Interactive Investor's New Fee Plans: Core, Plus, or Premium — Which One Actually Saves You Money?

Interactive Investor now operates three tiers, all effective from 1 February 2026:

Core — £5.99/month (£71.88/year)

• Portfolio limit: up to £100,000
• Fund trades: £3.99 each
• UK/US share trades: £3.99 each
• FX charge: 0.75%
• No Junior ISA, no family accounts
• Pension admin fee: £2.50/month (included in the £5.99)

Plus — £14.99/month (£179.88/year)

• No portfolio limit
• Fund trades: £1.49 each
• UK/US share trades: £3.99 each
• 1 free trade per month (£3.99 credit)
• 5 free family member accounts (up to £100k each)
• Junior ISAs included
• FX: 0.75% on first £50,000, then 0.25%
• Pension admin fee: £6.00/month (included)

Premium — £39.99/month (£479.88/year)

• No portfolio limit
• Fund trades: free
• UK/US share trades: £2.99 each
• 2 free trades per month (£5.98 credit)
• Unlimited family accounts
• FX: 0.25% flat
• Free dividend reinvestment
• Pension admin fee: £6.00/month (included)

The critical detail: you start on Core automatically. If your portfolio crosses £100,000, you're moved to Plus. You can voluntarily upgrade to Premium at any time, but you can't stay on Core above £100k.

The right plan depends on two variables: your portfolio size and how often you trade. I've modelled three investor profiles to show which plan wins.

Buy-and-hold investor: 4 fund trades per year, £50,000 portfolio

• Core: £71.88 + (4 × £3.99) = £87.84/year
• Plus: £179.88 + (4 × £1.49) = £185.84/year (minus 12 × £3.99 free trade credit = £137.96)
• Premium: £479.88 + £0 = £479.88/year

Core wins decisively. A buy-and-hold investor under £100k has no reason to upgrade.

Active investor: 24 fund trades and 12 share trades per year, £150,000 portfolio

• Plus (mandatory above £100k): £179.88 + (24 × £1.49) + (12 × £3.99) = £263.52/year (minus 12 free trade credits)
• Premium: £479.88 + £0 + (12 × £2.99) = £515.76/year (minus 24 free trade credits)

Plus still wins unless you're trading significantly more — Premium only justifies itself above roughly 60 trades per year.

International investor: significant US/European holdings with frequent FX conversions Here Premium shines. On a £200,000 portfolio with £50,000 in annual FX conversions:

• Core FX cost: £50,000 × 0.75% = £375
• Premium FX cost: £50,000 × 0.25% = £125

The FX saving alone (£250/year) covers more than half the Premium fee. If you hold US shares and reinvest dividends in dollars, Premium pays for itself quickly.

The family factor changes everything. The Plus plan gives 5 free family accounts — each getting their own ISA and trading account at no monthly cost. If your partner would otherwise need their own Core plan, you're saving £71.88/year immediately. With two children in Junior ISAs (only available on Plus/Premium), the family package becomes exceptional value. For more on Junior ISAs, — the full £9,000 Junior ISA allowance can grow tax-free. See our guide to the £9,000 tax-free allowance.

Interactive Investor's flat-fee model saves money as your portfolio grows. But below a certain threshold, percentage-fee platforms like AJ Bell (0.25%) or Hargreaves Lansdown (0.35%) are actually cheaper. Our flat-fee vs percentage-fee deep dive covers this in detail, but here are the key crossover points.

ii Core vs AJ Bell (0.25%) — breakeven: £28,752. Below this amount, AJ Bell costs less in platform fees. Above it, ii's flat fee wins.

ii Plus vs AJ Bell (0.25%) — breakeven: £71,952. The higher Plus fee means AJ Bell stays cheaper until your portfolio reaches about £72k. But remember — above £100k you're on Plus regardless, and at that point ii costs £179.88 vs AJ Bell's £250.

ii Core vs HL (0.35%) — breakeven: £20,537. HL's percentage fee is cheaper than ii's flat fee below roughly £20k.

ii Plus vs HL (0.35%) — breakeven: £51,394. Above £51k, ii Plus beats HL on platform fees alone — before considering HL's fund dealing charges and OCF discounts.

The takeaway: if you're just starting out with a small ISA — the £20,000 annual ISA allowance means your pot will grow quickly or SIPP, a percentage-fee platform costs less. Once your investments grow past £30,000-£70,000 (depending on which plan you're on), the flat fee becomes the better deal — and the advantage widens every year as your portfolio grows through contributions and returns.

At £500,000, the gap is dramatic: ii Plus at £179.88/year vs HL at £1,750/year. That's £1,570/year — enough to max out a Junior ISA annually with the money saved on platform fees alone.

Under the old ii pricing, holding a SIPP cost an additional £12.99/month on top of your plan fee. That's gone. Every plan now includes ISA, SIPP, and trading account access in the single monthly fee.

For someone with both an ISA and a SIPP, the savings are significant:

• Old cost (Investor plan + SIPP): £11.99 + £12.99 = £24.98/month = £299.76/year
• New cost (Core plan, both accounts): £5.99/month = £71.88/year

That's a £227.88/year saving — or £6,837 over 30 years before compounding. With compound growth, the actual impact on your pension pot is even larger.

Compare this with competitors for a combined ISA + SIPP portfolio:

• At £150,000 combined: ii Plus £179.88/year vs AJ Bell £375 vs HL £525
• At £300,000 combined: ii Plus £179.88/year vs AJ Bell £500 vs HL £1,050

The flat-fee advantage on a pension portfolio is dramatic. If you're building a retirement pot alongside your ISA — as virtually every working adult should be — ii's bundled pricing is the strongest argument for the platform.

ii's SIPP also allows you to hold multiple currencies without conversion — useful if you own US shares and want to reinvest dividends without paying FX charges each time. With the Bank of England base rate influencing cash returns on uninvested SIPP balances, keeping platform fees low ensures more of your pension compounds over time. This matters for investors holding US ETFs like Vanguard S&P 500 (VUSA) in their pension.

Pension tax relief makes SIPP fees especially important. If you're a higher-rate taxpayer contributing £30,000/year to a SIPP, you're receiving £12,000 in tax relief. Paying £1,000+ in unnecessary platform fees on the growing pot erodes the benefit of that relief over time. According to HMRC guidance on pension tax relief, you can contribute up to 100% of annual earnings with tax relief — making fee efficiency on large pots critical. See our analysis on Hargreaves Lansdown's new 0.35% fee structure.

The Core plan's £100,000 portfolio cap is the biggest issue. If your investments grow past £100k — which is the goal, after all — you're automatically bumped to Plus at £14.99/month. There's no grace period and no warning. Market fluctuations around the boundary could push you between plans month to month, creating billing unpredictability.

The auto-upgrade catches people off guard. If you opened an account expecting to pay £5.99/month indefinitely, a good year in the market could increase your monthly fee by 150%. This is a design choice that punishes successful investors — ironic for an investment platform.

Other drawbacks worth weighing:

• Dividend reinvestment costs £0.99 per holding on Core and Plus. If you hold 10 dividend-paying funds, that's £9.90/month or £118.80/year. On Premium, it's free. For income-focused investors building a retirement portfolio, this hidden cost adds up.

• No Junior ISA on Core. If you want to invest for your children, you need Plus (£14.99/month) minimum. HL offers free Junior ISAs at any portfolio size.

• Pension admin fee is embedded. Core includes a £2.50 pension admin fee; Plus and Premium include £6.00. This is baked into the monthly price, not charged separately — so the "true" platform fee is lower than the headline figure.

• £49 telephone dealing charge. If you can't or won't trade online, ii is eye-wateringly expensive. HL charges £29 for phone dealing — still painful but less so.

• International share costs escalate. On Core, international shares (non-UK, non-US) cost £9.99 per trade. For European dividend stocks or Asian market exposure, this adds up quickly.

ii is authorised by the FCA (firm reference 515730) and your investments are covered by the FSCS up to £85,000 if the platform fails — though as with all platforms, your underlying investments remain yours and are held in nominee accounts separate from ii's own assets. MoneyHelper provides independent guidance on switching investment platforms.

This article is for informational purposes only and does not constitute financial advice. You should seek independent financial advice before making any investment decisions.