My simple 3-step plan to build up a £1m ISA account

A £1m ISA could be in reach, but investors need a clear strategy, says Rupert Hargreaves.

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.

According to the Financial Times, there are just under 500 so-called ‘ISA Millionaires’ in the UK. The one thing that links all of these investors is age. The average age of the UK ISA millionaire is around 70. This suggests these investors have been squirrelling money away for decades, and patiently waiting for a return.

The other factor that links all of these millionaires is their love of investing. All of them have used the stock market to help them build wealth. Strategies differ from account to account (based on the limited information available), but the one thing they all have in common is a focus on long-term investing in high-quality companies.

Based on the above information, I’ve put together a three-step plan to build a £1m ISA account.

ISA saving 

The first step is to start saving. Investors are currently allowed to put away £20,000 a year in a stocks and shares ISA. This is a use-it-or-lose-it allowance. So, it makes sense to use as much of the quota as possible every year — even if you can only afford a couple of hundred pounds.

It’s not possible to build a £1m ISA overnight. It takes time. In fact, with contributions of £20k a year, it would take five decades, excluding any investment gains or losses. That’s why it’s essential to start saving as soon as possible. When you’ve started, you need to stick to the savings plan over the long term.

Trust the market

The next step is to invest your money. Over the long run, the FTSE 250 has returned around 10% per annum. At this rate of return, it would take just 18 years to build a £1m ISA account. That’s assuming an investor used up the full £20,000 ISA allowance every year.

It would be impossible to achieve the same kind of return with cash interest rates where they are today. The best flexible Cash ISA interest rate on the market today is just 1.3%. At this rate of return, it would take nearly four decades to build a £1m ISA account with annual top-ups of £20k.

Quality over quantity

The third and final step is to seek quality over quantity. One thing that links all successful long-term investors is a focus on high-quality stocks. This primarily means targeting companies that have a definite competitive advantage and a loyal customer base.

These are the kind of businesses investors can buy and forget, safe in the knowledge that they should generate attractive returns over the long run.

Successful long-term investors also avoid trading in and out of positions quickly. They tend to pick a few key companies and stick with them, rather than owning a broad range of businesses. The more investments you make, the higher the chances are that something will go wrong.

Buying a low-cost FTSE 250 or FTSE 100 tracker fund could be an excellent alternative for investors who don’t have enough time to find these sort of companies.

Rupert Hargreaves 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

Passive income text with pin graph chart on business table
Investing Articles

I asked ChatGPT for its top passive income ideas for 2026 and it said…

Stephen Wright is looking for passive income ideas for 2026. But can asking artificial intelligence for insights offer anything valuable?

Read more »

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

Here’s how a 10-share SIPP could combine both growth and income opportunities!

Juggling the prospects of growth and dividend income within one SIPP can take some effort. Our writer shares his thoughts…

Read more »

Tabletop model of a bear sat on desk in front of monitors showing stock charts
Investing Articles

The stock market might crash in 2026. Here’s why I’m not worried

When Michael Burry forecasts a crash, the stock market takes notice. But do long-term investors actually need to worry about…

Read more »

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

Is this FTSE 250 retailer set for a dramatic recovery in 2026?

FTSE 250 retailer WH Smith is moving on from the accounting issues that have weighed on it in 2025. But…

Read more »

Young Black woman using a debit card at an ATM to withdraw money
Investing Articles

I’m racing to buy dirt cheap income stocks before it’s too late

Income stocks are set to have a terrific year in 2026 with multiple tailwinds supporting dividend growth. Here's what Zaven…

Read more »

ISA Individual Savings Account
Investing Articles

Aiming for a £1k passive income? Here’s how much you’d need in an ISA

Mark Hartley does the maths to calculate how much an investor would need in an ISA when aiming for a…

Read more »

Two business people sitting at cafe working on new project using laptop. Young businesswoman taking notes and businessman working on laptop computer.
Investing Articles

Is investing £5,000 enough to earn a £1,000 second income?

Want to start earning a second income in the stock market? Zaven Boyrazian breaks down how investors can aim to…

Read more »

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

New to investing? REITs are an excellent way to earn passive income!

Zaven Boyrazian thinks that real estate investment trusts (REITs) could be a great way for investors to boost their passive…

Read more »