Chancellor George Osborne is expected to use his first all-Conservative Budget on Wednesday to deliver the party's promise to end inheritance tax on family homes worth up to £1 million.
It is understood that Mr Osborne is preparing to confirm that a new allowance enabling parents to pass on the main family home to their children tax-free after their death will come into effect from April 2017.
The pledge effectively to take all but the most expensive homes out of inheritance tax - at an estimated £1 billion cost to the Exchequer - was a key plank of the Conservatives' general election manifesto.
David Cameron said at the time that the party was responding to the "most basic, human and natural instinct there is" for parents to be able to pass on something to their children.
Mr Osborne and Mr Cameron had first promised to cut inheritance tax in 2007 – a move which was widely credited with deterring Gordon Brown from calling a snap general election he had been expected to win.
However, following the 2010 general election, the scheme was blocked by their Liberal Democrat coalition partners.
At the time of last May's election, the Tories estimated by 2020 that 22,000 families could benefit from the proposed new £175,000 main residence allowance.
The allowance will be transferable on the death of one spouse and added to the existing £325,000 transferable allowance to bring the tax-free total up to £1 million.
But on properties worth more than £2 million, the allowance would be gradually tapered away until it was worth nothing to those with homes worth more than £2.35 million.
Since the election, it is understood that the plan has been tweaked so that where couples have "downsized" to a smaller property after their children have left home, the allowance will still apply to the old family home.
The manifesto said that the scheme - which will be available to married couples or civil partners - would be funded by a raid on pension tax reliefs for people earning over £150,000.
In a joint article in The Times, Mr Cameron and Mr Osborne said: "It can only be right that when you've worked hard to own your own home, it will go to your family and not the taxman."