FACTBOX: Who pays what in inheritance tax:

LONDON - The Conservatives have pledged to raise the threshold for Inheritance Tax (IHT) to one million pounds. Here is some background on one of Britain's most hated taxes.

-- IHT was introduced in 1986, a successor to the old estate duty. It is payable at 40 percent on anything over the present 2007/8 threshold of 300,000 pounds. The threshold, which is due to rise to 350,000 by 2010, has been rising more slowly than people's wealth, meaning thousands more are being dragged into the net every year.

-- the government says that only six percent of estates pay IHT but a Scottish Widows survey put the figure at around 40 percent and the Conservatives say the figure is around 30 percent.

-- IHT's unpopularity, apart from its image as a tax on dying, stems mainly from the argument that a person's assets have already been taxed once, at source, and that IHT is just a second bite at the cherry.

-- it is often jokingly called a "voluntary tax" because of the large number of schemes that can be used to minimise or avoid it.

-- IHT revenues to the government have gone up 49 percent in the last five years. The tax is expected to bring in 3.6 billion pounds in 2006/7.