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 a Treasury fund, so most of its income is typically exempt from state and local tax. SPAXX is a government fund that also holds agency paper and repurchase agreements, and a large share of its income does not qualify for the state-tax break. If you live in a state with income tax and hold this cash in a taxable account, FZFXX is the better core. 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 September 2026
| Feature | FZFXX | SPAXX |
|---|---|---|
| Provider | Fidelity | Fidelity |
| Wrapper | Money-market fund | Money-market fund |
| Holdings type | Treasury | Government |
| 7-day SEC yield | 3.44% (7-day SEC yield, 2026-09-20) | 3.34% (7-day SEC yield) |
| 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 | Treasury-focused, so most income is typically exempt from state and local tax. Confirm the fund’s annual U.S. government obligations percentage for your tax year | 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, a default core/sweep position at Fidelity |
| Best for | Fidelity customers in a high-tax state who want the core position to hold Treasuries rather than agency paper | Fidelity customers who want their idle cash to earn a yield automatically |
Where FZFXX wins
- A Treasury-only core option at Fidelity, so more of the income escapes state tax than SPAXX or FDRXX
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 a Treasury fund, so most of its income is typically exempt from state and local tax. SPAXX is a government fund that also holds agency paper and repurchase agreements, and a large share of its income does not qualify for the state-tax break. If you live in a state with income tax and hold this cash in a taxable account, FZFXX is the better core. 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.