A 0.2 percentage point difference in platform fees sounds trivial until you run it across a £100,000 ISA held for twenty years, where it can quietly cost more than £10,000 in lost growth — more than most people would ever knowingly hand over in a single decision, yet almost nobody compares platform charges with the same scrutiny they apply to fund fees. UK investors obsess over a fund's ongoing charges figure and barely glance at what Hargreaves Lansdown, AJ Bell, or Vanguard UK actually charge just to hold the account itself, and that's backwards, because the platform fee compounds against your entire pot every single year regardless of performance. Part of the problem is that platform fees are quoted as small annual percentages, which the brain files as trivial in a way it never would with a £250 one-off charge — even though over two decades the two numbers can land in exactly the same place. Pull up your last annual statement and check the actual pounds-and-pence figure your platform charged you last year, not the percentage on the website, before deciding whether any of this matters for your own portfolio. The FCA has pushed platforms toward clearer cost disclosure in recent years, but the numbers still arrive buried in a PDF nobody opens rather than flagged anywhere near the login screen. Five minutes with that document tells you more about your real long-term returns than most of the market commentary you'll read this month. The headline rate on a comparison table rarely matches what you'll actually pay once your specific mix of funds, shares, and trading habits gets factored in.
How the big three actually charge
Hargreaves Lansdown charges 0.45% annually on funds held in an ISA, tiered down for larger portfolios, but crucially it's capped at £45 a year specifically for shares, investment trusts, and ETFs — not for open-ended funds, where the 0.45% keeps running uncapped as your pot grows. AJ Bell charges 0.25% on funds, capped at £3.50 a month (£42 a year) for shares and ETFs, which undercuts Hargreaves Lansdown on the share-dealing side while charging a similar rate on funds. Vanguard UK, by contrast, charges a flat 0.15% with no cap at all, but restricts you to Vanguard's own fund range plus a limited set of other providers — you're trading choice for a lower headline rate. The cap structure matters more than the headline percentage for anyone holding shares or ETFs rather than funds. A £150,000 portfolio of individual shares on Hargreaves Lansdown pays £45 a year once it crosses the cap threshold, while the same portfolio in funds would pay £675 a year with no cap in sight — that's the single most consequential detail buried in HL's fee structure, and it's why so many HL customers with large fund holdings eventually shift toward shares, trusts, and ETFs specifically to hit the capped rate. None of this is disclosed as clearly as the headline percentage, so it's worth reading the actual fee schedule PDF rather than the marketing page.
Where Vanguard actually wins — and where it doesn't
For a straightforward global tracker portfolio under Vanguard's own LifeStrategy or FTSE Global All Cap range, the 0.15% platform fee with no cap is genuinely the cheapest of the three for most portfolio sizes, and it stays cheap as the pot grows precisely because there's no cap to benefit from elsewhere. But Vanguard doesn't offer the breadth of individual shares, investment trusts, or third-party funds that HL and AJ Bell do, so if you want to hold, say, Scottish Mortgage Investment Trust alongside a global tracker, you're choosing a different platform or splitting your money across two.
Here's the part that catches people out: Vanguard's SIPP charges the same 0.15% with no cap, which makes it noticeably cheaper than HL or AJ Bell for a large pension pot invested purely in trackers — a £400,000 SIPP costs £600 a year on Vanguard versus potentially several times that on a platform without a fund cap. That gap only grows as the pension approaches retirement size, which is exactly when fees matter most.
Interactive investor's flat fee changes the maths again
Interactive investor takes a different approach entirely: a flat monthly subscription — currently £4.99 a month on the entry-level plan, rising to £11.99 on the plan that includes a free trade each month — rather than a percentage of assets. That structure is close to irrelevant for a £20,000 pot but becomes the cheapest option on the market by a wide margin once a portfolio passes roughly £75,000 to £100,000, because a flat £60 to £144 a year stops scaling while HL's and AJ Bell's percentage fees keep climbing with the portfolio. Investors who consolidated several ISAs into one large pot, which this blog has covered before, are exactly the people who should be checking interactive investor's flat-fee plans rather than assuming a percentage-based platform is still the right home for a six-figure sum.
The trade-off is the same one Vanguard presents in a different form: interactive investor's flat fee is a great deal for a large, low-turnover portfolio and a mediocre one for a small ISA just getting started, where £59.88 a year is a much bigger bite out of £8,000 than 0.25% would be.
Trading costs change the picture again
Platform fee comparisons often ignore dealing charges, and that's a mistake if you trade shares or investment trusts regularly rather than buying a fund and leaving it. AJ Bell charges £5 per online share trade (dropping to £3.50 if you traded more than 10 times the previous month), Hargreaves Lansdown charges £11.95 dropping to £5.95 for frequent traders, and Vanguard doesn't support individual share dealing on most of its platform at all. For someone who rebalances a share portfolio quarterly, HL's dealing costs alone can outweigh what looks like a modest platform fee advantage elsewhere.
Match the platform to how you actually invest
- Passive tracker investor with no interest in individual shares: Vanguard UK usually wins on pure cost
- Mixed portfolio of funds, trusts, and shares, buy-and-hold: AJ Bell's capped fee structure tends to edge out HL
- Frequent share trader who values research tools and customer service: Hargreaves Lansdown's higher fees buy genuinely useful extras, and for some investors that's worth paying for
- Large SIPP invested mostly in trackers: run the maths on Vanguard's uncapped 0.15% against your current platform — the gap widens every year the pot grows
The switching cost people forget to weigh
Moving an ISA or SIPP between platforms isn't free in time even when it's free in money — most platforms don't charge for in-specie transfers in, but the receiving platform can take four to eight weeks to complete a transfer of shares and funds without selling first, and during that window your money is neither fully accessible nor necessarily invested the way you'd choose today. That's a real cost even though no invoice shows up for it, and it's the reason a lot of investors stay on a platform that's costing them an extra 0.2% a year rather than face six weeks of administrative limbo.
It's not always worth switching. If your pot is under roughly £20,000, the pound-cost difference between these platforms is often small enough that the hassle of transferring outweighs the saving, particularly if you're actively contributing new money each month rather than sitting on a static lump sum. Run the actual numbers for your own pot size before assuming a switch pays for itself — a spreadsheet with ten minutes of work beats a gut feeling here.
What this looks like on a real portfolio
Take a £60,000 ISA split 70/30 between a global index fund and a handful of individual shares, contributing £500 a month. On Hargreaves Lansdown, the fund portion pays 0.45% uncapped while the share portion is capped at £45 — total platform cost lands somewhere around £250 to £280 a year. The identical portfolio on AJ Bell, with its 0.25% fund rate and £42 share cap, comes in closer to £150 to £170 a year. Over fifteen years, assuming steady growth and continued contributions, that gap alone is worth low five figures — not because either platform is doing anything wrong, but because fee structures compound the same way returns do, just in the opposite direction.
Run your own numbers through each platform's fee calculator before assuming any of this applies directly to you — portfolio mix, trading frequency, and pot size shift the answer more than most investors expect, and the "best" platform for a tracker-only ISA is often the wrong one for a SIPP two years from drawdown.