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.

Here’s how to build a £100k ISA starting with £5k today

Increase an ISA’s value 20-fold? It need not just be the stuff of dreams, according to this writer — though he doesn’t claim it’ll be easy!

| More on:
ISA coins

Image source: Getty Images

You’re reading a free article with opinions that may differ from The Twelfth Magpie’s Premium Investing Services. Become a member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn more, and get a free 'Best Buy Now' stock!.

A Stocks and Shares ISA can be an excellent way for an investor to try and build wealth. Some may aim to do that in the short- to medium-term. But I see serious attractions to long-term investing, not least the opportunity it allows for brilliant shares to show their true potential.

Let me illustrate by demonstrating how an investor could aim to turn a £5,000 ISA today into one worth £100,000 in future – if they are willing to take the long-term approach.

Should you buy Sunbelt Rentals Holdings shares today?

Before you decide, please take a moment to review this report first. Despite ongoing uncertainties from US tariffs to global conflicts, Mark Rogers and his team believe many UK shares still trade at substantial discounts, offering savvy investors plenty of potential opportunities to learn about.

That’s why this could be an ideal time to secure this valuable research – Mark’s analysts have scoured the markets to reveal 5 of his favourite long-term ‘Buys’. Please, don’t make any big decisions before seeing them.

Thanks to the ISA structure, for many investors that gain could even be completely tax-free (well, up to a point: the UK imposes stamp duty on individual share transactions of a certain size even inside an ISA, after all).

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.

Looking to the future

The easy part is the maths.

At a 10% compound annual growth rate (CAGR), turning £5k into £100k would take 32 years.

At a 15% CAGR, it would take 22 years. In the context of an ISA, I do not even see that as a particularly long time in the grand scheme of things especially when a 20-fold return is concerned.

Investing to build wealth

But while a 15% CAGR may not sound especially challenging, it definitely is.

It is hard for many investors to achieve that sort of return in any given single year. Achieving it on average year after year for decades, through good markets and bad, is even tougher.

I believe it is possible, though, if an investor takes time to do their homework and builds an ISA stuffed with carefully chosen shares in companies that have excellent future profit creation potential, but a weak share price when bought.

To illustrate how such an approach could work in practice, consider Ashtead (LSE: AHT). Over the past five years, its share price has shot up by 125%. It also offers a 2.3% dividend yield to boot.

The thing is, five years ago, Ashtead was already an excellent business hiding in plain sight.

Why do I say that?

For one thing, now as then it operates in an attractive market. Demand for hire equipment on building sites is often strong (though of course one risk is a housing downturn leading to lower demand, hurting revenues). As the cost of work on a site stopping can be high, companies that rent it out have pricing power.

Ashtead has a proven business model. Its large customer base, extensive depot network, and large asset base of equipment are all competitive strengths. That was true five years ago – and it it true now.

Despite that excellent share price performance over the past five years, Ashtead trades on a price-to-earnings ratio of 16. That is not cheap but it is attractive enough that I see it as a share investors should consider.

It also illustrates that, while achieving a 15% CAGR with a diversified portfolio is challenging, it is possible.

Getting ready to invest

The first move, of course, is having the right Stocks and Shares ISA to put the £5k in and set the wheels in motion.

With lots of options on the market, it pays to compare some choices as each investor’s needs are different.

After all, keeping a close eyes on fees and costs can also help boost the ISA’s CAGR.

C Ruane has no position in any of the shares mentioned. The Motley Fool UK has recommended Ashtead Group Plc. 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

Person holding magnifying glass over important document, reading the small print
Investing Articles

Closing in on £33 and around an all‑time high, is this FTSE 250 favourite seriously mispriced?

With the shares pushing into record territory, I’ve revisited the underlying business, its growth outlook and the valuation picture investors…

Read more »

Close-up of British bank notes
Investing Articles

£20,000 invested in Barclays shares a year ago is now worth…

Barclays shares have quietly delivered a 41% return in just 12 months — and the long term numbers suggest the…

Read more »

Young black woman walking in Central London for shopping
Investing Articles

£9,000 in an ISA? Here’s how to target a £675 passive income with 7% investment trusts

Investment trusts can offer a huge and stable passive income every year. Royston Wild reveals three to consider -- including…

Read more »

A rear view of a female in a bright yellow coat walking along the historic street known as The Shambles in York, UK which is a popular tourist destination in this Yorkshire city.
Investing Articles

These 3 shares could deliver a £1,840 second income in an ISA overnight!

With an average dividend yield of 9.2%, these top UK shares could deliver turn a £20,000 ISA into a huge…

Read more »

Wall Street sign in New York City
Investing Articles

Up 5.3%, the Dow Jones lags other US indices in 2026. Here’s why UK income investors should pay attention

Mark Hartley highlights how US indices blur the real market story with tech-driven hype, and why the Dow Jones matters…

Read more »

Businessman hand stacking money coins with virtual percentage icons
Investing Articles

£1,000 buys 531 shares in this UK defence and nuclear stock that’s tipped to soar

This UK stock offers growth and income at an attractive valuation. Could it be worth considering for an ISA or…

Read more »

A senior Hispanic couple kayaking
Investing Articles

How much money do you need to retire comfortably with a SIPP?

Buying shares in a Self-Invested Personal Pension (SIPP) can make hitting your retirement goals much easier. Royston Wild explains how.

Read more »

Santa Clara offices of NVIDIA
Investing Articles

Prediction: Nvidia stock will hit $500

Analysts at Baird expect Nvidia stock to more than double in the medium term. So is it time to get…

Read more »