Around 2 million eligible couples are still not claiming Marriage Allowance, leaving up to £252 a year on the table.
Four million couples claim Marriage Allowance, but HMRC estimates that roughly two million more are entitled to it and simply never have. That is up to £252 a year sitting unclaimed, and because backdating is allowed for up to four complete tax years, a first-time claimant in 2025/26 could receive a lump sum of more than £1,000.
The eligibility rules are narrow enough that most couples do not qualify, which is why so many people assume they never will. Both of the following must be true:
You must also be married or in a civil partnership. Unmarried couples living together are not eligible, no matter how long they have been together.
Say Priya earns £9,000 a year from a part-time job. Her Personal Allowance is £12,570, so she has £3,570 of allowance going to waste; she pays no income tax regardless. Her husband Dev earns £38,000 and pays 20% tax on his income above £12,570.
Priya transfers £1,260 of her unused allowance to Dev. His effective Personal Allowance rises from £12,570 to £13,830. He now pays tax on £38,000 minus £13,830, instead of £38,000 minus £12,570. The extra £1,260 shielded from 20% tax saves him exactly £252 for the year.
Priya's own position? She still pays no tax. Her remaining allowance after the transfer is £11,310, which still comfortably covers her £9,000 income.
If Dev's income crossed into the higher-rate band mid-year, HMRC would cancel the Marriage Allowance going forward. The couple should notify HMRC promptly to avoid an underpayment building up in Dev's tax account.
Once a claim is approved, HMRC adjusts both partners' tax codes automatically. The receiving partner gets the M tax code suffix, which signals that their Personal Allowance has been boosted by 10% (the transferred £1,260). The transferring partner receives the N tax code suffix, indicating they have given away that slice of their allowance.
If you are unsure whether the change has been applied correctly, you can check your tax code online through your Personal Tax Account or by contacting HMRC. It is worth doing, because if the code has not been updated, your employer or pension provider will carry on deducting the wrong amount of tax.
A claim made in the 2025/26 tax year can be backdated through the previous four complete tax years:
| Tax Year | Maximum Saving |
|---|---|
| 2025/26 | £252 |
| 2024/25 | £252 |
| 2023/24 | £252 |
| 2022/23 | £252 |
| 2021/22 | £252 |
| Total | £1,260 |
HMRC pays backdated amounts as a cheque or bank transfer to the receiving partner. You do not need to have been claiming in those years; you simply need to have been eligible. The most common reason people miss out on backdating is not realising it is possible at all.
If a spouse has died since the year you are claiming for, HMRC allows the surviving partner to still make a backdated claim, which is a detail many people and even some accountants overlook.
The single biggest error is the wrong partner making the transfer. The claim must be made by the lower earner (the transferor), not the higher earner. HMRC's online form defaults correctly once you enter both incomes, but if you apply by phone or paper, it is easy to get confused about which direction the transfer runs.
A second common mistake is assuming that because both partners work, neither qualifies. If one partner earns £14,000 and the other earns £45,000, they do not qualify because the lower earner's income already exceeds the Personal Allowance. But if one partner earns £11,000, the gap between their income and the £12,570 allowance means a transfer is well worth making.
The fastest route is through HMRC's online Marriage Allowance service, which takes under five minutes. You will need both partners' National Insurance numbers and an estimate of your incomes for the year. Once approved:
The claim stays in place automatically every year until one of you cancels it, your circumstances change, or one partner's income moves out of the qualifying bands.
Marriage Allowance is one of the few tax reliefs where the government hands you money back for doing almost nothing. If you qualify and have not claimed, do it today.
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