Recent data from HM Revenue & Customs reveals a significant rise in the number of investors holding Individual Savings Accounts (ISAs) valued at over £1 million, with figures showing more than 7,700 such investors as of April 2024—a 50% increase compared to the previous year. Given stock market gains of approximately 25% since then, industry experts estimate the number of ISA millionaires has now exceeded 10,000.

ISAs offer a tax-efficient investment vehicle, allowing investors to grow their savings free from income or capital gains tax, with the added benefit of flexible access to funds, unlike pensions. The opportunity to build substantial wealth through ISAs has attracted considerable interest, especially among long-term investors.

Among those achieving millionaire status through ISAs is Stephen Pavey, a 75-year-old retired finance director from Brighton, who credits his investment success to starting early in his 30s, maintaining steady contributions irrespective of market fluctuations, and holding a diversified portfolio. Pavey highlights the value of adopting a buy-and-hold strategy inspired by investor Warren Buffett and emphasizes that remaining invested through market volatility is critical to long-term growth. He also notes the educational aspect of investing, mentioning how attending annual general meetings of funds and trusts keeps him informed on emerging trends like artificial intelligence.

Another veteran investor, Lord Lee of Trafford, who became the first ISA millionaire in 2003, attributes his success to patience, consistent investing, and a disciplined approach that involves allocating a portion of disposable income to investments rather than spending it. Both investors stress the importance of beginning early, maximizing annual ISA allowances, and maintaining a long-term perspective.

Financial analysis by wealth manager JM Finn supports these views, illustrating how regular contributions combined with compound returns can generate million-pound ISA portfolios over time. For instance, an individual starting at age 21, contributing £8,000 annually with a 7% average return, could accumulate over £2.6 million by age 65. Higher contributions or greater returns could accelerate this growth, allowing some to achieve millionaire status before retirement. Conversely, those starting later, such as at age 55, face longer horizons to reach similar milestones, underscoring the advantage of early and sustained investing.

JM Finn’s research also explores the impact of increasing annual contributions to £15,600 or roughly £1,300 monthly. Under these conditions, even investors who begin later in life could potentially reach the ISA millionaire milestone within their lifetime, assuming steady market returns. However, the projections include several caveats: future market performance may vary, government policies on ISA allowances and tax benefits could change, and factors like inflation and management fees may erode returns.

Successful investors recommend several strategies for those aiming to build substantial ISA portfolios. These include setting up stocks-and-shares ISAs (including Junior ISAs for children to benefit from tax advantages early), investing what one can afford regularly, using the full annual ISA allowance, and constructing diversified portfolios comprising UK shares and global investment trusts with solid dividend histories. Reinvesting dividends to harness compounding effects and resisting the urge to frequently trade during market fluctuations are also advised.

Additionally, the investors advocate for maintaining interest and involvement in one’s investments, attending company meetings when possible, and developing an understanding of market and social trends. They caution against withdrawing funds prematurely during the accumulation phase but encourage planning for how to effectively utilize ISA wealth during retirement, whether for personal enjoyment, inheritance planning, or charitable giving.

While becoming an ISA millionaire requires discipline, time, and a favorable market environment, the experiences shared by established investors and the financial modeling suggest that building significant, tax-efficient wealth through ISAs is achievable for many who start early and invest consistently.