The number of ISA millionaires looks set to more than treble in just three years by April 2026, according to analysis of recent HM Revenue & Customs data by Rathbones.
The data, obtained via a Freedom of Information request from Rathbones, showed that at the start of the 2023/24 tax year, 5,070 people held ISA portfolios worth £1 million or more.
A further 48,160 individuals had ISA holdings between £500,000 and £750,000, 9,430 had between £750,000 and under £950,000 and 1,210 were on the cusp of millionaire status, worth between £950,000 and £1million.
Rathbones’ analysis suggests the number of ISA millionaires could have risen to around 17,600 by April 2026 from just 5,070 in April 2023, assuming 8% annual investment growth and full use of the £20,000 ISA allowance each year.
Historically, the number of ISA millionaires has at least doubled every three years since 2016 and more than trebled during periods when MSCI World returns exceeded 15%.
Angela Smith, senior investment director at Rathbones, said: “Our analysis of the data suggests the number of ISA millionaires is likely to have risen significantly over a relatively short period, even on modest assumptions. This means many more investors are now benefiting from tax-free growth, income and dividends on seven-figure portfolios.
“Our experience with clients shows that the not-so-secret ingredients behind building an ISA millionaire portfolio are patience, time, consistently using ISA allowances, and avoiding interruptions to the power of compounding.”
Rathbones said that even if savers stopped contributing to their ISAs altogether after April 2023, an 8% annual return could still lift the number of ISA millionaires from 5,070 to around 7,100 by April 2024, nearly 9,510 by April 2025 and almost 13,100 by April 2026.
Under a more cautious assumption of 5% annual investment returns, the number of ISA millionaires would still rise to around 12,300 by April 2026 if the ISA allowance were fully used each year, or to 9,300 if no further contributions were made.
Smith added: “Even after investment gains, £1 million is no longer what it used to be. To have the same £1 million buying power as 20 years ago, investors today would need £1.7 million. Inflation steadily erodes purchasing power, which is why saving alone is rarely enough. Investing wisely, across assets such as shares and funds, can help deliver returns that outpace inflation and protect and grow wealth over the long term.”
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