What is a PAYE tax code?
A tax code is a short combination of numbers and letters used by your employer or pension provider to work out how much Income Tax to deduct from your pay. HMRC normally sends the code to them and may send you an explanation if it changes.
The code is not a personal tax bill and does not, on its own, tell you how much tax you will pay for the year. Your pay, tax region, other jobs or pensions, benefits and payroll information all matter.
How do the numbers and letters work?
In a code such as 1257L, the number usually represents the tax-free income allocated to that job or pension. It is generally multiplied by 10, so 1257 broadly points to the standard £12,570 allowance for 2026/27.
The letter describes part of your circumstances or the way the allowance should be treated. L is commonly used for someone entitled to the standard Personal Allowance, while BR and D0 apply different treatments to a source of income.
Why might HMRC change a tax code?
HMRC may update a code when it receives information about a new job, previous pay, a pension, taxable benefits, untaxed income or tax owed from an earlier period. A code can also reflect how your Personal Allowance is shared across more than one source.
If your code changes, compare the explanation from HMRC with your current circumstances. Do not assume that a code is wrong simply because it is different from 1257L.
What should I do if my code looks wrong?
- Check the code on your latest payslip.
- Compare it with your HMRC Personal Tax Account.
- Check that your jobs, pensions, benefits and estimated income are up to date.
- Update HMRC if the information is missing or incorrect.
- Ask HMRC to review the code rather than changing it yourself.
WorkSmartMoney can explain common codes and estimate take-home pay, but HMRC is the organisation that issues your individual tax code.