Both are FCA-regulated and FSCS-protected. The real difference is fees, account types and how each platform feels to use. Verified against each provider’s published charges.
Fees verified July 2026. Capital at risk. Information, not financial advice.
Portfolios above roughly £60k where a flat fee beats percentage charges.
Index fund investors who want the lowest possible total cost and are comfortable with a newer app.
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Tick what you need above and we'll tell you which of the two covers it.
Account availability verified July 2026. Capital at risk. Information, not financial advice.
Long-standing customers value the flat fee and the breadth of investments.
The 1.5% headline FX fee and occasional platform outages are the recurring complaints.
Read Interactive Investor reviews on TrustpilotEarly adopters praise the zero fees and responsive founding team; roughly 84% of reviews are five stars.
The review base is small and some users want more account types and a web version.
Read Prosper reviews on Trustpilot| Fee | Interactive Investor | Prosper |
|---|---|---|
| Platform fee | Core £5.99/month (up to £100k); Plus £14.99/month (no limit); Premium £39.99/month | £0 |
| Share dealing | £3.99 per trade (£2.99 on Premium) | Not applicable (funds and ETFs) |
| Fund dealing | £3.99 per trade (£2.99 on Premium) | Free |
| FX fee | 1.5% on the first £25k, tiered lower above | None on GBP fund classes |
| Stocks & Shares ISA | Included in the monthly plan | Free |
| SIPP | Included in the monthly plan | Free |
| Withdrawals | Free | Free |
| Minimum to start | No minimum (£25/month for regular investing) | No minimum |
Interactive Investor charges a flat monthly subscription instead of a percentage. On a £200,000 portfolio, £5.99 a month is a fraction of what percentage-fee platforms charge, which is why ii keeps winning larger DIY investors.
The equation flips for small pots: £71.88 a year on £10,000 is 0.7%, more than almost any rival. Work out your portfolio size first, then decide.
Prosper's pitch is the cheapest total cost of ownership in the UK: no platform fee, no dealing fees, and refunded fund fees on a list of mainstream index funds. For a straightforward global tracker in an ISA or SIPP, the all-in cost really can be zero.
The counterweight is maturity. It is a young platform with a small (if very positive) review base and no individual shares. If that trade-off suits you, the price is unbeatable.
It depends on what you hold and how often you trade. Interactive Investor's platform fee is core £5.99/month (up to £100k); Plus £14.99/month (no limit); Premium £39.99/month, against £0 at Prosper. On dealing, Interactive Investor charges £3.99 per trade (£2.99 on Premium) for shares and £3.99 per trade (£2.99 on Premium) for funds, while Prosper charges not applicable (funds and ETFs) for shares and free for funds. Fees verified July 2026.
Interactive Investor is best for portfolios above roughly £60k where a flat fee beats percentage charges. Prosper is best for index fund investors who want the lowest possible total cost and are comfortable with a newer app. Both are FCA regulated and covered by the FSCS.
On Interactive Investor's ISA: Included in the monthly plan. On Prosper's ISA: Free. Prosper offers a flexible ISA and Interactive Investor does not. Minimums are No minimum (£25/month for regular investing) at Interactive Investor and No minimum at Prosper.
Interactive Investor offers a SIPP (included in the monthly plan). Prosper offers a SIPP (free).
Interactive Investor scores 4.6 out of 5 on Trustpilot (Excellent) from over 28,000 reviews. Prosper scores 4.6 out of 5 (Excellent) from around 300 reviews. The 1.5% headline FX fee and occasional platform outages are the recurring complaints. The review base is small and some users want more account types and a web version.
Yes. UK platforms accept ISA and SIPP transfers in, and you start the transfer with the receiving provider rather than the one you are leaving. Interactive Investor charges free on withdrawals and Prosper charges free. Transfer as cash and you are out of the market while it settles; transfer in specie and you keep your holdings but it takes longer.
Interactive Investor or Prosper, the account is the easy part. What decides when you can retire is how much goes in and for how long. Delphina works that out from what you already hold and what you pay in each month.
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