Stonekeel

Best Broker for Index Funds (2026)

Index funds are the cheap, simple core of most good portfolios. What to look for in a broker to hold them, and the low-cost options that fit.

Written by an 11-year retail-brokerage insider. · Updated 11/6/2026

If your plan is to invest in low-cost index funds, the broker’s job is simple: hold them cheaply, let you invest regularly, and stay out of the way. Here’s what matters and which brokers do it well.

What to look for

  • Low platform and dealing costs. Index funds are cheap, so don’t let a pricey platform undo that. For UK investors, watch the percentage-vs-flat fee model; work out the cheapest for your pot with the UK ISA fee calculator. See broker fees explained.
  • Free or cheap regular investing. You’ll be drip-feeding money in, so automated investing should be free.
  • The index funds you want. Most brokers cover the popular UCITS ETFs; check your specific fund (a broad all-world ETF, say) is available.
  • A tax wrapper. An ISA or SIPP in the UK, or local equivalents, so your returns aren’t taxed unnecessarily.
  • Low FX if your funds trade in another currency. See FX fees.

Brokers that fit

A starting point, not a verdict. Compare on Brokerlens and check current terms.

  • InvestEngine: ETF-only with a free DIY ISA and SIPP, about as cheap as it gets for an index-ETF portfolio.
  • Trading 212: commission-free, fractional, free UK ISA, easy for regular index investing.
  • Vanguard: simple and low-cost if you’re happy with its own index funds and all-in-one options.
  • Trade Republic / Scalable: free ETF savings plans for EU investors building an index portfolio.
  • Interactive Brokers: the lowest FX costs and widest range, for those who want global index ETFs cheaply.

The bottom line

For index-fund investing, the winning broker is simply the cheapest, properly regulated one that holds the funds you want and lets you invest regularly for free, ideally in a tax wrapper. Match that to your situation and you’ll keep the maximum of your returns. Compare the options on Brokerlens.

Educational information, not personal advice. Broker terms change, so always check current details. We may earn a commission if you open an account through our links, which never affects which brokers we recommend.