We have some exciting news to share! The Motley Fool UK has now become The Twelfth Magpie -- an independent, UK-owned company, led by our long-serving UK management team — Mark Rogers, Chris Nials and Heather Adlington. In practical terms, it’s the same team you know, now fully focused on serving our UK readers and members.

Just as importantly, our approach remains unchanged: long-term, jargon-free, and on your side. This site is our new home, and there will be extra tweaks made across the coming few days as we settle in. So if anything looks a little off, please bear with us!

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.

£20,000 in an ISA? Here’s how that could grow to £83,000 by 2040!

Our writer highlights a FTSE 100 investment trust that he believes could add some market-beating growth to a Stocks and Shares ISA.

| More on:
ISA coins

Image source: Getty Images

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’s well-documented that there are a fair few ISA millionaires knocking about in the UK. However, these are often people who max out the annual contribution limit — currently £20,000 — or come close to doing so on a regular basis over many years.

But what about someone who has a one-off lump sum of £20k? Well, they can still hope to increase that significantly over 15 years. Here’s how.

XXX

The magic of compound interest

When it comes to wealth building, the secret sauce is compounding. That’s because returns come not just from the original investment, but from the returns on the returns. Or interest upon interest. 

That’s the great thing about compounding — it works on all sums, small or large.

Of course, it has a more dramatic effect on larger amounts. But consider that £1,000 compounding at 10% per year would reach £1m after 73 years and £13m after a century! That’s without any further injections of cash.

For £20,000, the figure would be around £83,000 after 15 years (taking us to 2040), assuming the same 10% return. And all gains would be free from tax obligations!

Please note that tax treatment depends on the individual circumstances of each client and may be subject to change in future. The content in this article is provided for information purposes only. It is not intended to be, neither does it constitute, any form of tax advice. Readers are responsible for carrying out their own due diligence and for obtaining professional advice before making any investment decisions.

What approach to take?

Now, it should be noted that a 10% annual return isn’t guaranteed, despite that being the ballpark figure of the S&P 500 over recent years. In future, stocks in general may return less than this.

However, I still think this is an achievable goal to aim for, assuming the ISA portfolio is suitably diversified across enough quality stocks.

One I think worth considering right now is Scottish Mortgage Investment Trust (LSE: SMT). This FTSE 100 investment trust aims to deliver market-beating returns through its portfolio of about 100 growth companies.

These include e-commerce and cloud computing giant Amazon, AI chip leader Nvidia, and Facebook parent Meta Platforms. The idea is that this trust is a way to invest in such names without having to buy them individually.

Better still, the Scottish Mortgage share price has fallen 18% since mid-February. This actually means the shares are trading at an 11.7% discount to the underlying value of the portfolio. I find this double-digit discount attractive.

Another thing I like here is that the trust offers exposure to unlisted companies that cannot be bought on the stock market. For example, its largest holding today is Space Exploration Technologies (better known as SpaceX). This firm is an undisputed global leader in launching reusable rockets.

What could go wrong?

Naturally, any investment here would be a vote of confidence in the managers’ ability to identify the right stocks. That has worked out well for investors in the past — the share price is up around 250% in the past decade (above 10% a year) — but that’s not assured to continue.

One risk I see in the near term is a global recession. This would be bad for the stock market in general, but would likely hit the valuations of growth shares harder than most. So a high degree of volatility is to be expected with this stock.

On balance though, I continue to view Scottish Mortgage as one of the most attractive ways to invest in the digital revolution. Over a 15-year time frame, I think the stock could contribute nicely to an ISA portfolio’s growth.

John Mackey, former CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool’s board of directors. Randi Zuckerberg, a former director of market development and spokeswoman for Facebook and sister to Meta Platforms CEO Mark Zuckerberg, is a member of The Motley Fool's board of directors. Ben McPoland has positions in Nvidia and Scottish Mortgage Investment Trust Plc. The Motley Fool UK has recommended Amazon, Meta Platforms, and Nvidia. 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

Friends and sisters exploring the outdoors together in Cornwall. They are standing with their arms around each other at the coast.
Investing Articles

£503 buys 14 shares in this FTSE 250 stock that returned 23.9% annually for the last 15 years

This FTSE 250 stock has averaged a huge return for 15 years. At today's price, £503 buys 14 shares. But…

Read more »

Black woman using loudspeaker to be heard
Investing Articles

£1,000 buys 25 shares in this FTSE 100 stock that’s returned 29.2% annually for the last 10 years

This FTSE 100 mining stock has returned close to 30% a year for a decade. At 3,995p, £1,000 buys 25…

Read more »

Female student sitting at the steps and using laptop
Investing Articles

Down 47%, is this growth stock finally worth buying in May?

With a £288m order book and a hidden pipeline of defence and nuclear contracts, is this growth stock now too…

Read more »

House models and one with REIT - standing for real estate investment trust - written on it.
Investing Articles

2 REITs yielding 7%+ to consider for passive income in 2026

A REIT backed by the NHS and another backed by Tesco and Sainsbury's with both yielding 7%+. Here's why I'm…

Read more »

Woman riding her old fashioned bicycle along the Beach Esplanade at Aberdeen, Scotland.
Investing Articles

Just 97 shares of this UK dividend stock generate £238 in passive income

A 5.7% yield, £238 in passive income from just 97 shares, and one of the most divisive dividend stocks on…

Read more »

ISA coins
Investing Articles

£10,000 in an ISA generates a second income of…

The London Stock Exchange is home to some of the world's most generous dividends. But how big a second income…

Read more »

Shot of a senior man drinking coffee and looking thoughtfully out of a window
Investing Articles

Expert recommendations: 2 top income stocks yielding 7%+!

With yields of 7.2% and 7.8% respectively, these two income stocks are catching the eyes of institutional analysts. Should investors…

Read more »

Illustration of flames over a black background
Investing Articles

3 top income-focused stocks to buy in May 2026, according to experts

Looking for a stock to buy for income in May 2026? Experts have flagged these three UK dividend shares as…

Read more »