How you can become a Stocks and Shares ISA millionaire in 25 years

Regularly investing in a stocks and shares ISA could build a million-pound portfolio, but it will take time.

The content of this article was relevant at the time of publishing. Circumstances change continuously and caution should therefore be exercised when relying upon any content contained within this article.

You’re reading a free article with opinions that may differ from The Motley Fool’s Premium Investing Services. Become a Motley Fool member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn More.

It is possible to become a Stocks and Shares ISA millionaire. Investors shooting for a seven-figure portfolio need to save regularly and earn a decent return. The most important factor for building a million-pound portfolio, however, is time. Starting saving as soon as possible is the best thing a budding millionaire investor can do.

Stocks and shares 

The ISA deadline of 5 April is fast approaching, and many investors might be scrambling to make the most of the current annual £20,000 contribution limit. It is no bad thing to save as much as possible, and perhaps the looming deadline will prompt investors who have been delaying to start investing. However, I have found that a regular savings plan beats investing a lump sum. Once this year’s allowance has been taken advantage of, it is important to take regular slices of the next, and so on.

Some investors may be shying away from the stock market altogether, given the recent crash. This is a mistake. Stocks and shares have historically outperformed both bonds and cash, and a decent return on investment will make a million-pound portfolio more likely.

The longer the investment horizon and the higher return, the more annual taxes consume investment gains. Given that a million-pound portfolio will typically take a long time to build even with a high rate of return, an ISA account is perfect for the job. ISA accounts offer tax-free savings, even for stock investments and the capital gains and dividends they offer.

Now, stock market investments are riskier than cash or bonds. But a regular investment plan carried out over a long time horizon will help smooth out the volatility in the stock markets, by buying when stocks are falling (getting cheaper) and rising (becoming more expensive).

Making a million

According to the Office for National Statistics, the median after-tax monthly household income in the UK was £2,450 in 2019. The FTSE 100 has returned 8.3%, including dividend reinvestment, on average over the last 10 years. Over 25 years, the average FTSE 100 return has been 6.4%.

Let’s assume a £1,000 initial investment, and a long-term average annual return of 7%. Over time different amounts of wealth can be built up, depending on how much is saved each month:

It might be disappointing that see that saving 60% of the median household monthly income with a 7% annual return does not net a million-pound portfolio. However, £750,000 is a significant amount of money and could provide a substantial degree of financial freedom. Saving a bit over £100 a month could grow to over £66,000 in 20 years. That is a decent-sized pot that could supplement a pension nicely.

If an investor has 25 years or more, then million-pound portfolios are possible:

Investing for 40 years might sound fanciful, but it is possible for someone starting in their early twenties, or even thirties if retirement is delayed. Another point worth mentioning is that £980 a month might be out of reach at the moment, but that’s no reason to delay starting. Once mortgages get paid off or children leave the nest, it may be feasible to save £950 or another previously unthinkable amount each month.

Although becoming a Stocks and Shares ISA millionaire is possible, other amounts may look more achievable. Whatever the amount, the only way to get there is to start investing. Right now is as good a time as any.

James J. McCombie has no position in any of the shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

More on Investing Articles

British pound data
Investing Articles

The red lights are flashing again for Lloyds’ share price! Here’s why

Lloyds' share price continues to defy gravity. But Royston Wild thinks it's only a matter of time before the FTSE…

Read more »

Aston Martin DBX - rear pic of trunk
Investing Articles

Aston Martin shares are now only 41p!

Aston Martin shares just dropped to around the 41p mark! Is this a brilliant buying opportunity or a stock that…

Read more »

Artillery rocket system aimed to the sky and soldiers at sunset.
Investing Articles

Up 325% in 5 years! But are BAE System shares still a no-brainer buy?

BAE Systems shares would have been a brilliant buy five years ago. But could they still offer excellent returns if…

Read more »

Investing Articles

How much do you need to invest each month into FTSE 100 shares to aim for a million?

Simply by putting a few hundred pounds a month into FTSE 100 shares, how might someone aim to become a…

Read more »

Close-up as a woman counts out modern British banknotes.
Investing Articles

£10,000 invested in BAE shares at the beginning of 2026 is now worth…

Paul Summers tips his hat to those who invested in BAE Systems shares when markets opened back up in January.…

Read more »

A senior man and his wife holding hands walking up a hill on a footpath looking away from the camera at the view. The fishing village of Polperro is behind them.
Investing Articles

What size ISA do you need for £250-a-week retirement income?

Harvey Jones outlines the advantages of investing in a Stocks and Shares ISA rather than leaving money in cash, and…

Read more »

Mature Caucasian woman sat at a table with coffee and laptop while making notes on paper
Investing Articles

£5,000 invested in Legal & General shares 5 years ago is now worth…

Harvey Jones crunches the numbers to show how much an investor would have earned from Legal & General shares lately,…

Read more »

Investing Articles

Just check out the latest bumper forecasts for Lloyds, NatWest and Barclays shares

Harvey Jones says Barclays shares have had a terrific year and there could be more action to come. So what's…

Read more »