For many families, the thought of becoming millionaires might feel like a pipe dream. However, with smart investing and a bit of discipline, it’s possible for a family of four to have reached the coveted £1 million mark in as little as 10 years.  

A family of four who has diligently maxed out their ISA allowances for the past 10 years will be on the cusp of the £1 million milestone, thanks to generous ISA allowances and the compounding effect of investment growth.  

Currently, a family could invest £58,000 a year in ISAs, using two adult ISA allowances and two Junior ISA allowances. However, the current ISA limits are far more generous than they were a decade ago. Back then, the total amount needed to max out the ISA allowances for a family of four was £38,640.  

But if the family of four had invested their full allowance each year for the past 10 years in a global tracker fund like the Fidelity World Index (BJS8SJ3), their total investment would be worth approximately £990,582 as of March 2025. A little additional investment growth in the coming months or their contributions in the new tax year would push them past the £1 million mark. 

STARTING THE JOURNEY

What if you didn’t start your ISA journey 10 years ago but want to become a millionaire family today? It’s still possible, although unsurprisingly it requires a significant annual investment. We’ve modelled it based on annual ISA allowances remaining the same as they are today, meaning a family of four would need to invest £58,000 annually, no small feat. 

For this to work, the two parents would need to contribute £20,000 each year to their individual ISAs, which could grow to £372,000 each after 13 years, assuming an annual investment return of 5% after charges. Simultaneously, £9,000 would need to be invested in each child’s Junior ISA each year, growing to £266,000 per child over the same period if they saw the same 5% investment growth a year. After 13 years, this family could see a total ISA pot of £1,079,000, leaping past family millionaire status.

If you took more risk, and were rewarded with higher returns, you could reach that golden million faster: increasing the annual investment returns to 7% after charges could allow a family to reach millionaire status in just over 11 years.  

If the £58,000 annual investment isn’t feasible, it’s still possible to reach the £1 million target, but it will take longer. For instance, a family could hit the target in 18 years by investing £12,000 per year into each adult’s ISA (or £1,000 per month), alongside £5,000 annually into each child’s Junior ISA. With a 5% return after charges, this strategy could accumulate over £1 million by the time the children reach adulthood. 

MAXIMISING ISA ALLOWANCES 

With the tax year-end fast approaching, it’s important to consider how to make the most of your ISA allowances. While many people focus solely on adult ISAs, overlooking Junior ISAs can be a costly mistake. The Junior ISA allowance is very generous and investing it can significantly boost a family’s wealth.  

Reaching £1 million is just the beginning. Once the family’s ISA pot reaches millionaire status, there are many ways to put that wealth to work. By investing in income-generating assets, the family could potentially earn a tax-free income of around £40,000 per year, equivalent to a taxable salary of £51,000, which could significantly boost the family’s financial security. 

However, there’s an important consideration when it comes to Junior ISAs. These accounts are in the children’s names and will transfer to them once they turn 18. While this can be a great financial gift, it also means the children could choose to withdraw the funds at that time, potentially jeopardising the family’s millionaire status. 

Note: Data accurate as of 5th March 2025. 

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