UK Tax Codes Decoded: What 1257L, BR, and K Codes Actually Mean

Your tax code tells your employer how much of your salary is tax-free before PAYE kicks in. It appears on every payslip. If it is wrong, you overpay (and HMRC won't always refund automatically) or underpay (and they will come for it plus interest).

Reading the standard code: 1257L

• 1257 — You can earn £12,570 tax-free this year (Personal Allowance).
• L — You're entitled to the standard Personal Allowance, no complications.

Most employees have 1257L.

Common letters and what they mean

• L — Standard Personal Allowance
• M — You received 10% of spouse's Personal Allowance (Marriage Allowance)
• N — You gave 10% of your Personal Allowance to spouse
• T — Your tax affairs need review (high income, complex deductions)
• 0T — No Personal Allowance (used for new starters without P45, or income above £125,140)
• BR — All income taxed at Basic Rate (20%) — typically for a second job
• D0 — All income taxed at Higher Rate (40%)
• D1 — All income taxed at Additional Rate (45%)
• NT — No tax deducted
• K prefix — You have negative allowance (income owed from prior years, taxable benefits exceeding allowance). Example: K500 means £5,000 added to taxable income.

The Scotland prefix

• S1257L — Scottish taxpayer, standard Personal Allowance. Scotland has its own 5-band income tax.

Why your code might be wrong

1. You changed jobs and HMRC was slow — new employer uses emergency code (often 1257L W1/M1 — non-cumulative). 2. You have a second job — second job defaults to BR (20% on everything). 3. You got a company car or private medical — taxable benefit reduces your allowance. 4. You owe tax from a previous year — HMRC collects via reduced tax code. 5. Personal Allowance tapers above £100k — disappears entirely at £125,140.

How to check and fix

1. Log into Personal Tax Account on gov.uk 2. View your current tax code and the reasoning (allowances, deductions) 3. Update any wrong info (estimated income, benefits, pension contributions) 4. HMRC reissues corrected code within 2 weeks; employer applies it next payslip 5. Previous overpayment is refunded automatically via payroll or cheque

The emergency code trap

If your payslip shows 1257L followed by W1, M1, or X — you are on emergency code. Your tax is calculated on a non-cumulative basis (each month fresh, no year-to-date truing up). This often means overpayment. When HMRC issues your proper code, previous overpayment refunds.

Run the numbers

Use our UK Take-Home Pay Calculator — enter your gross and tax code, see what your actual net pay should be.