Interactive Investor SIPP Review 2026: The Flat-Fee Platform That Works Best for Larger Portfolios
- Alpesh Patel
- 3 days ago
- 5 min read
Updated: 2 days ago
Most UK SIPP platforms charge a percentage of your portfolio. Interactive Investor charges a flat monthly fee. That one structural difference makes II dramatically cheaper than HL, AJ Bell, and Fidelity for portfolios above a certain size — and the break-even point is lower than most investors expect.
Interactive Investor (II) is the UK's second-largest direct-to-consumer investment platform with over 400,000 customers and more than £60 billion in assets under administration. It is listed on the London Stock Exchange and is FCA-authorised. Its SIPP offering covers the full range of investments available on the platform: UK and international equities, ETFs, investment trusts, funds, and bonds.
The flat fee model is the defining feature. Unlike HL's 0.45% annual fee (capped at £200 for shares) or Fidelity's 0.35% (capped at £180), II charges a fixed monthly subscription regardless of portfolio size. For smaller portfolios, this is more expensive than percentage-based platforms. For larger portfolios, it is significantly cheaper — and the crossover point is approximately £50,000–£80,000.
Alpesh Patel OBE is a hedge fund manager, Bloomberg TV alumnus, Financial Times author, and former Visiting Fellow at Corpus Christi College, Oxford. Platform cost is a recurring topic in GIP portfolio reviews and Interactive Investor is a consistent recommendation for investors with portfolios above £80,000.
Interactive Investor SIPP Charges 2026: The Flat Fee Model
Interactive Investor operates on a subscription model with three tiers:
Investor Plan: £11.99/month (£143.88/year). Includes one free trade per month. Additional trades: £5.99 each. Best for buy-and-hold investors who trade infrequently.
Super Investor Plan: £19.99/month (£239.88/year). Includes two free trades per month, reduced deal fee of £3.99, and access to premium research tools. Best for more active investors making 6–15 trades per year.
FX conversion: 1.5% on currency conversions — higher than Fidelity (0.25%) and Trading 212 (0.15%), and comparable to HL's standard rate. For frequent US stock buyers, this is II's primary weakness.
Where II Wins: The Portfolio Size Crossover
For a buy-and-hold SIPP investor making 10 UK stock trades per year (no US stocks), annual platform and dealing costs:
£50,000 portfolio — HL: £225 + £89.55 dealing = £314.55/yr. II Investor: £143.88 + £53.91 dealing = £197.79/yr. Saving: £117/yr.
£250,000 portfolio — HL: £200 (capped) + £89.55 = £289.55/yr. II Investor: £143.88 + £53.91 = £197.79/yr. Saving: £92/yr.
£1,000,000 portfolio — HL: £200 (capped) + £89.55 = £289.55/yr. II Investor: £143.88 + £53.91 = £197.79/yr. Saving: £92/yr. The flat fee advantage becomes proportionally larger as a percentage saving on very large portfolios.
The annual saving vs HL on a pure UK stock portfolio is approximately £90–£120 per year - modest in absolute terms. The more significant advantage is certainty: as your portfolio grows from £250,000 to £500,000 to £1 million, your II subscription cost stays exactly the same. HL's cap means this is also true above £44,000 for shares — but II's all-in cost remains lower for infrequent traders at most portfolio sizes above £50,000.
Where II Falls Short: The FX Rate Problem
II's primary weakness for GIP investors is its FX conversion rate of 1.5% — the highest of the major UK platforms and significantly above Fidelity (0.25%) and Trading 212 (0.15%). For a GIP investor who regularly holds US-listed stocks and makes quarterly portfolio adjustments, the FX cost can exceed the platform fee saving entirely.
On a £10,000 US stock purchase: II costs £150 in FX vs Fidelity's £25 and Trading 212's £15. For a GIP investor making 10 US stock trades per quarter at £8,000 average, the annual FX cost difference between II and Fidelity is approximately £1,000. At that level of US stock activity, Fidelity or Trading 212 are materially better choices than II despite II's lower dealing commission.
II's Research Tools: Genuinely Strong
Interactive Investor's research and editorial offering is one of its genuine differentiators. Its in-house editorial team produces fund and stock analysis, regular market commentary, and the 'Super 60' list of independently rated funds and investment trusts. For investors who use platform-provided research as part of their investment process, II is meaningfully better than AJ Bell and Trading 212, and broadly comparable to HL. The platform's portfolio analytics tools are also solid for tracking allocation and performance across holdings.
The Verdict: Who Should Use Interactive Investor?
UK-focused portfolio, £50,000+, fewer than 20 trades/year: II is the most cost-efficient mainstream UK SIPP platform. The flat fee advantage is real and growing as the portfolio scales.
Regular US stock buyer (10+ US trades/year): II's 1.5% FX rate is a significant disadvantage. Fidelity (0.25% FX) or Trading 212 (0.15% FX) are better choices for this profile.
Values research tools and editorial: II is one of the strongest platforms for investor education and fund research. Worth paying the modest premium over AJ Bell for investors who actively use research content.
Frequently Asked Questions: Interactive Investor SIPP
What are Interactive Investor SIPP charges in 2026?
The Investor Plan is £11.99/month (£143.88/year) including one free trade per month. Additional trades are £5.99 each. The Super Investor Plan is £19.99/month with two free trades and £3.99 additional trades. FX conversion is 1.5% on all currency conversions. There are no percentage-based platform fees — the subscription is flat regardless of portfolio size.
Is Interactive Investor cheaper than Hargreaves Lansdown?
For most portfolios above £50,000 with infrequent US stock trading, yes. II's flat £143.88/year Investor Plan is lower than HL's £200/year cap for shares, and dealing commissions (£5.99 after the free monthly trade) are also lower than HL's £11.95. However, II's 1.5% FX rate is higher than HL's 1.0%, making HL cheaper for investors who regularly buy US stocks.
Is Interactive Investor SIPP safe?
Yes. Interactive Investor is FCA-authorised, listed on the London Stock Exchange, and FSCS-protected up to £85,000. Client assets are held under FCA CASS rules, segregated from II's own balance sheet. II is one of the most established UK retail investment platforms with over 25 years of operation.
Can I hold international stocks in an Interactive Investor SIPP?
Yes. II provides access to UK, US, and major international exchange equities, ETFs, and investment trusts. The investment universe covers the majority of stocks on the GIP Approved List. FX conversion at 1.5% applies for non-GBP purchases — this is the primary cost consideration for US stock buyers.
What is the Interactive Investor Super 60 list?
The Super 60 is Interactive Investor's independently researched list of rated funds, ETFs, and investment trusts across major asset classes and geographies. It is curated by II's in-house research team and reviewed regularly. It serves a similar purpose to HL's Wealth Shortlist - a curated selection of funds considered worthy of inclusion based on research quality, manager track record, charges, and fit for investors. It is a useful starting point for fund selection but is not a substitute for the GIP quantitative framework for stock selection.
For a platform assessment tailored to your portfolio size and trading pattern alongside the GIP investment framework, book a free portfolio review here.
Sources & Further Reading
Interactive Investor — SIPP charges, plans, and platform features (2026). ii.co.uk/sipp
Financial Times — SIPP platform comparison and flat fee vs percentage fee analysis. ft.com/personal-finance
Good Money Guide — Best SIPP providers 2026 and platform comparison. goodmoneyguide.com
Times Money Mentor — UK investment platform comparison 2026. thetimes.co.uk/money-mentor
Disclaimer: This article is for educational purposes only. Fee figures are based on publicly available Interactive Investor pricing as at April 2026 and are subject to change. This does not constitute a personal recommendation to use any specific platform. Always verify current charges directly with the provider.
Alpesh Patel OBE
You haven't covered that ii also charges £40 per trade over £99,999. I'm not totally surprised since teir fees and charges pages hides this further down. On their actual trade quote page, it's also easy to get caught out. You can put in a value close to £99,999, after receiving a market quote, the value will then show as <£100K (the £40 fee threshold), but there is a small dropdown arrow underneath. Click that and it will show the total trade order value which will often be >£100K with a £40 fee built in. It's worth noting that you only have 15 seconds at that point to accept the order. So I think many first time users may get …