What Are the Different Types of Money Market Funds?
Not all money market funds hold the same kinds of investments, even though they tend to get discussed as if they were interchangeable places to park idle cash. The differences between the main types come down to what the fund is allowed to buy, and that in turn shapes both its risk profile and how its yield tends to behave.
The short answer
Money market funds generally fall into a few broad categories based on what they hold: government funds invest mainly in short-term government securities and repurchase agreements backed by them, prime funds add short-term corporate and bank debt to the mix, and municipal (or “tax-exempt”) funds hold short-term debt issued by state and local governments. Each type carries a different balance of credit exposure, and municipal funds carry different tax treatment as well. The category a fund falls into says more about what’s under the hood than the phrase “money market” alone does.
Government money market funds
These funds stick to a narrow list of holdings: short-term government debt, and repurchase agreements collateralized by that debt. Because the underlying issuers carry government backing, this category is generally viewed as carrying less credit risk than the other types. That relative safety is also the tradeoff — a fund limited to this narrower set of holdings has less room to reach for extra yield than a fund that can also buy corporate debt.
Prime money market funds
Prime funds expand the toolkit to include short-term debt issued by banks and corporations, alongside government securities, in a way that sets them apart from a plain-vanilla high-yield savings account even though both are sometimes compared as places to hold cash. That broader opportunity set can translate into a higher yield relative to a government fund, but it also introduces a modest amount of credit risk tied to the health of the private issuers whose debt the fund holds. Prime funds were also the focus of reforms discussed in how stable and floating NAV structures differ, since certain prime funds are treated differently than government funds under current rules.
Municipal money market funds
Municipal funds hold short-term debt issued by state and local governments and their agencies. The main draw is the tax treatment: interest from many municipal securities is exempt from federal income tax, and sometimes from state tax as well if the investor lives in the issuing state. That tax treatment depends on the specific securities held and the investor’s own situation, and rules around it can change, so it’s worth checking a fund’s actual holdings rather than assuming a blanket exemption applies.
Comparing the tradeoffs
- Government funds. Narrower holdings, generally viewed as lower credit risk, often a lower baseline yield.
- Prime funds. Broader holdings including corporate and bank debt, generally a bit more credit exposure, often a somewhat higher yield.
- Municipal funds. Holdings tied to state and local government debt, with tax treatment that can offset a lower headline yield depending on an investor’s tax bracket and location.
None of these categories is inherently the better choice; the tradeoffs shift depending on what an investor is weighing, and none of them behaves exactly like a bank money market account, which is a deposit product rather than a fund investing in securities.
The bottom line
The label “money market fund” describes a general style of short-term, relatively stable investing, but the specific type — government, prime, or municipal — determines what’s actually being held and what risks and tax questions come with it. Reading a fund’s stated investment policy, rather than relying on the general category name, is the more reliable way to know what’s inside.