A money market mutual fund pools your money with other investors to buy short-term, low-risk debt

A money market mutual fund is a type of mutual fund that invests in short-term loans to governments and corporations — things like Treasury bills, commercial paper, and certificates of deposit. The fund buys these instruments, collects the interest payments, and passes the earnings to you minus a small fee. The goal is stability and steady income, not growth.

Think of it as a middle ground between a savings account and a stock mutual fund. Your money is safer than it would be in stocks, but you earn more than you typically would in a regular savings account. The tradeoff is that the returns are smaller and more predictable.

Key Takeaways

  • Money market funds invest in short-term debt instruments like Treasury bills and commercial paper, which mature in less than a year.
  • Your money is pooled with other investors, so you own a small piece of many different loans rather than one large loan.
  • The fund manager handles all the buying and selling, and you receive your share of the interest earned minus the fund's expense ratio.
  • Money market funds are considered lower-risk than stock funds but typically pay more interest than a regular savings account.
  • Your investment is not insured by the FDIC, though the underlying securities are backed by the U.S. government or established corporations.

What instruments does a money market fund actually hold

Money market funds buy several types of short-term debt. Treasury bills are loans to the U.S. government that mature in a few weeks to a few months. Commercial paper is short-term debt issued by large corporations to cover operating expenses. Certificates of deposit (CDs) are time deposits from banks. Repurchase agreements are loans backed by securities that the borrower promises to buy back at a set price.

All of these mature quickly — usually within 90 days, often much sooner. That's the defining feature. A money market fund does not hold bonds that mature in years, and it does not hold stocks. The fund manager is constantly buying new instruments as old ones mature, which is why the fund can respond quickly if interest rates change.

How your money grows in a money market fund

When you invest in a money market fund, you buy shares at a set price — usually $1 per share. As the fund collects interest from the Treasury bills, commercial paper, and other instruments it holds, that income is either paid out to you as a distribution or reinvested to buy more shares. Most funds let you choose which happens.

The return you earn depends on current interest rates. When the Federal Reserve raises rates, new Treasury bills and commercial paper pay more interest, so the fund's yield goes up. When rates fall, the yield falls too. This is why money market funds are sensitive to interest rate changes in a way that stock funds are not.

You also pay an expense ratio — a small annual fee, usually between 0.1% and 0.5%, that covers the fund manager's costs. This fee is deducted from the fund's earnings before distributions are paid to you.

The difference between a money market fund and a money market account

A money market account is a bank product — it's a savings account with a higher interest rate, usually tied to a minimum balance. Your money is insured by the FDIC up to $250,000. The bank pays you interest, and you can withdraw your money on demand.

A money market mutual fund is an investment product. It is not FDIC-insured, though the securities it holds are backed by the government or corporations. You own shares in the fund, not a deposit at a bank. If you need your money, you sell your shares, which typically takes one to three business days to settle.

Money market accounts are safer and more liquid, but they usually pay less interest. Money market funds typically pay more, but you have to wait a few days to access your cash and you carry a small amount of risk that the fund's value could decline if interest rates spike or a borrower defaults.

Who should consider a money market fund

Money market funds work well for money you want to keep safe but earn more on than a savings account would pay. They're often used as a temporary holding place for cash between other investments, or as a core holding for conservative investors who want steady income without stock market risk.

They're less useful if you need when ready access to your cash — the settlement delay matters. They're also not ideal if you're trying to build wealth over decades, because the returns are modest and don't keep pace with inflation the way stocks can. And they're not a substitute for an emergency fund, because you need that money when ready and FDIC insurance matters.

How to buy shares in a money market fund

You can buy money market fund shares through a brokerage account, a retirement account like an IRA, or directly from the fund company. Most brokerages offer several money market funds to choose from. You'll need to open an account, fund it with cash, and then place an order to buy shares.

The order is processed at the end of the trading day, and you'll own the shares the next business day. You can sell your shares the same way — place an order, and the cash will arrive in your account within one to three business days. There's usually no commission to buy or sell, though you'll pay the fund's expense ratio as long as you hold it.

What risks come with a money market fund

Money market funds are low-risk, but not risk-free. The main risk is credit risk — the possibility that a borrower (a corporation or government) fails to repay. This is rare with Treasury bills, which are backed by the U.S. government, but it's possible with commercial paper from a struggling company.

A second risk is interest rate risk. If rates rise sharply, the value of the fund's existing holdings falls, though this matters only if you need to sell before they mature. If you hold the fund to maturity, you get your full principal back.

A third risk is liquidity risk — the possibility that you can't sell your shares quickly if the market becomes stressed. This is rare but has happened during financial crises. Your cash won't arrive when ready the way it would from a bank account.

Frequently Asked Questions

Can I lose money in a money market fund?

Yes, though it's uncommon. If a borrower defaults or interest rates spike and you need to sell before maturity, your shares could be worth less than you paid. However, most money market funds hold very safe instruments and rarely experience losses.

Is a money market fund the same as a money market account?

No. A money market account is a bank savings product with FDIC insurance. A money market fund is an investment product with no FDIC insurance. Money market accounts are safer but typically pay less interest.

How long does it take to get my money out of a money market fund?

You can place a sell order anytime, but the cash usually arrives in your account within one to three business days. This is slower than withdrawing from a bank account, which is when ready.

Do I pay taxes on money market fund earnings?

Yes. Interest and distributions from a money market fund are taxable as ordinary income in the year you receive them. If you hold the fund in a tax-advantaged account like an IRA, taxes are deferred or eliminated depending on the account type.

What's the difference between a money market fund and a bond fund?

A money market fund holds very short-term debt that matures in weeks or months. A bond fund holds longer-term debt that matures in years. Bond funds have more interest rate risk and typically pay higher yields, but they're also more volatile.