Emergency tax code

An emergency tax code is a temporary tax code your employer uses when HMRC does not yet have full details of your income. GOV.UK lists three markers after the code:

• W1 if you are paid weekly, for example 1257L W1;
• M1 if you are paid monthly, for example 1257L M1;
• X if your pay dates vary.

Your payslip may show “NONCUM” instead. The code works on a non-cumulative basis: tax is based only on that week’s or month’s pay, and you are taxed as if you were paid that amount every period of the year.

You usually get one when you start a new job and your employer does not have details of your previous income, or when you start receiving company benefits or the State Pension. GOV.UK says HMRC normally sorts out a new job within 35 days once it has information from both employers.

Example: on 1257L M1 you get £1,047.50 tax-free each month (£12,570 ÷ 12), with no catch-up for months you were out of work. If you start a job in October after six months with no pay, a cumulative 1257L code would give you the unused allowance back; M1 does not, so you overpay until HMRC corrects it.

If you overpaid, you can claim a refund. Check your code in the UK tax code checker.