Marriage Allowance checker (1257M / 1257N)

The problem

Marriage Allowance is the most-missed tax saving in the UK. HMRC estimates over a million eligible couples have not claimed. The opposite mistake is also common: the allowance gets transferred to the wrong partner, or stays applied after a divorce or income change.

PayslipIQ helps you check whether you have an M or N suffix on your code and whether that matches your circumstances.

Plain-English explanation

How Marriage Allowance works:

• One spouse must be a non-taxpayer or earn below the personal allowance (£12,570).
• The other spouse must be a basic-rate taxpayer (income £12,571 to £50,270).
• The non-taxing spouse transfers £1,260 of allowance to the taxpaying spouse.
• Recipient code: 1257M (allowance £13,830).
• Transferor code: 1257N (allowance £11,310).
• Saving: 20% × £1,260 = £252/year for the recipient.

Marriage Allowance can be backdated up to 4 tax years if you were eligible but did not claim. The claim is made by the lower-earning spouse via gov.uk; HMRC then issues new codes to both employers.

Civil partners are eligible on the same terms. Marriage Allowance is separate from the older Married Couple's Allowance, which only applies if at least one spouse was born before 6 April 1935.

Worked example - £45,000 earner with non-earning spouse

Worked example uses 2026/27 UK figures and is illustrative. Do not use it as a personal tax calculation.

Step by step

1. 1

   Confirm eligibility

   One spouse non-taxpayer or below £12,570. The other a basic-rate taxpayer £12,571–£50,270. Civil partners qualify.

2. 2

   Identify your code

   Recipient should have M-suffix (e.g. 1257M). Transferor should have N-suffix (1257N). Mismatch = wrong allocation.

3. 3

   Reconcile the saving

   Recipient sees ~£21/month less tax than under 1257L. If your monthly tax did not drop after the change, the code may not have flowed through.

4. 4

   Backdate up to 4 years if missed

   Apply via gov.uk Marriage Allowance service. HMRC will refund any over-paid tax for prior years.

5. 5

   Run a free PayslipIQ check

   Upload your redacted payslip or enter the figures manually to confirm the M/N code is producing the expected tax.

What to ask payroll

• ?Is my tax code currently M-suffix or N-suffix?
• ?When did the suffix first appear, and was it backdated?
• ?Has the Marriage Allowance amount applied to the right partner (us vs spouse)?
• ?If we divorced or my spouse's income changed, has HMRC removed the suffix?
• ?Do you need a new P6 from HMRC to apply a backdated change?

When to contact HMRC

• Apply or remove Marriage Allowance via gov.uk/marriage-allowance.
• If circumstances changed (divorce, income change), tell HMRC via the personal tax account.
• Backdated claims for previous years are processed by HMRC repayment.

FAQ

How much is Marriage Allowance worth?

Up to £252/year for the recipient — 20% × £1,260 transferred allowance.

What is the difference between 1257M and 1257N?

1257M is the recipient code (allowance £13,830). 1257N is the transferor code (allowance £11,310). The numeric part stays £12,570 base; the suffix shows the £1,260 adjustment.

Can civil partners claim Marriage Allowance?

Yes. Civil partners are eligible on the same terms.

Can I backdate a Marriage Allowance claim?

Yes — up to 4 tax years if you were eligible. Apply via gov.uk and HMRC will refund any over-paid tax.

What happens after a divorce?

Marriage Allowance does not automatically end. Tell HMRC via your personal tax account; they will remove the M / N suffix and re-issue 1257L codes.

Related checkers

• Wrong tax code checker →
• Tax codes pillar →
• PAYE pillar →
• Emergency tax refund checker →