How Much Stocks and Shares ISA Income Can £240k Generate?

Targeting £1,000 a month in Stocks and Shares ISA income is a concrete goal with a straightforward arithmetic foundation, and one FTSE 100 dividend share is worth examining as a building block. The maths starts with the yield assumption: at 5%, generating £12,000 a year in dividends requires a portfolio worth £240,000. That is nearly double the current FTSE 100 average yield of 3%, but achievable by concentrating on quality income shares rather than tracking the index passively.

The Arithmetic Behind the £240k Target

The 5% yield figure does most of the work. Divide the annual income target of £12,000 by 0.05 and the required ISA value is exactly £240,000. Most investors will not arrive at that figure immediately, but compounding makes the path manageable. Contributing the annual ISA allowance of £20,000 each year and reinvesting dividends at 5% would push the portfolio past £240,000 within roughly a decade.

The reinvestment step is the part investors sometimes skip. Taking dividends as cash from day one slows the compounding materially. The choice is between income now at a modest level, or patience for a decade that delivers the full £1,000 monthly target thereafter.

Building Stocks and Shares ISA Income Around M&G

One share that merits attention as a portfolio anchor is M&G (LSE: MNG), the FTSE 100 asset and savings manager. Its dividend yield currently sits at around 6%, materially above the index average, and the payout direction is upward. Yahoo Finance reports the total dividend per share for 2025 was 20.5p, up from 20.1p in 2024 and 19.7p in 2023.

In March 2025, M&G formalised a new progressive dividend policy. According to the M&G press release, the company set targets to grow adjusted operating profit before tax by an average of 5% or more per annum through 2027, and to generate £2.7 billion of operating capital over the same period. A 2% increase was applied to the 2024 total dividend per share as the opening move under the new framework.

The underlying business has steadily improved. Full-year 2025 results, published on the M&G investor relations page, show adjusted operating profit before tax of £838m, broadly flat year-on-year, while the Shareholder Solvency II ratio strengthened to 242% from 223% a year earlier. Net flows from open business swung to a £7.8bn inflow in 2025, reversing a £1.9bn outflow in 2024, a shift of nearly £10 billion in a single year.

Q1 2025 added further evidence of stabilisation. The Investing.com report on M&G’s Q1 update noted net asset management inflows of £0.7bn, reversing a £0.1bn outflow in the same period of the prior year, with assets under management and administration closing the quarter at £344bn, up 10% year-on-year. The strongest demand came from European equities, structured credit and impact funds.

Strategic depth was added in May 2025, when M&G entered a long-term partnership with Dai-ichi Life Holdings, associated with an approximately 15% investment that made the Japanese insurer M&G’s largest shareholder. The M&G 2024 Annual Report provides the fuller context: AUMA stood at £345.9bn at year-end 2024, up from £343.5bn in 2023, while the IFRS result after tax was a loss of £347m against a profit of £309m the prior year, reflecting non-cash items rather than the operational picture.

Where the Thesis Could Come Under Pressure

The principal risk is the same one that has tested M&G before: policyholders withdrawing more from life and savings products than they contribute. The FT Markets announcement on the full-year 2024 results noted that the life business continued to face net outflows from legacy with-profits books, a structural drag that will persist as those books run off. In Q1 2025, life AUMA declined approximately 2% due to expected outflows from Traditional With-Profits and market headwinds.

A sustained equity market sell-off would also pressure fee income, given that much of M&G’s revenue scales with AUM. The solvency buffer of 242% provides headroom, but fee income contraction would test the pace of dividend growth rather than the dividend itself.

For an investor assembling a diversified income portfolio inside an ISA, MNG’s 6% yield and progressive dividend policy offer a higher starting income than most FTSE 100 alternatives at current prices. The net-flow reversal in 2025 and the Dai-ichi partnership both reduce near-term uncertainty. The more pressing question is whether the 5%-plus annual profit growth target through 2027 is achievable in a slower-growth asset management market, and the answer to that will determine whether the dividend compounds as the policy intends or merely holds.