Emergency tax codes

An emergency tax code is a temporary code your employer uses when HMRC has not yet sent the right one. For 2026/27 the emergency codes are 1257L W1, 1257L M1 and 1257L X. They give you the standard £12,570 allowance, but only one week’s or one month’s share of it each payday, with no credit for anything you did not use earlier in the tax year. Most people on one get the right code within a few pay periods, and any overpaid tax comes back through payroll.

When you get one

Emergency codes usually appear when you start a new job and payroll does not have enough information about your earlier earnings that tax year. That typically happens because:

• you did not hand over a P45 from your last job, or it arrived after the first payroll run
• you are starting your first job since 6 April and your starter checklist was incomplete
• you have started receiving a pension or benefits HMRC have not yet matched to your record
• you had a company benefit start or stop and HMRC is still updating your record.

Public sector starters often hit this because the gap between a conditional offer and a first payday can be short, and the paperwork goes to a payroll team in another building or another organisation entirely. The pre-employment checks guide lists the documents most employers ask for.

What W1, M1 and X actually do

Normal PAYE is cumulative. Each payday, payroll compares your total pay since 6 April with the total allowance due to date and charges tax only on the difference. If you were out of work for part of the year, the allowance you did not use builds up and you pay little or no tax until it is used.

A code ending in W1 (week 1) or M1 (month 1) switches that off. Each period is treated as if it were the first of the year. You get £1,048 of tax-free pay in a month (or £242 in a week) and no more, whatever happened earlier. X does the same job for payrolls that need a code without a W1 or M1 marker.

What it can cost

Say you start a council job in September on £30,000 a year after five months without earnings since 6 April. On a cumulative 1257L code, payroll would see roughly five months of unused allowance and take much less tax at first. On 1257L M1, you pay tax every month as if your allowance were only £1,048 a month. On £2,500 a month, that is 20% of £1,452, or about £290 a month, from the first payday.

If you had been working all year, an emergency code makes little difference, because the allowance due to date is roughly what you would have used anyway. It hurts most when you have had a gap, or when you have earned much less than usual so far that year.

An emergency code can also hide a second job problem. If you already have a main job using your allowance, payroll should be taxing the new job at BR. An emergency code gives the new job its own allowance, so you end up paying too little and HMRC collects it later. See BR tax code.

How to get it fixed

1. Give payroll your P45 from your last job if you have one. Parts 2 and 3 are the ones your new employer needs. If it is lost, ask your old employer for the figures; they cannot issue a second P45, but they can confirm your pay and tax to date.
2. If you do not have a P45, fill in the starter checklist the new employer gives you. Pick the statement that matches you: this is my first job since 6 April with no other income; this is now my only job but I have had another since 6 April; or I have another job or a pension. The statement you pick decides which code payroll uses until HMRC replies.
3. Check your HMRC personal tax account or the HMRC app after your first payday. Your new job should appear with its code. If the estimated income is wrong, update it there.
4. If nothing changes after a couple of pay periods, call HMRC with your National Insurance number and your employer’s PAYE reference (on your payslip or in the offer pack).

Once HMRC issues a cumulative code, payroll applies it from the next payday. The software recalculates the year to date, so any tax overpaid on the emergency basis is refunded in that pay packet. A big jump in take-home pay one month is usually this happening.

If the tax year ends first

If you are still on an emergency code at 5 April, the overpayment is not lost. HMRC reconciles your record after the end of the tax year and sends a calculation if you paid too much. You can also claim through your personal tax account; claiming a tax refund explains the routes. Your P60 from each employer shows the total pay and tax for the year, so keep it.

Emergency codes in Scotland and Wales

The same rules apply, but the code has a prefix: S1257L M1 for Scottish taxpayers and C1257L M1 for Welsh taxpayers. If you live in Scotland and payroll has an English-style emergency code, you may be paying the wrong rates. HMRC decides your residence status from the address it holds, so keep that up to date.

Checking what you were charged

Your payslip shows the code, the tax period (month 6 for September on a monthly payroll, for example) and tax paid to date. If the code ends in W1, M1 or X, you are on an emergency basis. If your take-home pay looks wrong for other reasons, how to read your payslip walks through each line, and the take-home pay calculator shows what a normal month should look like on a cumulative code.