Money Market Funds vs High-Yield Savings: Where Should Your Cash Live?

By Tom, CPA · Updated October 25, 2026

TL;DR: High-yield savings accounts are FDIC insured up to the limits and simple to use. Money market funds aren't FDIC insured but invest in very short-term, high-quality debt, often pay competitive yields, and Treasury-focused funds can save state income tax. Use the HYSA for emergency cash and consider a money fund for larger balances inside a brokerage account.

Educational only, not tax, legal, or investment advice. Examples are illustrations, not predictions. Rules and limits change; verify current figures and talk to a qualified professional about your situation.

The finance industry named two different products almost identically, apparently as a prank. A money market account is a bank deposit account, insured like savings. A money market fund is a mutual fund, held at a brokerage, and not FDIC insured. This page compares the fund version to a high-yield savings account (HYSA), because that's the decision most FIRE savers actually face with their cash.

Neither is a place to grow wealth for decades. Both are places to park money you'll need in the next few years without much drama. The question is which parking garage is closer, cheaper and safer for your situation. Rules below are as of Oct 2026. This is education, not personalized advice.

CPA Warning Label: A money market fund and a money market account walk into a bar. Only one of them is FDIC insured. The bartender is still confused.

Safety comparison

The SEC's investor education site is explicit: money market funds aren't FDIC insured and can lose value, though they're designed to be low risk and invest in high-quality, short-term securities. Losses have been rare, but they have happened, and fund sponsors aren't required to step in.

How to think about the risk

A government money market fund holding Treasury bills and repurchase agreements backed by Treasuries is about as close to cash as an investment gets. Prime funds, which also hold corporate debt, carry a bit more risk. For balances above FDIC limits, a Treasury-focused fund can arguably be safer than an uninsured bank deposit. For balances under the limit, the insured HYSA is simpler to reason about. See the FDIC limits guide for how coverage works.

Yields

Both products have floating rates that move with short-term interest rates. A few patterns tend to hold:

• Money market fund yields track short-term Treasury rates fairly closely, minus the fund's expense ratio. Low-cost funds pass more through.
• HYSA rates are set by the bank, and they're often adjusted with a lag. Promotional rates can drop after you sign up.
• The gap between the two is often small, sometimes in favor of one and sometimes the other.

Compare the fund's 7-day SEC yield, a standardized measure, with the bank's APY. Don't chase small differences; moving cash to earn a few hundredths of a percent rarely pays for the hassle.

Illustration (hypothetical rates): on $30,000, a 0.20 percentage point yield difference is $60 a year before tax. Real money, but not worth opening a new account in a new place unless it simplifies something else too.

State-exempt treasury funds

Here's where money funds can quietly win. Interest on U.S. Treasury obligations is exempt from state and local income tax (as of Oct 2026). HYSA interest is fully taxable by your state.

A government money fund that holds mostly Treasury bills passes much of that exemption through. The portion that qualifies depends on the fund's holdings; repurchase agreements generally don't qualify. Funds publish the percentage of income from U.S. government obligations each year, and some states require a minimum percentage before any of it is exempt. Check your state's rules and the fund's annual tax letter.

Illustration (hypothetical): Lavish Larry lives in a state with a 6% income tax and keeps $50,000 in cash. If both options yield 4%, he earns $2,000 either way. In a fund whose income is entirely from Treasuries, he avoids about $120 of state tax. In a no-income-tax state, the advantage is zero.

Both products' interest or dividends are taxed federally as ordinary income. Money market fund income is generally reported as dividends on Form 1099-DIV, while bank interest goes on Form 1099-INT if it's $10 or more. Either way, it's taxable even if you don't receive a form.

Access

• HYSA: transfers to checking typically take one to three business days at online banks. Some limit the number of withdrawals a month by policy.
• Money market fund: usually settles within a day inside your brokerage account. Moving money out to a bank still takes a transfer. Many brokerages use a money fund as the default place for cash waiting to be invested, which is convenient.

For a true emergency fund, the HYSA's direct link to your checking account is usually more practical. For cash you'll invest soon or use for a planned purchase, keeping it in a money fund inside the brokerage avoids extra transfers.

Watch the default sweep

Some brokerages hold uninvested cash in a low-yield bank sweep by default rather than a money fund. If your brokerage cash is earning far less than money funds or HYSAs, check whether you need to buy the money fund yourself.

Decision grid

Many FIRE households use both: a few months of expenses in an HYSA linked to checking, and larger planned cash in a Treasury money fund. See the high-yield savings guide and the emergency fund checklist.

Common mistakes with cash

• Confusing the two money market products. Read whether it says account or fund, and whether it mentions FDIC.
• Leaving brokerage cash in a low-yield sweep. Selling investments and letting the proceeds sit uninvested at a tiny rate is surprisingly common.
• Ignoring state tax. In a high-tax state, compare after-tax yields, not headline yields.
• Keeping too much cash. Cash is for safety and planned spending. Beyond that, inflation slowly eats it, and for long-term goals, a diversified portfolio has historically done better.
• Chasing the top rate monthly. Opening accounts to grab a slightly higher teaser rate costs time and creates more logins to secure.
• Forgetting the tax forms. Money fund dividends arrive on a 1099-DIV, often bundled in a brokerage's composite form; bank interest arrives on a 1099-INT. Both belong on your return.

None of these mistakes is catastrophic. They're small leaks, and FIRE is mostly a long series of small leaks plugged.

Other cash options worth knowing

• Treasury bills bought directly: same state tax exemption, fixed maturities, but more effort to roll over.
• Certificates of deposit: FDIC insured and locked in for a term, with an early withdrawal penalty.
• Bank money market accounts: FDIC-insured deposit accounts, sometimes with check-writing. Compare them like an HYSA.
• Credit union savings: insured by the NCUA, with similar limits.

The worst cash option is usually the one nobody chose: a traditional savings account earning close to nothing because it was opened years ago and forgotten. Frugal Fran checks hers once a year. That's enough.