What are investment funds? A plain-English guide

What is an investment fund?

An investment fund is a pool of money contributed by many investors and managed as a single portfolio by a professional management company. When you invest in a fund you buy units (sometimes called shares) in that pool. Each unit represents a proportional slice of everything the fund owns, so the value of your holding rises and falls with the value of the underlying investments.

The fund itself does not manufacture anything or sell a service. It simply holds securities such as shares, bonds or money market instruments, and occasionally other assets such as property, on behalf of its investors. The management company decides what to buy and sell within rules set out in a legal document called the prospectus; an independent depositary keeps custody of the assets and checks that those rules are respected.

The price of a unit is called the net asset value (NAV). It is calculated, usually once per business day, by valuing all the fund's holdings, deducting its liabilities and dividing by the number of units in issue. You buy and sell at that price, so there is no haggling and no spread between buyer and seller in the way there is with an individual share.

A fund is not a product you are sold; it is a portfolio you own a share of. Everything else follows from that.

How pooling works

Pooling is the mechanism that makes funds useful. On their own, most investors cannot afford to buy a meaningful stake in hundreds of companies, nor do they have the time to research them or the access to bond markets, which are largely wholesale. By combining their money, investors can collectively own a portfolio that none of them could assemble alone, and they can share the cost of the professionals who run it.

Three practical consequences follow from pooling. First, diversification becomes affordable: even a modest sum buys exposure to a broad portfolio. Second, costs are shared: research, trading, custody and administration are spread across all investors rather than borne by each individually. Third, liquidity is organised: most funds allow you to buy or sell units on any business day at the published NAV, with the fund itself handling the underlying trades.

Pooling also means you give up something. You do not choose the individual holdings, you cannot direct the manager to avoid a particular company unless the fund's rules already do so, and you share in the fund's costs whether or not you agree with every decision. Understanding this trade-off is the starting point for choosing well.

The main types of fund

Funds are usually classified by what they invest in. The categories below cover the great majority of funds available to private investors in Europe.

Within each category there are many variations. A fund's name is a rough guide at best; the investment objective and policy set out in its prospectus and Key Information Document are what matter.

Active or passive?

Funds differ not only in what they hold but in how they are managed. An actively managed fund employs a manager or team who select investments with the aim of outperforming a benchmark, or of achieving a particular outcome such as lower volatility or higher income. A passively managed fund, by contrast, aims only to track a chosen index as closely as possible, holding the same securities in the same proportions.

Each approach has merits. Active management offers the possibility of returns above the market, the flexibility to avoid overvalued or troubled companies, and the ability to pursue objectives an index cannot express. It costs more, and over long periods many active funds have not outperformed their benchmark after fees. Passive management is cheap, transparent and predictable relative to its index, but it will by construction never beat that index, and it holds every company in the index regardless of quality or price.

Many investors sensibly combine the two: a low-cost passive core for broad market exposure, and active funds where they believe a skilled manager can add value, for example in less efficient markets or where a specific risk objective matters.

What funds cost

Costs are the one element of fund investing that is known in advance, and they compound in the same way that returns do. A difference of one percentage point in annual charges, sustained over twenty years, is a substantial share of the final result. It is worth understanding every line.

Ongoing charges and the TER

The total expense ratio (TER), shown in EU documents as "ongoing costs", is the annual cost of running the fund expressed as a percentage of its assets. It includes the management fee, depositary and administration fees, audit, legal and regulatory costs. It is deducted from the fund's assets a little each day, so you never see an invoice; the published performance of a fund is already net of these charges. Our explainer What the TER does and does not include covers the costs it leaves out.

Entry and exit charges

Some funds charge a one-off fee when you buy (an entry charge, sometimes called a front-end load) or sell (an exit charge). These are expressed as a percentage of the amount invested or redeemed and are often negotiable or waived by the distributor. The KID shows the maximum that may be charged.

Transaction costs

When the fund buys and sells securities it pays brokerage, taxes and spreads. These are not part of the TER but are disclosed separately in the KID. Funds that trade frequently incur more of them.

Performance fees

A minority of funds charge an additional fee if performance exceeds a threshold. The structure matters a great deal: look for a hurdle rate, a high-water mark (so that you do not pay twice for recovering a loss) and a cap.

In the EU, the Key Information Document presents all of these costs together, both as percentages and as the amount in euros you would pay on an example investment over one year and over the recommended holding period. It also shows the reduction in yield, which is the impact of costs on your annual return. This is the number to compare between funds.

Returns are uncertain and costs are certain. Of the two, the one you can control deserves more of your attention than it usually receives.

Risk and return

Investment risk is the possibility that an investment will be worth less than you expected, or less than you paid, at the moment you need the money. Return is the compensation you receive for accepting that possibility. The two are inseparable: an investment that promises high returns with no risk is either misunderstood or misrepresented.

For funds, the most useful measure of risk is volatility, the degree to which the unit price fluctuates over time. A fund whose price has historically moved up or down by 20% in a year will feel very different to hold than one that has moved by 3%, even if their average returns are similar.

In the European Union, every fund sold to retail investors must display a summary risk indicator (SRI) on a scale of 1 to 7. The class is calculated from the historical volatility of the fund, together with the credit risk of its issuer where relevant, and assumes the fund is held for the recommended period. It is a standardised measure, so a class 4 fund from one provider is directly comparable with a class 4 fund from another.

Volatility is not the only risk. Credit risk is the chance that a bond issuer fails to pay. Liquidity risk is the chance that the fund cannot sell holdings quickly enough to meet withdrawals, which is why some property funds restrict redemptions. Currency risk arises when a fund holds assets in a currency other than yours. Concentration risk arises when too much of a portfolio depends on one company, sector or country. A good fund document explains which of these apply and how they are managed.

Can you lose money in a fund? Yes. The value of any fund can fall, sometimes sharply, and there is no guarantee that it will recover within your time horizon. What a well-diversified fund protects you against is not loss in general but the specific, catastrophic loss that comes from a single holding failing. That protection is valuable, but it is not the same as safety.

Why diversification matters

Diversification is the practice of spreading investments across many holdings so that no single outcome dominates the result. It works because different investments do not move in perfect step: when one company disappoints, another surprises; when equities fall, high-quality bonds often hold their value or rise.

There are several layers of diversification. Within an asset class, a fund spreads across many issuers. Across asset classes, a mixed fund combines equities, bonds and cash, whose returns respond differently to economic conditions. Across geographies and currencies, a global fund reduces dependence on any one economy. And across time, investing regularly rather than all at once reduces the risk of buying everything at a high point.

Diversification has a cost: a diversified portfolio will never perform as well as its single best holding would have. That is the price of not knowing in advance which holding that will be, and most investors are wise to pay it.

How to choose a fund

Choosing a fund is less about finding the best fund in the world and more about finding one that fits your situation. The following questions, asked in order, will narrow the field considerably.

1. What is the money for, and when? A goal five years away calls for a different fund than one twenty-five years away. The recommended holding period in the KID should be no longer than your own horizon.
2. How much fluctuation can you live with? Be honest. A fund whose falls would make you sell at the bottom is the wrong fund, however good its long-term record.
3. Which risk class follows from that? Use the SRI as a first filter. It is standardised across providers and tells you more than the fund's name.
4. What does the fund actually hold? Read the investment objective and policy. Check the top holdings, the regional and sector weights, and whether the fund can use derivatives or borrowing.
5. What does it cost, in full? Compare the reduction in yield figure in the KID, not just the management fee. Check for entry charges and performance fees.
6. Who manages it, and how? Look for a clear, repeatable process, a stable team, and a management company with sound governance and an independent depositary.
7. Does the fund's record make sense? Past performance tells you nothing about the future, but it can tell you whether the fund behaved as its description would suggest, especially in difficult years.

UCITS and the KID in the EU

Most funds sold to private investors in the European Union are UCITS (Undertakings for Collective Investment in Transferable Securities). A UCITS is a fund authorised under a common EU framework that sets rules on what it may invest in, how much it may concentrate in a single issuer, how it must manage liquidity and how it must be supervised. Once authorised in one member state, a UCITS can be marketed across the EU under a "passport".

The UCITS rules are designed with retail investors in mind. Among other things, they require a fund to be diversified (in broad terms, no more than 10% in any single issuer, with further limits on the aggregate of larger positions), to invest mainly in liquid, transferable securities, to allow investors to redeem at least twice a month, and to appoint an independent depositary. Funds that do not meet these standards, such as hedge funds, private equity and most direct property funds, are regulated instead as alternative investment funds (AIFs), which are generally aimed at professional investors.

Every UCITS and every other fund sold to retail investors must provide a Key Information Document (KID) before you invest. It is a standardised document of at most three pages that covers:

• what the fund is and what it aims to do, and who it is intended for;
• the summary risk indicator from 1 to 7, with a description of the main risks;
• performance scenarios showing what you might get back under unfavourable, moderate and favourable conditions, as well as in a stress scenario;
• what happens if the management company is unable to pay out;
• the costs over time and the composition of costs, in both euros and percentages;
• the recommended holding period and how to take money out early;
• how to complain.

Because the format is identical for every fund, the KID is the single most useful tool for comparing products from different providers. Read it alongside the fund's prospectus, which is longer and legally definitive, and the latest annual report, which shows what the fund actually held and what it actually cost. Reading a Key Information Document goes through each section in detail.

A note on tax

The tax treatment of fund investments depends on your country of residence, on the fund's domicile, on whether the fund distributes income or accumulates it, and on how long you hold your units. In some countries, accumulating funds are taxed only when sold; in others, investors are taxed annually on deemed income whether or not it was paid out. Dividends and interest received by the fund may also be subject to withholding tax in the countries where the investments are located.

None of this changes what a fund is or how it works, but it can change which share class or fund type is most efficient for you. This guide cannot cover individual circumstances; please consult a tax adviser in your country before investing.

Frequently asked questions

In summary

An investment fund is a shared portfolio: many investors pool their money, a professional manager invests it within published rules, and an independent depositary safeguards it. Funds make diversification affordable, costs shared and dealing straightforward. They come in many types, from low-risk money market funds to high-risk equity funds, and may be managed actively or passively.

Choosing well means starting from your own purpose and horizon, using the EU risk indicator and the Key Information Document to compare like with like, and paying close attention to costs, which are the one part of the equation you can know in advance. Funds can lose value, and diversification limits rather than removes that possibility. Approached with patience and clear eyes, they remain the most practical route to long-term investing for most people.