The credit crunch has cut the inheritance that 16m Britons intend to leave their families, says a survey of 2,000 people by Lincoln Financial — but plummeting asset prices could prove a boon for those who have acquired estates in the past few years.

House prices have dropped 22% since they began falling in November 2007, the Nationwide house-price index shows, and those who inherited estates before then could reclaim £1 billion from the Revenue, figures from Grant Thornton for The Sunday Times reveal. Beneficiaries must pay inheritance tax (IHT) within six months of the end of the month of the donor’s death (although they can apply to pay IHT on property in instalments over 10 years). The amount is based on “probate” value — a valuation of the assets on death. If assets are sold for less than that value in the next four years, IHT can be reclaimed on the difference, but must be done within 12 months of the sale.

More than 38,000 estates paid inheritance tax in 2005-6 on residential property worth £11.86 billion. They could reclaim IHT, levied at a penal 40%, on a collective fall in value of £2.59 billion, said Mike Warburton at Grant Thornton.

People who inherited property in the subsequent three tax years could also claim huge rebates. Those who miss the four-year window because of failure to sell on the open market, could sell to an “in-house buyer” — a relative or friend, for example — said Leonie Kerswill at Price Waterhouse Coopers.

However, Warburton warned of a potential trap. Until tax changes last year introduced the ability to transfer the IHT threshold (£312,000) between spouses, it was advisable to hold a property jointly, so that when one spouse died half the value of the home, up to that threshold, was passed to children.

When the second spouse died, the executors could claim a discount of 10%-15% on the value, to account for the difficulty in selling half a house. If beneficiaries later apply for a rebate, the discount will be clawed back, and could leave you worse off.

“Unfortunately, once you try to claim the rebate, you can’t go back, and I’ve come across a string of cases where executors have been caught out,” said Warburton.

Those who inherited share portfolios that have also fallen in value could, similarly, claim a rebate. The relevant forms are IHT38, for property, and IHT35, for shares.