3 ISA mistakes to avoid in 2025

Our writer outlines a trio of mistakes investors can make in their ISA, to their cost, and explains why he’s consciously avoiding them.

| 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.

Warren Buffett at a Berkshire Hathaway AGM

Image source: The Motley Fool

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.

An ISA can be a platform for building wealth over the long term – but that is never guaranteed. As well as making the right moves, it is important to try and avoid making the wrong ones.

Here are three mistakes I will be striving to avoid this year when making choices about what to do with my Stocks and Shares ISA.

1. Paying unnecessary costs

In a good restaurant or pub, you can get so caught up with what is going on inside that you do not pay much (or any) attention to the building itself.

An ISA can be a bit like that. Some investors focus so much on what shares to buy (or sell), or dividends coming in, that they pay scant attention to the ISA wrapper itself.

But there is a wide array of Stocks and Shares ISAs on the market and they can come with very different costs and fees. So I make sure to compare some of the options to try and make sure that I am getting what I need without spending more than I need to. I would rather the money in my ISA was used for investing, not keeping a stockbroker in clover!

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.

2. Trading too often

Legendary investor Warren Buffett has said his preferred holding time for a share is “forever” and indeed he has owned shares like American Express and Coca-Cola for many decades.

Another comment from Buffett that caught my eye was that he pins a large part of his success on one “truly good” decision every five years or so (and taking a long-term approach to investing).

That makes sense to me. It can be temping to keep chopping and changing the holdings in an ISA. But brilliantly successful investors like Buffett typically focus on buying stakes in outstanding companies and holding them for the long run.

3. Focusing too much on one share

One of the more interesting moves Buffett made last year was selling a significant chunk of his Apple (NASDAQ: AAPL) shares.

The reasons for that are not entirely clear, but one benefit is that it means his portfolio is now more diversified than it was before the sale.

Apple has been a phenomenally successful investment for Buffett, with his stake increasing in value by tens of billions of pounds since he bought it.

A lot of what has helped the share do well is still true. Apple has a strong brand, large customer base and proprietary technology that can help set it apart from rivals. No wonder it is massively profitable.

But – and I have seen this happen to shares in my ISA before – one risk of owning a great share is that it is indeed a great share. That can attract other investors, pushing the price up and meaning that the one share increasingly comes to dominate a portfolio.

That might not sound like a problem – but what happens if the price suddenly falls? Apple faces risks such as lower cost Asian competitors eating into its market share in developing countries. All shares face risks.

It is possible to have too much of a good thing when it comes to investing. That is why I like to keep my ISA diversified.           

American Express is an advertising partner of Motley Fool Money. C Ruane has no position in any of the shares mentioned. The Motley Fool UK has recommended Apple. 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 flag, Big Ben, Houses of Parliament and British flag composition
Investing Articles

After strong earnings, is Diploma still one of the UK’s top growth stocks?

Investors trying to find quality growth stocks don’t have to look beyond the FTSE 100. But is that where the…

Read more »

Rear view image depicting a senior man in his 70s sitting on a bench leading down to the iconic Seven Sisters cliffs on the coastline of East Sussex, UK. The man is wearing casual clothing - blue denim jeans, a red checked shirt, navy blue gilet. The man is having a rest from hiking and his hiking pole is leaning up against the bench.
Investing Articles

Why a £250K ISA won’t replace your salary – but could still transform your retirement

What could a £250,000 ISA really do for you? It won’t retire you overnight, but it could reshape your income,…

Read more »

Investing Articles

The BIGGEST holding in my stocks and shares ISA in 2026 is…

Zaven Boyrazian reveals the largest holding in his Stocks and Shares ISA that’s already surged by almost 2,700% since he…

Read more »

Storytelling image of a multiethnic senior couple in love - Elderly married couple dating outdoors, love emotions and feelings
Investing Articles

Here’s how you could build a £23,455 second income with just £100 a month!

Drip-feeding money into growth and dividend shares can eventually deliver a stunning second income in retirement. Royston Wild explains how.

Read more »

Portrait of elderly man wearing white denim shirt and glasses looking up with hand on chin. Thoughtful senior entrepreneur, studio shot against grey background.
Investing Articles

I’d back these FTSE stocks will deliver double-digit growth in 2026

The FTSE 100 has reached all-time highs above 10,000, but that doesn't mean there aren't once-in-a-decade bargains to pick up…

Read more »

Investing Articles

Here’s the forecast for the HSBC share price and dividends in 2026!

HSBC's share price was a big riser in 2025 as investors became increasingly bullish about an earnings super-cycle within the…

Read more »

Middle aged businesswoman using laptop while working from home
Investing Articles

A once-in-a-decade chance to buy Marks and Spencer shares?

Marks and Spencer shares endured a selloff after a cyberattack punches a hole in the company's sales and earnings. A…

Read more »

Black woman using smartphone at home, watching stock charts.
Investing Articles

How much do you need in an ISA for £1,618 of monthly passive income?

Dr James Fox explains how Britons could use the Stocks and Shares ISA to build a portfolio that can deliver…

Read more »