When interest rates are meaningful, where you park cash matters. The three most common options — high-yield savings accounts (HYSA), money market funds, and Treasury bills — can look similar on a yield screenshot and behave very differently in a stress week.
General education, not tax or investment advice. Rules vary by country.
Quick comparison
| Option | Best for | Watch-outs |
|---|---|---|
| HYSA | Everyday emergency cash, FDIC/NCUA-style protection where applicable | Yield can change anytime; transfer delays |
| Money market fund | Brokerage cash pending investment | Not a bank deposit; gating risk is rare but real |
| T-bills | Known hold period, state-tax treatment (U.S.) | Less flexible if you need money tomorrow |
High-yield savings accounts
An HYSA is a bank or credit-union deposit product. Strengths:
- Simple app experience and direct deposit
- Deposit insurance frameworks in many jurisdictions (limits apply)
- Ideal for true emergency funds you may need in days
Weakness: the advertised APY is not locked. When policy rates fall, HYSA yields usually follow.
Money market funds
Money market funds invest in short-term instruments (T-bills, commercial paper, repos). In a brokerage account they are convenient collateral for investing. Key points:
- Yield is a distribution rate, not a guaranteed APY
- Share price is designed for stability but not insured like a bank deposit
- Read whether the fund is government-only or broader prime exposure
Treasury bills
T-bills are short-term government securities bought at a discount and maturing at par. Why people use them:
- Clear maturity date and known payoff if held to maturity
- Often favorable state/local tax treatment for U.S. investors
- Laddering (4-week, 8-week, 13-week) can smooth reinvestment risk
Trade-off: selling early can mean a small gain or loss if rates moved.
Decision framework
- Need money in under a week? Prefer HYSA (or local equivalent).
- Cash sitting in a brokerage waiting to be invested? Money market fund is usually friction-light.
- Can lock cash for 4–13 weeks? T-bill ladder may maximize after-tax yield.
- Rate-cut cycle underway? Expect all three yields to drift down — do not chase yesterday’s APY screenshots.
More household money guides live under Personal Finance.
FAQ
Should I put my entire emergency fund into T-bills?
Usually no. Keep a truly liquid buffer in a savings account, then ladder only the portion you will not need immediately.
Are money market funds safe?
They aim for stability and are tightly regulated, but they are investments, not insured deposits. Know the fund type and your broker’s cash sweep rules.
What about inflation?
Cash vehicles prioritize liquidity and nominal yield, not long-term purchasing-power growth. For multi-year goals, investing risk assets may be appropriate — see Investing.
Bottom line
Match the tool to the job: HYSA for emergencies, money markets for brokerage float, T-bills for scheduled cash. Yield is only one column in the spreadsheet.
IFN Editorial. Disclaimer