Interactive Investor vs Interactive Brokers 2026: What FX Fees Really Cost You on US Shares
By Alpesh Patel OBE, hedge fund manager and author
Short answer: If you buy US shares in a Stocks and Shares ISA, the currency conversion fee usually costs far more than the dealing fee. Interactive Investor (ii) charges £3.99 to deal in US shares, but converting your pounds to dollars costs 0.75% on its Core plan, and on the first £50,000 on its Plus plan. Interactive Brokers (IBKR) adds about 0.03% to the exchange rate when it converts automatically in an ISA. On a £10,000 purchase, that's roughly £79 at ii against about £4 at IBKR. ii is simpler to use and has UK-based support. IBKR is much cheaper for anyone who trades a lot of US shares. The figures below come from both firms' own websites on 12 October 2026.
Despite the names, these are two unrelated companies. Interactive Investor is a UK flat-fee platform. Interactive Brokers is a global broker with a UK arm, Interactive Brokers (U.K.) Limited. Many UK investors who hold a lot of US shares end up asking which one costs less, and the answer comes down to foreign exchange.
Why FX fees matter more than dealing fees
When you buy Apple or Microsoft with pounds, your platform has to convert sterling into dollars first. It does this at the market exchange rate plus a fee. You pay again when you sell and bring the money back to pounds. In an ISA, dividends paid in dollars are converted back to pounds as well.
A £3.99 dealing fee on a £10,000 trade is 0.04%. A 0.75% FX fee on the same trade is £75, nearly 19 times as much. Most people compare dealing fees and never look at the FX line.
The ISA problem: you can't hold dollars
HMRC rules require ISAs to be funded in pounds, and both platforms say so on their websites. ii lets you hold up to nine currencies, including US dollars, in its Personal Pension (SIPP) and Trading Account, but not in its ISA. IBKR's ISA must also be funded in GBP, and it converts to dollars when you trade.
So in an ISA you can't convert once and keep your dollars, as you can in a trading account. Every US buy and every sale goes through a currency conversion, which makes the FX rate the number that matters most.
Interactive Investor vs Interactive Brokers fees at a glance
Interactive Investor (ii) | Interactive Brokers (IBKR UK) | |
|---|---|---|
Monthly account fee | Core £5.99 (portfolios up to £100,000), Plus £14.99, Premium £39.99 | No custody fee. ISA has a £3 monthly minimum activity fee |
US share dealing | £3.99 on Core and Plus, £2.99 on Premium. 0.04% of trade value on US trades over £100,000 | Fixed pricing: $0.005 per share, minimum $1, maximum 1% of trade value |
FX on US trades | Core 0.75%. Plus: 0.75% on the first £50,000 and 0.25% above that. Premium 0.25% | Auto-conversion in the trade: about 0.03% added to the exchange rate. Manual conversion: 0.002% (0.20 basis points), minimum $2 |
Hold US dollars? | Yes in the SIPP and Trading Account. Not in the ISA | ISA must be funded in GBP. Other accounts can hold multiple currencies |
Free trades | Plus: £3.99 trading credit a month. Premium: £29.90 a month | None |
Who it suits | Investors who want a simple flat fee and UK phone support | Active or larger investors comfortable with a more complex platform |
ii's charges are from its rates and charges document, last updated 1 October 2026. IBKR's are from its UK commissions, currency and ISA pages. IBKR's fixed US pricing does not include some US regulatory fees, which add a small amount when you sell.
Worked example: buying £10,000 of a US share in an ISA
Cost to buy £10,000 of US shares | ii Core or Plus | ii Premium | IBKR ISA |
|---|---|---|---|
Dealing fee | £3.99 | £2.99 | About $1 (under £1) |
FX fee | £75.00 (0.75%) | £25.00 (0.25%) | About £3.00 (0.03%) |
Total to buy | £78.99 | £27.99 | About £4 |
Buy and later sell | About £158 | About £56 | About £8 |
On a single trade the gap is £70 to £150. The bigger question is what happens over a year.
Worked example: £100,000 of US trades a year
Say your ISA is worth more than £100,000 and you buy or sell £100,000 of US shares a year in ten £10,000 trades. Here's the rough cost of each option, counting only these trades:
ii Plus: £179.88 a year in fees. The ten trades are covered by your £3.99 monthly credit. FX at 0.75% comes to £750. Total about £930.
ii Premium: £479.88 a year in fees. The ten trades are covered by your monthly credit. FX at 0.25% comes to £250. Total about £730.
IBKR ISA: up to £36 a year in minimum activity fees, about £10 of commission and about £30 of FX. Total about £76.
That's a saving of roughly £650 to £850 a year, before dividends. Over ten years, at the same level of trading, that's £6,500 or more, plus whatever growth that money would have earned. If you trade more, or have a bigger US allocation, the gap grows. If you mostly buy UK shares and funds, the gap shrinks and ii's flat fee can be very good value.
One caution on ii's Plus plan: it charges 0.75% on the first £50,000 and 0.25% above that. If you convert large amounts, check with ii how that threshold applies to your trades before you assume the 0.75% figure.
Watch: how platform fees quietly drain a portfolio
When Interactive Investor still makes sense
You mostly hold UK shares, investment trusts and funds. There's no FX to pay, and a flat fee beats percentage-based platforms on larger portfolios. I compare those percentage fees in AJ Bell vs Hargreaves Lansdown.
You use the ii SIPP or Trading Account for US shares. You can convert once, hold dollars and trade in and out without paying FX each time.
You want simplicity and UK phone support. IBKR's platform is powerful, but it's built for active traders and takes time to learn.
When Interactive Brokers makes sense
You hold a lot of US shares in an ISA. This is where the 0.75% vs 0.03% gap hurts most.
You trade regularly. Low per-share pricing and near-wholesale FX keep costs down.
You want one account for many markets. IBKR lets you trade shares in many countries from a single account.
If you're weighing up IBKR for a pension rather than an ISA, see my comparison of Interactive Brokers vs Hargreaves Lansdown for a self-directed SIPP.
Before you transfer an ISA
Transfer, don't withdraw. Use the new provider's ISA transfer form so you keep the tax wrapper. Taking cash out and paying it back in uses up your £20,000 allowance.
Check whether you'll be out of the market. A cash transfer means selling and sitting in cash for a while. An in-specie transfer moves the shares themselves.
Check exit and transfer fees. IBKR says it charges no fee to transfer an ISA in, and ii says it has no exit fees.
Count your real trading pattern. Add up last year's US buys and sells and apply the rates above. That's your real annual FX bill.
Fees are the easy part
Cutting FX costs from 0.75% to 0.03% is a quick win. But it won't fix a portfolio of shares picked from tips and headlines. The bigger costs for most self-directed investors are holding too many stocks, having no rules for when to sell, and owning things they can't explain. A cheap platform makes a good process cheaper to run. It doesn't replace one. If you're paying a percentage fee to an adviser as well, see what 1% a year really costs your portfolio.
FAQs
Is Interactive Investor the same as Interactive Brokers?
No. They're separate, unrelated companies. Interactive Investor is a UK flat-fee investment platform. Interactive Brokers is a global broker that serves UK clients through Interactive Brokers (U.K.) Limited.
What FX fee does Interactive Investor charge on US shares?
On 12 October 2026: 0.75% on the Core plan, 0.75% on the first £50,000 and 0.25% above that on Plus, and 0.25% on Premium. That's on top of the dealing fee of £3.99, or £2.99 on Premium.
What does Interactive Brokers charge to convert pounds to dollars?
When IBKR converts automatically as part of a trade, it typically adds 0.03% to the exchange rate and charges no separate commission. If you convert manually through its currency market, it charges 0.002% (0.20 basis points), with a minimum of $2 per order.
Can I hold US dollars in a Stocks and Shares ISA?
ISAs must be funded in pounds. ii doesn't allow foreign currency in its ISA, though it does in its SIPP and Trading Account. So US trades in an ISA involve converting pounds each time.
Does Interactive Brokers have an ISA fee?
There's no custody fee. IBKR UK applies a £3 monthly minimum activity fee to its Stocks and Shares ISA, and £1 a month to Junior ISAs.
Are Interactive Investor and Interactive Brokers safe?
Both are authorised and regulated by the Financial Conduct Authority, and client investments are held separately from the firm's own money. Eligible investments are covered by the Financial Services Compensation Scheme up to £85,000 if a firm fails and can't return your assets.
Want a second pair of eyes on your US holdings, whichever platform you use?
Book a call with my team. We'll look at what you hold, how you pick investments now, and whether the Great Investments Programme makes sense for you.
Important: This article is for education only and is not personal financial advice. Alpesh Patel Ventures Ltd provides general investment education and is not authorised by the Financial Conduct Authority to give regulated investment advice. Fees were taken from Interactive Investor's and Interactive Brokers' websites on 12 October 2026 and can change. Check the latest charges before you open or transfer an account. Currency movements can reduce the value of overseas investments in sterling. The value of investments can go down as well as up, and you may get back less than you invest. Tax treatment depends on individual circumstances and may change.
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