What Tax Code Should You Be On and How to Check It

If you have a single job or pension paying less than £50,270 a year and no unusual adjustments to your allowances, the tax code you should be on for 2026/27 is 1257L. That gives you the standard £12,570 Personal Allowance, spread evenly across your pay periods. Anything different means HMRC is applying an adjustment, and it’s worth understanding why before assuming the code is wrong.¹

What 1257L Actually Means

A tax code has two parts. The number is your tax-free allowance with the last digit removed, so 1257 stands for £12,570. The letter tells your employer which rules to apply. L is the standard letter for someone receiving the ordinary Personal Allowance with nothing unusual going on. Your employer takes that allowance, splits it across the year, and applies a slice to each payslip before working out tax on the rest.¹

If that describes your situation and your payslip shows 1257L, you’re on the right code. If it shows something else, the rest of this article helps you work out whether the difference is correct or a mistake worth fixing.

The Other Codes You Might Be On

The letters and prefixes on a tax code each carry a specific meaning:

BR taxes every pound from that job or pension at the basic 20% rate with no allowance. It’s the usual code for a second job when your Personal Allowance is already used by your main employer.¹
D0 taxes the whole income at 40%, and D1 taxes it at 45%. Again, these usually apply to secondary income sources.¹
M means you’ve received £1,260 of Marriage Allowance from a spouse or civil partner, so your tax-free amount is higher. N means you’ve transferred that £1,260 to your partner, so yours is lower.
T is a holding code while HMRC finalises calculations involving other items.
0T applies no allowance at all. New employers sometimes use it when they don’t have enough information about you, and it also appears when your allowance has been fully absorbed elsewhere.¹
NT means no tax is deducted, which is rare and usually tied to non-UK residency or income taxed separately.
A K code is the reverse of a normal code. When untaxed income or benefits are worth more than your allowance, HMRC turns the excess into extra taxable income and prefixes the number with K. Payroll can never take more than half your gross pay in a single period under a K code.²

S and C Prefixes

If your main home is in Scotland, your code starts with S, so the standard Scottish code is S1257L. Scottish Parliament sets its own rates and bands. Welsh taxpayers get a C prefix (C1257L for the standard allowance). Welsh rates currently match those in England and Northern Ireland, but the prefix tells payroll which country’s rules to apply. HMRC should update your prefix automatically after a move, but it’s worth checking once you’re settled.²

Emergency Codes

A code ending in W1, M1, or X is an emergency code. The suffix indicates weekly, monthly, or other pay frequency, and it tells payroll to treat each pay period on its own rather than cumulatively. You’ll see one after starting a new job before HMRC has your full record. If you hand over a P45 from your previous employer, the transition to a proper code is usually quick. Without a P45, your new employer will ask you to fill in a starter checklist so an interim code can be set.³ If you’re still on an emergency code by your second or third payslip, contact HMRC rather than waiting for it to correct itself.⁴

Reasons Your Code Might Not Be 1257L

Several ordinary circumstances legitimately shift your code away from the standard number:

Taxable benefits from your employer. A company car, private medical insurance, or an interest-free loan is reported to HMRC on a P11D. The value reduces your tax-free amount and lowers your code number.⁵
Multiple jobs or pensions. HMRC normally applies your full allowance to the highest-paying source and uses BR, D0, or D1 on the others.
Untaxed income such as rental income, significant savings interest, or the State Pension. Rather than making you file Self Assessment for smaller amounts, HMRC lowers your code so the tax comes out through payroll.
Unpaid tax from an earlier year. HMRC usually collects a shortfall by reducing this year’s code rather than demanding a lump sum.
Approved work expenses or professional subscriptions, which push the number up because they increase your tax-free amount.

Earnings Above £100,000

Once your income passes £100,000, your Personal Allowance starts to taper. You lose £1 of allowance for every £2 earned above the threshold, and by £125,140 there’s nothing left.⁶ Your code drops to reflect that, and it can shift year to year if your earnings hover near the boundary. Between £100,000 and £125,140, the combination of 40% tax and disappearing allowance produces an effective 60% rate on that slice of income.

How to Check Whether Your Code Is Right

Your payslip shows the code your employer is using, but it doesn’t tell you whether the code is correct. To check that, sign in to the Check your Income Tax service on GOV.UK. It shows your code, HMRC’s estimate of your income from every job and pension, the tax you’re expected to pay for the year, and each adjustment sitting on your record. You can update income details directly through the service. The HMRC app shows the same information. The service isn’t available if Self Assessment is your only way of paying income tax.⁷

To compare what HMRC holds against your real circumstances, gather:

Your P60, issued by your employer after each tax year ends on 5 April, showing your total pay and tax deducted for the year.⁸
Your P45, issued when you leave a job.⁸
Any P11D listing the taxable value of employer benefits.⁹
Your coding notice (P2), a letter from HMRC that shows exactly how the code was built up, with every addition to and deduction from your allowance itemised. This is the most useful document for spotting a wrong code.

If the coding notice includes income sources you no longer have, benefits you’ve stopped receiving, or an obviously wrong income estimate, the code is almost certainly wrong.

Fixing a Wrong Code

For most changes, use the online Check your Income Tax service. You can update your estimated income, correct employment or pension details, and remove benefits you no longer receive. HMRC processes the change and issues a new coding notice to both you and your employer.⁷

For anything more complex, call the HMRC Income Tax helpline on 0300 200 3300, Monday to Friday, 8am to 6pm. From outside the UK, the number is +44 135 535 9022. Have your National Insurance number, a recent payslip, and your coding notice ready before you call.¹⁰

Once the corrected code reaches your employer’s payroll, the adjustment shows up in the next pay run. Overpaid tax comes back through larger take-home amounts on the following payslips. Underpayments are collected gradually across the remaining months of the tax year rather than in a single deduction.

If a Wrong Code Isn’t Caught Until Year End

When a mismatch is only spotted after 5 April, HMRC sends a P800 tax calculation letter, usually between June and the following March. It compares what you actually earned with the tax deducted and tells you whether you’re owed a refund or owe more.¹¹

Common triggers include HMRC working from outdated income information, receiving pay from two employers in the same month after switching jobs, or starting a workplace pension. Refunds due are usually claimable online. Underpayments are typically collected by adjusting next year’s code, though larger amounts may need to be paid directly.

If you think you’ve overpaid but no P800 has arrived, contact HMRC through the online service or the helpline. The systems occasionally miss discrepancies, particularly when you’ve had several employers or income sources in the same year.¹¹

The best moment to check your code is right after a change: a new job, a pay rise, a company car added or removed, a pension starting. If your circumstances still match what HMRC has on file, and you have one job paying under £50,270 with no benefits or extra income, 1257L is where you should be.

1
GOV.UK. Tax Codes – What Your Tax Code Means
2
GOV.UK. Understanding Your Employees Tax Codes – What the Letters Mean
3
GOV.UK. Starter Checklist if Youre Starting a New Job
4
GOV.UK. Tax Codes – Emergency Tax Codes
5
GOV.UK. Your P45, P60 and P11D Form – P11D
6
GOV.UK. Income Tax Rates and Personal Allowances
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GOV.UK. Check Your Income Tax for the Current Year
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GOV.UK. Your P45, P60 and P11D Form – P60
9
GOV.UK. Expenses and Benefits for Employers – Reporting and Paying
10
GOV.UK. Income Tax – Enquiries
11
GOV.UK. Tax Overpayments and Underpayments