The Marriage Allowance is one of those reliefs that sounds complicated but is actually straightforward once you understand the basics. It's also one of the most consistently unclaimed tax reliefs in the UK — HMRC has repeatedly reported that millions of eligible couples have never applied. If you're married or in a civil partnership and one of you earns less than the personal allowance, there's a good chance you're leaving money on the table.
How it works
The personal allowance for 2026/27 is £12,570 — the amount of income each person can earn before paying income tax. If one partner doesn't use all of their personal allowance (because they earn less than £12,570, or don't work at all), they can transfer 10% of it — £1,260 — to their spouse or civil partner.
The receiving partner gets that £1,260 added to their own personal allowance, giving them a total allowance of £13,830 instead of £12,570. At the basic rate of 20%, that's a tax saving of £252 a year. Not life-changing, but over a few years it adds up — and it costs absolutely nothing to apply.
Who qualifies
You must be married or in a civil partnership — cohabiting couples do not qualify, which is worth noting if you're in a long-term relationship but haven't formalised it.
The transferring partner must have an income below the personal allowance of £12,570. This includes people who are not working, part-time workers with low earnings, and people whose only income is below the threshold — a small amount of rental income, pension income, or savings interest that puts their total below £12,570 all qualify.
The receiving partner must be a basic rate taxpayer — meaning their total income falls between £12,570 and £50,270 in 2026/27. If the receiving partner is a higher-rate taxpayer (earning above £50,270), they don't qualify for the Marriage Allowance. The logic is that higher-rate taxpayers already receive more tax relief on their allowances, and this specific relief is aimed at basic rate couples.
Both partners must also be resident in the UK for tax purposes.
What it's not
The Marriage Allowance is sometimes confused with the older Married Couple's Allowance, which is a different relief entirely and only applies to couples where at least one partner was born before 6 April 1935. The Marriage Allowance introduced in 2015 is a separate, modern relief for younger couples. If you're reading about the older one, check which your situation falls under.
How to claim
The lower-earning partner makes the claim, not the higher earner. You apply through the HMRC website at gov.uk/apply-marriage-allowance — you'll need both partners' National Insurance numbers and to confirm a few details. It takes about ten minutes online and there's no cost.
Once approved, HMRC will adjust the higher earner's tax code to reflect the increased personal allowance (the code will typically change from 1257L to 1383M). It's then applied automatically through payroll or Self Assessment going forward.
Backdating — this is where it gets interesting
You can backdate a claim by up to four tax years. As of May 2026, that means you could potentially claim for 2022/23, 2023/24, 2024/25, and 2025/26 — on top of the current year. The saving for each backdated year is £252 (based on the personal allowance in that year), so the total backdated refund could be over £1,000 if you've been eligible for all four years.
Backdated amounts are paid as a tax refund, usually directly to the lower-earning partner's bank account or deducted from any tax owed. HMRC is generally prompt about processing these — most people receive their backdated refund within a few weeks.
If you've never claimed and you've been married for a few years, it's genuinely worth spending ten minutes to apply. The sums aren't enormous but it's free money and the process is straightforward.
What happens if your circumstances change?
If the lower earner's income increases above £12,570 in a future year, you should cancel the transfer, because you'd no longer be eligible and could end up with an incorrect tax code. You can cancel via your HMRC Personal Tax Account online.
Similarly, if one partner becomes a higher-rate taxpayer — perhaps through a pay rise or additional income — the allowance no longer applies and should be cancelled.
The allowance also ceases if the couple separates or if one partner dies, though in the latter case there are specific rules about the year of death that your accountant or HMRC can advise on.
A note on the State Pension
One thing worth clarifying: the Marriage Allowance has no effect whatsoever on either partner's State Pension entitlement. State Pension is based on National Insurance contributions, not income tax. Transferring part of your personal allowance doesn't affect NI records.
Check now — it takes ten minutes
The honest answer to whether you should claim is: if you're eligible, yes, always. There's no downside. The lower earner doesn't lose their entire personal allowance — they keep 90% of it. The higher earner simply pays slightly less tax. It's one of the few tax reliefs that is genuinely simple and costs nothing to obtain.
Go to gov.uk/apply-marriage-allowance and check. If you're eligible and haven't claimed, do it today and backdate as far as you can.