Glossary · Investing & tax
What is Mutual fund?
A pooled investment vehicle that holds many securities. Trades once a day at NAV (4 PM ET); typically charges higher fees than ETFs. Common in 401(k) plans where ETF options aren't always available.
Last updated April 30, 2026
How it works
You give a mutual fund company (Vanguard, Fidelity, T. Rowe Price) cash; they pool it with other investors' cash and buy securities according to the fund's mandate. You receive shares of the fund proportional to your contribution.
Two structural differences from ETFs:
- Once-daily pricing. All buys and sells settle at the day's net asset value (NAV), calculated after market close. You can't trade intraday at varying prices.
- Less tax-efficient. When the fund manager sells appreciated holdings, every shareholder receives a capital-gains distribution — even if you didn't sell anything. The ETF creation/redemption mechanism avoids this.
| Mutual fund | ETF | |
|---|---|---|
| Trades when? | End of day at NAV | Live throughout market hours |
| Min investment | Often $1,000–$3,000 | One share (sometimes fractional) |
| Typical expense ratio | 0.10–1.00% | 0.03–0.50% |
| Tax efficiency | Capital-gains distributions | Generally none |
| 401(k) availability | Common | Less common |
Example
VFIAX (Vanguard 500 Index Admiral Shares):
- Tracks the S&P 500
- Expense ratio: 0.04%
- Min investment: $3,000
- Tracks essentially the same thing as VOO (Vanguard's S&P 500 ETF) at essentially the same cost
For a Vanguard customer, VFIAX and VOO are nearly interchangeable. The differences are operational:
- In a 401(k) or IRA at Vanguard: VFIAX often more available
- In a taxable brokerage account: VOO is slightly more tax-efficient
- For dollar-amount-based contributions ("invest exactly $500"): mutual funds buy fractional, ETFs typically buy whole shares (some brokerages now support fractional ETF shares too)
Why it matters
Mutual funds aren't going away — most 401(k) plans default to mutual funds and many target-date retirement funds (the most common 401(k) holding) are mutual-fund structures.
Practical guidance:
- In a 401(k): Pick the lowest-fee available index funds. Vanguard, Fidelity, and Schwab all offer extremely cheap index mutual funds (~0.04%) inside most plans.
- In an IRA or taxable brokerage: Prefer the ETF version of the same index when available. Same exposure, lower tax drag.
- Avoid actively-managed mutual funds with 1%+ expense ratios unless they're your only option — fees that high reliably trail index benchmarks over long periods.
- Watch for sales loads. Some advisor-sold mutual funds charge a 5%+ "front-end load" — meaning $5,000 of every $100,000 deposit goes to the salesperson. These are hard to ever recover from.
For most investors building wealth through retirement accounts, low-cost mutual funds and ETFs are functionally equivalent. The right answer depends on what your account allows and which has the lower fee.