Soaring house prices and frozen bands have pushed inheritance tax receipts collected between April and July this year up 14 per cent to £2.4bn.
The figure is £300mn higher than at the same point last year, according to HM Revenue & Customs.
The nil rate band, below which no inheritance tax is paid, has been £325,000 since 2009, and is due to be reviewed in 2026.
This is despite the average cost of a UK property having risen by £140,129 since April 2009 to June 2022, pushing more and more sellers above the band.
Tax and financial planning expert at Quilter, Shaun Moore, said the potential slowdown in property prices, supply and demand may keep them high.
“No longer is IHT the preserve of the rich and many estates are having to pay the tax simply because of their property wealth,” he said.
“IHT is proving to be more and more lucrative for the Treasury.”
Meanwhile, this week, the UK saw prices rise by the steepest gradient in 40 years last month, as concerns grew about the worsening cost of living crisis.
The consumer prices index leaped 10.1 per cent in the 12 months to July this year, according to the Office for National Statistics, confounding analysts’ expectations.
Wealth Club chief executive Alex Davies said "rampant” inflation will only increase the impact of frozen allowances in future years unless the new prime minister intervenes.
“While just four per cent of estates pay inheritance tax at the moment, without some review of the rules, more and more families are going to find themselves hit by death duties they might not have expected,” he said.
Homes or estates with a value above £325,000 are taxed at 40 per cent.
IHT reform is a potential vote winner for the new leader of the Conservative party, Davies said, but it is “hard to imagine” it will be top of their agenda in an emergency budget.
“Cutting inheritance tax will do nothing to ease the cost of living crisis engulfing the country, and it’s a real cash cow for the Treasury too," he added.
"IHT generates around £800mn in tax revenue each month, a very meaningful sum at a time when 29mn households are being given £400 each to offset energy bills.”
Inheritance tax receipts have been rising steadily in the past few months, with receipts for the second quarter of the year coming in £300mn higher than in the same period in 2020.
Group communications director at Just Group, Stephen Lowe, said it is increasingly important for people to assess the full value of their entire estate and seek help on how the tax rules apply to them.
“For some people, options such as lifetime mortgages can unlock a portion of the wealth tied up in bricks and mortar,” he said.
“Passing on this wealth through ‘living inheritances’ allows people to see the benefit for recipients and it can also help minimise the inheritance tax payable on their estates.”