Tax Code Checker — What Your Code Means

The standard code and why it changes

1257L has been the standard since April 2021 and remains so for 2026-27 under the freeze — the Personal Allowance (£12,570) divided by ten, plus the L for 'standard allowance'. Your code moves whenever HMRC learns something new: a benefit in kind reported by your employer, Marriage Allowance, jobexpense relief coded in, an older underpayment being collected, or estimated untaxed income. The number part is always the allowance; the letter is always the situation.

Codes that mean 'no allowance from this source'

• BR — basic rate on every pound; normal for a genuine second job or pension, a red flag on a main job.
• D0 / D1 — 40% / 45% on everything; used when one source already uses your lower bands.
• 0T — no allowance at all and no lower-band benefit; often follows a missing P45 and usually over-taxes until corrected.
• NT — no tax deducted; rare, and worth double-checking rather than celebrating.
• K codes — negative allowance: HMRC is taxing benefits or old debts through your pay, capped at half your gross pay per period.

Emergency codes: what W1, M1 and X really do

An emergency suffix means 'tax this payslip in isolation' — payroll ignores everything you earned and paid earlier in the year. It happens when a new employer has no P45 and no usable starter information. The result is usually too much tax early on, which HMRC's cumulative system normally corrects automatically once the code updates. If it doesn't correct within a couple of months, a free call to HMRC (or a note through your Personal Tax Account) fixes it — and any overpayment becomes a refund.

When to actually query your code

• Your number is below 1257 and you don't know why — check the deductions listed in your tax account first.
• BR or D0 on your main and only job.
• W1/M1 still showing after three or more payslips.
• A K code appeared and you can't identify the benefit or debt it represents.
• You changed jobs and the new code looks nothing like the old one.