# Money Market Fund: Parking Cash Without Treating It Like a Bank Deposit

Money market funds invest in short-term, high-quality instruments and can be useful for cash management, but they are investment products with yield, liquidity, credit, and rule risks.

Canonical: https://wiki.fcontext.com/stocks/money-market-fund/
Fact checked: 2026-07-20

> For educational purposes only; not investment advice.

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## Direct answer

A money market fund is a mutual fund that invests in short-term, high-quality debt instruments such as Treasury bills, government repurchase agreements, commercial paper, certificates of deposit, and other eligible money market instruments. Investors often use it to park cash and earn income linked to short-term rates.

It is not the same as a bank deposit. A money market fund is an investment product, generally not FDIC-insured, and it can have liquidity, credit, yield, fee, and rule risks. Many funds seek to maintain a stable net asset value, but investors should still read the prospectus and fund type.

The key items to compare are fund type, 7-day yield, expense ratio, holdings, weighted average maturity, minimum purchase size, settlement timing, and whether the fund is government, Treasury, or prime.

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## Mechanism

Money market funds earn income from very short-term instruments. When short-term market rates rise, new purchases inside the fund can gradually raise the fund’s yield. When rates fall, maturing assets are reinvested at lower yields and the fund’s 7-day yield can decline.

Government and Treasury money market funds usually focus on government securities and related repurchase agreements. Prime funds can hold high-quality private instruments such as commercial paper, which may offer higher yield but can carry more credit and liquidity risk.

The 7-day yield is a standardized recent yield measure, not a promise of future income. It can change quickly when policy rates, bill yields, repo rates, fees, or portfolio holdings change.

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## Example or formula

Suppose a fund shows:

| Item | Value |
| --- | ---: |
| 7-day yield | 4.80% |
| Expense ratio | 0.20% |
| Settlement | T+1 |
| Main holdings | Treasury bills and government repos |

If an investor holds $20,000 for 30 days and the annualized yield stayed near 4.80%, a rough income estimate is:

`$20,000 × 4.80% × 30 / 365 ≈ $78.90`

This is only an estimate. Actual distributions depend on daily yield, fees, reinvestment rates, fund rules, and tax treatment.

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## Risks

Money market funds are designed for stability and liquidity, but they are not risk-free. Extreme market stress can affect liquidity, portfolio pricing, or redemption mechanics.

Yield risk is common. A high current 7-day yield can fall after policy rate cuts or after high-yielding holdings mature.

Product confusion is a real risk. Brokerage cash sweep programs, bank deposits, Treasury bills, short-term bond ETFs, and money market funds have different insurance, settlement, price, and tax features.

Operational timing matters. Fund shares may need to settle before cash is available for another trade or withdrawal. Investors should confirm brokerage rules before assuming money market fund shares are the same as immediately available cash.

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## Common misconceptions

- “Money market funds are bank accounts.” They are funds, not deposits.
- “The yield is guaranteed.” 7-day yield is a recent annualized measure and can change.
- “All money market funds are the same.” Government, Treasury, municipal, and prime funds can hold different instruments.
- “Stable NAV means no risk.” Stability is a goal or convention, not an absolute guarantee.
- “Cash-like means instantly available.” Settlement and broker rules still matter.

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## Related topics

- [Liquidity Preference Theory](/stocks/liquidity-preference-theory/)
- [Bond ETF](/stocks/bond-etf/)
- [Interest Rate Impact](/stocks/interest-rate-impact/)

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## Authoritative sources

- SEC Investor Bulletin, “Focus on Money Market Funds.”
- Investor.gov, “Money Market Funds.”
- FINRA, “Money Market Funds.”
- SEC, 2023 money market fund reforms.