Index funds vs ETFs in the UK

Who this guide is for

It’s for anyone who has seen both index funds and ETFs on a platform and wants to know what the difference is. It assumes you know the basics of funds.

If you don’t yet, our beginner’s guide to investing in the UK explains how funds work first.

Side by side

General description of common structures, checked 5 October 2026. Individual funds and platforms vary, so check the fund’s documents and your platform’s charges.

How index funds are priced

Most index funds sold to UK investors are OEICs or unit trusts. Their price is worked out from a valuation of everything the fund holds, at set times called valuation points.

The rules require at least two valuation points a month (source: FCA). In practice, most index funds are usually priced once a business day, and the fund’s prospectus or factsheet gives the time.

So when you buy, your order is filled at the next price. You won’t know the exact figure until after the valuation point.

How ETFs trade

ETF shares are bought and sold on a stock exchange while it’s open, so the price changes during the day. You can see the price before you trade.

Firms called authorised participants, mainly market makers, can create and cancel ETF shares. This helps keep the market price close to the value of the fund’s holdings, but the two can drift apart, especially when markets are stressed (source: FCA).

You can trade an ETF several times a day. That isn’t needed for long-term investing, and each trade can add costs.

Costs: OCF, dealing charges and the spread

Both structures take an ongoing charge from inside the fund. The OCF covers the fund’s management charge and some other running costs (source: MoneyHelper). Your platform’s own fee comes on top for both.

ETFs can carry two extra costs each time you trade:

• A dealing charge. Some platforms charge a fee for each ETF trade.
• The bid-offer spread. The gap between the price you pay to buy and the price you get when you sell.

Index funds usually have a single price, so there’s no spread to pay. Many platforms charge less, or nothing, to deal in funds, but this varies. Our Stocks and Shares ISA fees guide shows how platforms charge for funds and ETFs.

Here’s a hypothetical example. On £10,000, a fund charge of 0.10% a year is about £10, and 0.20% is about £20.

Dealing charges and spreads are paid each time you trade, so they matter more if you trade often. Our guide to compound interest explains why yearly charges add up over time.

Tracking difference

No index fund or ETF follows its index perfectly. The gap between the fund’s return after costs and the index’s return is called the tracking difference.

That gap often tells you more than the label “fund” or “ETF”. Funds also track their index in different ways, and some offer currency-hedged versions. The fund’s key document explains how it tracks its index and whether it’s hedged.

Accumulation and income

Both structures usually come in two versions. Accumulation (or accumulating) versions reinvest any dividends or interest inside the fund. Income (or distributing) versions pay it out to your account.

Inside an ISA, there’s no tax on either, so the choice mainly depends on whether you want the income paid out.

Which can go in an ISA or SIPP?

A Stocks and Shares ISA can hold units or shares in UK UCITS funds and recognised overseas UCITS funds, among other investments (source: HMRC). An ETF qualifies because it’s an eligible fund, not just because it’s listed on an exchange.

Most mainstream index funds and ETFs offered by UK platforms can be held in a Stocks and Shares ISA. Your platform will only offer eligible ones.

Inside an ISA, you pay no tax on interest, income or gains, and there’s nothing to declare on a tax return (source: GOV.UK). The ISA allowance is £20,000 for 2026/27 (source: GOV.UK). Our ISAs for beginners guide covers how ISAs work, and our SIPP guide covers personal pensions.

Tax outside an ISA: UK reporting fund status

This only matters if you hold an overseas fund, such as an overseas-based ETF, outside an ISA or pension.

• Reporting funds. Gains are subject to Capital Gains Tax. You’re also taxed on your share of the fund’s reported income each year, even if it isn’t paid out to you.
• Non-reporting funds. Gains are usually taxed as income, at income tax rates, rather than as capital gains.

HMRC publishes a list of funds with reporting status (source: HMRC). Tax treatment depends on your circumstances and may change.

Fund documents to read

Every fund publishes a short document setting out its aims, risks and costs. From 6 April 2026, fund managers can replace the older key information document with a new product summary, and the rules apply in full from 8 June 2027 (source: FCA). You may see either one until then.

Complex products aren’t plain index funds

Some exchange-traded products use borrowing or aim to move opposite to an index, often resetting daily. They behave very differently from a plain index ETF and carry more risk. The FCA has looked at how firms sell these complex products.

Exchange-traded notes (ETNs) can look similar on a platform, but they aren’t funds. They’re a type of debt, so you rely on the issuer being able to pay.

What changes in April 2027

From 6 April 2027, new rules apply to Stocks and Shares ISAs (source: GOV.UK). Funds, ETFs, shares and bonds aren’t affected by the new cash-like test. However:

• a 22% charge applies to interest on uninvested cash held in a Stocks and Shares ISA
• money market funds can be held only as part of a wider portfolio, not as all of it
• the Cash ISA limit falls to £12,000 for people under 65

Our Cash ISA vs Stocks and Shares ISA guide explains the Cash ISA change.

When the choice matters less

If you invest regularly for the long term in a broad tracker, the structure is rarely the deciding factor. Your total costs, how much you put in and how long you stay invested usually make a bigger difference.

The gap between a low-cost tracker and a higher-cost active fund can also matter more than the choice between an index fund and an ETF. Our guide to investing £50 a month covers small regular amounts.

Protection

If an authorised investment firm fails and your money is missing, the FSCS can pay up to £85,000 per eligible person, per firm (source: FSCS). It doesn’t cover falls in the value of your investments. Our guide to FSCS protection limits has more.

If you’re unsure what to hold, you can get regulated financial advice. MoneyHelper explains how to find an adviser.

The catch

Key takeaways

• Index funds and ETFs can track the same index. The main differences are how you buy them and how they’re priced.
• Compare the OCF, your platform’s charges for each, and any spread.
• Most mainstream index funds and ETFs can go in a Stocks and Shares ISA or SIPP.
• Outside an ISA, check reporting fund status on overseas ETFs.
• Inside an ISA, the 2026/27 allowance is £20,000 (source: GOV.UK), and new cash rules start in April 2027.

Related reading

Related guides

Back to hub

FAQ

Is an ETF just an index fund that trades on an exchange?

Not always. Many ETFs track an index, but the structure differs: an ETF trades on a stock exchange during market hours, while an index fund is usually dealt once a day through your platform. Pricing and charges differ too.

Are ETFs allowed inside my ISA?

Yes. ETFs that are eligible funds, such as UK UCITS or recognised UCITS funds, can be held in a Stocks and Shares ISA. Your platform will only offer eligible ones.

Do I pay a spread every time I trade an ETF?

Yes. The bid-offer spread is the gap between the buying and selling price, so it’s built into every trade. How wide it is depends on the ETF and the market, and any dealing charge comes on top.

When does UK reporting fund status affect my tax bill?

It depends on where you hold the fund. Outside an ISA or pension, gains on an overseas fund without reporting status are usually taxed as income rather than as capital gains. Inside an ISA, it makes little tax difference.

Do ETFs carry more risk than index funds?

Not usually because of the structure itself. The risk mainly depends on what the fund holds. Exchange-traded products that use borrowing or move opposite to an index are different and carry much more risk.