Eligible married couples and civil partners can backdate claims for up to five tax years

Millions of married couples and civil partners across the UK are missing out on a tax break worth up to £252 a year, with many also able to claim a backdated lump sum of up to £1,260 from HM Revenue and Customs (HMRC).

Around 2.1 million eligible people have yet to claim Marriage Allowance, which lets couples reduce their tax bill when one partner pays little or no income tax.

The scheme allows one spouse or civil partner to transfer 10 per cent of their personal allowance to the other, increasing the recipient’s tax‑free allowance and reducing the amount of income tax they pay.

HMRC said that Marriage Allowance “keeps money in your pocket by reducing the amount of tax you and your spouse pay by up to £252 a year.”

Personal finance expert Martin Lewis has highlighted the scheme, explaining that eligibility depends on one partner not using their full personal allowance while the other pays income tax at the basic rate.

Mr Lewis said the scheme applies “provided one of you is aged under 90.”

He told viewers: “Clearly you have to be married or civil partners.

"Then what happens is this, each of you have your £12,570 personal allowance. That’s the amount you can earn that you don’t pay tax on each year.”

To qualify across most of the UK, one partner must earn less than the personal allowance of £12,570, while the other must be a basic rate taxpayer.

In Scotland, the higher‑earning partner must have an annual income between £12,571 and £43,662.

Eligible couples can apply through GOV.UK to transfer ten per cent of the non‑taxpaying partner’s personal allowance.

After the transfer, the partner giving up part of their allowance retains a tax‑free allowance of £11,310, while the receiving partner’s allowance increases to £13,830.

Mr Lewis explained: “Now that 10 per cent extra tax‑free allowance they have, remember they would have paid tax on it at 20 per cent, so the gain there is £252 a year.”

He added that most couples will be better off as long as the taxpaying partner earns more than £13,830.

For the current tax year, HMRC adjusts the recipient’s tax code automatically once a claim is approved.

Claims can also be backdated, with HMRC issuing any money owed by cheque or bank transfer.

Couples who have not claimed before can receive a lump sum of up to £1,260, covering the current tax year and the previous four years.

One couple described how they benefited after hearing about the scheme on Mr Lewis’s programme.

They said: “I had retired on medical grounds so I was not paying tax and he said that it is possible to transfer a non‑taxpaying spouse’s tax allowance to their partner.

"Following the show, I went on to the gov.uk website and was surprised how easy it was to complete the forms.”

They said they now receive around £250 each year and were able to claim about £1,000 in backdated tax, which they used to pay for a holiday in Cornwall.

Eligible couples can apply by searching Marriage Allowance on GOV.UK.