Mutual Funds: How They Work, Types, Fees, and How to Choose

Mutual funds are the most widely held pooled investment vehicle in the world. With over $20 trillion in U.S. long-term mutual fund assets as of 2024, they remain the foundation of most retirement accounts and individual investment portfolios. Whether you’re contributing to a 401(k), opening an IRA, or investing through a brokerage account, understanding how mutual funds work — their structure, pricing, fee layers, and tax treatment — is essential for making informed decisions that compound over decades.

What Is a Mutual Fund?

A mutual fund is an open-end investment company that pools money from many investors and invests it in a diversified portfolio of stocks, bonds, or other securities. Each investor owns shares proportional to the amount they invest, and a professional portfolio manager makes the day-to-day investment decisions.

Mutual funds serve four key functions for investors. First, they handle record keeping and administration — tracking dividends, capital gains distributions, and reinvestments. Second, they provide diversification and divisibility, allowing even small investors to hold fractional interests in hundreds of securities. Third, they offer professional management by employing full-time security analysts and portfolio managers. Fourth, because funds trade in large blocks, they achieve lower transaction costs than individual investors would face.

As an open-end fund, a mutual fund continuously issues new shares to investors who want to buy in and redeems shares from investors who want to sell — all at the fund’s NAV. This differs fundamentally from stocks or exchange-traded funds (ETFs), where buyers and sellers trade with each other on an exchange.

How Mutual Funds Work: NAV, Pricing, and Order Execution

Every mutual fund transaction revolves around net asset value (NAV) — the per-share value of the fund’s portfolio after deducting liabilities.

Total assets include the market value of all securities the fund holds, plus any cash. Total liabilities include fees owed to the investment adviser, rent, wages, and other operating expenses. The resulting NAV represents the price at which you buy or redeem shares.

A critical feature of mutual fund pricing is forward pricing. All purchase and redemption orders execute at the next computed NAV — not the current one. NAV is calculated once daily at 4:00 PM Eastern when U.S. markets close. Orders placed before the fund’s cutoff time (typically 4:00 PM ET) receive that day’s NAV. Orders placed after the cutoff execute at the following business day’s NAV. This means you never know the exact price you’ll pay or receive when you place a mutual fund order.

Types of Mutual Funds

Mutual funds are classified by their investment policy, which is described in the fund’s prospectus. Here are the major categories:

Management companies such as Vanguard, Fidelity, and BlackRock organize “fund families” — collections of mutual funds with different investment policies under one umbrella. This makes it easy for investors to allocate across asset classes and switch between funds while benefiting from centralized record keeping. For a deeper look at passive index fund strategies and the evidence behind them, see our guide to index funds.

Share Classes and Load Fees

Many mutual funds offer multiple share classes that represent ownership in the same portfolio but with different fee structures. The class you choose determines how — and how much — you pay for advice, distribution, and ongoing management.

Class A shares charge an upfront sales commission (front-end load) that reduces your initial investment but carry lower ongoing annual fees. Class C shares avoid the upfront load but compensate with a higher annual 12b-1 fee, typically around 1%, and may impose a contingent deferred sales charge (CDSC) if redeemed within the first year. Institutional shares (Class I or sometimes Class Y) carry no loads and no 12b-1 fees, but require high minimum investments — typically $1 million or more — and are commonly accessed through employer retirement plans.

Class B shares, which historically charged back-end loads that declined over a 6-to-8-year holding period before converting to Class A, are no longer widely available.

Mutual Fund Fees and Expenses

Every mutual fund charges an expense ratio — the annual percentage of assets deducted to cover operating costs. Understanding what goes into this number is critical because fees compound against you over decades.

The total expense ratio comprises three components:

• Management fee — the largest component, paying the portfolio manager and research team (typically 0.20% to 0.75%)
• 12b-1 fee — marketing and distribution costs, including broker commissions (capped at 1.00% by SEC rule)
• Other operating expenses — custodian, legal, accounting, and transfer agent fees

As of 2024, the asset-weighted average expense ratio for actively managed U.S. equity mutual funds is approximately 0.40%, while index equity mutual funds average roughly 0.05% — a gap that has narrowed dramatically over the past two decades as fee competition intensified.

Open-End vs Closed-End Funds

Most investors think of mutual funds as open-end funds — and they’re right, since open-end funds account for the vast majority of investment company assets. However, a related but structurally different vehicle exists: the closed-end fund (CEF).

The most notable feature of closed-end funds is the persistent discount to NAV puzzle. Many CEFs trade below their net asset value — sometimes by 10% or more — meaning investors can effectively buy a dollar’s worth of assets for less than a dollar. Research by Pontiff (1996) shows that a fund selling at a 20% discount has historically offered an expected 12-month return more than 6% greater than funds trading at NAV, as discounts tend to narrow over time.

Paradoxically, newly issued CEFs often sell at a premium to NAV (reflecting the underwriter’s commission), only to fall to a discount shortly after. Despite the apparent arbitrage opportunity of persistent discounts, they endure — making the CEF discount one of the enduring puzzles in financial economics.

Mutual Fund Example

To see how fees and loads affect real investment outcomes, compare two investors who each start with $10,000.

Mutual Funds vs ETFs

Mutual funds and exchange-traded funds (ETFs) both offer diversified, professionally managed portfolios, but they differ in several structural ways that affect how you trade, what you pay, and how your returns are taxed.

Neither structure is universally better — the right choice depends on how you invest. Mutual funds excel for automatic, recurring investments (e.g., payroll contributions to a 401(k)) because you can invest exact dollar amounts and partial shares. ETFs excel for tax-efficient, flexible investing in taxable brokerage accounts. Many investors use both: mutual funds inside retirement plans and ETFs in taxable accounts. For a deeper look at ETF mechanics and tax advantages, see our guide to exchange-traded funds.

How Mutual Funds Are Taxed

Mutual fund investment returns have pass-through tax status — the fund itself does not pay taxes. Instead, all income and realized gains are distributed to shareholders, who report them on their individual tax returns.

There are three types of taxable distributions:

• Ordinary dividends — taxed at your ordinary income rate (or the lower qualified dividend rate if held long enough)
• Short-term capital gains — from securities held less than one year by the fund, taxed at your ordinary income rate
• Long-term capital gains — from securities held over one year by the fund, taxed at the preferential capital gains rate

A significant drawback of mutual fund taxation is that you may owe taxes on gains you didn’t personally realize. When a fund manager sells securities at a profit, the resulting capital gains distribution is passed to all current shareholders — including investors who bought in the day before the distribution. This is particularly problematic late in the year, when many funds make large annual distributions.

Tax efficiency varies significantly across fund types. Actively managed funds with high portfolio turnover (50%+ annually) generate more frequent taxable distributions. Index funds, with turnover rates of just 2-5%, are considerably more tax efficient.

How to Select a Mutual Fund

Choosing the right mutual fund requires evaluating several factors beyond just past performance. Here’s a systematic approach:

1. Start with the expense ratio. Research consistently shows that the expense ratio is the single most reliable predictor of future fund performance — lower-cost funds tend to outperform higher-cost funds in the same category. For a comprehensive analysis of fund costs, see our guide to expense ratios.

2. Evaluate investment style consistency. A fund marketed as “large-cap value” should consistently hold large-cap value stocks. Style drift — where a manager chases performance by deviating from the stated mandate — introduces unintended risk to your portfolio.

3. Review the prospectus fee table. Look beyond the expense ratio: check for loads, breakpoint discounts (reduced loads for larger investments), load waivers, and the fund’s turnover rate as an indicator of hidden trading costs.

4. Consider fund size. Very large funds may struggle to execute their strategy effectively, particularly in small-cap or concentrated mandates where large trades move prices. However, size is an advantage for broad index funds where scale drives down costs.

5. Check manager tenure and track record. For actively managed funds, manager continuity matters. A fund’s 10-year track record is less meaningful if the current manager has only been in charge for two years. But remember: past performance does not guarantee future results.

6. Look at the fund family. Large families like Vanguard, Fidelity, and Schwab offer economies of scale (lower fees), easy rebalancing across funds, and consolidated account management. A strong fund family is especially valuable for retirement investors who need multiple fund types.

7. Assess risk-adjusted returns. Raw returns don’t account for the risk taken to achieve them. Metrics like the Sharpe ratio help you compare funds on a risk-adjusted basis — a fund earning 12% with half the volatility of one earning 14% may be the smarter choice.

Common Mistakes

Even experienced investors fall into these traps when investing in mutual funds:

1. Chasing past performance. The top-performing fund this year is statistically likely to underperform next year — a well-documented phenomenon called mean reversion. Star ratings and past returns attract money, but they don’t predict future results.

2. Ignoring fees. A seemingly small difference in expense ratios compounds dramatically over time. A 1% higher expense ratio on a $100,000 investment can cost you nearly $190,000 in lost returns over 30 years, assuming a 7% gross return.

3. Not understanding share classes. Many investors pay unnecessary front-end loads when no-load funds with similar strategies are readily available. Others choose Class C shares for a large, long-term investment without realizing that Class A’s lower ongoing 12b-1 fees would have cost less over time.

4. Holding too many overlapping funds. Owning five different large-cap growth funds doesn’t provide diversification — it provides duplication. Check the top holdings of your funds; significant overlap means you’re paying multiple expense ratios for essentially the same portfolio.

5. Buying shares just before a capital gains distribution. Purchasing a mutual fund shortly before its annual distribution date means you’ll owe taxes on gains the fund earned before you invested. Check the fund’s estimated distribution dates and record date before buying, especially in November and December.

6. Holding tax-inefficient funds in taxable accounts. Actively managed funds with high turnover belong in tax-advantaged accounts (IRAs, 401(k)s) where distributions aren’t taxed annually. Placing them in taxable accounts creates unnecessary tax drag.

Limitations of Mutual Funds

1. End-of-day pricing only. Because mutual funds use forward pricing with NAV calculated once daily, you cannot execute a trade at a known price during the day. If markets drop sharply at 2:00 PM and you place a sell order, it will still execute at the 4:00 PM closing NAV — not the price when you decided to sell.

2. Capital gains distributions create tax drag. Even if you haven’t sold your shares, you may receive — and owe taxes on — capital gains distributions from the fund’s trading activity. This is a structural disadvantage compared to ETFs in taxable accounts.

3. Style drift risk. An active manager may deviate from the fund’s stated investment mandate to chase performance, introducing risk that doesn’t match your intended asset allocation. Monitor a fund’s holdings periodically to ensure it stays true to its investment policy.

4. Minimum investment requirements. Many mutual funds require minimum initial investments of $1,000 to $3,000 (or much higher for institutional shares), which can be a barrier for newer investors or those who prefer to start with smaller amounts.