Glossary/Asset classes

Money Market Fund

Also known as MMF, Cash management fund

A money market fund is an open-ended pooled vehicle investing in short-term, high-quality debt and cash instruments under applicable regulatory rules. It seeks liquidity and capital stability while paying income linked to short-term rates.

Editorially reviewed 2026-07-30

Why money market fund matters

Money market funds are widely used for cash management, collateral, and temporary reserves, but they are investments rather than bank deposits. Credit, liquidity, interest-rate, sponsor, and regulatory risks remain. Fund type determines permitted assets, maturity limits, valuation, liquidity fees, and whether NAV is stable or floating.

How it is applied

Investors review portfolio maturity, weighted-average life, issuer concentration, government versus private credit, daily liquidity, yield net of fees, NAV structure, and redemption provisions. Treasury operations align settlement dates and avoid treating a fund as immediately available cash when dealing cutoffs apply. Investors compare weighted-average maturity, weighted-average life, liquidity buckets, credit quality, sponsor, fees, currency, and whether the fund seeks a constant or variable NAV. The correct comparison is the net yield available after fees and applicable tax.

Portfolio example

A fund yields 4.8% after expenses while a deposit pays 4.3%. The extra yield may reflect instrument mix and fee differences. If short-term rates fall, the fund yield declines as holdings mature and proceeds are reinvested. Two funds may advertise gross yields of 5.0% and 4.9%. After expenses of 0.40% and 0.10%, their net yields are 4.6% and 4.8%. The lower gross-yield fund therefore pays investors more before tax. A temporary fee waiver should not be assumed to continue through the full holding period. Yield conventions should also be compared consistently.

How to interpret it

A stable displayed NAV does not guarantee against loss. Yield should be compared after fees, tax, settlement, and credit risk. Very high yield relative to peers warrants examination of maturity, issuer, and structure.

Limitations and common misconceptions

Funds can face runs, liquidity fees, redemption restrictions, or rare NAV losses. Returns lag rate changes as holdings roll. Deposit insurance generally does not apply. Rules vary by jurisdiction and fund category. Money market funds are designed for capital stability but are not identical to insured bank deposits. Credit events, liquidity stress, negative rates, gates, or regulatory intervention can affect access or value, depending on the fund’s jurisdiction and structure.

Sources and further reading