What Is a Mutual Fund? Definition, Types, Fees, and How It Works
Last updated 04/14/2026 by
Ante Mazalin
Edited by
Andrew Latham
Summary:
A mutual fund is an SEC-registered investment vehicle that pools money from many investors and uses it to buy a diversified portfolio of stocks, bonds, or other securities managed by a professional fund manager.
Mutual funds fall into several categories based on what they invest in and how they’re structured.
- Equity funds: Invest primarily in stocks and are the most common type — suited to investors seeking long-term growth who can tolerate short-term volatility.
- Bond funds: Invest in fixed-income securities and generate regular income — better suited to conservative investors or those nearing retirement.
- Money market funds: Hold short-term, high-quality debt instruments and aim to maintain a stable $1 per share value — used as a low-risk cash equivalent.
- Hybrid funds: Hold a mix of stocks and bonds in a single portfolio, balancing growth potential with income and stability.
Mutual funds are one of the most widely used investment vehicles in the United States, with U.S. investors holding the largest share of regulated open-end fund assets of any country in the world.
For most individual investors, a mutual fund is also the first place they encounter diversified market exposure — through a 401(k) plan, an IRA, or a brokerage account. Understanding how the structure works, what it costs, and how it differs from other vehicles is the foundation for evaluating any fund you hold or consider buying.
How a mutual fund works
When you buy shares in a mutual fund, your money is pooled with that of other investors.
The combined pool is then managed by a portfolio manager — an investment professional employed by the fund company — who buys and sells securities according to the fund’s stated strategy and investment mandate.
You own a proportional share of everything in the fund’s portfolio. If the fund holds 300 stocks and earns dividends or capital gains, those proceeds are distributed to all shareholders in proportion to how many shares they own.
Mutual fund shares are not traded on a stock exchange. Instead, they are priced once per day at the close of the market, using a calculation called net asset value (NAV).
What is NAV?
NAV — net asset value — is the per-share price of a mutual fund. It equals the total market value of the fund’s holdings, minus liabilities, divided by the number of shares outstanding. If a fund holds $500 million in assets, has $5 million in liabilities, and 50 million shares outstanding, its NAV is $9.90 per share.
When you place a buy or sell order for a mutual fund during the trading day, your transaction executes at that day’s closing NAV — not the price at the moment you clicked. This is a key structural difference from ETFs and stocks, which trade at real-time prices throughout the day.
Open-end vs. closed-end mutual funds
Most mutual funds that individual investors encounter are open-end funds, but two distinct structures exist.
Open-end funds continuously issue and redeem shares directly with investors at NAV. There’s no fixed number of shares — the fund grows or shrinks as investors buy in or cash out. The vast majority of U.S. mutual fund assets are held in open-end funds.
Closed-end funds raise a fixed amount of capital through an initial public offering, then trade on a stock exchange like a stock. Investors who want to exit sell their shares to other buyers on the open market — the fund itself doesn’t redeem shares.
This means closed-end fund prices can trade at a premium or discount to NAV depending on market demand. SuperMoney’s entry on closed-end funds covers this structure in detail.
Types of mutual funds by investment strategy
Beyond structure, mutual funds are most commonly classified by what they invest in.
| Type | What it holds | Primary goal | Risk level |
|---|---|---|---|
| Equity (stock) fund | Common and preferred stocks | Long-term capital growth | Moderate to high |
| Bond (fixed-income) fund | Government, corporate, or municipal bonds | Regular income | Low to moderate |
| Money market fund | Treasury bills, commercial paper, CDs | Capital preservation + modest yield | Very low |
| Hybrid / balanced fund | Mix of stocks and bonds | Growth and income | Low to moderate |
| Index fund | Securities that replicate a market index | Match benchmark performance | Varies by index |
| Sector fund | Stocks in one industry (tech, healthcare, etc.) | Concentrated exposure to one sector | High |
Within equity funds, sub-categories are further divided by market capitalization (large-cap, mid-cap, small-cap), investment style (growth vs. value), and geography (domestic, international, emerging markets). Growth and income funds represent a common hybrid approach targeting both objectives simultaneously.
Active vs. passive management
Mutual funds are either actively managed or passively managed — a distinction that affects both cost and expected return.
- Actively managed funds employ portfolio managers who research securities, make buy and sell decisions, and aim to outperform a benchmark index. These decisions require analysts, research infrastructure, and higher trading activity — all of which raise costs. According to the Investment Company Institute’s 2025 Fact Book, the asset-weighted average expense ratio for actively managed equity mutual funds was 0.40% in 2024 — more than four times the average for passively managed index funds.
- Passively managed funds (index funds) simply replicate a benchmark index. They require no active research decisions, produce lower portfolio turnover, and charge significantly less. Most also have lower taxable capital gains distributions as a result.
For a direct comparison of how the two approaches differ in cost and historical performance, see SuperMoney’s index funds vs. mutual funds breakdown.
What mutual funds cost
Understanding mutual fund fees is essential — they compound over time and can significantly erode returns even when underlying performance looks strong.
- Expense ratio: The annual operating cost of running the fund, expressed as a percentage of assets. Covers management fees, administrative costs, and other fund expenses. Deducted automatically from fund returns — you never receive a bill, but you see the effect in your net returns over time.
- Front-end load (Class A shares): A sales commission paid when you buy shares — typically 3% to 5.75% of the amount invested. A 5% load on a $10,000 investment means $500 goes to the broker before any dollar is invested.
- Back-end load (Class B shares): A redemption fee charged when you sell, often on a declining schedule — higher if you sell in year one, decreasing to zero after several years. Also called a contingent deferred sales charge (CDSC).
- No-load funds: Charge no front- or back-end sales commissions. Most funds sold directly through fund companies (Vanguard, Fidelity, Schwab) and through fee-only advisors are no-load.
- 12b-1 fees: Annual fees charged by some funds to cover marketing and distribution costs — up to 1% of assets per year. They are disclosed in the fund’s prospectus and included in the stated expense ratio.
Pro tip: Always check whether a mutual fund charges a load before buying. A 5% front-end load on a fund with a 7% annual return takes more than eight months of market gains just to break even on the sales charge. Fee-only financial advisors and direct fund purchases eliminate load fees entirely.
How mutual fund distributions work
Mutual funds are required by law to distribute substantially all of their net income to shareholders each year. These distributions come in two forms:
- Dividend distributions: Pass through income the fund collected — dividends from stocks it holds, or interest from bonds. Distributed quarterly or annually depending on the fund.
- Capital gains distributions: Occur when the fund’s manager sells securities that have appreciated. Even if you didn’t sell any of your own shares, you receive a taxable capital gains distribution if the fund did — a hidden tax cost that catches many investors off guard in actively managed funds.
This is one reason many investors prefer ETFs for taxable accounts — their structure minimizes capital gains distributions. The fund’s cash management decisions also affect how and when these distributions occur.
Mutual funds vs. ETFs
Both mutual funds and ETFs pool investor money and offer diversified exposure, but they differ in structure, trading mechanics, and tax treatment.
- Trading: ETFs trade on an exchange throughout the day at real-time prices, like a stock. Mutual funds price once per day at NAV after the market closes.
- Tax efficiency: ETFs are generally more tax-efficient in taxable accounts because their in-kind redemption structure minimizes capital gains distributions.
- Contribution flexibility: Mutual funds suit automatic contribution schedules better — fractional-dollar purchases are seamless without tracking share prices or bid-ask spreads.
- Underlying strategy: Both vehicles can track the same index. For most long-term investors in tax-advantaged accounts, the performance difference between an ETF and mutual fund tracking the same benchmark is negligible — expense ratio is what matters.
How mutual funds are regulated
U.S. mutual funds are regulated primarily under the Investment Company Act of 1940 and are registered with the Securities and Exchange Commission. The SEC requires all funds to publish a prospectus disclosing their investment strategy, fees, risks, and historical performance before selling shares to the public.
Fund families — groups of multiple funds managed by the same company — are required to maintain consistent disclosures across all funds. SuperMoney’s entry on mutual fund families explains how these structures are organized and how investors can use them to consolidate accounts.
How to evaluate a mutual fund before investing
Five things to verify before you buy any mutual fund.
- Check the expense ratio. Find it in the fund’s prospectus or on the fund company’s website. For equity index funds, anything above 0.20% warrants scrutiny. For actively managed funds, compare to category peers.
- Identify whether a load applies. Search for “sales charge” or “load” in the fund prospectus. No-load funds are widely available — there’s rarely a reason to pay a sales commission.
- Review the investment strategy and mandate. Confirm the fund invests in what you think it does. A “growth fund” at one firm may be significantly different from a “growth fund” at another.
- Check the fund manager’s tenure and track record. For actively managed funds, the track record is only meaningful relative to the period the current manager has been running it.
- Assess tax efficiency for taxable accounts. Review the fund’s historical capital gains distributions. High turnover actively managed funds distribute more capital gains — a meaningful cost in taxable accounts.
Frequently asked questions
Are mutual funds safe?
Mutual funds are subject to market risk — the value of your shares rises and falls with the securities the fund holds. They are not FDIC-insured. Money market funds are the lowest-risk category, but even they are not guaranteed. Diversification within a mutual fund reduces individual security risk but does not eliminate broad market risk.
What is the minimum to invest in a mutual fund?
Minimums vary widely. Many retail mutual funds require $500 to $3,000 to open an account. Some fund companies — including Fidelity — have eliminated minimums entirely on certain funds. Employer-sponsored 401(k) plans often allow contributions in any dollar amount regardless of the fund’s stated minimum.
How are mutual fund gains taxed?
In a taxable account, dividends are taxed as ordinary income or qualified dividends, and capital gains distributions are taxed as short- or long-term capital gains depending on how long the fund held the securities. When you sell your own shares, any gain is a capital gain taxed at short- or long-term rates based on how long you held the fund. In a 401(k) or traditional IRA, gains are tax-deferred; in a Roth IRA, gains grow tax-free.
Can you lose all your money in a mutual fund?
A fund’s value could theoretically decline to near zero if all holdings became worthless — but a diversified equity fund holding hundreds of companies would require near-total market collapse to approach that outcome. The more practical risk is a significant but partial loss during market downturns, as was the case in 2008–2009 when many equity mutual funds lost 30–50% of their value before recovering.
What is the difference between a mutual fund and an index fund?
A mutual fund is a structure — a pooled investment vehicle. An index fund is an investment strategy — one that passively tracks a market benchmark rather than actively selecting securities. Index funds are a subset of mutual funds: all index funds are mutual funds (or ETFs), but most mutual funds are actively managed and are not index funds.
What is a mutual fund advisory program?
A mutual fund advisory program — sometimes called a mutual fund wrap — is a service in which an advisor constructs and manages a portfolio of mutual funds on your behalf for an annual advisory fee, usually 1–2% of assets. These programs bundle fund selection, rebalancing, and ongoing advice into a single fee structure.
Key takeaways
- A mutual fund pools money from many investors to buy a professionally managed, diversified portfolio of securities — giving individuals access to broad market exposure without selecting individual securities.
- Mutual fund shares price once per day at NAV (net asset value), unlike ETFs and stocks which trade at real-time prices throughout the day.
- The four main investment categories are equity funds, bond funds, money market funds, and hybrid funds — each with different risk profiles and income characteristics.
- The asset-weighted average expense ratio for actively managed equity mutual funds was 0.40% in 2024, versus 0.08% for passive index funds — a gap that compounds meaningfully over time.
- Load funds charge a sales commission (up to 5.75%) on top of ongoing fees; no-load funds eliminate that cost entirely and are widely available through major fund companies and fee-only advisors.
- Mutual funds must distribute substantially all income and realized capital gains annually, which can create unexpected tax events for investors in taxable accounts.
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