Emergency Tax Calculator

An emergency tax code is a temporary code your employer or pension provider uses when HMRC doesn't have full details of your income — most often after starting a new job without a P45, or taking a flexible pension withdrawal for the first time. Emergency codes usually end in W1 (weekly), M1 (monthly) or X, and work on a non-cumulative basis: each pay period is taxed as if it were the only one in the year, rather than averaging your Personal Allowance across all of it. BR, D0 and 0T often turn up in the same situation even though they aren't strictly "emergency" codes.

Under a normal, cumulative 1257L code, your employer gives you the share of the annual Personal Allowance built up since 6 April, applied against everything you've earned this tax year so far. Under the non-cumulative W1/M1/X basis, that history is ignored — you only get a 1/12 (monthly) or 1/52 (weekly) slice of the allowance and rate bands for that single payment, as if you were paid that amount every period of the year. If you started the job partway through the tax year, the cumulative code would have credited you several months of unused allowance in your first payslip; the non-cumulative emergency code never does, which is the main reason it usually over-taxes.

It lasts until HMRC has enough information to issue your employer or pension provider the correct code — usually once you submit a P45 or HMRC starter checklist, or after your first RTI submission flags your details. GOV.UK notes HMRC typically updates your code within about 35 days of starting a new job. Once the correct, cumulative code is applied, it automatically credits the allowance you missed out on, which is when the overpayment shown above gets refunded.

You usually don't need to claim anything separately. Once HMRC issues the correct cumulative 1257L code, your next payslip applies the full year-to-date Personal Allowance in one go, refunding the overpaid tax automatically through payroll. If the tax year has already ended before this happens, HMRC reconciles your record and sends a P800 confirming the refund (or, less often, that you owe more).

Pension providers almost always apply an emergency Month 1 basis to a first flexible withdrawal, because they don't hold a current tax code for you — this taxes the withdrawal as if you'll take the same amount every month for a year, giving you only 1/12 of your allowance and bands against the whole lump sum. You can reclaim the overpayment without waiting for the tax year to end using one of three HMRC forms, per gov.uk guidance: P55 if you've taken only part of your pot and won't take further regular payments this tax year; P53Z if you've emptied the whole pot and are still working or have other taxable income; P50Z if you've emptied the whole pot and have stopped working with no other income.

1257L W1/M1/X gives you a one-period slice of the standard Personal Allowance, non-cumulatively. 0T gives no Personal Allowance at all but still applies the normal 20%/40%/45% bands. BR taxes everything at a flat 20% with no allowance — the standard code for a genuine second job or pension. D0 and D1 do the same at the flat higher (40%) and additional (45%) rates. See the full list on GOV.UK.

Because the non-cumulative basis never credits the allowance you would have built up in the months before you started. If you start in month 6 with no other PAYE income so far this tax year, a correctly-operating cumulative code would give your first payslip roughly six months' worth of allowance — often enough to wipe out the tax due entirely. The emergency W1/M1 basis only ever gives you that one month's slice, so it withholds tax you shouldn't owe yet.