Emergency tax code: why you're on one and how to get your money back

In short

An emergency tax code is a temporary code your employer uses when HMRC hasn't given them your correct one yet. You can spot it by W1, M1 or X at the end (for example 1257L W1 or 1257L M1). Sometimes 0T or BR is used instead.

It usually isn't a disaster, but it often takes more tax than it should, especially if you started a new job partway through the tax year. Once your employer gets the right code, overpaid tax usually comes back through your pay. If it doesn't, or the tax year has already ended, you can claim it back for up to four previous tax years.

Why you've been put on an emergency code

Common reasons:

• You started a new job and your employer didn't get a P45 from your last one.
• You didn't fill in the starter checklist, or it was filled in wrongly.
• You started work after a gap, after self-employment, or after claiming benefits.
• You started getting a company benefit, such as a company car, or your State Pension started.
• You have a second job and HMRC hasn't yet split your Personal Allowance between them.

What the letters mean

• W1 (week 1): weekly paid, non-cumulative. You only get one week's share of your tax-free allowance each payday, with no catch-up for weeks you weren't working.
• M1 (month 1): monthly paid, non-cumulative. The same, per month.
• X: non-cumulative, used on newer payroll systems. The same as W1 or M1.
• 0T: no tax-free allowance at all. All pay is taxed.
• BR: basic rate on everything. All pay is taxed at 20% (see our BR tax code guide).

Scottish taxpayers see an S at the start (S1257L M1). Welsh taxpayers see a C. See Scottish and Welsh tax codes.

Why it can overcharge you

A normal code is cumulative: each payday, payroll looks at your pay and allowance for the whole tax year so far and corrects itself. W1, M1 and X codes are non-cumulative. Each payday is treated on its own.

So if you start a job in, say, October, having earned little or nothing since 6 April, a normal code would give you the unused allowance from April to October. An emergency code doesn't, and you pay tax you don't owe until it's corrected.

Worked example

2026/27, England. You earn nothing from 6 April, then start a job in October paid £2,000 a month. The standard Personal Allowance is £12,570, so one month's share is £1,047.50, and the basic rate is 20%.

On 1257L M1 your first payslip is looked at on its own: £2,000 less £1,047.50 leaves £952.50 taxed at 20%, so you pay £190.50.

On a normal cumulative 1257L, payroll adds up the year so far. By October you have built up seven months of allowance, £7,332.50, against £2,000 of pay. That is well under your allowance, so you pay nothing.

The emergency code costs you £190.50 in month one, and more each month until it is corrected. Once it is, the overpaid tax normally comes back through your pay.

How to fix it

1. Give your employer your P45 from your last job, or complete the starter checklist if you don't have one. See What is a P45?
2. Check your code in your HMRC personal tax account or the HMRC app, and update your income details if they're wrong. You'll need a Government Gateway user ID.
3. Wait for HMRC to send your employer a corrected code. When the code becomes cumulative again, the overpaid tax usually comes back in your next pay.
4. If the tax year has ended, HMRC reconciles your account and may send you a P800. If it doesn't, or the amount looks wrong, you can claim.

Can I claim back emergency tax from previous years?

Yes. You can claim back overpaid tax for up to four previous tax years. Right now that goes back to 2022/23, and the deadline for 2022/23 is 5 April 2027. See How far back can you claim?

People on emergency codes often also miss work expenses they could claim, such as uniform, mileage or professional fees. Taxpro checks both at the same time. No refund, no fee: see fees.

Check my rebate

Questions

How long does an emergency tax code last?

Until HMRC sends your employer your correct code. That's often one or two pay periods after your employer gets your P45 or starter checklist, but it can take longer if HMRC's details for you are out of date.

Is 1257L an emergency tax code?

Not on its own. 1257L is the standard code. It's only an emergency code if it ends in W1, M1 or X. See The 1257L tax code.

Will I get emergency tax back automatically?

Usually, once the code is corrected within the same tax year. If it isn't corrected before 5 April, HMRC should reconcile it after the year ends, but not always correctly. See Do you automatically get a tax rebate?

Does an emergency tax code affect my National Insurance?

No. National Insurance is worked out separately for each pay period and doesn't use your tax code.