You're on an emergency tax code if your code ends in W1 (paid weekly), M1 (paid monthly) or X (pay dates vary), or your payslip shows NONCUM. It means your tax is worked out only on what you're paid that week or month, as if you earned that much every period, instead of on your income for the tax year so far. It's usually temporary: HMRC normally sends a corrected code within 35 days of you starting a new job.
Most people see one in their first payslip at a new job and assume something's gone wrong. Usually it hasn't: your new employer simply doesn't have your previous pay and tax details yet. Everything below comes from GOV.UK's tax codes guide.
How to recognise one
| Your code ends in | Means | GOV.UK example |
|---|---|---|
| W1 | Emergency code, paid weekly | 1257L W1 |
| M1 | Emergency code, paid monthly | S875L M1 |
| X | Emergency code, pay dates vary | C663L X |
| NONCUM (on the payslip) | Emergency basis, depending on your employer's payroll software |
If your code doesn't end in W1, M1, X or NONCUM, you're not on an emergency code, even if it looks unfamiliar. The S and C prefixes in those examples just mean Scottish or Welsh rates apply. Our guide to the 1257L tax code explains the numbers and the L.
Why it can mean paying the wrong amount
Normally your tax is cumulative: each payday, your employer looks at everything you've earned and paid in the tax year so far, so any unused allowance from earlier months is picked up. On an emergency code, each pay period is taxed on its own. If you started mid-year after a gap, you won't get the benefit of the allowance you didn't use in the months you weren't working, so you can pay too much for a while. If you've had another job earlier in the year, it can go the other way.
The three usual reasons
- You've started a new job and your new employer doesn't have your previous income and tax details. When you're paid for the first time, your employer tells HMRC you've started, and without those details it has to use an emergency code.
- You've started getting a company benefit, such as medical insurance through work.
- You've started getting the State Pension.
With company benefits or the State Pension, GOV.UK says an emergency code is normal and helps you pay the right amount for that year. You'll keep it until the end of the tax year and move to a non-emergency code in the new one. Check the code online includes the benefit or pension, and update your details if it doesn't.
How to get off an emergency tax code
- Give your new employer the P45 from your last job. If your old employer didn't give you one, ask them for it.
- If you don't have a P45 (or you left your last job before 6 April 2025), your employer will ask you to fill in a starter checklist, which replaced the old P46.
- Wait for HMRC. It usually updates your code once it has details from your new and previous employers, and sends it to you and your employer. That can take up to 35 days from your start date.
- If it's been more than 35 days and you still think the code is wrong, update it through HMRC's tax code service or contact HMRC.
Getting overpaid tax back
Once HMRC has your income details, it works out the difference between what you've paid and what you should have paid, and asks your employer to refund it through your pay. Monthly-paid staff should see the new code used on their next or following payday; weekly-paid staff on their third payday after the employer gets it. If HMRC doesn't have your details yet, the refund waits until it does, which is another reason to hand over the P45.
After the tax year ends, HMRC checks everyone's income from employers, pension providers and the benefits office, and writes if you've paid the wrong amount. If you've underpaid, it may adjust your code to collect the tax over one or more years. Your P60 at year end shows what you paid in total.
Emergency code or something else?
| Code | What it means |
|---|---|
| 0T | Your Personal Allowance has been used up, or you've started a new job and your employer doesn't have the details they need |
| BR | All income from this job or pension is taxed at the basic rate, usually because it's a second job |
| K | You've untaxed income bigger than your Personal Allowance |
| NT | You're not paying tax on this income |
The numbers matter too. GOV.UK's example: the standard Personal Allowance is £12,570, but medical insurance from your employer worth £1,570 is a company benefit, so your tax-free amount drops to £11,000 and your code becomes 1100L (figures as of October 2026). A code change like that isn't an error, and it isn't an emergency code.
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0T isn't an emergency code on its own, but it often turns up in the same new-job situation. BR is common for second jobs and isn't a mistake if your allowance is used in your main job.
The verdict
Don't panic about an emergency code in your first payslip. Hand over your P45 straight away, or fill in the starter checklist, and give HMRC up to 35 days. If you're still on W1, M1, X or NONCUM after that and nothing's changed in your benefits or pension, update your code yourself rather than waiting for the end of the year.
Frequently asked questions
What does M1 mean on my tax code?
M1 means you're on an emergency tax code and paid monthly. Your tax is worked out only on that month's pay.
How long does an emergency tax code last?
It's usually temporary. HMRC normally updates your code once it has your details, which can take up to 35 days from when you start a job.
Will I get overpaid emergency tax back?
Yes. Once HMRC has your income details, it asks your employer to refund the difference through your pay, or sorts it after the tax year ends.
Is NONCUM an emergency tax code?
Yes. GOV.UK says you could see NONCUM on your payslip if you're on an emergency tax code, depending on your employer's payroll software.
