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

1 ISA mistake to avoid

This commonly overlooked investing mistake can cost ISA investors tens of thousands of pounds over time. Here’s how I’d try to avoid it.

| More on:

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.

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.

Investing regularly in a Stocks and Shares ISA can build substantial wealth over time. In fact, there are almost 5,000 ISA millionaires in the UK, according to the latest available data.

However, not every account is guaranteed to go up. Some can struggle, for a number of reasons.

Here, I want to look at one often overlooked mistake that can — quite literally — be very costly.

Fees and costs

I’m talking about the impact of fees associated with managing ISAs.

Now, some costs are unavoidable, including platform fees and stamp duty (a government tax) on dealing most UK stocks. This is the basic price we all have to pay to invest.

However, some UK brokers still charge customers for trading shares. Most US investors are shocked to learn this, as commission-free trading has been the norm for many years across the pond.

My Lifetime ISA and self-invested personal pension (SIPP) are with an online platform that still charges £5 per trade. So I’m careful not to overtrade. Thankfully though, it seems that trading fees in the UK are slowly going the way of the dinosaurs.

Foreign exchange fees can also be easy to overlook. These are paid on international shares (0.5%-1.5% per transaction, for example).

As we can see, regular trading (particularly with modest amounts) can quickly rack up a load of charges and significantly erode long-term returns.

That’s not all

Investors can also often underestimate the impact of annual management fees charged by funds.

A seemingly small 1% figure can dramatically reduce long-term gains due to compounding. For a £20,000 ISA growing at 7% annually, a 1% fee would cost more than £30,000 in lost returns over 30 years!

Most index trackers have expense ratios under 0.2% nowadays. But it’s always worth keeping an eye on the costs associated with actively managed funds. I try to prioritise low-cost options where possible.

I trust this one

One such fund that I hold is Scottish Mortgage Investment Trust (LSE: SMT). The share price is up 29% in one year and around 79% over five years.

The aim of the trust is to invest in the greatest growth companies in the world. Today, that includes Facebook owner Meta Platforms, AI chipmaker Nvidia, and e-commerce powerhouses MercadoLibre and Amazon.

Scottish Mortgage also gives investors exposure to exciting companies not listed on stock markets. These include internet payments platform Stripe and SpaceX, Elon Musk’s reusable rocket firm.

SpaceX is reportedly set to be valued at around $255bn next month, making it the most valuable private company in the US. Last month, it made history when it sent the world’s largest rocket into space and back, as well as catching the huge first-stage booster with the ‘chopstick’ arms of the launch tower. 

The opportunities that reliable Starship rockets would open up in space tourism, exploration and satellite launches are enormous.

One risk investing in Scottish Mortgage is that the portfolio is made up entirely of growth stocks. Were these to fall out of favour, as happened in 2022, the share price would likely underperform.

However, the ongoing charge for the trust is just 0.35%. That’s less than most actively managed rivals and significantly less than private equity funds.

As such, I reckon Scottish Mortgage offers my portfolio excellent value for money.

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 MercadoLibre and Scottish Mortgage Investment Trust Plc. The Motley Fool UK has recommended Amazon, MercadoLibre, 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

Young woman holding up three fingers
Investing Articles

Want to start investing in 2026? 3 things to get ready now!

Before someone is ready to start investing in the stock market, our writer reckons it could well be worth them…

Read more »

Investing Articles

Can the stock market continue its strong performance into 2026?

Will the stock market power ahead next year -- or could its recent strong run come crashing down? Christopher Ruane…

Read more »

Businessman hand stacking money coins with virtual percentage icons
Investing Articles

Here’s how someone could invest £20k in an ISA to target a 7% dividend yield in 2026

Is 7% a realistic target dividend yield for a Stocks and Shares ISA? Christopher Ruane reckons that it could be.…

Read more »

A quiet morning and an empty Victoria Street in Edinburgh's historic Old Town.
Investing Articles

How little is £1k invested in Greggs shares in January worth now?

Just how much value have Greggs shares lost this year -- and why has our writer been putting his money…

Read more »

Businessman using pen drawing line for increasing arrow from 2024 to 2025
Investing Articles

This cheap FTSE 100 stock outperformed Barclays, IAG, and Games Workshop shares in 2025 but no one’s talking about it

This FTSE stock has delivered fantastic gains in 2025, outperforming a lot of more popular shares. Yet going into 2026,…

Read more »

Close-up of British bank notes
Investing Articles

100 Lloyds shares cost £55 in January. Here’s what they’re worth now!

How well have Lloyds shares done in 2025? Very well is the answer, as our writer explains. But they still…

Read more »

Thoughtful man using his phone while riding on a train and looking through the window
Investing Articles

How much do you need in an ISA to target £2,000 a month of passive income

Our writer explores a passive income strategy that involves the most boring FTSE 100 share. But when it comes to…

Read more »

Investing Articles

£5,000 invested in a FTSE 250 index tracker at the start of 2025 is now worth…

Despite underperforming the FTSE 100, the FTSE 250 has been the place to find some of the UK’s top growth…

Read more »