How and where do ii ISA millionaires invest?

• The number of ii ISA millionaires has risen by 61%, from 1,001 at the end of January 2024 to 1,607
• The not-so-secret sauce to becoming an ISA millionaire: time, patience and investment compounding
• Early birds: 32% of total 12-month subscriptions from ii’s ISA millionaires were added between 6 and 30 April 2024
• Gender split: 67% of ii’s ISA millionaires are male, and 33% are female
• Flat-fee benefit: ii ISA millionaires’ monthly platform fee remains constant as the value of their investments grow. They keep more of what they make
• Calculated: how to become an ISA millionaire by the age of 65
• interactive investor has launched a new tool enabling investors to gauge how long it would take for them to achieve ISA millionaire status based on their current investing behaviour.

interactive investor (ii) is the most popular investment platform for ISA millionaires*, with the number of investors holding seven-figure accounts on the platform soaring to a record high of 1,607.

• Learn with ii: How to become an ISA millionaire | ISA Investment Ideas | Top ISA Funds

As of 28 February 2025, this represents a 61% increase from the 1,001 recorded at the end of January 2024. The average age of an ii ISA millionaire is 73 - one year younger than in January 2024.

ISA millionaires have likely benefited from a strong year for investments. The most recent ii Index, which tracks customer portfolio performance, shows that the average customer with a seven-figure portfolio (not limited to ISA millionaires) achieved an 11.2% return in 2024. This outpaced the 9.5% median return achieved by customers with lower-value portfolios.

Myron Jobson, Senior Personal Finance Analyst, interactive investor, says: “ISAs have been a game changer for investors, offering a tax-free shelter for savings and investments that allows every penny of profit to work harder. The not-so-secret recipe for building a seven-figure ISA portfolio is patience. The fact that the average ISA millionaire is 73 years old underscores a simple truth: time in the market is key to building long-term wealth.

“Many of these investors have benefited from decades of compounding, with some capital dating back to the days of TESSAs and PEPs before ISAs came into play. It’s a testament to the power of long-term investing and making the most of tax-efficient wrappers.”

How do ii ISA millionaires invest?

Like ii’s broader ISA customer base, investment trusts, equities, and funds are the most-popular asset classes among ii ISA millionaires — but their portfolio weightings differ significantly.

• Investment trusts: 41% of the average portfolio for ISA millionaires vs 34% for ii’s broader ISA base
• Equities: 35% vs 26%
• Funds: 13% vs 22%
• Cash holdings: 5% vs 7%
• Exchange-traded products (ETPs): 5% vs 9%

Average portfolio split among ii ISA millionaires and broader ii ISA cohort

Source interactive investor.

Where do ii’s ISA millionaires invest?

Top 10 most-held investments (by volume) among ii millionaires and broader ii ISA cohort

Source: interactive investor

Richard Hunter, Head of Markets, interactive investor, says:“Compounding is the effect of an initial lump sum plus interest earned, and then effectively interest on that interest. Over time, compound interest becomes an increasingly powerful engine of growth, leading Albert Einstein to describe the phenomenon as the eighth wonder of the world, adding that “He who understands it, earns it. He who doesn’t, pays it.”

“This is certainly not lost on our ISA millionaires, whose portfolios are littered with high-yielding shares which support this narrative. Quite apart from this list of blue-chip companies providing the additional possibility of capital growth, the high levels of income add to the total return which they have clearly enjoyed. Examples of those companies which are in our top 10 of shares held are Legal & General (dividend yield 8.4%), Aviva (6.6%), BP (5.7%), National Grid (4.8%), Lloyds Banking (4.4%) and Shell (4.1%). 

“While some have also reaped the benefit of exposure to what has been a burgeoning tech sector in the US through Scottish Mortgage, the income theme is the one which clearly shines the brightest among these shrewd investors.”

Gender breakdown

Some 67% of ii’s ISA millionaires are male, and 33% female. Both sexes have a similar portfolio asset allocation – although female ISA millionaires have more in investment trusts then men (37% versus 34%), and less in direct equities (47% versus 50% for men).

On average, male ISA millionaires make 14 more active trades per year than their female counterparts (34 vs 19.5).

Source: interactive investor.

ii ISA millionaire habits

• They start early: 32% of ISA millionaire contributions for the year were made between 6 and 30 April 2024 - just after the new tax year began.
• They trade actively: ISA millionaires made an average of 32 active trades per year (excluding regular investing).

How to become an ISA millionaire by the age of 65

ii has calculated how much first-time investors at different ages need to invest each year to reach £1 million by age 65. The assumptions are:

• 5% annual investment growth
• Contributions increasing by 2% per year
• Investments made at the start of each year

Under these assumptions for first time ISA investors:

• A 25-year-old would need to invest £6,000 in the first year, increasing contributions annually by 2%, leading to total contributions of £362,400 over time.
• A 35-year-old would need to start with £11,400 per year.
• A 40-year-old would need to begin with £16,400 per year.
• Note: those above the age of 42 would be required to contribute more than the permitted ISA allowance to become an ISA millionaire by 65.

Source: interactive investor. Assumptions - investment value at age 65, annual investment at the beginning of each year, 5% investment growth, 2% annual increase in contributions.

Myron Jobson says: “Time in the market is your best friend when it comes to building wealth. The sooner you start investing, the more you can harness the power of compounding returns, making it significantly easier to reach the coveted ISA millionaire status. Consistency is key - regular contributions, even modest ones, can snowball over the years into a substantial pot, especially with the generous tax benefits ISAs offer. 

“Becoming an ISA millionaire is a great goal, but it’s important to remember that inflation means £1 million in the future won’t be worth as much as it is today. £1 million today is the equivalent of almost £533,000 in 1999 when ISAs were launched.

“As prices rise over time, the real purchasing power of your investments erodes, meaning you’ll need to accumulate a larger nominal sum to maintain the same standard of living. This makes starting early even more crucial - not only does it give your money more time to grow, but it also helps counteract the effects of inflation through long-term investment returns.”

ii’s new ISA millionaire tool

interactive investor has launched a new tool allowing investors to estimate how long it would take to reach ISA millionaire status based on their current investing habits. Users can input their portfolio value and planned monthly contributions to get a personalised projection. Cookies must be enabled to use the tool.

*interactive investor: the most-popular investment platform for ISA millionaires

interactive investor is the most-popular investment platform among ISA millionaires. The number of ISA millionaires on interactive investor, the UK’s second largest DIY investment platform, now stands at 1,607 (as of 28 February 2025) - almost 300 more than the total from our largest competitor Hargreaves Lansdown (1,322 as of December 2024). 

There were some 4,850 Britons with a seven-figure ISA portfolio by the end of the financial year in 2022 (latest figure available), according to data obtained following a freedom of information (FOI) request.

Myron Jobson says: “Our popularity among ISA millionaires is a clear endorsement and recognition of the quality of our offerings – not least our flat monthly platform fee. By offering transparent and predictable charges on investments, we empower our clients to keep more of their wealth, even as the value of their portfolio increased compared to percentage-based fees that escalate with portfolio growth. These savings can be substantial and life-changing over a lifetime of saving.”