Both are FCA regulated and FSCS protected. The real differences are fees, investment range and how each platform feels to use. Here is the honest comparison.
Fees verified July 2026. Capital at risk. Information, not financial advice.
Fund investors who value guidance, tools and phone support.
Portfolios above roughly £60k where a flat fee beats percentage charges.
| Fee | Fidelity | Interactive Investor |
|---|---|---|
| Platform fee | 0.35% up to £250k (0.20% above); £90/year flat if under £25k without a regular savings plan | Core £5.99/month (up to £100k); Plus £14.99/month (no limit); Premium £39.99/month |
| Share dealing | £7.50 per online trade | £3.99 per trade (£2.99 on Premium) |
| Fund dealing | Free | £3.99 per trade (£2.99 on Premium) |
| FX fee | 0.75% tiered | 1.5% on the first £25k, tiered lower above |
| Stocks & Shares ISA | Platform fee applies | Included in the monthly plan |
| SIPP | Platform fee applies | Included in the monthly plan |
| Withdrawals | Free | Free |
| Minimum to start | £25/month or £1,000 lump sum | No minimum (£25/month for regular investing) |
Reviewers highlight helpful phone support and a straightforward transfer process.
The £7.50 share dealing charge and dated parts of the website draw criticism.
Read Fidelity reviews on TrustpilotLong-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 TrustpilotFidelity is a solid full-service choice for fund investors. Fund dealing is free, the ETF and share service fee is capped at £90 a year, and the guidance content is some of the best of the big platforms.
Costs are less friendly if you trade shares often or hold a small account without a regular savings plan. Compare it against AJ Bell if you want similar breadth with lower dealing charges.
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.
A 0.2% fee difference is worth optimising. Knowing whether you are saving enough in the first place is worth far more. Delphina models your pensions, ISAs and investments and tells you where you actually stand.