What a money market fund actually is

A money market fund is a type of mutual fund that holds short-term debt—mostly government bonds, corporate IOUs due within a few months, and other very safe, very liquid investments. When you buy shares in a money market fund, you own a tiny piece of that whole pile. The fund manager buys and sells these securities constantly, and you earn a share of whatever interest they generate.

Money market funds are not the same as money market accounts at a bank. A money market account is a deposit account with FDIC insurance. A money market fund is an investment product with no insurance—but it typically pays a higher interest rate because you're taking on slightly more risk, even though that risk is very small. You buy money market funds through a brokerage account, not at your bank's teller window.

The main reason people choose money market funds over money market accounts is yield. When interest rates are high, money market funds often pay more than banks do. The tradeoff is that your money is not insured by the FDIC, though the actual risk of losing principal is extremely low because the fund holds only the safest short-term debt.

Key Takeaways

  • You buy money market funds through a brokerage account—either one you already have or one you open with a bank, discount broker, or investment firm.
  • The fund holds short-term government and corporate debt, so it is very stable but typically pays less than longer-term bond funds.
  • Your money is not FDIC insured, but money market funds are designed to maintain a stable share price and carry minimal risk of loss.
  • You can usually move money in and out of a money market fund within one to three business days, making it more liquid than a CD but less liquid than a checking account.
  • Expense ratios—the annual fee the fund charges—vary widely, so comparing costs between funds matters more than comparing yields alone.

Opening a brokerage account to buy money market funds

You cannot buy a money market fund directly from the fund company. You need a brokerage account—a holding place for investments that you open with a bank, a discount broker like Fidelity or Schwab, or an investment firm. If you already have a retirement account (401k, IRA) or an investment account anywhere, you already have a brokerage account and can buy money market funds there.

If you don't have one, opening a brokerage account takes about 15 minutes online. You'll provide your name, address, Social Security number, and employment information. The firm will verify your identity and ask you to link a bank account so you can move money in and out. Most brokers do not charge to open an account or to hold money in it.

Once your account is open and funded, you can search for money market funds by name or ticker symbol, see the current share price, and buy as many shares as you want. The purchase happens instantly during market hours (usually 9:30 a.m. to 4 p.m. Eastern time on weekdays).

Comparing money market funds by cost and yield

Two money market funds holding nearly identical securities can pay very different returns because of their expense ratio—the annual percentage fee the fund charges to operate. One fund might charge 0.10% per year while another charges 0.50%. Over time, that difference compounds. If you have $10,000 in a fund, you're paying $10 per year versus $50 per year, which sounds small until you realize the lower-cost fund keeps more of your interest earnings.

When you're comparing funds, look at the expense ratio first. Then look at the current yield—the interest rate the fund is paying right now. Yield changes daily as interest rates move, so a fund paying 5.2% today might pay 5.1% next week. The expense ratio is stable. A fund with a 0.15% expense ratio and a 5.0% yield will almost always beat a fund with a 0.50% expense ratio and a 5.1% yield, because you keep more of that interest over time.

Most brokers let you filter money market funds by expense ratio and sort by yield. Read the fund's prospectus—a document the fund company must provide—to understand exactly what it holds and what fees apply. The prospectus is dense, but the first few pages tell you the fund's goal, its expense ratio, and what types of securities it buys.

Understanding share price and how your money grows

Money market funds are designed to keep their share price stable at $1.00 per share. When the fund earns interest, it doesn't raise the share price—instead, it pays out dividends, which are usually reinvested automatically to buy more shares. So if you own 10,000 shares at $1.00 each and the fund pays a dividend, you might end up with 10,050 shares at $1.00 each. Your total value grew, but the per-share price stayed the same.

This is different from stock funds, where the share price moves up and down. Because money market funds hold only very safe, short-term debt, the share price almost never changes. That stability is the whole point—you're not trying to make a killing, you're trying to park cash safely and earn a little interest.

The dividends are usually paid monthly or daily, depending on the fund. Daily dividend funds reinvest your earnings every single day, which compounds faster. Monthly funds reinvest once a month. Over a year, the difference is small, but daily reinvestment does give you a slightly higher return.

When you can access your money

Money market funds are liquid, meaning you can sell your shares and get your cash back fairly quickly. When you place a sell order during market hours, the transaction usually settles within one to three business days. That's faster than a CD (which locks your money up for a set term) but slower than a checking account (where you can withdraw instantly).

Some money market funds have restrictions on how often you can withdraw or how much you can move out in a given period. These are rare now, but check the prospectus if you think you might need to access the money frequently. Most funds let you move money out as often as you want with no penalty.

If you need the money in the next few days, a money market fund is not the right place for it. Use your checking or savings account instead. Money market funds are best for money you won't need for at least a week or two but want to keep accessible and earning interest.

Tax treatment of money market fund earnings

The interest you earn in a money market fund is taxable income. If the fund pays 5% and you earn $500 in a year, you owe income tax on that $500 at your regular tax rate. The fund will send you a Form 1099-DIV at the end of the year showing how much you earned, and you report that on your tax return.

If you hold the money market fund in a tax-advantaged account like a traditional IRA or 401k, the earnings are not taxed until you withdraw from the account. If you hold it in a regular taxable brokerage account, you pay tax on the earnings each year. This is one reason some people keep their emergency fund in a money market fund inside an IRA—the earnings grow tax-free.

Some money market funds hold municipal bonds (debt issued by cities and states) and pay interest that is exempt from federal income tax. These funds typically pay less interest than taxable money market funds, but if you're in a high tax bracket, the after-tax return might be higher. Your brokerage firm can show you the tax-equivalent yield to help you compare.

Money market funds versus other places to park cash

If you're deciding between a money market fund and a high-yield savings account, the choice usually comes down to yield and convenience. A high-yield savings account at an online bank might pay 4.5% to 5.0% and is FDIC insured up to $250,000. A money market fund might pay 5.0% to 5.3% but has no insurance. Both are very safe. The money market fund pays slightly more, but the savings account is easier to access and your money is insured.

If you're deciding between a money market fund and a CD, remember that a CD locks your money up for a set term (three months, one year, five years) and pays a fixed rate. A money market fund keeps your money liquid and lets the rate float with the market. CDs often pay more than money market funds because you're giving up access. If you might need the money, a money market fund is more flexible.

If you're deciding between a money market fund and a money market account at your bank, compare the yields. Many banks pay very little on money market accounts—sometimes less than 1%—while money market funds pay much more. But a money market account is FDIC insured and easier to access. If your bank's money market account pays nearly as much as a fund, the insurance might be worth it.

Frequently Asked Questions

Can I lose money in a money market fund?

It is extremely unlikely. Money market funds hold only the safest, shortest-term debt, and they're designed to keep the share price at $1.00. In the 2008 financial crisis, one large money market fund "broke the buck" (dropped below $1.00), but this was rare and happened only during an extraordinary panic. For practical purposes, money market funds are as safe as savings accounts, just without FDIC insurance.

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

A bond fund holds longer-term debt (bonds due in 5, 10, or 30 years), so the share price moves up and down as interest rates change. A money market fund holds only short-term debt (due within a few months), so the share price stays at $1.00. Bond funds usually pay more interest but are less stable. Money market funds are more stable but pay less.

Do I have to buy a whole share?

No. Most brokers let you buy fractional shares, so you can invest any dollar amount you want. If a share costs $1.00 and you have $500 to invest, you'll own 500 shares. If you have $1,000, you'll own 1,000 shares. There's no minimum investment at most brokers.

How often should I check the yield on my money market fund?

You don't need to check it constantly. Yields change daily, but the difference from day to day is tiny. If you're holding the fund for several months or longer, checking once a month is plenty. If rates drop significantly (which happens when the Federal Reserve cuts interest rates), you might want to compare your fund's yield to others and switch if you find a better option.

Can I buy a money market fund inside a retirement account?

Yes. You can hold a money market fund in an IRA, 401k, or any other retirement account. This is actually a smart move if you're not sure where to invest yet—you can park cash in a money market fund earning interest, and move it to stocks or bonds later without worrying about taxes.