Four million couples will benefit from a new marriage tax allowance to be unveiled by David Cameron on Saturday.
The Prime Minister believes marriage is an important institution at the heart of a strong society.
The new allowance – a Conservative manifesto pledge – shows the government values commitment by recognising marriage and civil partnerships in the tax system.
The proposal will let people transfer £1,000 of their personal tax allowance to their spouse or civil partner.
This is more generous than the £750 allowance promised in the Conservative manifesto. The scheme – which will start in April 2015 – will be worth up to £200 a year for four million couples, including 15,000 in civil partnerships.
They will receive the benefit from the scheme at the end of the tax year in 2016.
In an article for The Daily Mail on Saturday, Mr Cameron will say:
"I believe in marriage. Alongside the birth of my children, my wedding was the happiest day of my life. Since then, Samantha and I have been a team. Nothing I've done since – becoming a Member of Parliament, leader of my party or Prime Minister – would have been possible without her.
"There is something special about marriage: it's a declaration of commitment, responsibility and stability that helps to bind families. The values of marriage are give and take, support and sacrifice – values that we need more of in this country.
"When I ran for the leadership of my party back in 2005, I said that I wanted to do more for marriage in the tax system: a personal pledge that I made right at the start of my campaign – and I then backed that up with a pledge in our manifesto at the last election. So this week at the Conservative Party's conference in Manchester, I'm going to deliver on the promise I made.
"In effect, if you pay the basic rate of tax and your partner doesn't use all of their personal allowance, you'll be able to have some of it. Most couples who benefit will be £200 a year better off as a result.
"And of course this will be true if you're gay or straight – and in a civil partnership or a marriage. This summer I was proud to make Equal Marriage the law. Love is love, commitment is commitment."
Clare and Chris are a married couple. Chris works full-time and earns £25,000 a year, while Clare works three days a week and earns £9,000 a year. By 2015-16 they would both be expected to have a tax-free allowance of £10,200.
They go online and register for the new marriage tax allowance. Clare transfers £1,000 of her allowance to Chris.
In 2015-16, this means Chris now has a tax-free allowance of £11,200, while Clare's is £9,200 – and saves the couple £200 a year.