HMRC uses emergency tax codes when they do not have enough information about your income. As a result, it applies an estimated tax calculation to your pay. Normally, HMRC calculates your tax based on your total earnings across the tax year.
However, an emergency tax code ignores your earlier income. Instead, HMRC calculates your tax using only your current pay period. This means your tax is worked out weekly or monthly, rather than across the full year. Because of this, you may pay more or less tax than expected.
Read more: Your Tax Code Explained By Accountants
How to Identify Emergency Tax Codes
You can usually spot emergency tax codes on your payslip. They often appear near your National Insurance Number or earnings section.
Look for the following endings:
| W1 | Weekly pay |
| M1 | Monthly pay |
| X | Irregular pay periods |
| NONCUM | Another term for non-cumulative tax |
For instance, you might see 1257L W1 or 1257L M1 on your payslip.
Here, the number “1257” represents £12,570 of tax-free income. The letter “L” confirms that you receive the standard Personal Allowance.
If your tax code does not include one of these endings, you are not on an emergency tax code.
Common Emergency Tax Codes
Understanding the difference emergency tax codes can help you identify your situation quickly. The following codes can result in higher tax deductions until you update your details.
1257L Emergency Code
This is the standard Personal Allowance code for the 2026/27 tax year. It provides a £12,570 tax-free allowance. However, when combined with W1, M1 or X, it becomes non-cumulative. This means it only applies a portion of your allowance for each pay period.
BR Tax Code
All income is taxable at the Basic Rate of 20% and no Personal Allowance applies to this income. This code usually applies when you have a second job or pension income.
0T Tax Code
Income is taxable across all tax bands and no tax-free allowances applies to this income. This code usually applies when HMRC does not have enough information.
Why You Might Be on an Emergency Tax Code
Several situations can trigger an emergency tax code. These situations often involve changes to your employment or income.
Common reasons include:
- You start a new job without providing a P45
- You move from self-employment into employment
- You have more than one job at the same time
- You begin receiving company benefits
- You start receiving the State Pension
- Your employer submits incomplete or delayed information
Additionally, students working during holidays or people changing working hours may also be affected.
In most cases, HMRC applies this code automatically while it gathers the correct details. Therefore, it does not mean anything has gone wrong.
What This Means for Your Pay
Under normal circumstances, HMRC spreads your Personal Allowance across the full tax year. As previously stated, this allowance stands at £12,570.
However, emergency tax codes ignore your earlier earnings and an unused allowances.
Instead, they:
- Use only one week or month of your allowance
- Assume you earn the same amount every pay period
- Ignore unused allowance from earlier in the year
As a result, your tax calculation may not reflect your true position. Therefore, many people pay more tax than necessary at first.
If you start work halfway through the year, you may still have unused allowance. A normal tax code would take this into account. An emergency tax code would not.
How Much Extra Tax You Could Pay
If your Personal Allowance is not applied correctly, you could overpay tax during the year.
For instance:
- Basic Rate taxpayers could overpay up to £2,514
- Higher Rate taxpayers could overpay up to £5,028
These figures apply to the 2026/27 tax year. The exact amount depends on your income and circumstances. While this may seem concerning, it is usually only temporary. HMRC will correct the position once it receives accurate information.
How to Fix an Emergency Tax Code
The good news is that emergency tax codes usually correct themselves.
However, you can take the following steps to speed up the process:
- Provide your employer with your P45 as soon as possible
- Complete a Starter Checklist if you do not have a P45
- Check your tax code using your Personal Tax Account
- Contact HMRC if the issue continues after 35 days
You should also ensure your employer has accurate and up-to-date information. Once HMRC receives the correct information, it will issue a new tax code to both you and your employer.
Getting a Refund for Overpaid Tax
If you pay too much tax, HMRC will usually correct this automatically.
You may receive:
- A refund through your payslip once your code updates
- A P800 letter after the tax year ends
The P800 will confirm whether you have overpaid or underpaid tax. It will also explain how to claim any refund.
If needed, you can contact HMRC directly to claim back overpaid tax.
Contact Us
We are not just accountants; we are Chartered Accountants with one of the most reputable and premium accounting bodies. We are registered and regulated by ACCA; so you can rest assured that you are in good hands. Knowing this, don’t hesitate to get in touch with us if you require assistance: Pi Accountancy | Contact Us
This article is for general informational purposes only and does not constitute legal or financial advice. While we aim to keep our content up to date and accurate, UK tax laws and regulations are subject to change. Please speak to an accountant or tax professional for advice tailored to your individual circumstances. Pi Accountancy accepts no responsibility for any issues arising from reliance on the information provided.