What Are Money Market Funds?

A money market fund is a lower-risk type of mutual fund that invests in short-term, high-quality debt instruments, such as U.S. Treasury bills, government agency obligations, and short-term corporate notes. In general, the goal of investing in a money market fund is to keep your money's value stable, easy to access, and earning a competitive interest rate until you need it.

Depending on the current rate environment, money market funds have the potential to deliver income that exceeds the income earned in a traditional bank savings account. Keep in mind that the income potential of different cash management tools will vary across the economic cycle.

Money market funds work by pooling cash from a large number of investors to purchase assets that mature quickly and carry low risk. A money market fund earns interest from these investments and pays income to investors in the form of dividends.

If you're looking to invest in a money market fund, you can buy and sell shares through a brokerage account, similar to other mutual fund shares you may own. To access cash that you hold in a money market fund, you will sell shares of the fund that you own. You can generally then access your cash on the next business day. Some providers may offer same day access to your funds.

Every money market fund is built around three core priorities:

• Stability: By focusing on very short-term securities, money market funds are more insulated from the kinds of interest rate swings that can send longer-term bond funds on a roller coaster ride. These funds invest only in high-quality, low-risk securities issued by borrowers with strong credit ratings—the kind that are unlikely to default.
• Easy access: Money market funds are designed for liquidity. Liquidity is just another way of saying you can get to your money quickly when you need it.
• Income: Money market funds have the potential to generate higher income than bank checking and savings accounts. Income potential will vary over time. For a broad snapshot of current rates, the SEC reports average current income metrics for money market funds at their website, SEC.gov, while the FDIC reports current income metrics for bank products at their website, FDIC.gov.

Depending on your brokerage firm, available money market fund choices could include sweep or non-sweep funds. A sweep fund automatically moves idle cash from your brokerage or investment account into the fund's portfolio overnight. A non‑sweep fund is simply a money market fund you invest in manually. It does not automatically move your uninvested cash into the fund. A sweep fund may offer simplicity and convenience, while a non-sweep fund may offer investors more choice and control over how their cash is invested.

There are three main types that offer different tax treatments on the income they generate for you.

• Prime money market funds: These funds invest in short-term debt issued by corporations and banks, along with things like repurchase agreements and commercial paper. Because they take on slightly more credit exposure than government funds, they tend to offer higher yields. The income prime funds generate is taxable at both the federal and state level.
• U.S. government and treasury money market funds: These funds invest in short-term U.S. government debt—Treasury bills, government agency securities, and repurchase agreements backed by those instruments. Treasury-only funds are even more targeted, limiting themselves exclusively to direct U.S. Treasury obligations. Income from Treasury securities is exempt from state income tax, which can make them especially attractive if you live somewhere with high state taxes, such as California or New York.
• Municipal (tax-exempt) money market funds: These funds invest in short-term debt issued by states, cities, and other local governments. The income they generate is typically exempt from federal income tax—and in many cases, from state income tax too, if you live in the state that issued the underlying securities.

The Securities and Exchange Commission (SEC) regulates money market funds and has significantly strengthened the rules around them over the years, improving liquidity requirements, credit quality standards, and overall oversight.
 

Money market mutual funds held in a brokerage account are classified as securities, not bank deposits. That means they're protected by the SIPC (Securities Investor Protection Corporation) rather than the FDIC. SIPC covers up to $500,000 per customer at a failed brokerage firm, including up to $250,000 in cash. SIPC protection is designed to protect you if the brokerage firm itself fails—not to cover investment losses from the fund.

The income generated by money market funds will fluctuate as interest rates change. When rates fall, so does your income from the fund. When rates are rising, income from money market funds will typically rise as well.

In addition, while money market funds are designed for stability, there has been an extremely rare phenomenon called "breaking the buck," when a fund's net asset value (NAV) dips below $1.00 per share. It has happened only twice throughout the category's entire history (in 1994 and 2008). Enhanced SEC regulations have significantly reduced this risk but it's worth knowing about.

Finally, the income generated by money market funds typically won't protect you against the loss of purchasing power over time due to inflation. To protect against inflation, you'll generally need exposure to assets with more long-term growth potential, such as stocks.

Money market funds are a great fit for many situations, but they're not the only option. A few alternatives worth considering:

• Checking accounts at an FDIC-insured bank have a place in your toolkit for paying bills and conducting ordinary transactions. With a money market fund, you need to sell your shares and may need to wait one business day for the trade to settle before the cash is in hand.
• CDs (Certificates of Deposit) can be a smart move if you know you won't need a certain chunk of money for a defined period—say, anywhere from six months to five years. With a CD, keep in mind that your money will be locked up until the CD's maturity date. If you need to redeem your CD before it matures, you'll lose any interest you may have accrued and potentially pay a penalty. Further, CDs may pay interest at different intervals from other investing alternatives.
• Ultra-short duration bond funds and ETFs, which invest in very short-term Treasury bills and other short-term securities (typically less than 1 year), can be another attractive option, if you're comfortable with slightly more credit and interest rate risk. A key difference is that money market funds are designed to maintain a stable daily share price of $1.00, while bond ETFs may experience daily share price fluctuations.

A money market fund may be one of those underrated financial tools that quietly earns its keep. It has the potential to offer higher income than a traditional checking or savings account and may deliver more stability and accessibility than stocks or bonds. In general, it doesn't need much attention except to periodically make sure that the amount you may be holding in a money market fund is aligned with your financial needs and time frame for using the money. A money market fund is worth considering if you’re looking for a way to keep your cash reserves stable, accessible, and working harder than they would under the proverbial mattress. Whether you're building your first emergency fund or parking a down payment while you wait for the right house, a money market fund could make sense for your financial toolkit.