How to turn a £20k ISA into a £17,423 yearly second income

If I was starting from scratch with an ISA account, I think I’d aim to turn it into a useful second income, possibly even higher than £17k a year.

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.

Midnight is celebrated along the River Thames in London with a spectacular and colourful firework display.

Image source: Getty Images

Let’s say I had £20k in my ISA account. I think I could turn it into a second income of over £17,000 a year, or £17,423 to be precise.

Per month, that’s about £1,500. I’d love that kind of money flowing in. I could use it to top up a pension, cut down on hours at work or even retire earlier. 

And if I’m smart with how I manage it, I could keep a nest egg of a few hundred thousand. I’d sleep well with a rainy day fund like that. It could even be something to leave behind, eventually, to loved ones as well.

A Stocks and Shares ISA is how I’d work towards this income. It can help me build wealth perhaps better than any other option I’ve got here in the UK. I might aim for a yield of 8-10% on the money I put in and, because it’s an ISA, my returns are not taxed.

Other options aren’t nearly as good, I feel. Buy-to-let is popular and can be lucrative. But if I went for that, I reckon I’d be worse off. The average rental yield in the UK is only 3.63% right now, and there’s tax to think about on top of that. 

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.

4,000 millionaires

These ISA accounts are fairly popular these days too. I think it’s fair to say many Britons are using stocks to make money. And a recent report showed the number of ISA millionaires had tripled and was now up to around 4,000. 

Let’s see what I could achieve with my £20k ISA. I’ve also included what happens if I top it up with £100 a month. If I drip-feed even a little extra from a day job, it can make a life-changing difference to the final total.

£20k ISA£20k ISA + £100 p/m
DepositWith 9%DepositWith 9%
1 year£20,000£21,800£21,200£23,049
5 years£20,000£30,772£26,000£38,246
10 years£20,000£47,347£32,000£66,319
20 years£20,000£112,088£44,000£175,973
30 years£20,000£265,354£56,000£435,565

These sums look pretty nice to me, especially when I look at how small the deposits are. But I have to point out that I might not achieve a 9% annual return and could even lose money.

Of course, the nest egg isn’t useful to me just sitting there in my account. I want to use it to give me a second income, and the term ‘safe withdrawal rate’ (SWR) is useful here. 

An SWR refers to how much I can withdraw with still a good chance to keep the nest egg intact. A 4% withdrawal – usually considered pretty safe over decades – eventually gives that £17,423 second income each year.

A lot of people will like the look of that figure but be put off by the risks. It’s true that nothing is certain with the stock market. There will be ups, downs, crashes and corrections. It’s perhaps not for the faint of heart. And inflation means that amount will be worth less in the future.

But if I do want to invest in stocks, then every day or week I put off or delay my decision could cost me a lot in the long run. 

20 best days

In fact, over a recent 20-year period, all the returns from the stock market came from the best 20 days. Even a missed day or two could seriously dent the amount I make. It’s one reason why “time in the market beats timing the market”. 

That’s why if I was starting from scratch, I’d look to invest in a Stocks and Shares ISA today. With the right choices, I’d look to turn my cash into a sizeable income.

John Fieldsend 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

Investing Articles

I asked ChatGPT to settle the ISA v SIPP debate once and for all. It said…

Instead of working out whether an ISA or SIPP is the better tax wrapper, Harvey Jones called the robots in.…

Read more »

Middle-aged white male courier delivering boxes to young black lady
Investing Articles

Amazon shares: overpriced or a possible bargain?

Christopher Ruane thinks Amazon shares look pricier than he normally likes -- but also reckons they could be a potential…

Read more »

Female Tesco employee holding produce crate
Investing Articles

In a jittery market, could Tesco shares be a defensive choice?

Could Tesco shares be a safe haven in nervous markets, given that consumers always need to eat? Our writer is…

Read more »

British coins and bank notes scattered on a surface
Investing Articles

How much might £10,000 in Rolls-Royce shares soon be worth? Let’s ask the experts

Do Rolls-Royce shares look like a good buy after recent price falls? City analysts still appear bullish, but global events…

Read more »

Queen Street, one of Cardiff's main shopping streets, busy with Saturday shoppers.
Investing Articles

Take a deep breath! £10,000 invested in Greggs shares a year ago is now worth…

Someone who bought Greggs shares a year ago is nursing a paper loss. Our writer digs into the reasons why…

Read more »

Mature black woman at home texting on her cell phone while sitting on the couch
Investing Articles

Whatever happened to the stock market crash?

The stock market refuses to crash, despite the Iran war. But Harvey Jones says lots of FTSE 100 shares have…

Read more »

Petrochemical engineer working at night with digital tablet inside oil and gas refinery plant
Investing Articles

BP’s share price will keep surging in 2026, according to this broker

BP’s share price is in a strong upward trend right now. And one City brokerage firm seems to believe that…

Read more »

Picture of an easyJet plane taking off.
Investing Articles

These 4 red flags mean I’m avoiding easyJet shares like the plague!

easyJet shares have slumped by around a quarter during the past month. Does this represent a dip-buying opportunity? Royston Wild…

Read more »