A tax code M meaning is straightforward: the M at the end of your code tells you that you’ve received 10% of your spouse’s or civil partner’s Personal Allowance through the Marriage Allowance scheme. Your tax-free income is £1,260 higher than the standard £12,570, which saves you up to £252 in income tax over the year.1GOV.UK. What Your Tax Code Means The code is an instruction from HMRC to your employer or pension provider to apply that larger tax-free amount before working out your deductions.2GOV.UK. Tax Codes
What the M Suffix Tells You
Every UK tax code has a number and a letter. The number is your total tax-free allowance divided by ten, and the letter tells your employer how to treat it. An M specifically identifies you as the partner who has received a Marriage Allowance transfer.1GOV.UK. What Your Tax Code Means Your spouse or civil partner will have the mirror code, ending in N, because they’ve given up part of their allowance to you.3HM Revenue & Customs. PAYE Manual – PAYE11075
The transfer sits in sections 55B and 55C of the Income Tax Act 2007. The amount is fixed: 10% of the standard Personal Allowance, rounded up to the nearest £10, which comes to exactly £1,260 while the Personal Allowance is £12,570.4Legislation.gov.uk. Income Tax Act 2007 – Section 55B The Personal Allowance is frozen at £12,570 through at least the 2027/28 tax year, so the figures stay the same for now.
How Much It Changes Your Pay
With the transfer applied, your Personal Allowance rises from £12,570 to £13,830, and your code typically changes from 1257L to 1383M. That extra £1,260 of tax-free income is worth up to £252 a year at the 20% basic rate.5GOV.UK. Marriage Allowance – How It Works
The saving is capped at “up to” £252 because you only get the full benefit if you have at least £1,260 of income that would otherwise be taxed at 20%. If you earn less than that above the standard Personal Allowance, your saving is smaller. The transfer can’t be split across years or carried forward.
On the other side, your partner’s allowance drops from £12,570 to £11,310 and their code becomes 1131N. Since they need to be earning below the Personal Allowance to qualify in the first place, that reduction normally costs them nothing.
Who Can Hold an M Code
You must be married or in a registered civil partnership. Living together without either doesn’t count, however long you’ve been together.
As the receiving partner, your income needs to sit within the basic rate band. In England, Wales, and Northern Ireland that means £12,571 to £50,270.6GOV.UK. Income Tax Rates and Personal Allowances Higher-rate and additional-rate taxpayers are not eligible. Your partner, meanwhile, must earn less than £12,570, since they’re the one giving up unused allowance.5GOV.UK. Marriage Allowance – How It Works Neither of you can be claiming the older Married Couple’s Allowance at the same time.4Legislation.gov.uk. Income Tax Act 2007 – Section 55B
If You Pay Scottish Income Tax
Scotland has its own bands, so the rule is worded differently. As the recipient you can pay the starter rate (19%), basic rate (20%), or intermediate rate (21%) and still qualify, which generally means income between £12,571 and £43,662.5GOV.UK. Marriage Allowance – How It Works Scotland’s higher rate starts at £43,663.7Scottish Government. Scottish Income Tax 2025 to 2026 Factsheet The transfer amount and the £252 maximum saving are the same wherever in the UK you live.
How the Code Ends Up on Your Payslip
The lower-earning partner is the one who applies, because they’re the person electing to give up part of their allowance. Once HMRC accepts the application, they issue a revised coding notice to your employer or pension provider, and the M shows up on your next payslip.
The transfer then renews automatically each tax year. Neither of you needs to reapply.5GOV.UK. Marriage Allowance – How It Works That’s convenient, but it’s also the reason the next section matters.
When You Need to Cancel It
Because the M code stays put until someone actively removes it, you need to tell HMRC when your circumstances change. Divorce, dissolution of a civil partnership, or legal separation all require the Marriage Allowance to be cancelled. Either partner can do this online or by calling HMRC on 0300 200 3300.8GOV.UK. Marriage Allowance – If Your Circumstances Change
If you file Self Assessment, leaving the Marriage Allowance box blank on your return does not cancel the transfer. You have to cancel it separately through the online portal or by phone.8GOV.UK. Marriage Allowance – If Your Circumstances Change
The other trigger is your income rising above the basic rate threshold (£50,270 in England, Wales, and Northern Ireland; £43,662 in Scotland). At that point you’re no longer eligible, and if the M code stays on your record you’ll build up an underpayment that HMRC will later recover by adjusting a future tax code.
If your partner dies during the tax year, the law leaves the benefit in place for the remainder of that year rather than stripping it out mid-year.4Legislation.gov.uk. Income Tax Act 2007 – Section 55B