There’s no single “cheapest investment platform” — the answer depends on whether you hold funds, ETFs, or shares, how large your portfolio is, and how often you trade. Here’s a direct comparison of all nine major UK platforms, so you can see where each one wins.
The short answer
| If you mainly hold… | Cheapest platform | Why |
|---|---|---|
| Funds (unit trusts/OEICs) | Barclays Smart Investor | 0% platform fee, £0 dealing on funds |
| ETFs | InvestEngine or Trading 212 | 0% platform fee, £0 dealing |
| Shares | Trading 212 or Freetrade | 0% platform fee, £0 dealing |
| A large mixed portfolio (£100k+) | Interactive Investor | Flat £71.88–£179.88/year beats percentage fees at scale |
| A SIPP | Barclays (funds) or InvestEngine (ETFs) | Same zero-fee structure carries over from their ISAs |
Trading 212 does not currently offer a SIPP.
Compare investment platforms at a glance
| Platform | Fee type | Funds | ETFs/shares | SIPP available |
|---|---|---|---|---|
| Barclays Smart Investor | Free (funds), £6/trade (ETFs/shares) | 0% | £6/trade, no cap | Yes |
| InvestEngine | Free | — (ETFs only) | 0% | Yes |
| Trading 212 | Free | — (no funds) | 0% | No |
| Freetrade | Flat | — (ETFs/shares/some funds) | £5.99–£9.99/mo | Yes |
| Vanguard | Percentage, capped | 0.15%, capped £375 | 0.15%, capped £375 | Yes |
| AJ Bell | Percentage, capped on ETFs/shares | 0.25%, no cap | 0.25%, capped £42 (ISA)/£120 (SIPP) | Yes |
| Fidelity | Percentage, tiered | 0.35% (tiering down) | 0.35%, capped £90 | Yes |
| Hargreaves Lansdown | Percentage, tiered | 0.45%→0.25%, no cap | capped £45 (ISA)/£200 (SIPP) | Yes |
| Interactive Investor | Flat | £71.88/yr (Core, up to £100k) | same | Yes |
Figures as of June 2026. Verify current rates directly with each provider — see individual platform reviews for full breakdowns and our fee calculator for costs at your exact portfolio size.
Why “cheapest” depends on what you invest in
Platforms fall into three pricing models:
- Free platforms (Barclays for funds; InvestEngine, Trading 212, and Freetrade for ETFs/shares) charge nothing to hold investments, but usually restrict what you can hold — no funds on InvestEngine or Trading 212, for instance.
- Percentage-fee platforms (Vanguard, AJ Bell, Fidelity, HL) charge a proportion of your portfolio each year, sometimes capped. These get relatively cheaper as caps kick in, but expensive below the cap for large fund holdings.
- Flat-fee platforms (Interactive Investor) charge a fixed subscription regardless of portfolio size — expensive for small portfolios, very competitive for large ones.
For a full cost breakdown across portfolio sizes from £10,000 to £500,000, see the cheapest ISA by portfolio size.
What the free platforms give up
Zero fees usually come with trade-offs:
- Barclays: full fund range and free fund dealing, but £6/trade for ETFs and shares, and less research depth than HL or Fidelity.
- InvestEngine: ETFs only — no individual shares, funds, or investment trusts.
- Trading 212: ETFs and shares, fractional shares, but no funds and no SIPP.
- Freetrade: broader range including some funds, but a flat monthly fee (not free) and app-only access.
How to actually compare platforms for your situation
- Identify what you invest in — funds, ETFs, shares, or a mix. This alone eliminates several options.
- Estimate your portfolio size — percentage fees and flat fees cross over at different points; our calculator shows your exact crossover.
- Check account type support — not every platform offers a SIPP (Trading 212 doesn’t) or a Lifetime ISA.
- Weigh non-fee factors — research tools, customer service, and app quality vary significantly between the free platforms and full-service ones like HL and Fidelity.
Use the platform reviews for account-by-account detail, or head straight to a side-by-side comparison of any two platforms.