Tax Code M Explained
Tax code M means you have received the Marriage Allowance transfer from your spouse or civil partner. Your Personal Allowance is increased by 10% of the standard allowance — from £12,570 to £13,830. This extra £1,260 of tax-free income saves you up to £252 per year in Income Tax. The M suffix replaces your usual letter (e.g. ML would be written as M).
What does tax code M mean?
Tax code M means you receive the Marriage Allowance transfer from your spouse or civil partner. Your Personal Allowance increases from £12,570 to £13,830, saving you up to £252 per year. Both partners must be basic-rate taxpayers for this to apply.
Who gets tax code M?
Married couples or civil partners where one partner earns below the Personal Allowance (or pays basic rate tax only) and transfers 10% of their allowance to the higher earner. The receiving partner gets an M suffix on their tax code. Both partners must be basic-rate taxpayers — higher or additional rate taxpayers are not eligible.
Take-home pay on tax code M — 2025-26 examples
Examples below show Income Tax and take-home pay at common salary levels. National Insurance (NI) is also shown separately — NI is not affected by your tax code and applies on the same basis for all employees.
| Gross Salary | Income Tax | NI (est.) | Take-Home | Effective IT Rate |
|---|---|---|---|---|
| £20,000 | £1,234 | £594 | £18,172 | 6.2% |
| £25,000 | £2,234 | £994 | £21,772 | 8.9% |
| £30,000 | £3,234 | £1,394 | £25,372 | 10.8% |
| £35,000 | £4,234 | £1,794 | £28,972 | 12.1% |
| £40,000 | £5,234 | £2,194 | £32,572 | 13.1% |
| £45,000 | £6,234 | £2,594 | £36,172 | 13.9% |
| £50,000 | £7,234 | £2,994 | £39,772 | 14.5% |
| £60,000 | £10,928 | £3,211 | £45,861 | 18.2% |
| £75,000 | £16,928 | £3,511 | £54,561 | 22.6% |
| £100,000 | £26,928 | £4,011 | £69,061 | 26.9% |
Take-home = Gross − Income Tax − National Insurance. No pension, student loan or other deductions included. NI calculated at 8% between £12,570–£50,270 and 2% above. Effective IT Rate shows Income Tax as a percentage of gross salary.
Tax code M vs 1257L: take-home comparison
How much more or less you take home on M compared to the standard 1257L code at the same gross salary. A negative number means less take-home pay.
| Gross Salary | 1257L Take-Home | M Take-Home | Difference |
|---|---|---|---|
| £20,000 | £17,920 | £18,172 | +£252 |
| £25,000 | £21,520 | £21,772 | +£252 |
| £30,000 | £25,120 | £25,372 | +£252 |
| £35,000 | £28,720 | £28,972 | +£252 |
| £40,000 | £32,320 | £32,572 | +£252 |
| £45,000 | £35,920 | £36,172 | +£252 |
| £50,000 | £39,520 | £39,772 | +£252 |
| £60,000 | £45,357 | £45,861 | +£504 |
| £75,000 | £54,057 | £54,561 | +£504 |
| £100,000 | £68,557 | £69,061 | +£504 |
Both columns include Income Tax and National Insurance. No pension or student loan deductions. 1257L = standard Personal Allowance of £12,570.
If you have tax code M, here's what you should know
- Your tax code appears on your payslip, P60, and any correspondence from HMRC about your PAYE tax.
- Your employer uses this code to calculate how much Income Tax to deduct from each pay period — they do not set it themselves.
- If your circumstances change (new job, change in benefits, marriage allowance), your code should update automatically — but it is worth checking.
- You can view and update your tax code online via your Personal Tax Account at gov.uk.
- If you think your code is wrong, contact HMRC on 0300 200 3300 or use the HMRC app.
- An incorrect tax code can mean you overpay or underpay tax — overpayments are refunded, underpayments are collected in future years.
Frequently asked questions
What does tax code M mean?
Tax code M means you have received the Marriage Allowance transfer from your spouse or civil partner. Your Personal Allowance is increased by 10% of the standard allowance — from £12,570 to £13,830. This extra £1,260 of tax-free income saves you up to £252 per year in Income Tax. The M suffix replaces your usual letter (e.g. ML would be written as M).
Who gets tax code M?
Married couples or civil partners where one partner earns below the Personal Allowance (or pays basic rate tax only) and transfers 10% of their allowance to the higher earner. The receiving partner gets an M suffix on their tax code. Both partners must be basic-rate taxpayers — higher or additional rate taxpayers are not eligible.
How much do I take home on tax code M earning £30,000?
On tax code M with a £30,000 salary, you take home £25,372 per year (£2,114 per month) after Income Tax of £3,234.
Is tax code M correct for me?
Your tax code is set by HMRC based on your individual circumstances. If you believe your tax code is wrong, contact HMRC on 0300 200 3300 or check your Personal Tax Account at gov.uk. An incorrect code could mean you are paying too much or too little tax.
How do I change tax code M?
To change tax code M, contact HMRC directly on 0300 200 3300 or update your details via your Personal Tax Account at gov.uk. Your employer cannot change your tax code — only HMRC can issue a new one. Once HMRC updates your code, they will notify your employer and the change will appear on your next payslip.
Will I get a refund if tax code M was applied in error?
If tax code M was applied incorrectly and caused you to overpay Income Tax, HMRC will refund the overpayment. This typically happens automatically via a P800 tax calculation sent after the tax year ends (April). For a faster refund, contact HMRC directly once the correct code has been issued. Overpayments can also be reclaimed through Self Assessment if you file a return.
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