How Much Does Tax Code M Take From Your Pay?

Tax code M means your spouse or civil partner has transferred £1,260 of their unused personal allowance to you through the Marriage Allowance, lifting your tax-free amount from £12,570 to £13,830 and saving you up to £252 in income tax each year.¹ Anything you earn above £13,830 is taxed at the normal rates for your band.

What the M Suffix Tells Your Employer

The letter at the end of a PAYE code tells your employer or pension provider how to work out your tax-free amount. An M suffix specifically flags you as the recipient of a Marriage Allowance transfer.² The numbers before the letter give you your allowance with the last digit dropped, so the standard 1257L represents £12,570 tax-free and 1383M represents £13,830.

Your employer spreads that tax-free amount evenly across every pay period, which is why the benefit appears in each payslip rather than as a refund at year-end.

How Much You Actually Pay

With code M, the first £13,830 of your annual income is tax-free. In England, Wales, and Northern Ireland, income above that is taxed at the standard bands:

Basic rate of 20% on income from £13,831 to £50,270
Higher rate of 40% on income from £50,271 to £125,140
Additional rate of 45% on income above £125,140

The personal allowance and the basic rate limit are frozen at these levels through the 2027/28 tax year.³

The full-year saving is £252, which is £1,260 multiplied by the 20% basic rate. On a monthly payroll that works out to roughly £21 more in your take-home pay each month. Take someone earning £30,000. Without the transfer they pay 20% on £17,430, a bill of £3,486. With code M they pay 20% on £16,170, a bill of £3,234. The gap is that £252.

The saving caps out at £252 because that’s the tax on the transferred £1,260. Marriage Allowance does not benefit higher-rate taxpayers: if your income takes you into the higher band, you are not eligible and HMRC will not issue the M code.¹

If You Live in Scotland

Scottish taxpayers can still hold code M, and the £1,260 transfer still adds to your tax-free amount, but Scotland uses its own bands: a starter rate of 19%, basic rate of 20%, intermediate rate of 21%, higher rate of 42%, advanced rate of 45%, and top rate of 48%.⁴ Eligibility runs up to the intermediate rate ceiling, meaning the recipient’s income must fall between £12,571 and £43,662. Above £43,662 you no longer qualify.¹

Who Can Receive Code M

Marriage Allowance is only for married couples and civil partners. Cohabiting couples do not qualify no matter how long they have been together. Both partners have to meet income conditions:

The person giving up allowance must earn less than the £12,570 personal allowance, so they have unused tax-free income to transfer.
The recipient must be a basic-rate taxpayer, typically earning between £12,571 and £50,270 in England, Wales, and Northern Ireland, or between £12,571 and £43,662 in Scotland.

If either partner claims the remittance basis for foreign income, Marriage Allowance is not available.¹

Applying and Backdating

The lower-earning partner is the one who applies, not the recipient. The fastest route is the online service on GOV.UK, where you will need both National Insurance numbers. HMRC usually confirms within 24 hours by email.⁵ If you file Self Assessment, you can claim through the return instead.

You can backdate a claim to 6 April 2021, covering any earlier years in which you were both eligible. That can be worth over £1,000 as a lump-sum refund to the recipient, paid on top of the current year’s saving.¹ Once you are set up, the transfer renews automatically each tax year until one of you cancels it.

What Happens to Your Partner’s Code

Every M code has a matching N code on the other side. If you receive the transfer, your partner’s code changes from 1257L to 1191N, dropping their tax-free amount to £11,310. Because they earn below the personal allowance anyway, this normally makes no practical difference to their tax. It only matters if their income rises above £11,310 mid-year, at which point they start paying tax sooner than they otherwise would.

When to Cancel

Marriage Allowance does not always end on its own, and forgetting to cancel is where couples run into trouble. The transfer keeps renewing automatically, so an ex-partner can carry on receiving the benefit while your allowance stays reduced.

On divorce or separation, either partner can cancel, and the cancellation can be backdated to the start of the tax year on 6 April.⁶
If the recipient’s income moves above the basic rate, HMRC should update the code, but check your coding notice so you don’t get an unexpected bill.
If your partner transferred their allowance to you and then died, your higher allowance runs to the end of the tax year on 5 April, and their estate is treated as having the reduced allowance.⁶
If you transferred your allowance and your partner died, your own allowance returns to the normal amount for the rest of the tax year.

If Your Code Looks Wrong

If you have been put on an emergency code after starting a new job, hand your new employer the P45 from your previous one. HMRC generally updates the code within 35 days of receiving details from both employers.⁷ If more than 35 days have passed and the code still looks wrong, check and update it through the HMRC online service or by calling the Income Tax helpline.

Overpayments caused by a wrong code entitle you to a refund. Underpayments are usually collected by adjusting next year’s code rather than demanding the shortfall in one go. Catching the error early is what keeps the bill small.

1
GOV.UK. Marriage Allowance: How It Works
2
HM Revenue & Customs. PAYE Manual – Coding: Codes: How They Are Used and Calculated: Suffix Codes: The Suffix
3
GOV.UK. Income Tax Personal Allowance and the Basic Rate Limit From 6 April 2026 to 5 April 2028
4
Scottish Government. Scottish Income Tax 2025 to 2026: Factsheet
5
GOV.UK. Apply for Marriage Allowance Online
6
GOV.UK. Marriage Allowance: If Your Circumstances Change
7
GOV.UK. Emergency Tax Codes