There's no single "cheapest investment platform" — the right answer depends on your portfolio size, what you're investing in, and how often you trade. Percentage-fee platforms like Vanguard or AJ Bell tend to suit smaller portfolios; flat-fee platforms like Interactive Investor tend to win once you're holding six figures. Below is a starting-point ranking for a typical £20,000 Stocks & Shares ISA invested in index funds — click through to any review for the full fee breakdown at your own portfolio size.
Cheapest platforms for a £20,000 ISA (funds, monthly trading)
| Rank | Platform | Annual cost |
|---|---|---|
| 1 | Barclays Smart Investor | £0/year |
| 2 | Freetrade | £0/year |
| 3 | Dodl | £30/year |
| 4 | Vanguard | £48/year |
| 5 | AJ Bell | £68/year |
| 6 | Interactive Investor | £120/year |
| 7 | Fidelity | £875/year |
| 8 | Hargreaves Lansdown | £898/year |
Ranking based on fund fees at £20,000 with monthly trading — this will differ for ETFs, shares, or other portfolio sizes. InvestEngine and Trading 212 are excluded here as neither offers funds. Use the calculator on the homepage or any review below for your exact numbers.