For the 2026/27 tax year, 1257L is the standard UK tax code, signifying a tax-free Personal Allowance of £12,570. This amount is the income a UK taxpayer can earn before any income tax deductions apply. This Personal Allowance has been frozen at £12,570 since the 2021/22 tax year and is currently scheduled to remain so until April 2028, following the Autumn Statement 2022. Individuals whose payslip shows 1257L are on the standard cumulative tax code.

What does 1257L mean and why is it standard?

A tax code combines numbers and a letter. The numbers represent the tax-free amount divided by 10. Thus, 1257 in your tax code signifies a £12,570 tax-free allowance. This Personal Allowance is the income a UK taxpayer can earn before income tax deductions begin. It remains frozen at this level until April 2028. The 'L' suffix indicates entitlement to the standard Personal Allowance. An individual with the 1257L code is on the standard cumulative tax code.

What do non-standard tax codes signify?

While 1257L is the standard, many UK workers have different codes due to individual circumstances. A non-standard code may be correct, but it is also where most over- and under-collection of tax happens. Understanding these variations can clarify a payslip.

Common non-standard codes: BR, 0T, D0, D1, and K

• BR (Basic Rate): All income from that specific source is taxed at the basic rate of 20 per cent, with no Personal Allowance. This code is common for a second job or pension income when the Personal Allowance is used elsewhere.
• 0T (Zero Allowance, All Rates): This code means no Personal Allowance is applied, and income is taxed at basic, higher and additional rates as appropriate. 0T often appears when an individual starts a new job without a P45.
• D0 (Higher Rate): A D0 code indicates all income from that source is taxed at the higher rate of 40 per cent. It is typically for a second income where the primary source uses the Personal Allowance and basic-rate band.
• D1 (Additional Rate): This code means all income from that specific source is taxed at the additional rate of 45 per cent.
• K Codes (Negative Allowances): Codes starting with 'K' (e.g., K475) signify that an individual's allowances are less than their Personal Allowance. This is usually due to benefits-in-kind or unpaid tax from a previous year. K codes result in more tax being deducted.

Emergency and special codes: W1, M1, X, NT, M, and N

• W1, M1, or X: These emergency or non-cumulative codes tax income based only on that specific pay period (week or month), not year-to-date earnings. These codes are frequently used when an individual starts a new job without a P45.
• NT (No Tax): This rare code means no tax is deducted at source. It applies in specific situations, such as for certain Lloyd's of London underwriters or foreign residency arrangements.
• M or N Suffixes (Marriage Allowance): Tax codes with an 'M' suffix (e.g., 1383M) indicate the recipient of Marriage Allowance, while 'N' (e.g., 1131N) signifies the transferring spouse. Eligible couples not claiming this allowance might miss annual savings and back-claims for up to four years.

How can a tax code become incorrect?

Millions of UK workers are on an incorrect tax code in any given year, often leading to over- or under-collection of income tax. Several common scenarios contribute to these errors. A frequent cause is starting a new job without providing a P45 from a previous employer. Without this document, HMRC may lack current information, leading to an emergency or inappropriate code like 0T or a W1/M1/X code. Another issue arises when an old benefit-in-kind, such as a company car from a previous employer, continues to incorrectly reduce an individual's tax-free allowance.

HMRC's processing times also play a role. Delays in updating records after significant changes, such as commencing or ending a second job, starting a taxable State Pension, or changes in pension income, can result in an outdated code. Similarly, gaining or losing Marriage Allowance entitlement could alter a code to include an 'M' or 'N' suffix; if not processed, this leads to an incorrect code. These situations underscore the importance of regularly checking one's tax code.

How do you check your tax code and correct an error?

Verifying your tax code is crucial for paying the correct income tax. You can find your current tax code on a recent payslip. Your P60, issued by your employer after each tax year, also displays the code used. If you left a job, your P45 shows the tax code applied up to your departure. For an up-to-date check, sign into your personal tax account on the gov.uk website and use the "Check your Income Tax" service at gov.uk/check-income-tax-current-year.

If you believe your tax code is incorrect, your employer cannot change it directly; corrections must come from HMRC. To request a review or correction, contact HMRC by phone, by post or through your personal tax account. Providing HMRC with accurate, up-to-date information about your employment, benefits and income sources will facilitate a swift resolution.

How does HMRC's P800 process work for refunds?

HMRC conducts an annual reconciliation of tax paid versus tax owed. After the tax year ends, if HMRC's records show an individual has either over-paid or under-paid tax, a P800 tax calculation letter is issued. This letter details the calculation and provides instructions on claiming a refund or settling any underpayment.

When a P800 letter confirms an overpayment, the taxpayer is usually owed a refund. This refund can typically be claimed online through their gov.uk personal tax account. Once claimed, payment is generally processed to a UK bank account within 5 working days. Codes like BR, 0T, D0, D1, and K, or emergency codes such as 1257L W1, 1257L M1, or 1257L X, can signal potential over-collection if not correctly applied throughout the year.

Overpaid tax can be reclaimed for up to four previous tax years. Each year requires a separate claim or HMRC review. In limited circumstances, older claims may be possible. If the P800 letter indicates under-collected tax, HMRC typically amends the tax code for the following year to recover the underpayment through future PAYE, or issues a Simple Assessment letter requesting direct payment.

What should you do next?

Regularly checking your tax code is an essential financial practice. Ensure your code, especially for the 2026/27 tax year, reflects your current financial situation, particularly if you have multiple income sources, company benefits, or have experienced a change in personal circumstances. Utilise the gov.uk online service to verify your code against your payslip. If you identify an error, contact HMRC promptly to prevent future over- or under-payments and to reclaim any tax owed to you for past years.