What You'll Learn in This Guide

I've been investing for over a decade, and I still remember the first time a client asked me: "Can I actually lose money in a money market fund? I thought it was like a savings account." That question is more common than you'd think. The short answer is yes, you can lose money, but in most cases, the loss is tiny and temporary. However, there are specific scenarios where the damage can be significant. Let's break down exactly what can go wrong and how to protect your cash.

The Short Answer: Yes, But It’s Rare

Money market funds are not insured by the FDIC (unlike bank savings accounts). They are investments in short-term, high-quality debt securities. While they aim to maintain a stable $1 net asset value (NAV), they can "break the buck" if the underlying assets lose value. That means your $1 per share could drop to $0.99 or even lower. But here's the thing: since the 1970s, only a handful of money market funds have actually broken the buck. The most famous case was the Reserve Primary Fund in 2008, which fell to $0.97 after Lehman Brothers’ collapse. That was a rare event, but it shows the risk is real.

Key point: You're more likely to lose purchasing power than principal in a money market fund, especially when inflation is high. The yield might not keep up with inflation, meaning your money buys less over time.

What Actually Is a Money Market Fund?

Think of a money market fund as a pool of short-term IOUs from governments, banks, and big corporations. The fund buys things like Treasury bills, commercial paper, and certificates of deposit. Because these are short-term (usually less than 90 days), they're considered very safe. But safety isn't absolute.

I always tell my friends: if you need the money within a few months, a money market fund is fine. But if you're saving for a down payment next year, consider a high-yield savings account or a CD instead. The difference? FDIC insurance.

How Can You Lose Money? 3 Key Risks

1. Credit Risk: When the Underlying Assets Default

The biggest fear is that one of the securities in the fund defaults. Prime money market funds invest in corporate debt, which can go bad. If a large issuer like a major bank fails to repay, the fund's NAV can drop below $1. That's exactly what happened with the Reserve Primary Fund: it held $785 million in Lehman Brothers commercial paper that became worthless.

Government money market funds avoid this by holding only U.S. Treasury securities. But even those aren't 100% immune – in theory, if the U.S. government defaults (very unlikely), you'd lose money. However, for practical purposes, government funds are nearly risk-free.

2. Liquidity Risk: The Panic Withdrawal Trap

What if everyone wants their money back at once? During a financial crisis, fund managers might struggle to sell assets quickly without taking a loss. If too many investors redeem simultaneously, the fund may impose redemption fees (up to 2%) or even temporarily halt withdrawals. That happened in March 2020 when the Fed had to step in to support money market funds during the COVID panic.

I personally witnessed a client panic-sell his money market fund shares in 2020, only to see them recover a week later. The loss wasn't from the fund itself – it was from his own fear. So keep that in mind: liquidity risk often becomes a self-fulfilling prophecy.

3. Interest Rate Risk: The Unseen Erosion of Yield

Money market fund yields float with short-term interest rates. When rates drop, your yield drops too. You don't lose principal, but your income shrinks. In a low-rate environment like 2020–2021, some funds yielded just 0.01%, essentially zero after expenses. If inflation is 2%, you're losing purchasing power.

Conversely, when rates rise, fund yields rise with a lag. So you might miss out on higher rates if you're locked into a longer-term CD. The loss here is opportunity cost, not a direct hit to your balance.

Real-World Cases: When Money Market Funds “Broke the Buck”

Let's look at a few historical examples so you know it's not just theory.

Fund Name Date Loss per Share Cause
Reserve Primary Fund September 2008 $0.97 (3% loss) Exposure to Lehman Brothers debt
Community Bank & Trust money market fund 1994 $0.94 (6% loss) Derivative losses
Several small institutional funds during 2020 COVID crisis March 2020 Minor NAV fluctuation (less than 1%) Liquidity pressure on commercial paper

Notice that all these cases involved either corporate debt exposure or extreme market stress. Government money market funds have never broken the buck. That's why I personally keep my emergency fund in a government money market fund.

How to Protect Your Principal: Practical Tips

Based on my experience managing cash for both personal and client accounts, here's what I recommend:

  • Stick with government money market funds if you want near-zero credit risk. They invest exclusively in Treasuries and repurchase agreements backed by the U.S. government.
  • Diversify across providers – don't put all your cash in one fund, especially if it's a prime fund. Use two or three different fund families.
  • Keep an eye on the fund's holdings. Check the fact sheet quarterly. If you see a lot of commercial paper from risky sectors, reconsider.
  • Avoid redemption during panics unless you absolutely need the cash. The worst losses happen when you sell at the bottom.
  • Consider FDIC-insured alternatives for your true emergency fund: high-yield savings accounts or no-penalty CDs. They offer similar yields with zero credit risk.
My personal rule: If I need the money within 3 months, I use a government money market fund. If I need it within 6-12 months, I use a high-yield savings account. If I can lock it up for 1 year+, I buy a CD or T-bill.

Money Market Funds vs. Other Cash Options

Feature Money Market Fund (Prime) Money Market Fund (Government) High-Yield Savings Account CD (1-year) Treasury Bill (3-month)
FDIC Insured No No Yes (up to $250k) Yes No (but backed by US gov)
Principal Risk Low but possible Extremely low None None (if held to maturity) None (if held to maturity)
Current Yield (Approx) 5.0% – 5.4% 5.0% – 5.2% 4.5% – 5.0% 4.5% – 5.3% 5.1% – 5.3%
Liquidity Same-day (except during crises) Same-day Same-day Penalty for early withdrawal Can sell on secondary market
Minimum Investment $1,000-$5,000 typical $1,000-$5,000 $0 $500-$1,000 $100

Yields change constantly, so check current rates. As of 2025, money market funds offer competitive yields, but remember they're not insured.

FAQ: Common Concerns About Losing Money in Money Market Funds

If I invest $10,000 in a money market fund today, what's the worst-case loss in a normal year?
In a normal year, the chance of losing even $1 is extremely low. The worst-case probably isn't a dollar loss but a yield shrink. For example, if rates drop suddenly, your yield might go from 5% to 1%, meaning you earn $400 less than expected over a year. That's an opportunity loss, not a principal loss. As for principal erosion, only prime funds with risky holdings face any real danger. I'd say 99.9% of the time, your $10,000 stays $10,000.
How can I check if my money market fund has ever broken the buck?
Look up the fund's prospectus and financial statements. The Securities and Exchange Commission (SEC) requires funds to publicly report their NAV daily. You can also search for "[fund name] NAV history" or check Morningstar for any drops below $1. For most funds, you'll see a flat line at $1. A simple trick: avoid funds with a heavy allocation to commercial paper (over 10%) – they're the ones that tend to wobble.
What happens if my money market fund breaks the buck while I'm holding it?
If the NAV drops to, say, $0.99, you lose 1% of your principal. But here's the catch: you can either sell immediately and realize the loss, or hold on and hope the NAV recovers. In the 2008 case, the fund liquidated at $0.97 after freezing redemptions. Investors had to wait months to get their money back. That's why it's smarter to have a government fund – they've never broken the buck.
Are money market funds safer than stocks?
Absolutely. Money market funds are designed to be cash equivalents, not growth investments. A stock can easily drop 20% in a year. A money market fund has never lost more than 3% in history. The trade-off is lower returns. If you're comparing safety of principal, money market funds win hands down – but you won't build wealth in them.
Should I avoid prime money market funds altogether?
Not necessarily. Prime funds offer slightly higher yields than government funds (maybe 0.1-0.2% more). If you have a large portfolio and can tolerate a tiny risk of temporary loss, prime funds are fine. But for your emergency fund or money you can't afford to lose a penny of, stick with government funds or FDIC-insured accounts. Personally, I split my cash: 70% in a government fund, 30% in a high-yield savings account.

This article reflects my personal experience as an investor and advisor. While I'm not a certified financial planner, the strategies here have served me well. Always check a fund's prospectus and consult a professional for your specific situation.