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 I’d invest £100 per week in an ISA in 2021

We might not be out of the 2020 stock market crash yet, but I’m already thinking about my 2021 Stocks and Shares ISA for the years ahead.

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.

2020 has been one of those rare years in which a Cash ISA would have almost certainly have beaten a Stocks and Shares ISA. That’s making a few assumptions, of course. That the stock market won’t make a sudden surge past last year’s close by the end of the year. And that we’d invested our Stocks and Shares cash across the market rather than being clever enough to pick the big winners.

But there are always exceptions. And, as a long-term investor, I’ll always expect a stock market crash from time to time. And I reckon a Cash ISA in 2020 would still be a lousy investment anyway. With interest rates so low, there’s so little gain to be had it really doesn’t seem worth trying to save a minuscule bit of tax. So, whatever cash I choose to keep for safety will just stay in a plain savings account.

XXX

Isn’t it a bit early to be thinking about next year’s Stocks and Shares ISA? Well, in such a tough year as 2020, it helps me a lot to think about how much regular investment in an ISA could earn in the years ahead. Especially when I work out how much I could accumulate from investing modest sums of money regularly.

Long-term stock market returns

Now, yes, we’re in a tough year for shares. But years which end with the stock market down are often followed by years with better-than-average gains. So, I reckon it’s an especially good year to get started. But I won’t make any assumptions of an out-of-the-ordinary 2021. No, I’ll just stick with long-term averages for my ISA projections.

According to a Barclays study, the UK stock market has been turning in a long-term average annual return of 4.9% above inflation. That’s counting dividends and share price gains. Inflation is way down this year as spending has been massively slashed. But I’ll assume a future long-term average of 1.8% per year. So that’s a stock market return of 6.7% per year.

So, what if I invest £100 per week in a Stocks and Shares ISA? Firstly, the practicalities. Most ISA providers allow us to drip-feed small sums into our accounts, often as little as £20 per week. So I’d set that up to invest my ton every week. Depending on trading costs, I’d buy a stock every time I’ve accumulated £500-£1,000. But how much might I hope to earn, and over how long a timescale?

Nowhere near the ISA limit

Over the next 10 years, I’d have invested a total of £52,000. But my total ISA value, assuming that 6.7% return per year, would come in at £73,400. But how much would it come to after 20 years? A bit more than twice that perhaps? How about £213,000? Yes, that’s how much a Stocks and Shares ISA could get me in 20 years.

And that’s nowhere near the annual ISA limit of £20,000. The more I can use of my limit every year, the fatter my pension pot should get. And it will all be tax-free.

Alan Oscroft has no position in any of the shares mentioned. The Motley Fool UK has recommended Barclays. 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 »