HomeTaxWhat Does the M1 Tax Code Mean?

What Does the M1 Tax Code Mean?

We delve into a topic that often leaves many scratching their heads: the M1 tax code. Tax codes can be complex, but understanding them is crucial for ensuring accurate tax payments and avoiding potential penalties. In this article, we’ll demystify the M1 tax code, explaining its meaning, implications, and what it means for taxpayers. So, if you’ve ever wondered about the M1 tax code stamped on your payslip, read on to gain clarity and insight into this essential aspect of taxation.

What Does the M1 Tax Code Mean?

What Does the M1 Tax Code Mean?

The M1 tax code is one of the many codes used by HM Revenue & Customs (HMRC) in the United Kingdom to determine how much tax an individual should pay on their income. This specific tax code is typically assigned to individuals who have received the Marriage Allowance transfer from their spouse or civil partner.

The Marriage Allowance allows couples to transfer a portion of their personal allowance to their partner, reducing their tax bill. With the M1 tax code, the recipient of the Marriage Allowance transfer is entitled to a portion of their partner’s personal allowance, which is then deducted from their taxable income.

This helps to lower their overall tax liability. It’s important for individuals with the M1 tax code to ensure that their tax affairs are in order and that they’re receiving the correct tax relief based on their circumstances. Keeping track of tax codes and any changes to personal circumstances can help individuals manage their finances more effectively and ensure compliance with HMRC regulations.

How Does the M1 Tax Code Work?

How Does the M1 Tax Code Work?

Here’s a breakdown of how the M1 tax code works:

  • Personal Allowance: The M1 tax code signifies that the individual is entitled to the full personal allowance for the tax year, which is the amount of income they can earn before paying any income tax.
  • Tax-Free Threshold: In the tax year of 2021/2022, the personal allowance is £12,570. This means that individuals assigned the M1 tax code can earn up to this threshold without being subject to income tax.
  • Primary Source of Income: The “1” suffix in the M1 tax code indicates that this is the individual’s primary source of income. It signifies that they are entitled to the standard personal allowance for their primary employment or pension income.
  • Taxable Income Calculation: Any income earned above the personal allowance threshold will be subject to income tax. The M1 tax code ensures that income up to the personal allowance is tax-free, while income exceeding this threshold is taxed at the applicable rates.
  • Regular Review: Taxpayers should regularly review their tax codes to ensure they accurately reflect their circumstances. Errors or discrepancies in tax codes could lead to incorrect tax calculations and potential financial penalties.
  • Potential Adjustments: In some cases, individuals may be entitled to additional allowances or deductions, which could result in adjustments to their tax code. It’s essential to report any changes in circumstances to HM Revenue & Customs (HMRC) promptly to ensure tax codes are updated accordingly.

What is the Difference Between M1 and W1 Code?

The key difference between the M1 and W1 tax codes lies in their application and the type of income they represent:

M1 Tax Code:

  • The M1 tax code indicates that the individual is entitled to the full personal allowance for the tax year, typically for their primary source of income, such as employment or pension.
  • It is commonly used for individuals whose income from one job or pension is their main source of earnings.

W1 Tax Code:

  • The W1 tax code signifies that the individual is entitled to the basic personal allowance, but on a weekly basis instead of annually.
  • It is typically applied when an individual has multiple sources of income or starts a new job during the tax year. In such cases, the personal allowance is spread out evenly over the tax year, with one week’s worth of personal allowance applied to each week.

How to Change the M1 Tax Code?

How to Change the M1 Tax Code?

To change your M1 tax code, follow these steps:

  • Check Your Tax Code: Review your current tax code to ensure it needs to be changed. You can find your tax code on your payslip, P60 form, or through your HM Revenue & Customs (HMRC) online account.
  • Update HMRC: Notify HMRC of any changes in your circumstances that warrant a tax code change. This could include starting a new job, changes in income, benefits, or allowances, or any other relevant factors.
  • Provide Necessary Information: HMRC may require additional information to process your tax code change. Be prepared to provide details such as your National Insurance number, employment details, and any relevant documentation.
  • Contact HMRC: You can update your tax code by contacting HMRC directly through their website, by phone, or by mail. Alternatively, your employer or pension provider may also update your tax code on your behalf.
  • Submit Request: Follow the instructions provided by HMRC to submit your request for a tax code change. Provide any requested information accurately and promptly to expedite the process.
  • Wait for Confirmation: Once your request is processed, HMRC will issue a new tax code. You should receive confirmation of the change either through your online HMRC account, by post, or through communication with your employer or pension provider.
  • Review Payslip: Check your next payslip to ensure that your new tax code has been applied correctly. If you notice any discrepancies or have further questions, contact HMRC or your employer for clarification.

Benefits of M1 Tax Code

Benefits of M1 Tax Code

The benefits of the M1 tax code include:

  • Full Personal Allowance: Individuals assigned the M1 tax code are entitled to the full annual personal allowance, allowing them to earn a certain amount of income tax-free each tax year.
  • Tax Efficiency: Maximises tax efficiency by ensuring that individuals can benefit from the full amount of their personal allowance, reducing their overall tax liability.
  • Simplicity: The M1 tax code simplifies tax calculations for individuals by providing a clear and straightforward indication of their tax-free allowance for their primary source of income.
  • Financial Planning: Enables individuals to effectively plan their finances by knowing the amount of income they can earn before they start paying income tax, helping them budget and manage their finances more effectively.
  • Compliance: Helps ensure compliance with tax regulations by accurately reflecting the individual’s entitlement to the personal allowance, reducing the risk of underpayment or overpayment of taxes.
  • Stability: Provides stability and consistency in tax treatment for individuals with a single primary source of income, offering predictability in their tax affairs.
  • Reduced Administrative Burden: Minimises the need for frequent adjustments or updates to tax codes for individuals with stable employment or pension arrangements, reducing administrative burdens for both taxpayers and HM Revenue & Customs (HMRC).


The M1 tax code holds significant importance in the realm of taxation, impacting how much tax you pay and how your income is calculated. It signifies that you are entitled to the full personal allowance for the tax year, which determines the amount of income you can earn before paying tax. Understanding the M1 tax code empowers taxpayers to ensure accuracy in their tax affairs, avoid overpaying or underpaying taxes, and maintain compliance with HM Revenue and Customs regulations.


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