UK tax codes explained

Scope: This guide is for employees and pension recipients using PAYE in the UK during the 2026 to 2027 tax year. It explains how to read a code; it does not calculate the correct code for every personal situation.

The short answer

A PAYE tax code tells an employer or pension provider how HMRC wants Income Tax deducted from that source of income. Most codes combine numbers and letters: the numbers usually indicate the amount of tax-free income allocated to that job or pension, while the letters describe circumstances that affect allowances or tax rates. The code 1257L is currently used for most people with one job or pension, but it is not automatically correct for everyone.

Use HMRC’s official tax-code checker to understand the code shown on your payslip or pension statement. If the income, benefits or employment details behind it are wrong, use HMRC’s current-year Income Tax service to update them.

What the numbers mean

HMRC starts with the tax-free allowance available to you and adjusts it for items that need to be collected or allowed through PAYE. Those adjustments can include untaxed income, taxable company benefits or other deductions included in the code. HMRC then normally removes the final digit when forming the number in the code.

The number is therefore an instruction for that particular employment or pension. It is not a statement that all your income is tax-free up to that amount, and it may not represent your overall Personal Allowance if you have more than one income source.

Worked example: an allowance reduced by a company benefit

HMRC’s example starts with a standard tax-free Personal Allowance of £12,570 and a medical-insurance benefit valued at £1,570. Subtracting the benefit leaves £11,000 to allocate through the code, producing 1100L.

This illustrates the coding method; it is not a valuation of anyone else’s benefit and does not show the final tax bill.

What common letters mean

These are summaries, not a complete coding calculation. Use the HMRC checker for the full meaning of the exact code.

When a code deserves a closer check

Check the supporting details when:

• you have started or left a job;
• you receive income from more than one job or pension;
• a company benefit, State Pension or untaxed income is missing or has stopped;
• the code has a K, 0T, BR, D0 or D1 element you did not expect;
• the code ends in W1, M1 or X, or shows NONCUM, for longer than expected; or
• the estimated annual income in HMRC’s service does not match what you reasonably expect.

Do not ask an employer to invent a different code. Employers normally have to operate the code HMRC supplies. Correct the underlying details with HMRC when they are wrong.

How to check and update your tax code

1. Find the code on your latest payslip, pension statement or HMRC coding notice.
2. Use HMRC’s tax-code checker to see what its numbers, letters and deductions mean.
3. Compare the listed jobs, pensions, estimated income and benefits with your records.
4. Use HMRC’s current-year Income Tax service to report incorrect income or employment details, or contact HMRC if you cannot use the service.
5. Check a later payslip to confirm that the new code has been applied and that the year-to-date figures make sense.

Common mistakes

• Treating 1257L as proof that the code is correct for every taxpayer.
• Multiplying the code number and assuming that figure is the person’s complete annual Personal Allowance across every source.
• Missing a Scottish S or Welsh C prefix.
• Assuming 1257L is always an emergency code. It is an emergency code only when operated with an emergency marker such as W1, M1, X or NONCUM.
• Changing an income estimate without checking whether a benefit, pension or earlier employment is also affecting the code.

What to do next

• Use the official checker for the exact code.
• Update incorrect source information through HMRC, not through an unofficial refund agent.
• Keep the coding notice and compare it with the next payslip.
• If the code is non-cumulative, read what an emergency tax code means.
• When the rebuilt tool is live, use it to check a tax-code calculation without treating the estimate as an HMRC instruction.