The Prime Minister has proposed married couples should get breaks worth up to £200 a year.
However the allowance will not be available to couples that include higher rate taxpayers – in which one spouse is paid £42,285 from 2015/16 – this could be a double blow for higher earners, particularly in the wake of the child benefit cuts on families with one earner on more than 60,000 a year.
The proposal, will also let people transfer £1,000 of their personal tax allowance to their spouse or civil partner.
The measure will come into force in April 2015 if passed by parliament, just one month before the next national election and is expected to benefit around 4 million couples including same-sex couples in civil partnerships. From next year, same-sex couples will be able to marry under a new law passed by parliament in July.