According to new data on ISA millionaires, nearly a quarter of a billion pounds is now held in a handful of ISA accounts.
A series of Freedom of Information requests from Investengine has revealed that the top 25 highest-value ISAs in the UK now hold a combined total of £222m in assets.
The findings mean each of the top 25 account holders has, on average, £8.9m in their accounts.
Introduced in 1999, the ISA initially allowed only £2,400 to be deposited annually, though this has gradually increased over the years. The current limit is £20,000, up from £15,240 in 2017.
An ISA that had been maxed out since their existence would have only seen £345,816 deposited, meaning ISA millionaires must have tripled their original investment.
John Lee, a stock picker and Financial Times columnist became the first publicly declared ISA millionaire in 2003. He reached it on contributions of £126,200 made over a period of 16 years. His annualised returns during the period were 21 per cent.
Now, new data has revealed that the number of ISA millionaires in the UK surged to 4,850, a near 10-fold increase since 2016, when there were only 450 ISA millionaires, according to HMRC.
“A quarter of a century on from their launch, ISAs continue to be a crucial vehicle for so many when it comes to growing their wealth over time,” said Andrew Prosser, head of investments at Investengine.
“We are now seeing that approach paying dividends, with the rapid increase in the number of both ISA millionaires and now multi-millionaires.
“Given the comparably limited long-term potential of cash ISAs, even for those who have maxed their accounts since their inception and received good interest rates, we can be confident that those attaining millionaire status have invested tax free in the stock market via their ISAs.