Money market funds are safe for most investors, but the answer depends on which type of fund you hold. Government funds, which hold U.S. Treasury securities and account for most of the roughly $7.8 trillion invested in this category, have never caused investor losses. Prime and tax-exempt funds carry more credit and liquidity risk, and since 2024 they operate under a new SEC framework that can impose liquidity fees on redemptions during periods of stress. Money market fund shares are not FDIC-insured, which is the single most important thing to understand before treating one like a savings account.
The Three Fund Types Have Very Different Safety Profiles
A money market fund is a mutual fund that invests only in short-term, high-quality debt. The goal is capital preservation: a dollar in, a dollar out, plus interest. The category splits into three types, and the safety gap between them is wider than most investors realize.
Government Money Market Funds
Government funds hold U.S. Treasury securities, government agency debt, and repurchase agreements backed by those instruments. They are the safest category by a wide margin. During both the 2008 financial crisis and the March 2020 market panic, government funds received large inflows as investors fled riskier options. No government money market fund has ever broken the buck. If safety is your priority and you can accept a slightly lower yield, this is where most of the $7.8 trillion in the industry sits for good reason.
Prime Money Market Funds
Prime funds hold corporate commercial paper, bank certificates of deposit, and other private-sector debt alongside government securities. The extra credit risk typically produces yields 15 to 30 basis points higher than government funds. That fraction of a percent comes with real tradeoffs. Prime funds experienced severe redemption pressures in both 2008 and 2020, and institutional prime funds now operate under a mandatory liquidity fee framework that can raise your cost of redeeming shares during stress.
Structure also differs by share class. Institutional prime funds must use a floating net asset value, meaning the share price moves to four decimal places rather than staying pinned at $1.00. Retail prime funds, which are limited to individual investors, still maintain a stable $1.00 NAV. If you invest through an employer cash management program or a corporate treasury account, you are likely in an institutional fund with floating-NAV exposure.
Tax-Exempt Money Market Funds
Tax-exempt funds hold short-term municipal securities issued by state and local governments. The income is generally exempt from federal income tax, which makes these attractive at higher tax brackets. Municipal issuers default far less often than corporations, but the market for short-term municipal debt is thinner than the Treasury or commercial paper markets, which can create liquidity problems during a crisis. Like prime funds, institutional tax-exempt funds use a floating NAV and are subject to mandatory liquidity fees.
What “Unsafe” Has Actually Looked Like
In the entire history of money market funds, only two have broken the buck, meaning their share price fell below $1.00. The one that matters is the Reserve Primary Fund in September 2008.
The Reserve Primary Fund held $785 million in Lehman Brothers commercial paper when Lehman filed for bankruptcy on September 15, 2008. The next day, the fund marked its Lehman holdings to zero, and its NAV dropped to $0.97 per share. Investors rushed to redeem, the fund froze withdrawals above $10,000, and liquidation began within two weeks. Investors recovered about 79 cents on the dollar by December 2008. The final distribution did not arrive until December 2014, when total recoveries reached 99.1 cents per share. Waiting six years to get nearly all your “cash” back is the nightmare scenario every subsequent regulation has tried to prevent.
The fallout was worse than the fund itself. The Reserve Primary Fund’s collapse triggered a run on prime money market funds across the industry. Within two days, investors pulled more than $300 billion from prime funds. The Treasury Department stepped in with a temporary guarantee program, and the Federal Reserve created emergency lending facilities to stabilize the commercial paper market. The episode showed that money market funds, despite looking like cash, can transmit panic through the financial system.
What the SEC Requires Now
The SEC’s Rule 2a-7 restricts what money market funds can buy, how long they can hold it, and how much liquidity they must keep on hand. The current requirements:
- At least 25% of the fund’s total assets must be in securities that convert to cash within one business day.
- At least 50% must be in securities that convert to cash within five business days.
- Funds can hold only securities with minimal credit risk, as determined by the fund’s board.
- No individual security can have a remaining maturity longer than 397 days, and the fund’s overall weighted average maturity cannot exceed 60 days.
Even in a crisis, at least half the fund’s assets should be convertible to cash within a week. The 25% and 50% liquidity thresholds were increased under the SEC’s 2023 reform package, up from 10% and 30% previously.1U.S. Securities and Exchange Commission. Money Market Fund Reforms
The 2023 Reforms Now in Effect
The SEC adopted major amendments to Rule 2a-7 in July 2023 in response to the March 2020 disruption, when institutional prime and tax-exempt funds again saw destabilizing redemption surges.2U.S. Securities and Exchange Commission. SEC Adopts Money Market Fund Reforms and Amendments to Form PF Reporting Requirements for Large Liquidity Fund Advisers Two changes matter most to whether your money is safe.
First, redemption gates are gone. Under the old rules, a fund’s board could temporarily block withdrawals if weekly liquid assets dropped below 30%. The SEC concluded that this power actually made crises worse, because investors would race to redeem before a gate could be imposed. The new rules eliminate gates entirely.1U.S. Securities and Exchange Commission. Money Market Fund Reforms
Second, mandatory liquidity fees replaced gates. Institutional prime and institutional tax-exempt funds must now impose a liquidity fee when daily net redemptions exceed 5% of the fund’s net assets, unless the liquidity cost is negligible. The board of any non-government money market fund can also impose a discretionary liquidity fee whenever it determines that doing so is in the fund’s best interest.2U.S. Securities and Exchange Commission. SEC Adopts Money Market Fund Reforms and Amendments to Form PF Reporting Requirements for Large Liquidity Fund Advisers The logic is straightforward: if you pull money out during a liquidity crunch, you bear the cost of that withdrawal rather than imposing it on investors who stay.
Transparency requirements were tightened too. Money market funds must publish daily disclosures showing the percentage of assets in daily and weekly liquid buckets, net inflows and outflows, and the fund’s NAV per share. Monthly disclosures include a full schedule of holdings with issuer names, maturity dates, and values.3U.S. Securities and Exchange Commission. ADI 2025-15 – Website Posting Requirements You can check your fund’s actual risk exposure any business day.
A Money Market Fund Is Not a Savings Account
The most common confusion is treating a money market fund like a bank savings account. They look similar on a brokerage statement, they pay comparable interest, and you can usually access the money within a day. The legal protections are completely different.
Bank savings accounts and CDs are insured by the FDIC up to $250,000 per depositor, per bank, per ownership category.4FDIC.gov. Understanding Deposit Insurance If your bank fails, the FDIC pays you back. This coverage applies to losses from any cause, including the bank making terrible lending decisions.
Money market fund shares are not FDIC-insured. They are covered by SIPC, but only against the failure of your brokerage firm, not against a decline in the fund’s value. SIPC protection covers up to $500,000 in securities and cash, with a $250,000 sublimit for cash.5Securities Investor Protection Corporation (SIPC). What SIPC Protects If your brokerage goes bankrupt and your money market fund shares go missing from the account, SIPC steps in. If the money market fund itself loses value, SIPC does nothing. That distinction matters.
If you need every dollar guaranteed and do not need more than $250,000 in coverage, a high-yield savings account gives you similar returns with FDIC insurance. Money market funds become more attractive when you are parking larger sums, want to stay within a brokerage account for easy reallocation, or need the tax advantages of a government or tax-exempt fund.
How to Check Whether Your Specific Fund Is Safe
Knowing the broad categories is not enough. Within each category, individual funds vary in credit quality, liquidity, fees, and yield. A few things worth checking:
- Fund type. Confirm whether you are in a government, prime, or tax-exempt fund. If safety is your top priority and you are not chasing every basis point, government is the straightforward choice.
- Institutional vs. retail share class. If you invest as an individual, confirm you are in a retail class. Institutional funds carry the floating NAV and mandatory liquidity fee provisions that make them less cash-like.
- Weekly liquid assets. The SEC minimum is 50%, but many well-run funds keep 60% or higher. A fund consistently near the floor is running tighter than it needs to.
- Weighted average maturity. A shorter WAM lets the fund adapt to rate changes faster.
- Net yield after fees. Compare the 7-day yield, which already reflects the expense ratio. During the near-zero rate environment of 2020-2021, many fund sponsors voluntarily waived fees to keep net yields positive; if rates fall further, check whether your fund’s waiver is still in place.
Most of this information sits on the fund company’s website, updated daily. The SEC also requires monthly filings on Form N-MFP with a complete breakdown of every security the fund holds.3U.S. Securities and Exchange Commission. ADI 2025-15 – Website Posting Requirements If a fund makes this data hard to find, that alone tells you something.