interactive investor sees a 79% increase in ISA millionaires over the last year: how and where do the millionaires invest? 

interactive investor (ii) has seen a 79% increase in ISA millionaires on its platform, as the number of investors holding seven-figure accounts on the platform hit a record-high of 2,869* – up from 1,607 recorded at the end of February 2025.

The average age of an ii ISA millionaire is 72 – one year younger than in February 2025.

ii’s ISA millionaires’ portfolios have returned an impressive 57% in the last six years. This compares to 47.7% across the entire ii customer base**.

Camilla Esmund, senior manager at interactive investor, says: “ISAs can be powerful tools for long-term wealth, offering investors a tax-free shelter that allows their money to work harder for them. Naturally, ISA millionaires on interactive investor are fee-savvy, which can make a huge difference over time, and time is one of the greatest assets when it comes to investing.

“We can’t control the markets, but we can control how much we pay to invest. If you know what you are paying in fees and you’re confident that those fees are not eating into your pot which should be compounding over time, you’re going to be keeping more of your money.

“The other core building blocks for a seven-figure ISA pot are staying invested and being diversified. It doesn’t sound glamourous, but ultimately, it requires time and patience. This isn’t always an easy strategy, considering the inevitable ups and downs in the markets, but the impressive performance of interactive investor customers is a powerful case study in the power of holding your nerve and letting compounding do the heavy lifting. Time in the market is what counts, especially if your portfolio is well-balanced.”

How do ii ISA millionaires invest?

ISA millionaires have a mix of funds, equities, and investment trusts, but their portfolio weightings differ to the average ii customer portfolio.

• Investment trusts: 33% of the average portfolio for ISA millionaires vs 15% for ii’s broader ISA base
• Equities: 36% vs 33%
• Funds: 18% vs 28%
• Cash holdings: 4% vs 8%
• Exchange-traded products (ETPs): 8% vs 13%

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

Source interactive investor.

Over the last year, ISA millionaires have slightly changed how they fill their own portfolios. They have lowered their allocations to investment trusts (33%, down from 41%) and allocated more to funds (18%, up from 13%) and ETPs (8%, up from 5%).

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

Commenting, Richard Hunter, Head of Markets, interactive investor, says: “It is not just a question of getting there, but of staying there.

“The list of most popular holdings among ISA millionaires suggests that these investors do not stop when they hit the psychological £1 million mark, but rather keep adjusting their portfolios to reflect the changing investment landscape.

“There are examples of stocks which may have helped in the ascent to the magic number, where the likes of National Grid (dividend yield 3.4% even after a recent dividend cut), Shell (3.6%) and BP (5.2%) have been traditionally generous payers, enabling the investor to benefit from the wonders of compound interest over a period of time. In addition, the likes of Lloyds Banking and Rolls-Royce, whose shares have risen by 126% and 271% respectively over the last two years, will have provided a timely boost to these portfolios.

“In any event, these investors are to be congratulated on two fronts. Firstly, by recognising and adapting to the sectors which are currently seeing the benefit of an evolving investment landscape, and doing so without losing sight of the gains to be made from investment over the long term, which has clearly been a successful strategy.”

Gender breakdown

Some 69% of ii’s ISA millionaires are men, and 31% women. Both have a similar portfolio asset allocation, although female ISA millionaires have more in investment trusts then men (18% versus 13%), less in direct equities (31% versus 33% for men), and less in ETPs (11% versus 13%).

On average, male ISA millionaires make 12 more active trades per year than their female counterparts (34 vs 22, respectively).

Source: interactive investor

ii ISA millionaire habits

They start early: 28% of ISA millionaire contributions for the year were made between 6 and 30 April 2025 – just after the new tax year began.

They trade actively: ISA millionaires made an average of 30 active trades per year (excluding regular investing).

How can I become an ISA millionaire?

interactive investor 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
• Monthly investments needed

Under these assumptions, for first time ISA investors:

• An 18-year-old would need to invest £320 per month, totalling £3,840 in the first year, increasing contributions annually by 2%, leading to total contributions of £294,977 over time.
• A 25-year-old would need to start with £490 per month.
• A 35-year-old would need to start with £960 per month.
• A 40-year-old would need to begin with £1,380 per month.

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. Assumes 5% annual growth, and contributions increase by 2% per year.

*Data to 18 February 2026

**Data from interactive investor’s latest ii Index

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