ETFs explained: how exchange-traded funds work, UCITS, KIDs and ETF CFDs

An exchange-traded fund (ETF) is an investment fund whose shares are listed on a stock exchange and can be bought and sold during the trading day like an ordinary share. Most ETFs track an index, such as a broad stock market, a bond index or a commodity benchmark, so one trade gives exposure to many underlying holdings. A mechanism called creation and redemption keeps the ETF's market price close to the value of what it holds. In the EU, retail investors mostly use UCITS ETFs, because US-listed ETFs usually do not provide the key information document that EU rules require before they can be sold to retail clients.

What an ETF actually is

An ETF combines two familiar things: a fund and a listed share.

• The fund: a pool of assets (shares, bonds, commodities or derivatives) managed according to a stated objective, usually to track an index. The fund is legally separate from the company that runs it, so investors' assets are held for them by a depositary or custodian.
• The listing: the fund's shares trade on an exchange throughout the day, with a bid and ask price set by market makers, just like a company share.

That is the main difference from a traditional mutual fund, which you buy and sell directly with the fund manager once a day at a single price calculated after the market closes. With an ETF you see a live price, can place limit and stop orders and can trade at any point while the exchange is open.

The first US ETF tracking the S&P 500 was launched in January 1993. Since then ETFs have grown into one of the most widely used ways of investing in an index, and the range now spans broad equity markets, sectors, countries, government and corporate bonds, commodities and more specialised strategies.

Physical and synthetic replication

ETFs track their index in one of two broad ways:

• Physical replication: the fund holds the securities in the index, either all of them (full replication) or a representative sample (sampling, common for indices with thousands of bonds or small companies).
• Synthetic replication: the fund holds a basket of other assets and enters a swap agreement with a bank, which pays the index return. This can track some indices more closely or cheaply, but adds counterparty risk, which UCITS rules limit and which funds manage with collateral.

The fund's prospectus and factsheet say which method it uses. Neither is automatically better; they carry different trade-offs.

Creation and redemption: why the price stays close to value

An ETF has two values: its market price on the exchange, and its net asset value (NAV), the value of its holdings per share. If the price drifted far from NAV, buyers would overpay or sellers would be short-changed. The creation and redemption process prevents that.

Only specialist firms called authorised participants (APs), typically large banks and trading firms, can deal directly with the ETF issuer, and they do so in large blocks called creation units.

1. Creation: if the ETF trades above its NAV, an AP can buy the underlying securities, deliver them (or cash) to the issuer, and receive new ETF shares, which it sells on the exchange at the higher price. That extra selling pushes the price down towards NAV.
2. Redemption: if the ETF trades below its NAV, an AP can buy ETF shares cheaply on the exchange, hand them to the issuer, and receive the underlying securities, which it sells at full value. That buying pushes the ETF price up towards NAV.

This arbitrage usually keeps the gap small for ETFs holding liquid assets during normal hours. Gaps can widen when the underlying market is closed (an ETF of Asian shares trading during European hours, for example), when underlying assets are illiquid (some bond markets in stress), or during sudden market disruptions. That is why it is worth checking the bid–ask spread and, where available, the indicative NAV before trading.

Worked example: creation arbitrage

Illustrative numbers only. An ETF holds shares worth exactly 50.00 euros per ETF share (its NAV). Strong buying pushes the ETF's market price to 50.20.

• An AP buys the underlying shares for 50.00 per ETF share's worth, delivers them to the issuer and receives new ETF shares.
• It sells those ETF shares on the exchange at 50.20, capturing about 0.20 per share before its trading and hedging costs.
• As APs do this, the extra supply of ETF shares pulls the market price back towards 50.00.

In practice the profit window is tiny and APs compete for it, which is precisely why the gap usually stays small.

What an ETF costs you

The ongoing charge (TER or OCF)

The total expense ratio (TER), often called the ongoing charges figure (OCF) in Europe, is the annual fee the fund takes to cover management, administration and custody. It is not billed to you; it is deducted gradually from the fund's assets, so it shows up as a slightly lower return. Broad index ETFs often have low ongoing charges, while specialised or actively managed ones usually charge more.

Tracking difference and tracking error

• Tracking difference is the gap between the ETF's actual return over a period and the index's return. A fund with a 0.20% TER might lag its index by roughly that amount, or by more (because of trading costs or cash drag) or less (because of securities lending income or efficient tax handling of dividends).
• Tracking error measures how variable that gap is from day to day or month to month.

For a long-term holder, tracking difference is the more useful figure because it captures what the fund actually delivered, not just its headline fee.

Trading costs and currency conversion

• Spread: the difference between bid and ask. Large, liquid ETFs often have narrow spreads; small or specialised ones can be wider, especially near the open and close. See spreads and commissions for how spreads work generally.
• Commission: many brokers charge a fee per trade.
• Currency conversion: if you buy an ETF quoted in a different currency from your account, or the ETF holds assets in other currencies, conversion costs and exchange rate movements both affect your return. The guide to currency conversion and account base currency explains how brokers apply conversion fees.
• Platform and custody fees: some providers charge account or holding fees; hidden broker fees lists what to look for.

Worked example: all-in cost over a year

Illustrative numbers only. You invest 10,000 euros in an equity ETF with an ongoing charge of 0.20%, paying a 0.10% commission each way and crossing a spread of 0.05% on the way in and out.

• Ongoing charge for one year: about 0.20% × 10,000 = 20 euros (taken inside the fund).
• Commission: 10 euros to buy, about 10 euros to sell.
• Spread: about half the spread on each side, roughly 2.50 euros in and 2.50 euros out.
• Total: about 45 euros, or 0.45% for one year. Over several years, the one-off trading costs matter less and the ongoing charge and tracking difference dominate.

UCITS, PRIIPs and why EU investors usually cannot buy US ETFs

UCITS

UCITS (undertakings for collective investment in transferable securities) is the EU framework for funds that can be sold to retail investors. It sets rules on diversification, liquidity, leverage, custody and disclosure, and a fund authorised in one member state can be marketed across the EU. Most ETFs sold to European retail investors are UCITS ETFs, many of them domiciled in Ireland or Luxembourg. "UCITS" in a fund's name tells you it meets this framework; it does not mean the investment is low-risk.

The PRIIPs KID requirement

Under the EU PRIIPs Regulation, which has applied since 1 January 2018, anyone selling a packaged retail investment product to a retail investor in the EU must provide a key information document (KID). The KID is a short standardised document covering the product's objectives, a risk indicator, performance scenarios and costs. UCITS funds were exempt for a transition period, during which they used their own key investor information document; since 1 January 2023 they have also been required to provide a PRIIPs KID.

US-listed ETFs are regulated in the US, where there is no KID requirement, and their issuers generally do not produce one. Because EU firms cannot sell a PRIIP to a retail client without a KID, EU-regulated brokers usually block retail clients from buying US-listed ETFs. This is why an EU retail investor often sees a message that a well-known US ETF is "not available", while a European-domiciled UCITS version tracking the same or a similar index can be bought. Many large US issuers offer such UCITS versions.

Some points worth knowing:

• The restriction is about the KID, not about whether the US fund is good or bad.
• Investors classified as professional clients are outside the PRIIPs retail requirement, but professional status comes with fewer protections and has qualifying criteria; see broker account types explained.
• Holding a US ETF you already own is generally a separate question from buying more; brokers set their own policies.
• Domicile also affects matters such as withholding tax on dividends and the tax treatment of the fund in your country. Tax depends on individual circumstances and local rules; this guide does not cover it in detail.

The UK position

The UK kept its own version of the PRIIPs rules after leaving the EU and has been replacing it with a new Consumer Composite Investments (CCI) disclosure regime, which began on 6 April 2026 with a transition period. How the new rules affect access to US-listed ETFs depends on the detailed rules and on each provider's approach, so UK investors should check with their provider rather than assume the EU position applies.

ETF CFDs versus owning an ETF

Some providers offer CFDs on ETFs. A CFD is a contract with the provider that pays the difference in price between opening and closing; you never own the ETF shares. Because a CFD is not a share in the fund, the PRIIPs position is different: the CFD provider must supply its own KID for the CFD. CFDs on US-listed ETFs are therefore offered by some EU providers even where the ETF itself cannot be bought, but that is a very different product.

The key differences

• Ownership: owning ETF shares gives you a claim on the fund's assets, held by its depositary. A CFD gives you a contract with the provider, with no ownership of the fund.
• Leverage: ETF shares are normally bought outright. ETF CFDs are leveraged; under ESMA rules, retail leverage on CFDs referencing individual equities and other reference values is capped at 5:1, and the leverage your provider applies to a given ETF CFD is in its product terms.
• Costs: owning involves the ongoing charge, commissions and spreads. A CFD involves spreads and possibly commissions, plus daily financing on positions held overnight. Over months, financing can far exceed the costs of owning; see swap and overnight financing.
• Distributions: if the ETF pays a distribution, CFD longs usually receive an adjustment and shorts are debited, similar to dividend adjustments on share CFDs.
• Going short: a CFD lets you take a short position; buying an ETF does not.
• Risk of loss: with an ETF bought outright, the most you can lose is what you paid. With a CFD, leverage magnifies losses; EU retail accounts have negative balance protection, but you can still lose your whole balance. Most retail CFD accounts lose money.
• Investor protection: your ETF shares are held in custody and the fund's assets are separate from the issuer's. A CFD exposes you to the provider, protected by client money rules and, if the firm fails, an investor compensation scheme up to its limits.

Worked example: owning versus a CFD over six months

Illustrative numbers only. You want 5,000 euros of exposure to an equity index ETF priced at 100.00 for six months, and it ends the period at 104.00.

• Owning: buy 50 shares for 5,000 euros. End value 5,200 euros, a 200-euro gain before about 5 euros of ongoing charge for six months and trading costs of perhaps 15 euros. Net around 180 euros.
• CFD at 5:1: margin of 1,000 euros controls 5,000 euros of exposure. Price gain is again 200 euros, but daily financing at, say, an illustrative 6% a year on 5,000 euros for six months costs about 150 euros, plus spreads. Net around 40–50 euros.
• If the price had fallen to 92.00: owning, a 400-euro loss on a 5,000-euro investment (8%). With the CFD, the same 400-euro loss plus about 150 euros of financing, roughly 550 euros, more than half of the 1,000-euro margin.

The comparison shows the general pattern: CFDs suit short holding periods and are expensive to hold for long, while ownership involves no leverage and lower holding costs. The profit and loss calculator and margin calculator can help you run your own numbers.

Types of ETF and their quirks

• Broad equity index ETFs: track markets such as the S&P 500, MSCI World or FTSE 100. The what is a stock index guide explains how such indices are built.
• Bond ETFs: hold baskets of government or corporate bonds. Unlike a single bond, most never mature, so their price stays sensitive to interest rates indefinitely. See bonds and yields explained.
• Commodity products: some hold physical metal, such as gold; others hold futures. Futures-based products face roll costs in contango and can diverge from spot prices over time; see how commodity futures work. In Europe, single-commodity exposure is often structured as an exchange-traded commodity (ETC) rather than a UCITS fund, which is a debt security with different risks.
• Accumulating and distributing: accumulating share classes reinvest income inside the fund; distributing classes pay it out.
• Currency-hedged classes: aim to reduce the effect of exchange rate moves between the fund's assets and its share class currency, at a cost.
• Leveraged and inverse products: aim to deliver a multiple or the inverse of an index's daily return. Because they reset daily, their returns over longer periods can differ substantially from the multiple of the index's return, especially in volatile markets. They are complex products designed mainly for short-term use.

Common mistakes

• Choosing on the ongoing charge alone. Check tracking difference, spreads and the total cost of trading and holding.
• Ignoring what the index contains. A "world" index can be heavily weighted to one country or a few large companies. Read the factsheet.
• Trading at the open or when the underlying market is shut. Spreads tend to be wider and prices can deviate further from NAV.
• Assuming a commodity ETF tracks the spot price. Futures-based products are affected by roll yield.
• Holding leveraged daily products for long periods without understanding compounding.
• Using CFDs for long-term exposure without counting financing. Over months, financing can make the CFD much more expensive than owning.
• Confusing UCITS with safe. UCITS is a regulatory framework; the value of any fund can fall.

Any leveraged product, including ETF CFDs, carries a high risk of losing money; see the risk warning and why most retail CFD traders lose.

Frequently asked questions

What is the difference between an ETF and an index fund?

An index fund is any fund that tracks an index; an ETF is a fund whose shares trade on an exchange. Many ETFs are index funds, but a traditional index mutual fund is bought from the manager once a day at NAV, while an ETF trades all day at a market price.

Why can't I buy US ETFs as an EU retail investor?

EU rules require a PRIIPs key information document (KID) before a packaged investment product can be sold to a retail investor. US-listed ETFs generally do not produce one, so EU brokers usually block retail purchases. UCITS ETFs domiciled in Europe, often tracking the same indices, do provide KIDs.

What is a UCITS ETF?

It is an ETF authorised under the EU UCITS framework, which sets rules on diversification, liquidity, custody and disclosure and allows the fund to be sold to retail investors across the EU. Many are domiciled in Ireland or Luxembourg.

What is TER?

The total expense ratio, or ongoing charges figure, is the annual cost of running the fund, expressed as a percentage of assets and deducted inside the fund. It is not the whole cost: tracking difference, spreads, commissions and currency conversion also affect what you get back.

Is an ETF CFD the same as owning an ETF?

No. A CFD is a leveraged contract with a provider on the ETF's price. You do not own fund shares, you pay daily financing on overnight positions, you can go short, and losses are magnified by leverage. Owning the ETF means holding fund shares outright with no leverage.

Can an ETF trade at a different price from its holdings?

Yes, slightly, and occasionally by more. Creation and redemption by authorised participants usually keeps the gap small, but it can widen when the underlying market is closed, the assets are illiquid, or markets are under stress.