Emergency tax codes: W1, M1 and X
Emergency tax usually appears when payroll does not yet have all the information needed to tax you on the normal cumulative basis. For 2026/27, the common emergency forms are 1257L W1, 1257L M1 and 1257L X.
Why emergency tax happens
It can happen when you start a new job without complete previous pay and tax details, after a change in circumstances, or while HMRC and payroll records catch up. It is a payroll basis, not a separate tax rate.
How W1 and M1 work
A non-cumulative code does not look back across the whole tax year in the normal way. W1 applies the allowance and tax bands to that week only; M1 applies them to that month only. That can mean deductions differ from a normal cumulative code.
Will emergency tax sort itself out?
Often HMRC updates the code once it has the information it needs. If the code is wrong, HMRC says to check and update the details it holds about your jobs, pensions, income and benefits.
Can you get a refund?
If too much tax has been deducted and your code is corrected during the year, payroll may repay the overpayment through a later payslip where the new cumulative code allows it. Otherwise HMRC can reconcile the position after the tax year.
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FAQs
Is 1257L always an emergency tax code?
No. 1257L on its own is commonly a normal code. The emergency versions usually have W1, M1, X or NONCUM attached.
Does emergency tax mean 40% tax?
No. Emergency tax is about the PAYE calculation basis, not a fixed 40% rate.
How do I get off an emergency tax code?
Check that HMRC has correct employment and income information. Your employer uses the code HMRC provides.