What Is a Tax Code and How Do You Check Yours?
Your tax code is used by your employer or pension provider to calculate how much income tax to deduct from your pay before you receive it. An incorrect tax code means you could be paying too much tax — or not enough, which creates a bill at year end. Checking your tax code is quick and should be done at the start of each tax year.
How Tax Codes Work
A standard tax code is a number followed by a letter. The number (divided by 10 and appended with a 0, or multiplied by 10 in some systems) tells the employer how much of your annual income is tax-free. The letter indicates any adjustments or special circumstances. The standard code for 2025/26 is 1257L: 1257 represents £12,570 (the Personal Allowance) divided by 10, and L means you are entitled to the standard Personal Allowance.
Common Letters and Their Meaning
L means you receive the standard Personal Allowance. M means your spouse or civil partner has transferred part of their allowance to you (Marriage Allowance). N means you have transferred part of your allowance to your partner. T means your allowance involves other calculations (for example, income between £100,000–£125,140). BR means all income from this source is taxed at the basic rate (20%) — used for a second job or pension. D0 means all income taxed at 40% (higher rate). D1 means 45% (additional rate). K means you have income that reduces your allowance below zero — typical for high benefits in kind. 0T means no allowance — all income taxed, often when HMRC has no information.
Why Your Tax Code Might Be Wrong
Tax codes can be wrong for many reasons: you received a benefit in kind worth more or less than HMRC estimated; you changed jobs and the new employer was given the wrong information; you have multiple jobs or income sources; you claimed (or stopped claiming) Marriage Allowance; HMRC collected last year's underpaid tax through your code; you started or stopped receiving state benefits or a pension.
How to Check Your Tax Code
Log in to your personal tax account at gov.uk/personal-tax-account or use the HMRC app. You can see your current tax code for each employment or pension, the reasons for any adjustments, your estimated annual income for the current year as known to HMRC, and your Personal Allowance and any reductions. Check this at the start of each new tax year (April) and whenever your circumstances change.
How to Correct a Wrong Code
If your code is wrong, contact HMRC on 0300 200 3300 or update your details online. HMRC will issue a new tax code notice to your employer, who must apply it from the next payroll run. If you have overpaid tax due to a wrong code, HMRC will usually refund the overpayment through an adjusted code or a direct repayment at the end of the tax year.
Emergency Tax Codes
If you start a new job and do not have a P45 from your previous employer, you may be put on an emergency tax code (typically W1, M1, or X suffixed). These codes tax each pay period independently, without regard to the full year's earnings — meaning you may over-pay tax in the early weeks. Provide your new employer with your P45 or complete a starter checklist as soon as possible to correct this.
