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Index funds are the most powerful tool available to ordinary investors — not because they’re complicated, but because they’re not. They require almost no financial knowledge to use effectively, outperform the majority of professional fund managers over the long term, and cost a fraction of actively managed alternatives.
If you’ve heard of index funds but haven’t started, this guide covers the practical steps for UK investors.
What Is an Index Fund?
An index fund is a type of investment fund that tracks a market index — such as the FTSE 100 (the 100 largest UK-listed companies) or the S&P 500 (the 500 largest US companies). Rather than a fund manager trying to pick which shares to buy and sell, the index fund simply buys everything in the index in proportion to its size.
The key advantages:
Low cost: Because index funds don’t require active research and trading, they charge very low ongoing fees (known as an Ongoing Charges Figure or OCF). A typical index fund charges 0.05–0.20% per year. Actively managed funds often charge 0.75–1.5% or more.
Diversification: A single global index fund might hold thousands of companies across dozens of countries. This diversification reduces the risk that any one company’s failure significantly damages your portfolio.
Performance: Most active fund managers underperform their benchmark index over long periods (10+ years), after costs. Picking a consistently outperforming active manager in advance is very difficult. Index funds guarantee you the market return, minus a small fee.
Types of Index Fund
ETFs (Exchange-Traded Funds): Index funds that trade on the stock exchange, like shares. You can buy and sell them during market hours. Generally slightly cheaper than equivalent unit trusts.
Unit trusts / OEICs: Priced once daily. Slightly simpler for beginners — you invest a fixed amount and receive a number of units. Available through most UK investment platforms.
Both are fine. The difference matters more if you’re trading frequently (ETFs offer more flexibility) than for buy-and-hold long-term investing.
Which Index to Track?
The most commonly recommended starting point for UK investors:
Global index funds: Track thousands of companies worldwide. The most diversified, lowest-maintenance option for long-term investors.
– Vanguard FTSE Global All Cap Index Fund — covers ~7,000 companies globally, including small caps
– Vanguard FTSE All-World UCITS ETF (ticker: VWRP) — similar but as an ETF
– iShares Core MSCI World UCITS ETF (IWDG) — developed markets (excludes emerging markets)
UK index funds:
– Vanguard FTSE UK All Share Index Unit Trust — tracks all listed UK companies
– iShares Core FTSE 100 UCITS ETF — the 100 largest UK companies only
US index funds:
– Vanguard S&P 500 UCITS ETF — the 500 largest US companies
For most beginners, a single global index fund (like the Vanguard FTSE Global All Cap) is the most sensible starting point — no need to split between UK, US, and international funds yourself.
Where to Buy Index Funds in the UK
You need an investment account with a platform:
For ISA investing (tax-free):
– Vanguard Investor: Low cost (0.15% platform fee, capped at £375/year), but only offers Vanguard funds
– Hargreaves Lansdown: Wide fund range; higher charges (0.45%) for smaller accounts
– AJ Bell: Good range; competitive charges
– Fidelity: Good range; reasonable charges; good for regular investors
For pension investing (SIPP):
– The same platforms offer SIPPs — contributions receive tax relief
For general (non-ISA) investing:
– Same platforms, but investment gains and income above annual allowances are taxable
The platform fee is your annual cost for holding the account. The fund’s OCF is an additional ongoing charge built into the fund price. Add them together for your total annual cost.
The ISA Wrapper: Use It
Invest inside a Stocks and Shares ISA rather than a general investment account wherever possible. Inside an ISA, all investment growth and income is completely tax-free. The annual allowance is £20,000 (2024/25). There’s no reason not to use the ISA wrapper unless you’ve already used your allowance.
How to Actually Get Started
- Open a Stocks and Shares ISA on your chosen platform (Vanguard Investor is the simplest starting point for index fund investors)
- Choose your fund — if in doubt, the Vanguard FTSE Global All Cap Index Fund or the equivalent global ETF
- Decide how much to invest monthly — even £25/month starts the habit and builds exposure
- Set up a regular monthly contribution by direct debit — automatic investing removes the temptation to time the market
- Leave it alone
The single most important rule: don’t check it obsessively and don’t sell when markets fall. Index fund investing works through decades of compounding. Short-term volatility is noise; long-term growth is the signal.
What Returns to Expect
Global stock markets have historically returned approximately 7–10% per year on average over long periods, though not in a straight line. Some years are strongly positive; some are significantly negative. Over 20–30 years, the long-term upward trajectory has been consistent.
£200/month invested for 30 years at 7% average annual return produces approximately £240,000. The same amount in a savings account at 4% produces approximately £140,000. The difference — £100,000 — is the compounding return from equity investment over cash saving.
This is not a guarantee of future returns, but it represents the historical case for long-term equity investing.
Summary
Index funds are the most effective and accessible way for most UK investors to build long-term wealth:
- A single global index fund (e.g. Vanguard FTSE Global All Cap) is all most investors need
- Always invest inside an ISA to protect growth from tax — annual allowance is £20,000
- Choose a low-cost platform — Vanguard Investor is the cheapest for straightforward index fund investing
- Invest monthly by direct debit — automation removes timing risk and emotional decisions
- Don’t sell when markets fall — long-term index investors who hold through downturns consistently outperform those who don’t
Next read: How to start investing in your 40s: is it too late? | https://moneyunpacked.co.uk/how-to-start-investing-in-your-40s-is-it-too-late/