An emergency tax code is a temporary code used when your employer does not yet have enough information to work out the right tax. You will usually see it as 1257L W1, 1257L M1 or 1257L X, the suffix is the important part.
This is part of our UK tax codes explained series.
What do W1, M1 and X mean?
These suffixes make a code non-cumulative. A normal code is cumulative, it looks at everything you have earned and the tax you have paid so far this year, and smooths the right amount across your pay. An emergency code ignores all of that and taxes each pay period in isolation:
- W1, week 1, used when you are paid weekly.
- M1, month 1, used when you are paid monthly.
- X, a general non-cumulative marker some payrolls use.
You still get the £12,570 allowance, but spread one period at a time, so you cannot benefit from any unused allowance from earlier in the year.
Why am I on an emergency tax code?
It usually happens when HMRC and your employer are missing year-to-date details:
- You started a new job without a P45 from your last one.
- You moved from self-employment into employment.
- You started drawing a pension or took flexible pension cash.
- You began receiving company benefits mid-year.
Does an emergency code mean I overpay?
Not always, but it can. Because each period is taxed on its own, you may pay slightly too much (or too little) until HMRC issues a cumulative code. Once the right cumulative code is applied, the year-to-date figures are recalculated and any overpayment is normally refunded through your next pay.
What to do if the code is wrong
If you think your tax code is wrong, do not just wait, an incorrect code is corrected from the date HMRC updates it, and any over- or under-payment is squared up afterwards. Steps to take:
- Check your latest tax code notice (the "PAYE Coding Notice", form P2) in your HMRC personal tax account. It shows how the code was built up.
- Compare it to your real situation, one job or several, any benefits in kind, untaxed income, or earlier-year underpayments being collected.
- Make sure your employer has your P45 or a completed new-starter checklist, that is what lets HMRC switch you to a cumulative code.
- Check the suffix has dropped on a later payslip, a plain 1257L (no W1/M1/X) means you are back on a cumulative code.
- Tell HMRC if anything is out of date, online, via the HMRC app, or by phone. They will issue a revised code to your employer.
- Watch your next payslip to confirm the new code has been applied and any refund has come through.
Frequently asked questions
How long does emergency tax last?
Usually only a pay period or two, until HMRC has your full details and issues a cumulative code. Giving your employer your P45 or completing the starter checklist speeds it up.
Will I get emergency tax back?
If you overpaid, yes, it is normally refunded automatically through your pay once the correct cumulative code is applied, or reconciled by HMRC after the tax year.
Is BR an emergency tax code?
BR is sometimes used for a new starter, but it is a normal code in its own right (a flat 20%). The true emergency markers are W1, M1 and X. See our BR code guide.
Think your tax code is wrong? It is one of the most common payroll errors, and HMRC will not always spot it for you. Zmartly's Self Assessment and personal tax team can check your code against your circumstances and deal with HMRC on your behalf. Get in touch for a free review, or book a free Tax Health Check.
