Revealed: UK’s biggest ISAs stand at more than £11.6 million each

The top 25 ISAs are worth an average of £11,660,000 each, according to HMRC data - bigger than the country’s largest pension pot. We uncover the secrets of the ISA millionaires.

Pile of pound coins and pound notes
(Image credit: Getty Images)

Britain’s most dedicated ISA investors have built up pots worth more than £11.6 million, overtaking the country’s largest pension pot.

According to a Freedom of Information (FOI) request by wealth manager RBC Brewin Dolphin, the 25 largest ISAs in the country are worth £11,660,000 each on average. The top ISA millionaires will have fortunes even higher than this figure.

The wealth manager said the millionaires would have “amassed this war chest through stocks and shares investing”. 

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Rob Burgeman, investment manager at RBC Brewin Dolphin, said: “It’s highly unlikely you will ever make it to millionaires’ row by patiently saving into a cash ISA.”

Meanwhile, the largest ISAs are bigger than the country’s top pension pot. A separate FOI request by RBC Brewin Dolphin last year revealed the biggest pension pot tracked by the Office of National Statistics currently stands at £11 million.

We look at how ISA investors could have racked up eight-figure sums, how many ISA millionaires there are, and how ISAs compare to pensions.

The secrets of the ISA millionaires 

HMRC data reveals that according to the latest figures for 2020-21, the 25 largest ISA pots in the UK are worth an average of £11,660,000.

The most anyone could have saved into an ISA, or its predecessor personal equity plan (PEP), is £310,760, according to RBC Brewin Dolphin.

The wealth manager found that an ISA investor maxing out their allowances over the 34 years from when PEPs launched in 1987 to 2020-21 would have required annualised returns of 18.9% to reach a pot worth £11.6million. Turbo-charged growth of this kind could only have been achieved through stocks and shares investing, said Burgeman. 

In comparison, average cash savings over the same 34-year period would have grown from £310,760 to just £424,966 - but because of inflation savers would actually have been worse off in real terms.

“In fact, you would have needed your savings to grow by a further £40,000 to £464,669 just to maintain purchasing power.”

In terms of how quickly someone could have amassed £11.6 million in their ISA, the wealth manager estimates that starting in 1987, the investor would have needed about 20 years to reach £1 million with contributions of around £127,200 assuming an 18.9% annualised return after fees. 

It would have taken a further eight years to reach £5 million on contributions of £215,520. The £11.6 million figure would have been reached after 34 years on total contributions of £310,760.

Someone starting from scratch today could get there quicker due to the £20,000 annual ISA allowance. The limit has grown since ISAs were introduced 25 years ago. In 1999, the limit was £7,000. A decade ago, in 2013-14, the annual allowance had risen to £11,520. It has now been frozen at £20,000 since 2017-18.

RBC Brewin Dolphin says someone maxing out the current allowance into a stocks & shares ISA could “reasonably expect to reach millionaires’ row in around 25 years assuming annualised returns of 5% after fees”.

Who are the ISA millionaires?

According to the most recent HMRC figures, ISA millionaire numbers trebled year-on-year to hit a record high of 4,070 in 2020-21. The average ISA millionaire has a pot of £1.39 million. 

Lord Lee of Trafford, an expert stock-picker, became the first publicly declared ISA millionaire in 2003, reaching the seven-figure milestone on contributions of £126,200 made over 16 years. 

The fund supermarket Interactive Investor says it has 1,001 ISA millionaires on its platform. Their average age is 74, compared with an average age of 57 for the overall ISA cohort. About 65% of them are male, and 35% female, which is in line with the platform’s wider ISA customer base. 

ISA millionaires tend to be early birds: 40% of the total 12-month subscriptions from Interactive Investor’s ISA millionaires were added between 6 and 30 April last year. 

Meanwhile, investment trusts account for more than 40% of a typical ISA millionaire portfolio.

Over at Hargreaves Lansdown, it has 836 ISA millionaires on its platform - up from 573 last year. 

Investment platform AJ Bell has also seen a rise in its number of ISA millionaires, with an increase of 119% over the past year.

AJ Bell ISA millionaires tend to hold shares over funds, with 75% in company stocks and trusts, preferring blue-chip dividend-paying stocks over blue-sky companies. Their average age is 72. The youngest ISA millionaire on the platform is just 36 years old.

How do ISAs compare to pensions?

It can be tricky weighing up whether an ISA or pension is better to build your wealth. Pensions offer generous tax breaks on contributions, but ISAs can be more flexible when it comes to the type of accounts and how you can access your money.

Burgeman said: “Many will be surprised to learn that the largest ISA pots have overtaken the largest pension pots - especially when you consider that the current annual allowance on pensions is three times greater than the current ISA allowance (£60,000 versus £20,000).”

He added: “While a good investment plan should undoubtedly incorporate both ISAs and pensions, the ISA’s phenomenal appeal is perhaps underpinned by the flexibility it offers investors in terms of liquidity.

“Investors can make withdrawals at a time of their choosing regardless of their age, whereas pension savers must wait until they turn 57 to start spending their retirement pot.”

We have lots of analysis on how ISAs and pensions compare in Saving for retirement: ISAs vs. SIPPs.

While an £11.6 million ISA might seem unattainable, reaching £1 million across both ISAs and pensions is more achievable, especially when you factor in tax relief and employer contributions to your pension.

“Money saved regularly into tax wrappers over long periods can produce impressive results, thanks to the mathematical phenomenon of compounding, or interest on your interest. As your pots grow, so does the interest you earn each year,” commented Burgeman.

Ruth Emery

Ruth is passionate about helping people feel more confident about their finances. She was previously editor of Times Money Mentor, and prior to that was deputy Money editor at The Sunday Times. 

A multi-award winning journalist, Ruth started her career on a pensions magazine at the FT Group, and has also worked at Money Observer and Money Advice Service. 

Outside of work, she is a mum to two young children, a magistrate and an NHS volunteer.