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.

How to turn a £20K ISA into a £500 monthly second income

Taking a long-term approach could let investors generate a regular second income from a Stocks and Shares ISA. Christopher Ruane explains the details.

Man writing 'now' having crossed out 'later', 'tomorrow' and 'next week'

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.

A second income does not always mean taking a second job. For example, by investing in shares, millions of people regularly earn dividend income. That may be pennies in some cases – but with the right approach, it can be substantial.

Here is an example of how I could aim to turn a £20,000 Stocks and Shares ISA into a moneymaking machine earning me an average monthly second income of £500.

XXX

The basic principle

If I invest in dividend shares, the amount I will hopefully earn each year depends on two factors – the size of my ISA and the average dividend yield I earn from my portfolio.

Starting with £20,000, it may seem that the amount I invest is fixed. For example, at an average yield of 4%, I would earn £800 annually in dividends. If I could push my average yield up to 7%, I would be looking at £1,400 each year in dividends.

But even if I only invest £20,000 into my ISA, I might end up having a lot more than that available for me to invest. If I reinvest the dividends I earn rather than taking them as cash (something known as compounding), I can start to build the size of my ISA and essentially earn dividends on my dividends.

Taken from a long-term perspective, that can have a huge impact.

If I compounded dividends of 8% annually, after 18 years my average second income from dividends would already have topped £500 each month. Not only that, but having invested £20,000 of my own money 18 years earlier, I would hopefully keep earning that second income for the rest of my life… without investing another penny in my ISA.

In practice, that happening would depend on whether the shares I owned maintained their dividends. That is never guaranteed. The payouts could be cut. On the other hand, they might increase over time.

Investing in winners

In fact, that is exactly what I would aim for when investing. If I buy into great businesses with strong growth prospects, I think it is realistic to hope that they may increase their dividends (and my second income) over time.

Every share has risks, so I would diversify my portfolio across multiple shares. But the characteristics I would look for in each share would remain the same.

I try to find proven businesses in areas I expect to experience strong customer demand. In each case, I hunt for a source of long-term value that can set the business apart from competitors. That could be owning an iconic brand like Coca-Cola, patented products like AstraZeneca, or a unique distribution network like National Grid.

Price also matters as my yield will be determined by what I pay for a share.

The sort of 8% yield I used in my example above is not common. But I do think it is achievable. I currently own FTSE 100 shares with an 8% yield, or better, such as M&G and Legal & General. I am using them to build my second income today!

C Ruane has positions in Legal & General Group Plc and M&g Plc. The Motley Fool UK has recommended M&g 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

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 »