How do I choose an investment platform — and when should I switch?
The best investment platform depends on how much you hold and what you invest in. Percentage-fee platforms (around 0.25–0.45% a year) suit smaller portfolios; flat-fee platforms (a fixed monthly or annual charge) become cheaper once your pot grows past roughly £50,000–£100,000. Switching platforms is straightforward via an in-specie transfer, and is worth doing when fees, fund choice, or service no longer fit.
The two fee models, and why size decides
UK platforms charge in one of two ways. Percentage-fee platforms (Hargreaves Lansdown, AJ Bell, Vanguard) take a slice of your portfolio each year — typically 0.25% to 0.45%. Flat-fee platforms (Interactive Investor, and some others) charge a fixed amount regardless of size. The maths is simple: a 0.25% charge on £20,000 is £50 a year; on £200,000 it's £500. A flat fee of around £120–£240 a year doesn't move. Below roughly £50,000–£100,000, percentage platforms are usually cheaper. Above it, flat-fee platforms pull ahead — and the gap widens every year your pot grows.
It's not only about the headline fee
- What you hold — some platforms cap the percentage fee on shares, ETFs and investment trusts but not on funds. If you hold ETFs, a capped or flat-fee platform can be dramatically cheaper.
- Dealing charges — flat-fee platforms often charge per trade (£5–£10). Frequent investors or monthly drip-feeders should check for free regular-investing options.
- Fund and wrapper range — not every platform offers a SIPP, a Lifetime ISA, or every fund. Make sure it covers the wrappers you actually need.
- Service and tools — app quality, transfer speed, and customer service matter once real money is involved.
When switching is worth it
Switch when your portfolio has grown past the point where a flat fee would be cheaper, when your platform doesn't offer a wrapper or fund you need, or when service has become a genuine problem. The savings compound: moving a £150,000 pot from 0.45% to a £240 flat fee saves over £400 a year, every year. The UK Broker Fee Index 2026 shows the exact annual cost of every major platform at five portfolio sizes.
How switching actually works
You don't sell up and start again. An in-specie transfer moves your existing holdings to the new platform as they are, so you stay invested and never realise a capital gain. A cash transfer sells everything first — faster, but it crystallises gains outside an ISA and puts you out of the market briefly. In-specie is usually the better choice. Transfers can take a few weeks; the new platform handles the paperwork, and many cover any exit fees the old one charges.
Key takeaway: There's no single best platform — only the best one for your portfolio size and holdings. Re-check the maths as your pot grows, because the platform that was cheapest at £20,000 is rarely the cheapest at £150,000.
Arken totals your real platform and fund costs across everything you hold, projects the drag over decades, and shows whether a different fee model would leave more in your pocket.
