Investment Platform Fee Calculator UK 2026
Calculate and compare investment platform fees over time. See how platform charges (percentage vs flat fee) erode your investment returns at different portfolio sizes.
Platform Fee Types at a Glance
- Percentage fee: charged as % of portfolio each year (e.g. 0.25%). Costs grow as your wealth grows.
- Flat fee: fixed annual charge regardless of portfolio size (e.g. £150/year). Very cost-effective for large portfolios.
- Crossover point: typically £50,000–£100,000 where flat fees become cheaper.
- Total cost: always add fund OCF (typically 0.05%–0.75%) to the platform fee for a true comparison.
Platform Fee Comparison Tool
See which platform is cheaper at your portfolio size — and by how much over the long term.
Investment Platform Fee Calculator
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Projections assume consistent contributions and constant return. Fund OCF not included. Not financial advice.
Why Platform Fees Matter So Much
Platform fees compound in reverse — they silently erode wealth over decades. A 0.25% annual fee on £200,000 costs £500 in year one, but as the portfolio grows to £500,000, the same percentage costs £1,250/year. Over 30 years the difference between a 0.25% fee and a £150 flat fee can easily exceed £100,000 on a large portfolio.
There is no universally “best” platform — it depends entirely on your portfolio size. For portfolios below £50,000, a low percentage fee platform is typically cheaper. Above £75,000–£100,000, a flat-fee platform usually wins. Smart investors switch platforms as their portfolio grows.
Frequently Asked Questions
1. Which investment platform is cheapest in the UK 2026?
It depends entirely on portfolio size. Percentage-fee platforms (typically 0.15%–0.45%/year) are cheapest for portfolios below £50,000–£100,000. Flat-fee platforms (£100–£200/year regardless of size) become significantly cheaper above that threshold. Use our calculator to find the exact crossover for your figures.
2. Flat fee vs percentage platform fee — which is better?
Percentage fees grow with your portfolio. A 0.25% fee on £500,000 costs £1,250/year — far more than a £150 flat fee. Flat fees win for large portfolios; percentage fees win for small ones. The typical crossover is £50,000–£100,000.
3. How much do investment platform fees cost long term?
Platform fees compound in reverse. A 0.25% fee versus a £150/year flat fee on a £100,000 portfolio growing at 7% can represent over £65,000 in lost returns over 30 years. Even a 0.1% difference in fees can cost tens of thousands over a long investment horizon.
4. What is the best ISA platform in the UK 2026?
For large portfolios (above £100,000), flat-fee platforms like Interactive Investor tend to be cheapest. For smaller portfolios or regular savers, percentage-fee platforms like Vanguard, Fidelity (capped), or AJ Bell are competitive. Always compare total cost including fund OCF, not just platform fee.
5. How do I compare investment platform fees accurately?
Compare the total annual cost: platform fee + fund OCF + dealing charges. Multiply percentage fees by your portfolio value; use the stated amount for flat fees. Then project both forward using an expected growth rate to see compounding. Our calculator does this across 10 and 30-year horizons automatically.