Wealthy PotFZFXX vs SPAXX (2026)
Both are Fidelity core-eligible money-market funds at the same 0.42% expense ratio, so the decision is entirely about tax. FZFXX is Treasury-focused: 61.5% of its 2025 income came from U.S. government obligations, against 50.9% for SPAXX, which also holds agency paper and more repurchase agreements. If you live in a state with income tax and hold this cash in a taxable account, FZFXX keeps more of the income out of state tax. One exception: California, Connecticut and New York exempt this income only when a fund meets a 50% asset test, and neither fund met it for 2025. Inside an IRA the distinction buys you nothing, because the income is not state-taxed as it accrues either way.
By Wealthy Pot · Last updated October 2026
| Feature | FZFXX | SPAXX |
|---|---|---|
| Provider | Fidelity | Fidelity |
| Wrapper | Money-market fund | Money-market fund |
| Holdings type | Treasury | Government |
| 7-day SEC yield | 3.52% (7-day yield, Sep 30, 2026, SEC filing) | 3.48% (7-day yield, Sep 30, 2026, SEC filing) |
| Share price | Stable $1.00 NAV (targeted, not guaranteed) | Stable $1.00 NAV (targeted, not guaranteed) |
| Expense ratio | 0.42% | 0.42% |
| Minimum | $0 | $0 |
| State tax | Partly state-tax-exempt (61.5% U.S. government obligations, 2025, below the CA/CT/NY threshold) | Partly state-tax-exempt (50.9% U.S. government obligations, 2025, below the CA/CT/NY threshold) |
| Auto-sweep? | Yes, available as a Fidelity core position in taxable brokerage accounts | Yes, one of Fidelity's core position choices (the FDIC sweep is the other option in some accounts) |
| Best for | Fidelity customers who want a Treasury-focused core position (61.5% state-tax-exempt income in 2025; residents of CA, CT and NY got no exemption) | Fidelity customers who want their idle cash to earn a yield automatically |
Where FZFXX wins
- A Treasury-focused core option at Fidelity: more of its 2025 income was state-tax-exempt (61.5%) than SPAXX's (50.9%)
Where SPAXX wins
- The default Fidelity core/sweep position: idle cash earns automatically
- No minimum investment
- Government fund (holds government debt and repos), lower credit risk than prime
- Portion of income is state-tax-exempt
Which should you choose?
Both are Fidelity core-eligible money-market funds at the same 0.42% expense ratio, so the decision is entirely about tax. FZFXX is Treasury-focused: 61.5% of its 2025 income came from U.S. government obligations, against 50.9% for SPAXX, which also holds agency paper and more repurchase agreements. If you live in a state with income tax and hold this cash in a taxable account, FZFXX keeps more of the income out of state tax. One exception: California, Connecticut and New York exempt this income only when a fund meets a 50% asset test, and neither fund met it for 2025. Inside an IRA the distinction buys you nothing, because the income is not state-taxed as it accrues either way.
Compare these against every fund in our money-market fund comparison.
We summarize the funds' published facts, not user reviews. Yields are variable, change daily, and are re-checked against each fund's official page. Neither money-market funds nor ETFs are FDIC-insured, and an ETF's share price can fall as well as rise. Some outbound links may be affiliate links. That never affects our comparisons. Nothing here is financial advice.