Tax Code M and N Explained: Marriage Allowance UK 2026/27

UK tax codes ending in M or N indicate that one half of a married couple or civil partnership is using the Marriage Allowance. The M-suffix code goes to the higher-earning partner (who receives part of their spouse's Personal Allowance), and the N-suffix code goes to the lower-earning partner (who gives away part of theirs). The annual saving for the couple is £252.

This guide explains both codes, how to verify they're correct on your payslip, and what to do if you spot one and don't recognise it.

What M and N mean

The Marriage Allowance lets one partner transfer 10% of their Personal Allowance to the other. For 2026/27 that's £1,260 transferred (10% of £12,570).

When the transfer is in effect:

• The lower earner's tax code is reduced by £1,260 of allowance and gets the N suffix.
  • Example: 1257L becomes 1131N (£11,310 allowance - £12,570 minus £1,260).
• The higher earner's tax code is increased by £1,260 of allowance and gets the M suffix.
  • Example: 1257L becomes 1383M (£13,830 allowance - £12,570 plus £1,260).

The maths nets to a £252 saving for the couple per year (£1,260 of additional tax-free allowance × the basic rate of 20% = £252).

How to spot it on your payslip

Look at the tax-code field on your payslip. If it ends in:

• M - you're the receiver. Your tax-free allowance has been increased.
• N - you're the giver. Your tax-free allowance has been reduced.
• Plain L - neither code is in effect; either you haven't claimed Marriage Allowance, or the claim hasn't yet propagated.

Common variants you'll see:

• 1383M / 1131N (the standard Personal Allowance pair).
• 1257M / 1132N (in years where the Personal Allowance has shifted).
• S1383M / S1131N (Scottish residents).
• C1383M / C1131N (Welsh residents).

Verifying the code is correct

Three checks:

1. Your circumstances qualify

You qualify if all of these are true:

• You're married or in a civil partnership (cohabiting partners don't qualify).
• One of you earns LESS than £12,570 (the Personal Allowance).
• The other earns BETWEEN £12,571 and £50,270 (basic-rate UK), or £12,571-£43,662 (basic-rate Scotland).
• Neither of you was born before 6 April 1935 (which would qualify you for the older Married Couple's Allowance instead).

If any of these aren't true, the M/N codes shouldn't be in effect - check whether someone in the household made the application by mistake.

2. The code direction matches who-earns-what

• The LOWER earner gets the N code (gives away part of their allowance).
• The HIGHER earner gets the M code (receives part of their partner's allowance).

If you have the wrong code direction (you're the higher earner but you have N, or vice versa), the application was filed in the wrong direction. The fix: cancel the application and re-apply with the correct partner as the claimant.

3. The numeric portion is right

For 2026/27 with Personal Allowance £12,570:

• N code numeric portion: 1131 (£11,310 allowance)
• M code numeric portion: 1383 (£13,830 allowance)

Other adjustments (BIKs, prior-year underpayments) may change the numeric portion further. Your P2 coding notice will explain.

Why your code might be M or N when you didn't apply

Three possibilities:

1. Your spouse applied without telling you

The Marriage Allowance application is made by the LOWER earner (the one giving away part of their allowance). If your partner applied, you'd see the M suffix on your code without doing anything yourself. This is the most common reason for an unexpected M code.

2. HMRC made an automatic application after a Self Assessment return

In some cases HMRC reviews Self Assessment returns and identifies eligibility for Marriage Allowance, applying it automatically and informing both partners by P2 coding notice.

3. Carried over from a previous year

Once Marriage Allowance is granted, it auto-renews each year unless cancelled. If you applied 3 years ago and your circumstances have changed (you separated, the lower earner's income rose above £12,570), the codes can stay in place even though they're no longer correct.

How to claim Marriage Allowance

If your codes are not M/N and you think you should qualify:

1. The lower-earning partner signs in to their HMRC Personal Tax Account.
2. Search "Marriage Allowance" or visit gov.uk/marriage-allowance.
3. Enter the higher earner's National Insurance number and your date of marriage / civil partnership.
4. Tick the years to claim (current + up to 4 backdated).
5. Submit.

The codes update from the next pay cycle. Backdated refunds (worth up to £252 × 4 = £1,008 plus current year) are paid by cheque or direct payment within ~6 weeks.

See our full Marriage Allowance step-by-step guide.

How to cancel Marriage Allowance

You should cancel if:

• You separate or divorce.
• The lower earner starts earning above £12,570.
• The higher earner crosses into the higher-rate band (above £50,270 UK or £43,662 Scotland).

Cancellation is done from the HMRC Personal Tax Account. Either partner can cancel at any time. The codes update from the next tax year - you don't lose the current year's benefit if you cancel mid-year.

Why we don't recommend a Marriage Allowance refund firm

Various firms market themselves as "Marriage Allowance specialists" and offer to claim for a fee. They take 20-35% of the refund.

For an annual £252 (or backdated max £1,512 for 4 years), the firm fee is £50-£530. The HMRC online claim takes ten minutes and is free. Doing it yourself is overwhelmingly the right call.

Disclaimer

PayslipIQ provides automated educational guidance based on the figures you supply. It is not regulated tax advice. The Marriage Allowance interacts with other tax codes (BIKs, K codes, Self Assessment income) in ways outside the scope of this guide. For unusual circumstances or contested HMRC determinations, contact HMRC on 0300 200 3300 or use a CTA-qualified tax adviser.