What does the M suffix mean on my tax code?

M means you have received the Marriage Allowance transfer from your spouse or civil partner — your Personal Allowance is increased by £1,260, saving you £252 in income tax per year. Code 1383M = £13,830 tax-free.

What does the N suffix mean on my tax code?

N means you have given £1,260 of your Personal Allowance to your spouse or civil partner — your PA is reduced from £12,570 to £11,310. Code 1131N. You may pay slightly more tax if your income exceeds £11,310, but the couple's overall saving is £252 per year through your spouse's reduced bill.

Can I backdate Marriage Allowance?

Yes, up to 4 tax years. So a claim in May 2026 can backdate to 6 April 2022. HMRC refunds the previous years separately — either via tax-code adjustment, P800 letter, or direct refund. Potential first-claim refund: ~£1,000.

What do tax codes M and N mean?

Last reviewed by the UK Tax Drag editorial team · 12 May 2026 · How we review · Next review due 12 November 2026 · See what changed · Report an error

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Tax codes ending in M (e.g. 1383M) mean you have received the Marriage Allowance transfer — you get an extra £1,260 of PA. Codes ending in N (e.g. 1131N) mean you gave your spouse £1,260 of your PA. Net effect: £252/yr of income tax saving for the couple, claimed by the higher earner. Eligible only when one spouse earns under £12,570 and the other under £50,270.

How Marriage Allowance changes your tax code

The Marriage Allowance transfer is exactly £1,260 per year — 10% of the £12,570 Personal Allowance. The codes shift to reflect the change:

	Standard code	After Marriage Allowance transfer
Recipient (higher earner)	1257L (£12,570 tax-free)	1383M (£13,830 tax-free)
Giver (lower earner)	1257L (£12,570 tax-free)	1131N (£11,310 tax-free)

Net effect for the couple:

Recipient saves 20% × £1,260 = £252 in income tax per year
Giver pays slightly more tax only if their income exceeds £11,310 (which is below the standard £12,570)
If the giver earns less than £11,310, the transfer is "free" — no tax impact on them

Who qualifies for Marriage Allowance

Both spouses (or civil partners) must meet all conditions:

Married or in a civil partnership. Cohabiting couples don’t qualify.
Lower earner has income under £12,570 (their unused PA is what gets transferred).
Higher earner has income under £50,270 in England, Wales, Northern Ireland (or £43,662 in Scotland, the intermediate-rate threshold).
Both spouses were born after 6 April 1935 (older couples may qualify for Married Couple’s Allowance instead, which is more valuable).

If the higher earner crosses into higher rate at £50,270, eligibility ends. The transfer auto-renews each year until one spouse signals a change.

When MA isn't worth it

Almost always worth claimingThe £252/yr saving is small but free if both spouses meet the criteria. It can be backdated 4 tax years (potentially £1,000+ refund), and auto-renews each year. The HMRC application takes 5 minutes online.

The only cases where MA isn’t worth claiming:

The lower earner’s income is between £11,310 and £12,570 — they actually owe some tax after the transfer (because £1,131 of their PA was transferred away). Net household saving may be tiny or zero.
The higher earner is so close to the £50,270 higher-rate threshold that they expect to cross it within the year. Once in higher rate, MA is no longer available and the giver’s PA stays at £11,310 unnecessarily.
You’re separated or divorced — MA only applies to couples living together (or briefly apart for work).

Worked example — couple with £8k + £40k income

Wife earns £8,000 (well under £12,570). Husband earns £40,000 (basic rate).

	Without Marriage Allowance	With Marriage Allowance
Wife’s code	1257L	1131N
Wife’s tax	£0	£0 (still under £11,310 PA)
Husband’s code	1257L	1383M
Husband’s tax	£5,486	£5,234
Household tax saving	£252 per year

£252 a year × backdated 4 years = potential £1,008 refund on first claim. The Marriage Allowance checker confirms eligibility.

How to claim or cancel Marriage Allowance

To claimThe lower earner applies via gov.uk/marriage-allowance. You need your NI number and your spouse’s NI number plus date of birth. The application takes 5 minutes. HMRC updates both tax codes within 30 days.

To backdateYou can claim for the previous 4 tax years (i.e. up to April 2022 from a May 2026 claim). HMRC refunds those years separately — either via tax-code adjustment in the current year, P800 letter, or direct refund to bank account.

To cancelIf circumstances change (e.g. lower earner’s income rises above £12,570, or higher earner crosses into higher rate), cancel via gov.uk. The change takes effect from the start of the next tax year. Cancelling doesn’t trigger any clawback if you were eligible at the time.

Check Marriage Allowance eligibility

The Marriage Allowance checker confirms whether you qualify based on both spouses’ income, including the 4-year backdate.

Open the MA checker →

Other UK tax codes explained

Sources and methodology

Marriage Allowance rules from gov.uk/marriage-allowance. Tax code letter explanation from gov.uk/tax-codes. How does Marriage Allowance work at gov.uk/marriage-allowance/how-it-works.

UK Tax Drag is not authorised by the Financial Conduct Authority and does not provide regulated financial advice — see the content disclaimer for the full position. The methodology page documents how every calculator is built and reviewed.

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