How Brits can hit the ISA jackpot and become a millionaire | Personal Finance | Finance

Putting away a steady slice of your salary and investing it wisely could be enough to turn an ordinary saver into an ISA millionaire – in little more than two decades.

Fresh analysis shows that someone maxing out their ISA allowance and achieving solid long-term investment returns could build a £1 million tax-free pot far sooner than many expect.

Dan Coatsworth, Head of Markets at AJ Bell, said becoming an ISA millionaire “needn’t be a fantasy” for those prepared to be disciplined.

“Becoming an ISA millionaire needn’t be a fantasy if you are diligent with saving and investing,” he said.

“It can become a reality in just over 21 years for those able to contribute the maximum allowed in an ISA each year and achieve a reasonable rate of return. Even though you might have to make some sacrifices along the way, the rewards certainly make it worthwhile.”

Savers can invest up to £20,000 a year into ISAs. For those without a lump sum, that works out at £1,666.66 a month if the full allowance is used. Mr Coatsworth said someone investing that amount and achieving a 7% annual return after charges could reach £1 million after 21 years and 10 months, based on historical trends.

Not everyone can afford to save that much, however. A more realistic contribution for many might be £1,200 a month – around a third of take-home pay for someone earning £60,000 a year, once rent or mortgage costs and bills are covered.

At that level, and assuming the same 7% annual return after charges, it would take 25 years and nine months to hit the £1 million mark.

“It would take someone 25 years and nine months to hit £1 million in an ISA based on £1,200 monthly contributions and 7% annual investment returns after charges,” Mr Coatsworth said.

“If you’re in your thirties or early forties and feel like it’s time to get serious about investing, these figures could provide the pick-me-up you need to form a plan and get going.”

He added that a 35-year-old investing £1,200 a month could, in theory, reach retirement at 60 with a £1 million ISA – although inflation would reduce its future buying power.

Can you get there faster?

While 7% is considered a reasonable long-term return, some parts of the market have historically delivered far higher gains. AJ Bell tested what would have happened if an investor had followed the £1,200-a-month plan from 1 January 2000, investing into different Investment Association (IA) sectors.

Using this approach, seven out of 10 sectors had already passed the £1 million mark by the end of January 2026, with one more almost there.

For simplicity, the calculations assumed the ISA allowance was always £20,000, even though it only reached that level in 2017. Returns are based on total returns, including reinvested dividends. Mr Coatsworth stressed the figures are illustrative only and not a guide to future performance.

How did the sectors perform?

India proved the standout performer, hitting £1 million in just 15 years and eight months and topping £2 million after 23 years and nine months.

“India was the most lucrative money maker,” Mr Coatsworth said, pointing to strong earnings growth, rising domestic consumption, better corporate governance and political reform.

China came second, reaching £1 million in June 2020, followed by North America in March 2021, helped by booming US technology stocks. However, he warned that high equity valuations are now a concern in both India and the US, noting that their main indices lagged markets such as Brazil, Japan, Europe, the UK and China during 2025.

The global sector reached £1 million after 24 years, with Europe ex-UK just three months behind – a result that may surprise many investors. UK and Japanese shares delivered returns close to the long-run 7% average. An investor in the IA UK All-Companies sector would now have £979,746, putting them 98% of the way to the £1 million target.

Multi-asset funds lagged behind, reflecting their greater exposure to bonds. Someone investing £1,200 a month into the IA Mixed Investment 40–85% sector would have around £900,000, while the more cautious 20–60% sector would be only 71% of the way to £1 million.

Mr Coatsworth said it would be “highly unlikely” for most investors to put all their ISA money into a single sector.

“Most people will take a pick ’n’ mix approach, filling their ISA with goodies from around the world,” he said.

“Diversification is an investor’s best friend as you never know when one part of your portfolio will need propping up by another bit.”

His final advice was simple: consistency matters more than clever guesses.

“Form a plan, don’t miss a monthly payment into your ISA, and stick with it through good and bad times,” he said.

“It’s just like eating healthily and exercising regularly – stick at it, and you could see big results.”