Tax Code 1383M: What It Means for Your 2025/26 Payslip?

Your tax code is a combination of numbers and letters that helps your employer know how to tax your earnings.

You’ll have one for each job you have, and it’s important to keep track of them. The last thing you want is to be over or underpaying tax due to the wrong tax code.

Let’s take a look at the ins and outs of what the 1383M tax code means and how it might affect your tax-free personal allowance.

What Is Tax Code 1383M And Why Is It Used?

The tax code 1383M is issued by HMRC to individuals who receive a portion of their partner’s personal allowance under the Marriage Allowance scheme.

It enables employers to apply the correct level of tax deduction via PAYE, based on the adjusted personal allowance figure.

The standard tax code for most UK taxpayers is 1257L, which reflects the personal allowance of £12,570 for the 2025/26 tax year.

When Marriage Allowance is applied, 10% of the lower-earning partner’s personal allowance, which equates to £1,260, is transferred to the higher earner.

This increases their total tax-free income to £13,830, resulting in the 1383M tax code.

The letter ‘M’ indicates that the code has been modified due to the Marriage Allowance claim.

This tax code ensures that the additional allowance is factored into monthly payroll deductions, providing a more accurate calculation of income tax liability for those benefiting from the transfer.

How Does The 1383M Tax Code Affect Your 2025/26 Income?

Receiving the 1383M tax code increases your tax-free income threshold, meaning you are taxed on a smaller portion of your salary.

This can lead to a noticeable improvement in your monthly take-home pay if you were previously on the standard code.

The calculation for taxable income changes as follows:

• Personal Allowance: £12,570
• Marriage Allowance Transfer (10%): £1,260
• Total Tax-Free Allowance: £13,830

If you earn £20,000 per year and are on the 1383M tax code, only £6,170 of your income will be subject to tax, as shown below.

Income Tax Example Under 1383M

This difference reduces your tax bill compared to the standard code, which would only provide a £12,570 tax-free allowance, making more of your income taxable.

Why Might Your Tax Code Change To 1383M?

A change to the 1383M tax code usually occurs when you or your spouse have applied for and been granted the Marriage Allowance by HMRC.

This allowance allows the lower-earning partner to transfer 10% of their unused personal allowance to the higher earner, effectively increasing the recipient’s tax-free income.

Once HMRC processes the application, they update the tax codes accordingly to reflect this change.

However, this is not the only reason your tax code might change to 1383M. Several situations may prompt HMRC to apply this code:

• Marriage or Civil Partnership Registration: If you recently got married or entered a civil partnership, and you meet the eligibility criteria, a successful Marriage Allowance application may result in your code changing to 1383M.
• Change in Employment or Income: A new job, promotion, or shift in your annual salary can lead HMRC to reassess your tax status. If Marriage Allowance is already in place, they may assign or reaffirm the 1383M code.
• End-of-Year Reconciliation: Sometimes, after submitting your Self Assessment or once employers submit year-end payroll information, HMRC may identify underpayments or overpayments. If adjustments are required, a new tax code might be issued to reflect the Marriage Allowance benefit more accurately.
• Automatic Renewal by HMRC: In many cases, once Marriage Allowance is approved, HMRC continues to apply it automatically in future tax years unless informed of a change in your circumstances. Therefore, your code might switch back to 1383M at the start of a new tax year without the need for reapplication.
• Transfer of Marriage Allowance from Previous Year: If there was a delay in applying the allowance or if it was granted retrospectively, HMRC may apply 1383M mid-year to adjust your tax position moving forward.

In all of these instances, HMRC should notify both partners of the change. You may receive a notice of coding (P2 form) explaining the reason for the updated tax code.

It’s always advisable to read these notices carefully and cross-check the information with your personal and financial records to ensure accuracy.

What Should You Do If Your Tax Code 1383M Is Incorrect?

An incorrect tax code can lead to you paying too much or too little tax, which might cause financial stress later in the year.

While the 1383M code is typically a sign that you’re receiving a Marriage Allowance, it may be wrong if your circumstances have changed or if HMRC has made an administrative error.

If you believe the 1383M code does not apply to you, take the following steps:

1. Check Your Eligibility for Marriage Allowance

Confirm whether you or your partner submitted a valid Marriage Allowance application and whether your income qualifies. You must be married or in a civil partnership, with one partner earning below the personal allowance threshold (£12,570 in 2025/26) and the other earning less than the higher-rate tax band.

2. Review Your Payslip or Tax Documents

Your tax code appears on your monthly payslip, P45 (if you’ve left a job), P60 (issued at the end of the tax year), and your HMRC Personal Tax Account. Compare the code shown with your employment and financial situation. If you’re not supposed to receive Marriage Allowance, the ‘M’ suffix may indicate a mistake.

3. Log In to Your Personal Tax Account

Use your HMRC online account to review your tax code and personal information. The platform provides a breakdown of how your code was calculated and allows you to update employment details, marital status, or income figures.

4. Contact HMRC Immediately

If the information is incorrect, contact HMRC directly. You can do this:

• • Via your Personal Tax Account online
  • By calling their income tax helpline
  • Through your employer or accountant, who may assist in resolving the issue

When contacting HMRC, be prepared with:

• • Your National Insurance number
  • Details of your current income
  • Recent payslips or P60
  • Marriage or civil partnership dates (if relevant)

5. Request a Code Correction

Once the error is identified, HMRC can issue a corrected tax code to your employer, usually within a few working days. This will be applied in your next payroll, and any overpaid or underpaid tax will be adjusted accordingly.

6. Monitor Your Payslip

After HMRC makes the update, check your following payslips to ensure the new code has been applied and the correct tax is being deducted. If you’ve overpaid tax as a result of the incorrect code, you may receive an automatic refund or need to claim it through HMRC’s online services.

Common Indicators Your Tax Code Might Be Wrong:

• Unexpected reduction in take-home pay
• Tax deductions seem too high or too low
• Code does not match your circumstances (e.g. no Marriage Allowance claim made)

Staying proactive by reviewing your tax code each time your income or situation changes helps prevent costly errors.

Resolving incorrect tax codes early in the tax year makes it easier to balance your tax contributions throughout the year rather than facing adjustments later.

How Is The 1383M Tax Code Calculated?

The numerical part of a tax code indicates the amount of tax-free income you are entitled to, divided by 10. For 1383M, the total allowance of £13,830 becomes 1383.

The ‘M’ suffix identifies the recipient of the Marriage Allowance transfer. This letter helps HMRC distinguish between different types of allowances and circumstances, such as:

• M: Receiving Marriage Allowance
• N: Giving Marriage Allowance
• L: Standard personal allowance
• T: Other tax code adjustments required

This code ensures payroll systems apply the increased allowance throughout the year.

Breakdown Of Tax Code 1383M Components

Understanding this calculation allows you to determine whether the code on your payslip accurately reflects your entitlement.

Where Can You Find Your Tax Code On Your Payslip?

Your tax code is typically located in the PAYE or tax section of your payslip. It is usually displayed alongside your National Insurance number and gross pay.

You may also find your tax code in the following documents:

• P60: Issued at the end of the tax year
• P45: Provided when leaving a job
• HMRC Personal Tax Account dashboard

Knowing where to look helps you monitor changes and take action quickly if the code is incorrect or unfamiliar.

What Are The Most Common Tax Code Errors In The UK?

Errors in tax codes can cause significant discrepancies in how much tax you pay. While HMRC updates most codes automatically, certain situations may lead to inaccuracies.

Some common mistakes include:

• Being assigned an emergency tax code such as 1257L W1 or M1
• Failing to apply the Marriage Allowance, leading to a lower threshold
• Incorrectly coded second jobs or pensions
• Delays in updating income or employment records

If your code begins with BR or 0T, it usually means no personal allowance is applied. This might be correct for second jobs but should be checked carefully.

Employees should be proactive in reviewing their payslips and tax documents. Prompt communication with HMRC can resolve most code errors before they result in financial loss.

When Should You Contact HMRC About Your 1383M Tax Code?

HMRC should be contacted whenever there is a change that might affect your tax status. This includes:

• Starting or leaving employment
• A change in salary or benefits
• Marriage, civil partnership, or divorce
• Applying for or cancelling Marriage Allowance
• Discrepancies noticed in your payslip or tax code

You can update your details and request code reviews through the HMRC Personal Tax Account or by calling their helpline.

Quick action helps avoid tax underpayments that can result in future deductions or delayed refunds.

How Does The 1383M Tax Code Compare To Other UK Tax Codes?

Understanding how 1383M compares with other common UK tax codes gives context to your own situation.

Here’s a comparison of several typical tax codes and their impact on personal allowance:

Tax Code Comparison Table

Each tax code serves a specific purpose based on an individual’s employment and marital status.

The 1383M code is one of the few that results in an increased allowance, offering more favourable tax conditions for eligible earners.

Conclusion

Understanding the 1383M tax code is essential for ensuring you’re paying the correct amount of tax and taking full advantage of the Marriage Allowance benefit.

With a higher personal allowance, this code can reduce your tax liability and boost your take-home pay.

Always monitor your tax code regularly, especially after changes in your income or personal circumstances.

If anything seems incorrect, contacting HMRC promptly will help you avoid potential issues and ensure your finances remain on track.

FAQs

What does the ‘M’ mean in my tax code?

The ‘M’ signifies that you’ve received a Marriage Allowance transfer from your partner, increasing your tax-free income.

Can I update my tax code if I think it’s wrong?

Yes, you can log into your HMRC Personal Tax Account or contact HMRC directly to request a change.

Is 1383M a good tax code?

Yes, it means you have a higher tax-free allowance due to Marriage Allowance, reducing your overall tax bill.

Will 1383M apply every year?

Only if your eligibility for Marriage Allowance remains valid. Otherwise, HMRC may revert your code.

What if my partner stops earning or our circumstances change?

Your eligibility for Marriage Allowance could change, affecting your tax code. Inform HMRC to keep your code accurate.

How can I claim Marriage Allowance?

You can apply online via HMRC if you meet the eligibility criteria as a married couple or civil partners.

What happens if I’ve overpaid tax but don’t claim it?

It may go unclaimed unless HMRC identifies it through a P800 calculation. It’s better to check proactively.