The average value of the top 25 stocks and shares ISA pots is approximately 17 times greater than the average of the largest cash ISA accounts, according to data from HM Revenue and Customs (HMRC). A freedom of information (FOI) request submitted to HMRC by InvestEngine revealed that the average value of the top 25 highest value stocks and shares ISAs stands at £10,980,000.

In contrast, the average value of the top 25 highest value cash ISAs is only £640,000 for the tax year 2022/23. These figures, based on the number of accounts rather than account holders, were rounded to the nearest £10,000.

The HMRC document also disclosed that there were roughly 3,080 ISA accounts with a market value exceeding £1 million in 2022/23. It recorded 30 cash ISA accounts holding over £500,000 and 38,680 stocks and shares accounts containing at least £500,000 during the tax year 2022/23. The figures were rounded to the nearest 10.

While around 1,530 cash ISAs held more than £250,000, the total for stocks and shares ISAs was £244,570 in 2022/23. Speculation regarding potential changes to the cash ISA limit has heightened in the lead-up to the Budget.

Andrew Prosser, head of investments at InvestEngine, stated that the data obtained through the FOI “reveals a clear and growing divide between saving and investing”.

He said: “While cash ISAs will always have an important role, especially for shorter-term financial needs, the figures set out clearly the value of long-term investing, with the highest-value stocks and shares ISAs now worth 17 times that of the top cash ISAs on average.

“Even beyond the top tier, the pattern is the same. Only 30 cash ISAs across the country hold over £500,000, compared to almost 39,000 stocks and shares ISAs. The difference reflects how consistent investing has proven to be the most effective route to building meaningful, long-term wealth. It’s these kinds of numbers that truly help demonstrate the potential that investing holds.”