What Is a Money Market Account? How It Works

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A money market account (MMA) is an interest-bearing deposit account at a bank or credit union that combines features of savings and checking. You earn interest like a savings account, and you usually also get a checkbook and a debit card. The trade-off is that the bank may cap how many withdrawals or transfers you can make each month. Banks often call it a money market deposit account (MMDA), and some label it “MMA savings” or “money market savings.” All of these names describe the same product: an insured bank deposit, not an investment.

How a money market account works

You open an MMA much like a savings account: you meet the bank’s identity requirements, make any required opening deposit, and then add money whenever you like. Deposits are generally unlimited. The differences from other accounts show up in how you take money out and how interest accrues.

Withdrawals and transaction limits

Most MMAs let you pay from the account directly. You can write a check for rent, use the debit card for a purchase or an ATM withdrawal, or transfer money electronically. Each of these counts as a withdrawal, and many banks set a monthly limit on them.

The limit comes from federal rules. Under the Federal Reserve’s Regulation D, savings deposits, money market deposit accounts included, were capped at six “convenient” transfers and withdrawals per month. That cap covered preauthorized and automatic transfers, telephone transfers, overdraft-protection transfers, checks and debit card payments. In April 2020 the Federal Reserve removed the requirement, but banks are free to keep their own limits, and many do. Going over the bank’s limit can trigger an excess withdrawal fee, a conversion of the account to checking, or closure of the account. In-person and ATM withdrawals were historically outside the cap. Today the bank’s account disclosure, not federal law, decides what counts and how many withdrawals you can make.

How interest is calculated

MMA interest is variable. The bank sets a rate and can raise or lower it, usually following broader short-term interest rates. Some banks pay tiered rates, with a higher rate on larger balances.

Two figures appear on rate disclosures:

• Interest rate (APR-style nominal rate): the stated annual rate before compounding.
• Annual percentage yield (APY): the effective yearly return once compounding is included.

The relationship is:

APY = (1 + r / n)^n − 1

where r is the nominal annual rate and n is the number of compounding periods per year. Banks compound at different intervals. Some compound daily and others monthly, and the interval changes the APY for the same nominal rate. The difference between APR and APY matters most when you compare quotes that use different conventions.

Hypothetical example: a $20,000 balance at a 4.00% nominal rate, held for one year with no deposits, withdrawals or rate changes.

The gap is about $1.32 a year at this balance and rate, small next to the effect of the rate itself. Because APY already includes compounding, comparing APYs across banks handles the compounding question for you. The projection holds only if the variable rate stays put.

Deposit insurance

An MMA at an FDIC member bank is covered by the Federal Deposit Insurance Corporation. At a federally insured credit union, the National Credit Union Administration provides equivalent coverage. The standard limit is $250,000 per depositor, per insured institution, per ownership category. A joint account owned by two people is a separate ownership category, which effectively gives the couple $500,000 of joint coverage at that institution.

The limit applies to all your deposits in the same ownership category at the same institution combined. Your MMA, checking, savings and CDs held individually at one bank share a single $250,000 limit. To confirm a bank is insured, look for “Member FDIC” on its website or check the regulator’s own lookup tool.

Example: what an MMA earns after fees

The rate is only half the calculation, because fees and balance requirements decide what you keep. A minimum daily balance of $2,500 is a common threshold, and some banks also require a minimum deposit to open the account.

Hypothetical example: an MMA pays 4.00% APY, requires a $2,500 minimum daily balance, and charges a $15 monthly fee in any month the balance falls below it.

• Saver A keeps $10,000 in the account all year. Interest is about $400, no fee applies, and the net gain is about $400.
• Saver B keeps about $2,000 in the account all year. Interest is about $80, but the $15 fee applies every month, for $180 a year. Saver B ends the year about $100 behind.

Excess withdrawal fees work the same way. A bank that charges $10 for each withdrawal beyond its monthly limit would take $30 in a month with three extra checks, close to a month’s interest on Saver A’s $10,000. Some banks charge no excess withdrawal fee, and others charge a small amount with a daily cap.

When a money market account makes sense

An MMA fits money you want to keep safe, earn interest on, and be able to reach without a transfer delay:

• Emergency funds. You can write a check or use the debit card directly when an unexpected bill arrives, and your principal does not fluctuate.
• Short-term goals. A vacation fund, a car down payment or money set aside for a home purchase in the next year or two.
• Large irregular payments. Property taxes, insurance premiums or tuition that you pay a few times a year by check.
• Holding cash between decisions. For example, proceeds from a sale that you have not yet committed elsewhere.

It is a poor fit for long-term goals such as retirement. Over long periods, accounts built for investing, such as IRAs and 401(k)s holding diversified investments, have historically offered more growth potential. Cash in a deposit account can also lose purchasing power when its rate trails inflation.

Limitations of a money market account

• Variable rates. The rate at opening carries no guarantee, while a CD’s rate is fixed for its term.
• Transaction limits. Withdrawal caps and the fees for exceeding them make an MMA awkward as a primary spending account. A common setup pairs an MMA for savings with a regular checking account for daily transactions.
• Minimum balances. Opening deposits and daily minimums are often higher than for basic savings accounts, which can shut out smaller savers or produce fees.
• Fees. Monthly maintenance, excess withdrawal and overdraft fees can all apply, depending on the bank.
• Not always the top rate. The best high-yield savings accounts now often match or beat the best MMAs, sometimes at the same bank.

Money market account vs. other accounts

Savings accounts

A standard savings account also earns variable interest and may cap monthly withdrawals, but it usually has no checks or debit card. You move money to checking before you spend it. MMAs have tended to pay higher rates on average, and they often require higher balances.

High-yield savings accounts

High-yield savings accounts, often offered by online banks, pay rates well above the national savings average and can look almost identical to an MMA apart from the missing checks and debit card. If you never need to write a check from your savings, a high-yield savings account with a competitive APY may do the same job with fewer balance requirements.

Checking accounts

Checking accounts are built for daily spending, with unlimited transactions, checks and a debit card, and many pay little or no interest. Check writing does not make an MMA a checking account. In regulatory terms, a money market deposit account is a savings deposit, which explains the withdrawal limits.

High-yield and rewards checking accounts

High-yield checking accounts can pay rates comparable to MMAs, and rewards checking accounts may offer sign-up bonuses, cash back, miles or ATM fee refunds. Both usually pay only if you meet monthly conditions such as a minimum number of debit card transactions. If you mainly want to save and spend occasionally, an MMA asks less of you each month.

Certificates of deposit

A CD locks your money for a fixed term, from about a month to as long as 10 years, in exchange for a fixed rate. Withdrawing before maturity usually costs an early withdrawal penalty unless it is a no-penalty CD, and partial withdrawals are generally not allowed. An MMA gives up the guaranteed rate in return for ongoing access. Some savers use both: the MMA for money they may need soon and CDs for money with a known future date.

Money market account vs. money market fund

The names are similar, but the products are not. A money market mutual fund is an investment, usually bought through a brokerage. It pools investors’ money into short-term, low-risk instruments such as Treasury bills and other government securities, CDs and commercial paper. You own shares of the fund rather than holding a deposit, and you get money out by redeeming shares. Some funds offer check writing, often with a minimum check amount.

Money market funds have tended to yield more than bank MMAs, and they report returns as a yield rather than an APY. They are not FDIC or NCUA insured, and their stable share price is not guaranteed. Cash held at a brokerage may be protected by SIPC against the failure of the broker, which is not protection against investment losses. Brokerages use the money market name for these funds and for cash sweeps, so check whether your money is a bank deposit or a fund holding.

The Bottom Line

An MMA suits savers who want insured cash for emergencies, short-term goals or large irregular bills while keeping direct access by check or debit card. Before opening one, compare APYs and read the bank's disclosure for minimum balances, monthly fees and withdrawal limits, since fees can erase the interest on small balances. For long-term goals or savers who never write checks, other accounts may fit better.