There are now 5,070 confirmed ISA millionaires and an additional 2,770 investors sitting on pots of between £900,000-£999,999, according to HMRC.
There were 4,700 ISA investors with pots between £800,000 and £899,999 within the data from 5 April 2023 shared with money app Plum by HMRC under a Freedom of Information request.
Assuming these investors achieved a typical global tracker rate, many of these are now likely to have seen their ISA fortunes surpass £1m by this year.
Plum’s analysis of the HMRC data suggests that ISA millionaire numbers should pass 40,000 within the next 10 years.
It also suggests that there are now more ISA millionaires than lottery millionaires.
Since its launch in 1994, the UK National Lottery has created more than 7,700 millionaires across all games and is currently creating around 400 a year.
Rajan Lakhani of Plum said: “Few people could ever have imagined that when the ISA launched, it would one day be creating tens of thousands of millionaires and changing more lives than the National Lottery.
“But this is exactly the scenario that’s on the horizon according to HMRC’s own numbers, even allowing for the kind of stock market dips which are part and parcel of the investing cycle.”
ISAs were introduced in 1999, replacing their predecessor Personal Equity Plans (PEPs) which were launched in 1987 by then chancellor Nigel Lawson with an annual allowance of £2,400.
Liberal Democrat peer Lord Lee of Trafford became the first publicly declared ISA millionaire in 2003.
A new £12,000 contribution limit for Cash ISAs will take effect on 6 April 2027, as the government looks to spur greater investment in Stocks & Shares ISAs, which will keep their £20,000 ceiling.