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 much do I need to invest in my ISA for a second income of £20,000 a year?

Looking to earn a £20k second income from a portfolio of dividend stocks? Charlie Carman explores the amount he’d need to invest to achieve this goal.

Mature Caucasian woman sat at a table with coffee and laptop while making notes on paper

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.

Earning a second income from the stock market is a key objective for many investors, including me. With the ability to earn tax-free capital gains and dividends from a Stocks and Shares ISA, I think it’s possible to achieve this ambition by pursuing a long-term investing strategy.

But how much would I need to invest to earn £20,000 in annual dividend income? And how long would it take to build a big enough portfolio? Let’s crunch the numbers.

XXX

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.

Buying dividend stocks

With passive income as a priority, I’m looking for dividend shares.

The average dividend yield for FTSE 100 stocks is currently 3.8%. However, some sectors are renowned for high-yield dividend stocks. These include tobacco, banking and housebuilding, among others.

Examples of FTSE 100 shares that feature in my portfolio are:

  • British American Tobacco — 9% yield
  • Lloyds Bank — 5.4% yield
  • Taylor Wimpey — 8.2% yield

With a £20k annual passive income goal, there are two key numbers for my modelling assumptions to ascertain how much I need to invest and how long the journey will take.

Dividend yield

First, there’s my target dividend yield. Essentially, this is the average yield across my stocks. Variations in the yield can produce very different numbers in terms of my required portfolio value.

To illustrate this, here’s the amount I’d need to invest to earn a £20k second income from a range of yields.

Dividend yieldPortfolio value required
3%£666,667
4%£500,000
5%£400,000
6%£333,333
7%£285,714

Compound returns

Second, I need to focus on my portfolio’s compound annual growth rate (CAGR). Essentially, this figure is the percentage increase in the value of my shareholdings from ISA contributions, share price appreciation and dividends reinvested.

For instance, if I aimed for a 5% average yield, I’d need a £400k portfolio. Let’s assume I saved and invested £10 a day. Here’s how long I’d need to hit my target at different rates of return.

CAGRTime taken
3%48 years, six months
4%42 years, one month
5%37 years, four months
6%33 years, nine months
7%30 years, 10 months

So it’s clear the amount I’d need to invest for a £20k second income varies enormously depending on my average yield and my portfolio’s CAGR over time.

For example, if I invested £10 a day, stuck with a 5% target yield and my portfolio’s CAGR was 7%, I could invest £112,847 to hit my target £400k value in under 31 years.

Conversely, at a 3% CAGR, I’d need to invest £177,331 over a whopping 48.5 years to reach my goal! That’s an extra £64,484 and 17 years, eight months.

Managing risks

Dividend investing isn’t risk-free. Underwhelming returns resulting from bear markets or poor stock picks could mean my investing journey would take an incredibly long time. Or even require larger regular ISA contributions, as the above numbers demonstrate.

In addition, if companies cut or suspended their dividends, my required portfolio value would increase, as my average yield would drop.

However, via diversification and reliable dividend stock picks, it’s possible to unleash the enormous potential of compound returns. Which means I could generate a £20k second income in a reasonable timeframe for as little as a tenner a day.

Charlie Carman has positions in British American Tobacco P.l.c., Lloyds Banking Group Plc, and Taylor Wimpey Plc. The Motley Fool UK has recommended British American Tobacco P.l.c. and Lloyds Banking Group 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 »