Tax Codes Explained

Your tax code is a combination of numbers and letters that tells your employer or pension provider how much Income Tax to deduct from your pay or pension. HMRC issues a tax code for each job or pension you have, based on your expected income, allowances, and reliefs for the tax year. This guide explains how tax codes are constructed, what each letter means, and what to do if your code looks wrong.

How Tax Codes Are Calculated

The number in your tax code represents your tax-free Personal Allowance divided by 10, minus any adjustments for income you receive that has not been taxed yet (such as State Pension, rental income, or savings interest that exceeds your allowance), plus adjustments for reliefs (such as professional subscriptions, pension contributions, or Gift Aid). For example, the standard code 1257L means your tax-free amount is £12,570. If you have a company car valued at £5,000, HMRC would deduct this from your Personal Allowance (£12,570 minus £5,000 = £7,570) and issue a code of 757L. The calculation is done by HMRC based on information from your employer, pension provider, and your Self Assessment returns. HMRC may also adjust your code for underpaid tax from earlier years (up to £3,000).

Tax Code Letters and Their Meanings

Each letter tells you something about your tax status. L means you are entitled to the standard tax-free Personal Allowance. M means you have received a Marriage Allowance transfer from your spouse (an extra £1,260 of allowance). N means you have transferred £1,260 of your Personal Allowance to your spouse. T means your code includes other calculations that HMRC needs to review annually (for example, if you have complex deductions or benefits). BR (Basic Rate) means all your income from this source is taxed at 20%, with no Personal Allowance applied — typically used for a second job or pension. D0 means all income is taxed at 40% (higher rate). D1 means all income is taxed at 45% (additional rate). K means your total untaxed income or benefits exceed your Personal Allowance, creating a negative tax-free amount — your employer deducts additional tax to cover the shortfall. NT means no tax is deducted. S prefix (for example, S1257L) indicates you are a Scottish taxpayer and Scottish rates apply. C prefix (for example, C1257L) indicates you are a Welsh taxpayer.

Emergency Tax Codes

When you start a new job and your employer does not have your correct tax code from HMRC, they use an emergency code. The most common emergency code is 1257L with a "week 1" or "month 1" basis. This means you receive 1/52 or 1/12 of the Personal Allowance each pay period, and previous pay from the same tax year is ignored. Emergency codes often result in overpayment of tax because they do not take into account any untaxed income or benefits you may have. Once HMRC issues your correct code, the overpayment is automatically refunded through your pay. You can help this process by contacting HMRC and providing your new employer's PAYE reference. Check your first payslip in a new job to see if an emergency code is being used.

How to Check Your Tax Code

You can check your tax code at any time on GOV.UK using your personal tax account. Log in with your Government Gateway ID and navigate to the "PAYE" section. You will see your current tax code, an estimate of your tax position for the year, and the reasons for any deductions from the standard allowance. You can also find your code on your payslip (near the top, usually labelled "tax code" or "code") and on your P60 annual statement. If you have multiple jobs or pensions, each will have its own tax code. Check each one separately. If your code changes, HMRC sends you a "PAYE Coding Notice" by post or through your online account — do not ignore these notices.

How to Correct a Wrong Tax Code

If you think your tax code is wrong, you can correct it online through your personal tax account. Use the "tell HMRC about a change" function to update your income, benefits, or employment details. You can also call the HMRC PAYE helpline on 0300 200 3300. If the error is because your employer gave HMRC the wrong information, contact your employer's payroll department. Common mistakes include: HMRC not knowing about a new job, a company car that was returned but still on your code, the State Pension being double-counted, or benefits in kind being estimated incorrectly. If you are due a refund because of the wrong code, HMRC will process it automatically once the code is corrected. If you have underpaid because of a wrong code, HMRC may ask you to repay through your tax code (if under £3,000) or in a lump sum (if over £3,000).

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