Legacy incomes will reach £5bn a year by the start of the next decade, new figures show.
Research by the charity legacy consortium Legacy Foresight estimates legacy income will be worth £19.6bn between now and 2025 and climb to £23bn in the second half of the decade.
The consortium predicts that charities will receive £5bn in legacy income in 2030 from 146,000 bequests.
Total UK legacy income grew from £800m in 1990 to £3bn in 2020, an annual growth rate of 4.5 per cent a year, it said.
After considering inflation, income is up by 2.7 per cent a year, which means that the real value of gifts in wills to UK charities has doubled over 30 years.
Over the same period the number of charitable bequests rose by almost 50 per cent to 112,000 in 2020.
Legacy Foresight said that because of the size, wealth and lifestyles of the Baby Boomer generation, legacy incomes are expected to double again in real terms by 2050.
The consortium estimates that 40 per cent of all UK deaths result in a will at probate and 16 per cent of those wills at probate are now charitable.
On average, there are 3.3 charitable gifts per will, as 38 per cent of charitable wills contain just one bequest and 28 per cent include four or more.
Legacy Foresight also found that more specialised and often local cause areas are gaining ground.
Over the past 10 years, the fastest-growing sub-sectors have been air ambulances (14 per cent a year) and wildlife trusts, followed by arts and education charities, NHS hospitals and mental health charities.
Legacy notifications are expected to reach record numbers in 2021 and 2022.
The consortium found that grants of probate were 30 per cent higher in the first half of 2021 than the same period in 2020.
At the same time, Legacy Monitor Consortium notifications in the three months to March 2021 were the highest Legacy Foresight has seen in the 14-year history of its monitor, up 18 per cent on the same time last year.
This suggests that some of the problems related to probate applications could be starting to unwind, said the consortium, but those applications started to fall away again over the summer.
It said anecdotal evidence suggested there were ongoing delays throughout the process, so the challenges for the sector would likely continue well into 2022.
Jon Franklin, economist at Legacy Foresight, said: “After a difficult couple of years, the outlook for legacy incomes is promising.
“However, the strength of the recovery is highly dependent on the pace at which delays in the estate administration process can be unwound.”
A report published at the end of last month by Legacy Foresight revealed legacy income growth in Scotland had outstripped the rest of Britain over the past five years.