What a Stocks and Shares ISA turned £20k into over five years

The question of what a Stocks and Shares ISA does to £20,000 over five years has a range of answers, and the spread between the best and worst outcomes is wide enough to matter. Index choice, stock selection and platform fees all pull in different directions.

Index returns: the passive starting point

For investors who took the passive route, the destination depended heavily on which market they tracked. The London Stock Exchange‘s FTSE 100 is up 51% over the past five years, which would have lifted a £20,000 starting position to over £30,000. The FTSE 250 tells a different story: up just 6%, leaving that same pot a little over £21,000.

The S&P 500 complicates the comparison further. Over the same five-year window, the US index has risen 75%, translating a £20,000 ISA into roughly £35,000 before accounting for exchange-rate movements. Dividends add another layer: the FTSE 250 currently yields 3.5%, the FTSE 100 yields 3%, and the S&P 500 offers 1.1%. Whether those payments were reinvested or drawn as income would have shifted the final figures further still.

Fees matter too. ISA providers levy different charges and those differences compound over five years, which is why comparing platforms before committing is worth the time.

Victrex: what active stock-picking looked like in practice

Individual stock selection could have done considerably better or considerably worse than any index. Victrex (LSE: VCT), the specialist polymer maker with over 40 years in the business, illustrates the risk side. Its share price has fallen 73% over five years, yet the dividend per share has remained flat, pushing the yield to an eye-catching 8.3%. That yield is not currently covered by earnings, which raises the prospect of a cut.

The financial backdrop explains the pressure. Victrex’s preliminary FY 2025 results showed revenue of £292.7m, up 1%, but underlying profit before tax fell 21% to £46.4m and group margin compressed to 45.3%, down 90 basis points. At the reported level, the company posted a pre-tax loss of £44m after exceptional charges of £63m, the bulk of which was a £61m non-cash impairment tied to its manufacturing facility in Liaoning province, north-east China.

The China plant opened in late 2024 but has failed to reach its intended 1,500-tonne annual capacity and is expected to remain loss-making and cash negative through the 2026 financial year. As of 30 September 2025, the total capital expenditure facility for the Chinese operations stood at RMB 250m, with £24.6m due at that date. Analysts at Jefferies noted that the FY 2025 underlying PBT of £46.4m came in below their consensus forecast of £46.6m and said the results served to ‘highlight ongoing mix/price pressure, and self-help is unlikely to be enough to offset these, in our view.’

Victrex is responding with a profit improvement plan that includes cutting around 10% of its workforce, mainly in central functions. The interim dividend was maintained at 13.42p per share, for now.

There are tentative signs of operational recovery. The H1 2026 half-year results, released 10 May 2026, showed group sales volume of 2,137 tonnes, up 6% on the 2,018 tonnes recorded in H1 2025, with revenue up 1%. Capital expenditure in the half fell to £7.4m, below the lower end of management’s 8–10% of revenues guidance range. FY 2025 full-year capex similarly came in at £21.8m, under that same guidance floor. The company is at least spending less while volumes edge higher.

Victrex’s polymers serve aerospace, automotive, medical devices, oil and gas, and consumer electronics. Pricing power derived from proprietary materials has historically been a strength, and recent cost discipline supports the investment case at current levels. Whether that is enough to restore earnings cover for the dividend, and arrest the share-price decline, is the test the next set of results will need to address.

For ISA investors weighing the Stocks and Shares ISA route today, Victrex is a useful case study in the asymmetry of individual-stock exposure: a high yield that may not survive, a recovery thesis that is real but unproven, and a valuation that already prices in considerable doubt. The interim dividend decision in the next earnings announcement will be the clearest signal of management’s confidence in the recovery.