What do the M and N suffixes on my tax code mean for Marriage Allowance?

Full answer

Marriage Allowance lets a spouse or civil partner who is a non-taxpayer (or has unused Personal Allowance) transfer up to £1,260 of that unused allowance to a partner who is a basic rate taxpayer, and this transfer is reflected directly in both partners' tax codes using specific suffix letters that often confuse people who spot them on a payslip without understanding what they mean. **The 'M' suffix -- you are receiving the transfer** If your tax code ends in 'M' (for example 1383M for 2026/27, reflecting the standard £12,570 Personal Allowance plus the £1,260 transferred amount, expressed in the code's numerical format), this means your partner has successfully transferred their Marriage Allowance to you, increasing your own tax-free Personal Allowance by £1,260 -- meaning you pay £252 less tax over the year (20% x £1,260), spread across your pay periods via a slightly higher tax-free amount each time you are paid. **The 'N' suffix -- you are giving away part of your allowance** If your tax code ends in 'N' (for example 1131N, reflecting £12,570 minus the £1,260 transferred away), this means YOU are the partner who has given up £1,260 of your own Personal Allowance to transfer to your spouse or civil partner -- your own tax-free amount is reduced by £1,260, meaning slightly more of your income becomes taxable, but since you were (by definition, to qualify for the transfer) not using all of your allowance anyway as a non-taxpayer or low earner, this generally does not create any actual extra tax for you, while your partner benefits from the extra allowance. **Worked example** Emma earns £11,000 a year (below her full £12,570 Personal Allowance, so she is not fully using it and pays no Income Tax anyway) and transfers £1,260 of her unused allowance to her husband Tom, a basic rate taxpayer earning £35,000. Emma's tax code changes to reflect the 'N' suffix (her allowance reduced to £11,310, coded as 1131N) -- but since her income was already below her ORIGINAL allowance, this reduction makes no practical difference to her tax bill (she still pays no tax, since her income remains below even the reduced allowance). Tom's tax code changes to reflect the 'M' suffix (his allowance increased to £13,830, coded as 1383M), meaning £1,260 more of his income is tax-free, saving him £252 over the year (20% x £1,260) through slightly lower tax deductions each payday. **Why understanding the suffix matters** If you unexpectedly see an 'N' suffix on your tax code and did NOT deliberately apply for Marriage Allowance transfer, this could indicate an application was made (correctly or in error) that you should check, since it directly reduces your own tax-free allowance -- conversely, if you were expecting to see an 'M' suffix reflecting an application your partner made on your behalf but your tax code has not updated, it is worth checking with HMRC that the transfer has actually been processed and applied to your code, since the tax saving only takes effect once the code changes. **How the transfer is set up in the first place** The partner giving up allowance (who will end up with the 'N' suffix) applies via HMRC's online Marriage Allowance service, gov.uk, or by phone -- the transfer, once approved, automatically updates both partners' tax codes with the 'N' and 'M' suffixes respectively, and can also be backdated up to 4 previous tax years if eligibility existed but the transfer was never claimed.

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