Glossary · UK

What is Emergency Tax Code?

A temporary tax code used when HMRC lacks full information, often taxing you on a non-cumulative basis.

Full Definition

An emergency tax code is applied when your employer or pension provider does not yet have full details of your income and previous tax paid. The most common emergency codes for 2026/27 are 1257L W1, 1257L M1 or 1257L X — the W1 (weekly), M1 (monthly) or X markers mean the code is applied on a non-cumulative basis, so each pay period is taxed in isolation without accounting for earlier pay or unused allowance. A more aggressive emergency code is 0T, which gives no Personal Allowance at all and is common on pension drawdown lump sums. Emergency codes often lead to overpaid tax. To fix it, give your employer a P45 from your last job or complete a new-starter checklist; HMRC will then issue a correct cumulative code, and any overpayment is refunded automatically or can be reclaimed online.