Share your opinion and earn yourself a free Motley Fool premium report!

We are looking for Fools to join a 75 minute online independent market research forum on 15th / 16th December.

To find out more and express your interest please click here

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

Night Takeoff Of The American Space Shuttle
Investing Articles

4 dirt-cheap growth shares to consider for 2026!

Discover four top growth shares that could take off in the New Year -- and why our writer Royston Wild…

Read more »

Road 2025 to 2032 new year direction concept
Investing Articles

I asked ChatGPT how to start investing in UK shares with just £500 and it said do this

Harvey Jones asks artificial intelligence a few questions about how to get started in investing, before giving up and deciding…

Read more »

Three signposts pointing in different directions, with 'Buy' 'Sell' and 'Hold' on
Dividend Shares

Yielding 10.41%, is this the best dividend share in the FTSE 250?

Jon Smith points out a dividend share with a double-digit yield, but explains why digging below the surface provides important…

Read more »

Investing Articles

Is 2026 the year it all goes wrong for the Rolls-Royce share price?

2025 has been another stellar year for the Rolls-Royce share price but Harvey Jones wonders just how long its magnificent…

Read more »

Night Takeoff Of The American Space Shuttle
Investing Articles

A SpaceX IPO could light a fire under this FTSE 100 stock

Shareholders of this FTSE 100 investment trust may have just got an early Christmas present from Space Exploration Technologies (SpaceX).

Read more »

Portrait Of Senior Couple Climbing Hill On Hike Through Countryside In Lake District UK Together
Investing Articles

Can dividends REALLY provide a second income you can live on?

Achieving a strong and sustained passive income in retirement may be easier than you think, even as yields on UK…

Read more »

Market Movers

33p penny stock Made Tech could be set for huge gains in 2026, if City analysts are right

This penny stock just experienced a sharp move higher. However, analysts reckon that there are plenty more gains to come…

Read more »

Elevated view over city of London skyline
Investing Articles

FTSE shares: a simple way to build long-term wealth?

Christopher Ruane explains some factors he thinks an investor should consider when trying to build wealth by investing in FTSE…

Read more »