What Is a Tax Code? 1257L and Other Codes Explained

What is a tax code, and what does 1257L mean?

Your employer or pension provider uses your tax code to work out how much Income Tax to take from your pay. HMRC tells them which code to use. You get a separate code for each job or pension you have.

In 1257L, the number is 1257 and the letter is L. The number stands for your tax-free amount from that job. The Personal Allowance for 2026/27 is £12,570. Drop the final digit and you get 1257. The letter L means you get the standard Personal Allowance.

So a code of 1257L is a short way of saying: the first £12,570 of your income this tax year is tax-free.

The same page of rates shows what happens above that. In 2026/27, income from £12,571 to £50,270 is taxed at the basic rate of 20%, outside Scotland. For the full picture, see Income Tax explained.

How is the number in a tax code worked out?

HMRC starts with your Personal Allowance. It then takes away anything that reduces it, such as:

• income you have not paid tax on, like untaxed interest or part-time earnings
• other deductions, like company benefits or the High Income Child Benefit Charge

It then replaces the last digit with a letter.

Example from gov.uk: the standard allowance is £12,570. A £1,570 medical insurance benefit from an employer reduces it to £11,000. The tax code would be 1100L.

A lower number means less of your pay is tax-free, so more tax comes off each payday. A K code works differently, which is covered below.

What do the letters in a tax code mean?

The letters tell your employer which rules to apply. These are the ones you are most likely to see:

If your code starts with S or C, your income is taxed using the rates in Scotland or Wales. For example, gov.uk lists S0T and CBR as the Scottish and Welsh versions of 0T and BR.

Not sure what your own code means? The take-home pay calculator shows how tax and National Insurance affect a salary.

What is an emergency tax code (W1, M1 or X)?

An emergency tax code is a temporary code. Instead of using your total income so far in the tax year, your tax is based only on that week’s or month’s pay. gov.uk says this could mean you pay the wrong amount of tax.

The extra letters show how often you are paid:

• W1 is used when you are paid weekly, for example 1257L W1.
• M1 is used when you are paid monthly, for example S875L M1.
• X is used when your pay dates vary, for example C663L X.

Your payslip may show NONCUM instead, depending on your employer’s payroll software.

Why does a first job often start on an emergency code?

If you start a job and your new employer does not know your previous income details, you may be put on an emergency tax code. That is common in a first job, because there is no earlier employer to supply those details.

gov.uk says HMRC usually updates your code after a new job, and that this can take up to 35 days from when you start. Giving your new employer a P45 from a previous job is one way to supply the missing details. If you do not have one, you can ask your previous employer for it.

An emergency code does not always mean you pay too much. It means the tax is worked out on limited information, so it can be wrong in either direction.

How does HMRC find out about my income?

HMRC usually updates your code using information your employer or pension provider sends. gov.uk also lists things that can change your code, including:

• starting a new job
• getting taxable state benefits
• starting income from an extra job or pension
• savings interest going above your Personal Savings Allowance
• your employer reporting that you have started or stopped getting job-related benefits
• claiming Marriage Allowance

gov.uk also states that it is your responsibility to make sure you are paying the right amount of tax. If your code has changed, you can use the Check your Income Tax online service to find out why.

How do I check my tax code?

gov.uk lists four places where you can find your tax code:

• online, in the Check your Income Tax service for the current year (you sign in with a GOV.UK sign-in, and may need to prove your identity)
• in the HMRC app
• on your payslip
• on a Tax Code Notice letter from HMRC, if you get one

The online service covers the current tax year, 6 April 2026 to 5 April 2027. It lets you check your tax code and Personal Allowance, and see your estimated income and tax from jobs and pensions. If you check online or in the app, you can also sign up for paperless notifications so HMRC emails you when your code changes.

What if I think my tax code is wrong?

gov.uk says that if you think the tax taken is wrong, your tax code may be incorrect. Its page on fixing a wrong code says the quickest way to correct it is the Check your Income Tax online service, where you can review and update your employment, pension and income details.

If you cannot use the online service, gov.uk says to contact HMRC through its Income Tax enquiries page for individuals, pensioners and employees. If you have just started a new job, it says to wait 35 days before contacting HMRC so they can receive your new income details.

Once HMRC updates a code, gov.uk says it will tell you and your employer the new code within 15 working days. Monthly-paid employees should see it on their next or following payslip. Weekly-paid employees should see it on their third payslip.

Official guidance: gov.uk/tax-codes/how-to-update-your-tax-code.

How do tax refunds work?

If you have paid too much tax, a refund can come in a few ways, according to gov.uk:

• Through your pay. When HMRC updates your code and has your full income details, it works out the overpayment and asks your employer or pension provider to refund the difference in your pay. For monthly pay, that is usually on your next or following pay. For weekly pay, it is usually on your third pay.
• If HMRC lacks your details. You cannot get a refund until HMRC gets your income details from your employer, pension provider or benefits office.
• After the tax year ends. HMRC reviews what you paid and lets you know how to get your refund, if you have paid too much.

It works the other way too. If you have underpaid, HMRC may adjust your code to collect the tax over one or more tax years, if possible. After the year ends it checks your tax and sends a letter if you have not paid the right amount.

Sources

• Tax code overview and where to find your code: gov.uk/tax-codes
• What the number and letters mean: gov.uk/tax-codes/what-your-tax-code-means
• Emergency codes (W1, M1, X): gov.uk/tax-codes/emergency-tax-codes
• Why a code changes: gov.uk/tax-codes/why-tax-code-change
• Fixing a wrong code: gov.uk/tax-codes/how-to-update-your-tax-code
• Refunds and underpaid tax: gov.uk/tax-codes/if-youve-paid-too-much-or-too-little-tax
• Checking your code online: gov.uk/check-income-tax-current-year
• 2026/27 Personal Allowance and rates: gov.uk/income-tax-rates

Tools and guides

• Take-home pay calculator: see what you keep after tax and National Insurance.
• Income Tax explained: the allowance, the bands and the rates.
• National Insurance explained: what comes off your pay besides tax.