and without completing a starter checklist, leaving your employer with nothing to go on.

K codes

A K code means your allowance has gone negative, so instead of subtracting tax-free pay it adds to your taxable pay. K500 adds £5,000. It's used when a company car or other taxable benefit is worth more than your allowance, or when you owe tax from an earlier year and HMRC is collecting it through your pay. There's a limit: a K code can't take more than half your pay in tax.

Emergency codes: W1, M1 and X

A code ending in W1, M1 or X is non-cumulative. Normally your code works on a running total, so by month 4 you've built up four months of allowance and payroll takes account of everything you've earned so far. An emergency code throws that away and treats each pay period as if it were the first, giving you one month's allowance and nothing else.

Take a new job on £36,000, or £3,000 a month, starting in July after a few months out of work. On 1257L M1 you get £1,047.50 tax-free, leaving £1,952.50 taxed at 20%, so £390.50 comes off. On a proper cumulative code you'd have £4,190 of unused allowance available against £3,000 of pay, and the tax that month would be nothing. The whole £390.50 is money you don't owe yet.

You normally get it back without doing anything. Once HMRC issues a cumulative code, the next payslip recalculates the year to date and refunds the difference through your pay.

The S prefix: Scottish tax codes

An S at the front means HMRC has you down as a Scottish taxpayer and your pay runs through Scotland's six bands rather than the three used elsewhere in the UK. It's decided by where your main home is, not where your employer is based or where you do the work. Live in Edinburgh and work for a London company and you should still be on an S code.

S1257L. The standard Scottish code. Same £12,570 allowance, Scottish bands above it.
SBR. Everything at the Scottish basic rate of 20%.
SD0, SD1, SD2 and SD3. Everything at the intermediate rate of 21%, the higher rate of 42%, the advanced rate of 45% and the top rate of 48%.

A missing S is worth checking. On £30,000 a Scottish taxpayer pays £3,451 against £3,486 elsewhere in the UK, so the wrong code there costs you about £35. The gap flips at roughly £30,300 and widens fast above it, because the Scottish higher rate of 42% starts at £43,662 while the rest of the UK stays at 20% until £50,270. Being on the wrong band structure at that level builds up a bill you'll be asked for later. The Scotland vs England tax comparison sets out the full difference at each salary.

Wales has its own prefix, C, for Welsh taxpayers. Welsh rates currently match those in England and Northern Ireland, so a C code changes who receives the tax rather than how much you pay.

Checking your code and claiming money back

Your current code is in the HMRC app or your personal tax account on gov.uk, alongside HMRC's estimate of what you'll earn and any deductions they've applied. That estimate is where most errors start. If HMRC thinks you're getting a benefit you gave up two years ago, or has your salary badly wrong, the code follows the mistake.

Codes go wrong most often after a change: a new job, a second job starting, a gap between jobs, a company car arriving or going back, the State Pension starting, or self-employment ending. If any of those happened in the last year or so, your code is worth a look.

Tell HMRC what's wrong and they issue a corrected code to your employer. For the current tax year, a cumulative code fixes itself in your next pay packet. For a year that's already ended, HMRC works out the difference and sends a P800 calculation, and you claim the refund online. You have four years from the end of a tax year to make the claim, so 2022/23 stays open until 5 April 2027.

The M and N codes are worth £252 a year

If your code ends in M or N, Marriage Allowance is already running. If you're married or in a civil partnership, one of you earns under £12,570 and the other is a basic rate taxpayer, and neither code ends in M or N, you're leaving money on the table. The lower earner transfers £1,260 of unused allowance and the higher earner's tax bill drops by £252 a year.

Claims backdate up to four years, so the current year plus four earlier ones comes to as much as £1,260. Apply free on gov.uk. Claims companies charge 30% to 50% of a refund you can get yourself in ten minutes.

When a wrong code means you owe money

A code that's too generous is the uncomfortable case. If HMRC has given you an allowance twice, once against each of two jobs, you'll have underpaid all year and the money will be collected through a lower code next year. Spotting it early keeps the correction small. Leaving it means a bigger deduction later, at a point you weren't planning for.

The check itself takes a few minutes. Work out what your income tax should be with the take-home pay calculator, or the Scottish income tax calculator if you're north of the border, then hold it next to the tax line on your payslip. If the two don't match, your code is the first place to look.

Frequently asked questions

What does the 1257L tax code mean?

1257L means you get £12,570 of tax-free pay for the year, which is the standard Personal Allowance for 2026/27. The number is your tax-free pay with the last digit dropped, and the L means you get the standard allowance with nothing added or taken away. It is the most common code in the UK and it is spread evenly across your pay periods, so £1,047.50 a month if you are paid monthly.

Why is my tax code not 1257L?

Usually because HMRC has adjusted your allowance for something. A company car, private medical cover, or another taxable benefit lowers the number. Tax you still owe from an earlier year lowers it too. A second job or pension often gets a BR or D0 code because your allowance is already used by your main job. If nothing in your situation explains the change, check it, because the code can simply be out of date.

What does the S in my tax code mean?

The S prefix means HMRC has you down as a Scottish taxpayer, so your pay is taxed using Scotland's six bands instead of the three used in England, Wales and Northern Ireland. It is based on where your main home is, not where your employer is or where you work. S1257L is the standard Scottish code. SBR, SD0, SD1, SD2 and SD3 tax everything at 20%, 21%, 42%, 45% and 48% respectively.

What is an emergency tax code and will I get the money back?

An emergency code ends in W1, M1 or X. It taxes each pay period on its own, ignoring what you have earned so far this year, so you get only one month's or one week's worth of allowance rather than the running total you are owed. You normally get the money back automatically: once HMRC issues a cumulative code, your next payslip corrects the overpayment. If the tax year ends before that happens, HMRC works it out and sends you a P800.

How do I claim back tax I overpaid on the wrong code?

Check your code in the HMRC app or your personal tax account and tell HMRC what is wrong. For the current year, they issue a corrected code and your employer refunds the overpayment through your pay. For earlier years, HMRC usually sends a P800 calculation and you claim the refund online. You have four years from the end of a tax year to claim, so the deadline for 2022/23 is 5 April 2027.

Does my tax code affect my National Insurance?

No. Your tax code only controls income tax. National Insurance is worked out separately on each pay period against its own thresholds, and no tax code changes it. That is why a wrong code shows up as a change in the income tax line on your payslip while the National Insurance line stays where you would expect.