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More than a million married and civil partnered couples are still eligible for a tax break but have yet to claim it, HM Revenue and Customs has said.

The Marriage Allowance is worth up to £238 a year, and backdated payments of up to £662 could also be available.

There was criticism that the allowance, aimed at couples with one major source of income, was not easy to claim.

However, the government said that the new online application took fewer than 10 minutes to complete.

So far, about three million couples have successfully applied for the allowance.

Financial secretary to the Treasury Mel Stride said: "This is a really important tax relief and reflects the social importance of marriages and civil partnerships. I'd urge those that haven't yet managed to claim the money to do so right away."

HMRC has organised several advertising campaigns to persuade people to apply for Marriage Allowance, but has been frustrated by the lack of take-up.

How Marriage Allowance works