Tax code
UK tax glossary · Last reviewed: April 2026
A tax code combines a number (your tax-free allowance divided by 10) and one or more suffix letters that tell your employer additional rules. 1257L is the most common code for employees with the full Personal Allowance.
The L suffix means you have the standard Personal Allowance. Other common suffixes include M (recipient of Marriage Allowance transfer), N (donor of Marriage Allowance), T (other adjustments), and 0T (no allowance at all).
Wrong codes cause over- or under-payment. Check yours whenever you change jobs, start a second job, receive a new taxable benefit, or get a significant pay rise.
Worked example
Code 1257L: 1257 × 10 = £12,570 tax-free. Monthly tax-free amount: £12,570 ÷ 12 = £1,047.50. Everything earned above that in the pay period is taxed at your applicable rate.
Common questions
How do I get my tax code changed?
Contact HMRC via your Personal Tax Account, the HMRC app, or by phone. Changes are usually applied within a few weeks. Your employer cannot change it independently.
What does it mean if my tax code has a W1 or M1 suffix?
W1 (weekly) or M1 (monthly) makes your code non-cumulative — tax is calculated from scratch each pay period, ignoring earlier months. This commonly causes overpayment and should be resolved with HMRC.
Related resources
TaxHelper provides general information based on published HMRC rates and guidance. It is not regulated financial or tax advice. For decisions involving significant sums, complex circumstances, or if you are unsure, speak to a qualified accountant or HMRC directly.