Key takeaways
- On a £50,000 stocks and shares ISA held in funds, the published annual account charge runs from £71.88 at interactive investor to £175 at Hargreaves Lansdown.
- interactive investor's £71.88 Core plan overtakes Hargreaves Lansdown's 0.35% at £20,537 of funds and AJ Bell's 0.25% at £28,752. Vanguard's 0.15% holds out to £47,920.
- The crossover vanishes for ETFs and shares. AJ Bell caps that charge at £42 a year and Hargreaves Lansdown at £150, so both become flat fees too.
- One £10,000 international share purchase costs £99 in FX at Hargreaves Lansdown against £75 at AJ Bell — more than a full year of interactive investor's £71.88 Core fee.
- The FCA found in December 2023 that 71% of 42 sampled firms retained cash interest, keeping 50% on average and earning £74.3m in June 2023 alone.
The cheapest platform depends on six numbers, and the headline is only one
Which UK investment platform costs least? Nothing on the front of a tariff page answers that, and the tariff pages themselves show why.
Six charges make up the stack. There's the annual account fee and any cap on it, the dealing charge, the discount for regular monthly investing, the foreign exchange spread on overseas trades, exit and transfer fees, and the interest the platform keeps on your uninvested cash. Only the first appears in most comparisons.
Every figure below was taken from the provider's own published charges page on 8 August 2026. Tariffs move — AJ Bell's cash interest rates have applied only since 1 February 2026, and Hargreaves Lansdown's since 10 June 2026. Treat the arithmetic as the durable part and the numbers as perishable.
At £50,000 in funds, the published annual charge runs from £71.88 to £175
Take a stocks and shares ISA holding £50,000, all of it in funds rather than exchange-traded products. The chart above shows what each platform's own published account charge comes to over a year.
interactive investor charges £5.99 a month on its Core plan. That's £71.88 a year, and it doesn't move with your balance. Vanguard charges 0.15% a year above £32,000, so £75. AJ Bell charges 0.25% on the first £250,000 of funds, so £125. Hargreaves Lansdown and Fidelity both charge 0.35% at this size, so £175 each.
That's a spread of £103.12 a year on an identical portfolio, before anyone places a trade. It's also the narrowest the comparison ever looks, because it holds every other variable still.
Where a flat fee overtakes a percentage, computed from the published tariffs
The crossover is one division. Take the flat annual fee, divide by the percentage rate, and you get the portfolio value where the two charges meet.
interactive investor's Core plan costs £71.88 a year. Against Hargreaves Lansdown's 0.35%, that's £20,537 of funds. Against AJ Bell's 0.25%, £28,752. Against Vanguard's 0.15%, £47,920. Below those values the percentage platform charges less; above them, the flat fee does.
Vanguard is a hybrid, and it shows the mechanism plainly. Below £32,000 it charges £4 a month — £48 a year, flat. Above £32,000 it switches to 0.15%, capped at £375 a year. That cap bites at £250,000, above which Vanguard is a flat-fee platform again.
interactive investor has its own ceiling running the other way. The Core plan carries a £100,000 portfolio limit, after which the Plus plan applies at £14.99 a month, or £179.88 a year. Against Vanguard's 0.15%, £179.88 is the charge on £119,920. So Vanguard's percentage sits under interactive investor's flat fee below £47,920, rises above it, then drops back under between £100,000 and £119,920 where the Plus plan takes over. A crossover isn't always a single point.
The crossover disappears the moment you hold ETFs instead of funds
Here's the strongest objection to the whole flat-versus-percentage framing, and it comes from the percentage platforms' own tariffs.
On shares, ETFs and investment trusts, three of them cap the account charge outright. AJ Bell caps it at £3.50 a month, which is £42 a year. Fidelity caps it at £7.50 a month, or £90. Hargreaves Lansdown caps it at £12.50 a month, or £150.
A cap converts a percentage into a flat fee above a threshold. AJ Bell's bites at £16,800 of shares, Fidelity's at £25,714, Hargreaves Lansdown's at £42,857. Above those values an exchange-traded holding pays a fixed number at all three. And £42, £90 and £150 all sit below interactive investor's £179.88 Plus plan.
So the crossover the headline arithmetic produces is a fund investor's crossover. Fund charges stay uncapped to £250,000 at both AJ Bell and Hargreaves Lansdown. On the exchange-traded side the difference between the two fee models largely dissolves, and the caps decide it instead.
Dealing charges run the other way, and they scale with your activity
The account fee is annual and scales with your balance. Dealing charges are per transaction and scale with how often you trade.
A one-off fund trade costs £1.50 at AJ Bell and £1.95 at Hargreaves Lansdown. Fidelity charges nothing for fund deals at all. On interactive investor's Core plan it's £3.99. Twelve one-off fund purchases over a year come to £47.88 at interactive investor and £23.40 at Hargreaves Lansdown — two-thirds of interactive investor's entire annual platform fee, in dealing costs alone.
Regular monthly investing wipes most of that out. AJ Bell, Hargreaves Lansdown and interactive investor all charge nothing for a scheduled monthly investment, and AJ Bell's service starts at £25 a month. Fidelity never charges for a fund deal, though a share deal inside a regular savings plan still costs £1.50. That one feature moves the total more than the fee model does at small balances.
Share dealing tilts back. A UK or US share trade costs £3.99 on interactive investor's Core plan, £5.00 at AJ Bell, £7.50 at Fidelity, and £6.95 at Hargreaves Lansdown — falling to £3.95 there if you placed 20 or more trades the previous month.
One overseas trade can cost more than a year of platform fees
The FX charge is the least visible line in the stack, because it's a spread on a conversion rather than a fee on a statement.
On a £10,000 purchase of a US share, Hargreaves Lansdown charges 0.99%, which is £99. AJ Bell, Fidelity and interactive investor's Core plan each charge 0.75% on that band, or £75. Hargreaves Lansdown's own note is explicit that the charge is banded: on a £15,000 deal it's 0.99% of the first £10,000 and 0.50% of the next £5,000.
That £99 is more than interactive investor's Core plan costs for a whole year. It's one trade. The bands matter as much as the headline rate — AJ Bell drops to 0.25% above £20,000 and Hargreaves Lansdown to 0.20% above £25,000, while interactive investor's Core plan stays at 0.75% however large the conversion.
Dividends get converted too. Hargreaves Lansdown adds a 1% spread to the interbank rate on foreign currency from dividends and corporate actions; AJ Bell charges 0.5% on the same conversions. Our piece on FX charges, platform fees and withholding tax works through what that costs a US-heavy holding across a full year.
Uninvested cash carries a charge that never appears on the tariff page
The Bank of England's official Bank Rate was 3.75% when this was written. Platforms deposit your uninvested cash with banks and keep part of what it earns.
Hargreaves Lansdown says so in its own words. It "expects to receive interest of between 0.5% below and 0.5% above the prevailing Bank of England base rate", and it "retains the difference between the interest HL receives and the interest paid to you." It pays 1.30% on the first £19,999.99 of ISA cash. Against 3.25% to 4.25% received, that's 1.95 to 2.95 percentage points retained.
interactive investor is equally direct: "Any interest received on such balances belongs to us." It pays 1.10% on the first £20,000 of sterling ISA cash. AJ Bell pays 1.75% on ISA cash at any balance, and on a Dealing account pays 0.75% on the first £2,000 and 0.00% on anything above that.
The FCA examined this in December 2023. It surveyed 42 platforms and SIPP operators and found 71% retained at least some of the interest, keeping 50% on average across a range of 10% to 100%. In June 2023 alone those firms earned £74.3m from the practice. It also found 61% of the interest-retaining platforms charged a platform fee on the same cash — "double dipping", which the regulator told firms to stop. This cost scales with your cash balance rather than your portfolio, which is why the drag from portfolio cash is worth measuring on its own.
The whole stack, on one £40,000 ISA over one year
Put the pieces together for a single year at Hargreaves Lansdown. Say £40,000 in funds, one £10,000 US share purchase, and £2,000 sitting in cash throughout.
The account charge is 0.35% of £40,000, or £140. The share purchase costs £6.95 in dealing plus £99 in FX, so £105.95. The cash earns 1.30% while the platform expects to receive 3.25% to 4.25%, forgoing £39 to £59 of interest.
That totals £284.95 to £304.95 for the year. The 0.35% headline accounts for under half of it. Nothing here is concealed — every line is published on a page you can read — but only one of them shows up in a comparison table.
Exit fees have gone, and that is a change worth dating
The FCA's 2019 market study found that "exit fees can act as a barrier to consumers switching to a platform that better meets their needs", and proposed restricting them through a cap or a ban.
All five providers here now publish none. Hargreaves Lansdown states that you won't be charged any exit fees on leaving or transferring out. AJ Bell charges nothing to transfer out, and covers an old provider's exit fees up to £500 where the incoming account is worth £20,000 or more. interactive investor charges nothing for transfers in or out, Vanguard lists transferring out and closing an account among its no-charge items, and Fidelity lists exit fees at no charge.
That deletes one line from the stack. It doesn't delete the friction. The same study found consumers who want to switch "find it difficult to do because of the time, complexity and cost of switching" — and cost was only one of those three.
What this comparison cannot tell you
It leaves out what the funds themselves charge. A platform fee sits on top of an ongoing charges figure that Fidelity says starts as low as 0.05% and Vanguard puts between 0.06% and 0.79%. On a cheap index tracker the platform is the larger cost; on an active fund it usually isn't. Our pieces on fund fees compounded over 30 years and the costs beyond the expense ratio take that half of the stack.
It covers one wrapper. SIPP tariffs differ, drawdown differs again, and several caps apply per account rather than across everything you hold with a provider.
It also prices nothing but price. Service, research, app reliability and the range of investments available don't appear in any of these numbers. The FCA's 2019 market study found charges on £5,000 in a stocks and shares ISA ranging from 20 bps to 240 bps, worth £650 of returns over five years at 5% growth, and still concluded that "the market is working well in many ways for both advised and non-advised consumers."
The limitations run to the evidence on behaviour too. The FCA's 2019 finding that 43% of non-advised consumers researched charges, with 14% saying the information was difficult to find, is seven years old. Its cash-interest work rests on a sample of 42 firms in 2023, not a census, and firms were required to make changes by February 2024. Neither dataset tells you where any individual platform sits today.
What would change the arithmetic
A different Bank Rate. The retained-interest line is the one that scales with rates rather than with your balance. At 3.75% it's a live cost for anyone carrying meaningful cash, and it appears on no tariff table. Near zero it stops mattering, and the comparison collapses back to fees.
A cap on a percentage fund charge. Vanguard's £375 ceiling already turns its percentage into a flat fee at £250,000. If a percentage platform capped its fund charge the way it caps its share charge, the fund investor's crossover would move to wherever that cap sat.
What you actually hold. Flat versus percentage is a funds question. On ETFs and investment trusts, the £42, £90 and £150 caps have already settled it, and the ranking depends on dealing frequency instead.
The useful number isn't which platform is cheapest in the abstract. It's your own crossover — the flat annual fee divided by the percentage rate, for the two tariffs in front of you and the assets you hold. LedgerTouch tracks what a portfolio costs across accounts, though a calculator and two charges pages settle this particular question. Then run it again when a tariff moves, because the dates on these pages say they do.