What Is Emergency Tax?

Emergency tax codes are temporary and are used to ensure tax is collected while HMRC gathers the correct information about your income. Once HMRC has the right details, they'll issue your correct tax code and you'll usually get a refund automatically or see your tax adjusted in future pay periods.

How to identify emergency tax

Tax code ending in W1 or M1

Emergency tax codes often end in W1 (week 1) or M1 (month 1). For example, 1257L W1 or 1257L M1. These codes mean your tax is calculated on that pay period only, without considering your previous earnings in the tax year or your full Personal Allowance spread across the year.

Higher tax deductions

If you're on an emergency tax code, you'll pay more tax than you should because you're not getting the benefit of your full Personal Allowance spread across the year. This can make your take-home pay lower than expected.

When it's applied

Emergency tax is usually applied when:

• You start a new job and your employer doesn't have your P45
• HMRC doesn't have enough information about your income
• You have multiple jobs and HMRC needs to determine how to allocate your Personal Allowance
• Your circumstances change (like starting work after being unemployed)

Why emergency tax happens

Emergency tax is used as a temporary measure to ensure tax is collected while HMRC gathers the correct information. It's not a penalty – it's a way to make sure you pay tax while your correct tax code is being determined.

If you're on an emergency tax code, it means HMRC doesn't have enough information to calculate your correct tax code. This is common when you start a new job, especially if you don't have a P45 from your previous employer.

How to fix emergency tax

Provide your P45

If you've started a new job, make sure you give your new employer your P45 from your previous job. This tells them your tax code and how much tax you've already paid in the tax year, which helps them apply the correct code.

Check your personal tax account

You can check your tax code online through your personal tax account on GOV.UK. If your code is wrong, you can update it online or contact HMRC directly.

Contact HMRC

If you think you're on an emergency tax code incorrectly, contact HMRC. They can review your circumstances and issue the correct tax code. Once your correct code is applied, you'll usually get a refund automatically or see your tax adjusted in future pay periods.

Wait for automatic correction

In many cases, emergency tax corrects itself automatically once HMRC has the correct information. This usually happens within a few pay periods, and you'll get a refund of any overpaid tax.

What you can do

Check your payslip to see if your tax code ends in W1 or M1. If it does, you're likely on an emergency tax code. Make sure your employer has all the correct information about your employment situation.

Use our tax calculator to estimate what your tax should be based on your income. If you're paying significantly more than expected, you may be on an emergency tax code.

Keep your payslips and P60 forms. If you've overpaid tax due to an emergency tax code, you'll usually get a refund automatically after the tax year ends or once your correct code is applied.

Related guides

For more information about UK tax and tax codes, see our UK Tax Guide. If you want to understand other tax codes, read our guide on what BR tax code means or what PAYE tax is.