Money market accounts vs. money market funds

A common point of confusion: a 'money market account' and a 'money market fund' sound identical but are completely different products with different risks, different rates, and different places to buy them. Knowing the distinction matters if you're parking more than $10k somewhere.

Money market account (MMA)

A money market account is a type of deposit account at a bank or credit union. It's FDIC-insured up to $250k, often pays slightly higher interest than a regular savings account, and usually comes with limited check-writing or debit access. Your principal is safe — this is bank money, not market money. Rates typically hover near HYSA rates.

Money market fund (MMF)

A money market fund is an investment product — a mutual fund that invests in very short-term, very safe debt instruments (Treasury bills, commercial paper, certificates of deposit). It's not FDIC-insured. Your principal is not guaranteed, though MMFs almost always maintain a stable $1-per-share price in practice. Rates can be higher than HYSAs and MMAs, especially in high-rate environments. Bought through a brokerage account, not a bank.

The risk nobody talks about

Money market funds are almost always safe, but 'almost' is doing work. In 2008, one major money market fund 'broke the buck' — its shares fell below $1 during the financial crisis. Post-2008 reforms made this much less likely, especially for government money market funds (which only hold Treasury securities). Prime money market funds are marginally less safe than government ones. For absolute safety, Treasury-only MMFs or regular FDIC-insured accounts are the right answer.

Side by side

A worked example: $40,000 parked for a year

Say you're holding $40,000 for a home purchase roughly a year away, and the rate environment offers a 4.2% money market account at an online bank versus a 4.6% government money market fund at your brokerage. The MMA earns about $1,680; the MMF earns about $1,840 — $160 more. But the comparison shifts with taxes: if the fund holds mostly Treasury securities and you live in a 9% income-tax state like California or New Jersey, a big chunk of the fund's income escapes state tax, worth perhaps another $120–$150 on this balance. For a high-state-tax saver, the fund's real edge might be $300 a year on $40,000. For a Texas or Florida resident, it's just the $160 — real, but hardly worth opening a brokerage account over if you don't already have one.

What 'stable in practice' really means

The reassurance that money market funds 'almost always' hold their $1 share price deserves one honest paragraph. Since 2008's reforms, government money market funds — the kind most brokerages now use as defaults — hold only Treasury and agency securities and overnight loans backed by them, which is about as close to riskless as finance gets. In the March 2020 panic, government MMFs sailed through without incident while some prime funds (which hold corporate paper) saw heavy outflows and needed the Fed's backstop. That episode is the practical rule written in recent history: if you're going to hold six figures in a fund instead of a bank, hold the government flavor, and treat the extra few hundredths of a percent that prime funds dangle as compensation for a risk you have no need to take.

How to choose in practice

1. 1
   Match the product to where the money lives

   Money at a bank that needs same-day access and insurance: money market account or HYSA. Money already at a brokerage: money market fund. Moving money between institutions to chase 0.2% is rarely worth the friction.

2. 2
   If choosing a fund, prefer government or Treasury-only

   The yield gap between prime and government funds is usually a few hundredths of a percent — not worth the extra (small) structural risk or the potential liquidity gates prime funds can impose in a crisis.

3. 3
   Check the expense ratio

   MMF yields are quoted after expenses, but two funds holding identical Treasuries can differ 0.3% in yield purely on fees. Compare 7-day SEC yields directly.

4. 4
   Confirm the settlement timeline

   Selling MMF shares and getting cash to your bank takes a business day or two. If the money's job requires instant availability — closing-day wires, emergency access — the bank account wins regardless of yield.

Common mistakes

• Assuming 'money market' means insured. The account is; the fund isn't. Plenty of people learned the difference for the first time reading 2008 headlines.
• Leaving large cash in a brokerage sweep without checking its rate. The gap between a 0.4% sweep and a 4.6% MMF on $100,000 is $4,200 a year.
• Ignoring MMA fine print: some money market accounts impose minimum balances, monthly transaction caps, or tiered rates where the headline number only applies above $25,000.
• Using an MMF as an emergency fund while its brokerage takes two days to move money to your bank. Keep at least the first month of emergency expenses somewhere instantly reachable.
• Treating the two products as competitors and agonizing over the pick. They serve different locations in your financial plumbing; most organized savers eventually use both.

The tax detail that changes the ranking

Yield comparisons between MMAs and MMFs usually ignore the line that decides them for high earners: state income tax. Interest from a bank money market account is fully taxable at both federal and state levels. Income from a money market fund is taxable federally, but the portion derived from Treasury securities is exempt from state tax — and Treasury-only funds pass through nearly all of their income with that exemption. For a saver in a 6% state bracket holding $60,000, that's roughly $160 a year of tax that the bank account pays and the Treasury fund doesn't, on identical headline yields. Fund companies publish the exact exempt percentage each January; it takes one search at tax time and most software applies it automatically once you enter it.

The bottom line

One vowel of difference, two different animals: the money market account is insured bank money with instant access; the money market fund is a very safe investment with slightly better yield and a settlement delay. Keep the fast, insured account for money that guards your life, use the fund for cash that happens to live at your brokerage, favor government funds over prime, and never — ever — let five figures idle in a default sweep without checking what it pays.