The number of Isa millionaires has surged by more than 50% in a year – to reach around 7,730, according to figures obtained by a money app.

Plum obtained the figure, which was rounded to the nearest 10, from HM Revenue and Customs (HMRC), following a freedom of information (FOI) request.

HMRC said that, as at April 5 2024, the estimated number of individuals with total Isa holdings of £1 million or more was 7,730.

The figure marks a 52% jump – or 2,660 new members of the Isa millionaires club – compared with 5,070 Isa millionaires that HMRC previously said were recorded by April 2023.

According to HMRC’s latest response to Plum, the average Isa millionaire was sitting on a pot worth around £1,348,000 in April 2024.

The mean average market value of the top 25 Isa millionaire holdings was £11,928,000, rounded to the nearest £1,000.

The majority of Isa millionaires, at around 7,300, were sitting on amounts worth £1,000,000 to £1,999,999 in April 2024.

Meanwhile around 60 had pots worth £4,000,000-plus. The average value of holdings among this group was £7,708,000.

HMRC also cautioned that figures should be used as a “guide” – as individual level Isa data is provided to it annually by Isa managers, however each year a proportion will enter records incorrectly, or fail to submit.

Isas enable savers to turbo-boost their funds as accounts that are ringfenced from tax.

Will Bryant, director of wealth strategy at Plum, said: “A jump of more than 50% in a single year is really telling.”

He said the Isa millionaires are not people who “suddenly saved” their way to £1 million.

Highlightng the benefits of compound interest boosting pots over time, he added: “It’s the result of years of patient investing, where the growth on your growth starts doing the heavy lifting. That’s the bit people underestimate.

“These figures underline the value of investing and the importance of taking a long-term approach.

“Despite the geopolitical volatility of recent years, global markets powered by the US stock market have continued to climb.”

In April 2027, the annual cash Isa limit will be slashed from £20,000 to £12,000 for savers aged under 65, although the overall annual Isa allowance will remain at £20,000.

The cash Isa allowance for people aged 65 and over will remain at £20,000.

Mr Bryant said the changes “may lead people to use more of their stocks and shares Isa to make full use of their tax-free allowance,” but he added: “Many people simply won’t know what’s changing.”

Figures released by HMRC in September showed around £135.7 billion was subscribed to adult Isas in the tax year 2024-25 – a £32.7 billion annual increase.

The £32.7 billion increase was driven by a rise in cash Isa subscriptions, which grew by 37.5% or £26.1 billion.

Stocks and shares Isa subscriptions saw a 19.7% or £6.1 billion annual increase, and Lifetime Isa subscriptions had a 20.1% or £472 million rise.

Maike Currie, vice president of personal finance at PensionBee, said: “Isas are one of Britain’s great savings success stories.

“Their beauty lies in their simplicity: a straightforward, tax-efficient way for ordinary people to build wealth and take greater control of their financial futures.

“And you don’t need to become an Isa millionaire to benefit.”

Ms Currie said cutting the cash Isa allowance and introducing additional restrictions “risks making a simple product unnecessarily complicated, potentially undermining confidence at precisely the time we need more people saving and investing”.

Katie Horne, banks relationship manager at Flagstone, said: “The beauty of the Isa is that it allows savers to take risk through stocks and shares investments at points in their lives when it makes sense, and then to de-risk through cash savings at others.

“The appeal of the Isa has been its completeness and simplicity – two factors which are now at risk.”