That cryptic string on your payslip decides how much tax you pay — and millions of them are wrong. Type yours in and get it translated into plain English, with the warning signs to check. Free, instant, and nothing is recorded.
Find it on any payslip, your P60, a PAYE coding notice letter, or in your HMRC personal tax account. Each job or pension has its own code.
Based on 2026/27 rules. A tax code is only ever an instruction to your employer — if it’s wrong, only HMRC can fix it (your employer can’t). This is an illustration, not tax advice; nothing you type is stored or sent anywhere.
Your tax code is HMRC’s best guess about your year, sent to your employer as an instruction. It’s built from last year’s information — benefits you may no longer get, estimated interest and side income, old underpayments — and it doesn’t update itself when your life changes. Job moves, second jobs, company cars that went back, pay rises past £100,000: each one can leave you on a code that quietly takes the wrong amount every single month.
Once your code is right, see exactly what should be landing in your account with the salary calculator — or jump straight to a ready-made breakdown like £25,000, £30,000 or £40,000 after tax. If your payslip doesn’t match the calculator, your code is the first suspect.
HMRC recalculates whenever new information lands: a P11D showing benefits, bank interest reported by your bank, a second job starting, a pay estimate crossing £100,000, or an under/overpayment from a previous year. You should get a coding notice (letter or in the app) explaining the change — the calculator above translates the result, and the notice explains the ingredients.
Typically your full allowance goes against the main job (e.g. 1257L) and the second job gets BR, so it’s all taxed at 20%. If the second job pushes you into higher rate it may be D0 instead. You can ask HMRC to split the allowance differently — useful when the main job pays under £12,570.
Log into your personal tax account or the HMRC app, check the income and benefit lines behind the code, and correct anything stale — most fixes apply within days. No online account? Call HMRC on 0300 200 3300. Current-year overpayments come back automatically through your next payslips; previous years arrive as a P800 calculation and refund.
They all mean the same thing: non-cumulative. Each payday is taxed as if it were week 1 or month 1 of the year, ignoring what’s happened so far. It’s a holding position while HMRC waits for information — normal for a month or two after starting a job, worth chasing if it persists.
No. The decoding happens entirely in your browser on this page — nothing is saved, sent or shared, and you won’t be asked for an email address.
See exactly what your salary should pay after tax, NI, student loan and pension — then compare it against your payslip.
