What is a tax code (and why 1257L matters)?
Your tax code tells your employer how much tax-free pay you get before PAYE deductions — 1257L means the standard £12,570 personal allowance. A wrong code silently over- or under-taxes you every month.
How to read your code
The number is your tax-free allowance divided by 10 (1257 = £12,570); the letters modify it: L standard, M/N Marriage Allowance received/given, BR all income taxed at 20% (typical second jobs), 0T no allowance, K codes mean extra taxable amounts (company car, unpaid tax) exceed your allowance, and W1/M1 "emergency" codes tax each payday in isolation. Scottish taxpayers have an S prefix, Welsh a C.
Why wrong codes are so common
Job changes, second jobs, benefits in kind and pension withdrawals all confuse the system — emergency codes on new jobs routinely overtax people for months. Check the code on your payslip against your Personal Tax Account on gov.uk; refunds go back four years.
Why it matters now
With the personal allowance frozen to 2031, code 1257L is set to be the longest-lived tax code in history — and every year it stays put, fiscal drag taxes more of your pay through it. If Reform's £20,000 allowance ever happened, the nation's payslips would read 2000L.
Plain-English guide for general information only — not financial, legal or tax advice. Rates are 2025/26 unless stated. Last reviewed 5 July 2026.
Frequently asked questions
What does tax code 1257L mean?
You get the standard £12,570 personal allowance spread across the year before PAYE tax starts. It's the default code for most employees with one job and no taxable perks — and it's been frozen in place since 2021.
Why am I on an emergency tax code?
Usually a new job without a P45, a first pension withdrawal, or a second job. Emergency codes (ending W1/M1, or BR/0T) often overtax you; HMRC usually corrects them within a couple of months, but you can force it via your Personal Tax Account.
How do I claim back overpaid tax?
Through your Personal Tax Account at gov.uk or form P800 when HMRC reconciles the year. Claims can go back four tax years — and it's free, so never pay a rebate firm a percentage for it.