Stocks and Shares ISA: turning £20k into £15,815 a year

A Stocks and Shares ISA, used consistently over a working lifetime, can turn a single year’s allowance into a meaningful retirement income stream. Put £20,000 to work inside one now, leave it invested for 30 years at the average annual growth rate of 9.64% recorded over the last decade, according to Unbiased, and that sum compounds to £316,301. Apply a 5% income yield to that pot and the annual passive income comes to £15,815, all of it sheltered from income tax, dividend tax and capital gains tax.

The numbers are not guaranteed. A lower long-run return produces a smaller pot; a higher one produces a larger one. But the structure of the calculation is sound: time, compounding, and tax-free reinvestment of dividends are doing most of the work, not market-timing or stock-picking genius.

How a Stocks and Shares ISA compounds wealth over three decades

Of that projected £316,301 terminal value, £296,301 represents pure growth on the original £20,000 invested. That gap between cost and outcome is what makes the ISA wrapper so valuable over decades: every dividend reinvested buys more shares, those shares pay more dividends, and the cycle continues without HMRC taking a slice at any stage.

The strategy is straightforward in principle: invest in a spread of FTSE 100 and FTSE 250 stocks that offer both capital growth and dividend income, reinvest every payment automatically, and resist the temptation to trade. Volatility in the short run is the price of higher long-run returns. History shows equities work capital harder than almost any other asset class over periods of 20 years or more.

One practical note: the £20,000 annual ISA allowance can be used in full each year. The more capital deployed inside the tax-free wrapper, the larger the eventual income base. A single year’s contribution is an illustration of the maths, not a ceiling.

British American Tobacco as an income example, and its growing legal risks

British American Tobacco (LSE: BATS) is one of the most-cited dividend compounders on the London market. The company has raised its dividend for 28 consecutive years. For the year ended 31 December 2024, BAT’s dividend per share was 240.24 pence, representing growth of 2.0%, and the board announced a £900 million share buy-back programme for 2025. The trailing yield sits at 5.34%, which maps almost precisely to the 5% assumption in the income calculation above.

The share price has added roughly 75% over five years and around 15% over the last 12 months. On the operational side, BAT reported FY2024 revenue of £25,867 million, down 5.2% year-on-year, weighed partly by a £6.2 billion provision for the proposed settlement in Canada. Free cash flow came in at £7,901 million.

The smokeless transition is progressing: products outside traditional cigarettes accounted for 17.5% of Group revenue in FY2024, up 1.0 percentage point from FY2023, as the company added 3.6 million adult consumers to reach 29.1 million total users of its smokeless range. Chief executive Tadeu Marroco has guided for a return to 3–5% revenue growth and 4–6% adjusted profit-from-operations growth on a constant-currency basis by 2026, with the longer-term ambition of becoming a predominantly smokeless business by 2035.

The legal exposure, though, is real and accumulating. In April 2023, the US Department of Justice accused BAT of violating bank fraud and sanctions laws in connection with business conducted with North Korea through front companies in Singapore and China. BAT entered into a Deferred Prosecution Agreement on 25 April 2023 and agreed to pay $629 million in combined penalties and fines to resolve criminal charges with the DOJ and related civil enforcement by the US Department of the Treasury, according to Broadridge.

On 29 July 2026, a divided US appeals court ruled that BAT must face class-action litigation over claims that its Natural American Spirit cigarettes were marketed as safer than other cigarettes. Reuters reported that consumers in 12 states can proceed with claims, with the certification upheld on the question of whether menthol counts as an additive. Reynolds American, R.J. Reynolds and Santa Fe all declined to comment.

The dividend record and smokeless growth story are genuine positives. The litigation pipeline is extensive, however, and investors who hold BAT for income need to assess whether the yield adequately compensates for the headline and regulatory risk that now runs alongside it.

BATS is one illustration of how dividend compounders can serve an ISA income strategy. Plenty of other FTSE 100 and FTSE 250 names offer comparable yields without the same concentration of legal exposure. The ISA thesis does not depend on any single stock. It depends on time, diversification, and the discipline to keep reinvesting. The next test for BAT investors is the 2026 revenue growth target: if the smokeless transition delivers on Marroco’s guidance, the case for a sustained dividend becomes considerably stronger.