Cash, coins and a notebook illustrate short-term financial planning. Money market funds combine pooled investments with variable income and specific access rules. Photo: Katie Harp / Pexels
Learn how money market funds work, how to read seven-day yields, and what to check about fund types, fees, access and protections compared with bank accounts.
Money waiting to pay a bill or make an investment can earn income in a money market fund. The name sounds similar to a bank account, but buying fund shares creates a different financial relationship, with different costs and protections.
This guide focuses on US-regulated money market funds and builds on our introductions to mutual funds and Treasury bills. It explains how to read the yield, identify the holdings, and check when invested money can actually be spent.
What Is a Money Market Fund?
A money market fund pools investors’ money in a portfolio of liquid, short-term debt instruments and cash. Investors own shares in the fund, rather than a particular bill or deposit within its portfolio.
The SEC’s fund overview describes these funds as relatively low-risk investments compared with many other funds. Their main purposes are cash management, access, and income tied broadly to short-term interest rates.
The fund receives income from its holdings, pays expenses, and distributes income to shareholders. Reinvesting distributions purchases additional shares; taking distributions as cash sends that income out of the investment.
Government, Prime and Municipal Funds
Government money market funds hold cash, government securities, and qualifying repurchase agreements. Treasury-focused funds concentrate on Treasury-related instruments, while a broader government fund can hold a different mix.
Prime funds can hold short-term corporate and bank debt, such as commercial paper and certificates of deposit. That introduces different credit exposures from a Treasury-focused portfolio.
Municipal, or tax-exempt, money market funds hold qualifying municipal instruments. Their tax advantages depend on the holdings and the investor’s circumstances; a “tax-exempt” label does not mean every possible tax disappears.
The SEC’s investor bulletin distinguishes these categories. Check the actual investment policy and eligible investors before comparing percentages on a fund list.
What a Stable Share Value Means
Many traditional retail and government money market mutual funds seek to maintain a stable net asset value, commonly $1 per share. Income is generally reflected through distributions rather than a steadily rising share price.
Maintaining that value is an objective, not a contractual repayment guarantee. Losses in the portfolio can cause a stable-value fund to reprice below its target, an event commonly called “breaking the buck.”
Institutional prime and institutional tax-exempt funds use floating values. Exchange-traded money market products can also have different pricing and trading arrangements, so the traditional $1 convention should not be applied automatically to every product carrying the name.
How to Read a Seven-Day Yield
A seven-day SEC yield annualizes recent income over a seven-day measurement period. It provides a current comparison measure, rather than a forecast or a promise that the same rate will persist for a year.
Vanguard’s yield explanation describes this annualization. Always check the observation date and whether the figure is net of expenses, includes fee waivers, or uses another stated convention.
For a simplified illustration, $10,000 earning a constant 4% annual rate would generate approximately $400 over a year. On a simple 365-day basis, seven days would produce about $7.67, not $400.
That calculation is not a prediction for a particular fund. Actual income depends on the rate earned each day, the balance held, expenses, and the treatment of distributions.
Why the Income Changes
As short-term investments mature, the fund replaces them at the rates then available. If market rates fall, the income generated by replacement holdings can fall too. The adjustment occurs as the portfolio turns over, rather than fixing every shareholder’s rate on the purchase date.
Two funds can report different yields because of their holdings, expenses, share classes, or fee waivers. A small yield difference should be considered alongside those differences rather than treated as free additional income.
Schwab’s fund-yield notes illustrate how waiver-adjusted yields, expense ratios, and investor eligibility are disclosed separately.
Expenses and Share Classes
The expense ratio represents ongoing fund operating costs as a percentage of assets. A published net yield already reflects relevant fund expenses, so subtracting the expense ratio again can double-count those costs.
Separate account, advisory, transaction, or transfer charges may still apply. The SEC’s fee bulletin distinguishes costs inside a fund from charges paid through an intermediary.
Compare the share class actually available in your account. A class with a lower expense ratio may have a higher minimum investment or eligibility requirements. Temporary waivers can also make a currently attractive yield less durable.
Access, Cutoffs and Liquidity Fees
Traditional money market mutual funds generally allow redemptions on business days, subject to their dealing procedures. The time an order must arrive, when proceeds become available, and when a bank receives a transfer are separate questions.
Check weekends, holidays, transfer holds, and whether the account automatically sells fund shares to meet withdrawals. A fund manually purchased in a brokerage account may operate differently from its default cash position.
Some funds can impose liquidity fees under the applicable rules, including in periods of heavy redemptions. Review the current prospectus for the particular fund type. Exchange-traded versions add exchange trading, bid-ask spreads, and settlement considerations.
Funds and Bank Accounts Have Different Protections
A money market deposit account is a bank deposit. Eligible deposits at an FDIC-insured bank receive deposit insurance within the applicable limits and conditions. A money market fund is an investment product and does not receive FDIC deposit insurance.
The SEC’s cash-sweep bulletin explains why similarly named cash options can have different protections. SIPC protection for assets held at a member brokerage addresses certain custody shortfalls when the firm fails; it does not insure against investment losses.
Comparing a Fund With Individual Bills
An individual Treasury bill has a specified maturity date and repayment amount. Its purchase price determines the return if the obligation is met and it is held to maturity. A conventional money market mutual fund continuously manages a portfolio and has no comparable personal maturity date for each shareholder.
A fund offers pooled management and diversification; an individual bill gives control over a particular repayment date. Our Treasury-bill guide explains purchase, reinvestment, and early-sale mechanics.
A Practical Review Before Investing
Identify the fund category, share class, holdings, minimum balance, net yield date, and expenses. Then check redemption cutoffs and the full path from selling shares to paying an actual expense.
Consider taxes, inflation, and the currency in which the money will be spent. Even a positive nominal income may leave purchasing power lower if prices rise faster. The useful comparison joins the yield to the risks, access arrangements, and purpose of the money.
Frequently Asked Questions
Is a Money Market Fund a Bank Account?
No. It is an investment fund holding short-term instruments and cash. A money market deposit account is a bank product. Money market funds do not have FDIC deposit insurance.
Does a Seven-Day Yield Show What I Earn in One Week?
No. It annualizes income measured over a recent seven-day period. It is a comparison measure and does not promise the same rate over the next year.
Can a Money Market Fund Lose Value?
Yes. A stable share value is an objective rather than a guarantee. Losses can cause a fund to reprice, while floating-value funds can change in value as their holdings change.
Can I Withdraw Money Immediately?
Check the fund and account procedures. Business-day dealing cutoffs, settlement, bank-transfer timing, holds, and applicable liquidity fees can affect when money becomes spendable.
Should I Subtract the Expense Ratio From a Net Yield?
A published net yield already reflects relevant fund expenses. Subtracting them again can double-count costs. Separate account, advisory, or transaction charges may still apply.
