Wealthy PotFDLXX vs SPAXX (2026)
Both are Fidelity money funds, but they solve different problems. SPAXX is the automatic core/sweep — cash earns a yield with no effort — while FDLXX is a Treasury-only fund you buy deliberately for its largely state-tax-exempt income. In a high-income-tax state, FDLXX can win on after-tax yield; if you value the hands-off sweep, SPAXX is simpler.
By Wealthy Pot · Last updated September 2026
| Feature | FDLXX | SPAXX |
|---|---|---|
| Provider | Fidelity | Fidelity |
| Fund type | Treasury | Government |
| 7-day yield | 3.38% (7-day SEC yield) | 3.34% (7-day SEC yield) |
| Expense ratio | 0.42% | 0.42% |
| Minimum | $0 | $0 |
| State tax | Largely state-tax-exempt — 98.7% U.S. Treasury (2025); qualified for the CA/CT/NY exclusion | Partly state-tax-exempt (50.9% U.S. government obligations, 2025 — below the CA/CT/NY threshold) |
| Auto-sweep? | No — buy/sell it manually (not a default core position) | Yes — a default core/sweep position at Fidelity |
| Best for | High-tax-state investors who want to avoid state tax on their cash yield | Fidelity customers who want their idle cash to earn a yield automatically |
Where FDLXX wins
- Largely state-tax-exempt Treasury income
- No minimum investment
- Very low credit risk
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 money funds, but they solve different problems. SPAXX is the automatic core/sweep — cash earns a yield with no effort — while FDLXX is a Treasury-only fund you buy deliberately for its largely state-tax-exempt income. In a high-income-tax state, FDLXX can win on after-tax yield; if you value the hands-off sweep, SPAXX is simpler.
Compare these against every fund in our money-market fund comparison.
We summarize the funds' published facts, not user reviews. 7-day yields are variable, change daily, and are re-checked against each fund's official page. Money-market funds are not FDIC-insured. Some outbound links may be affiliate links — that never affects our comparisons. Nothing here is financial advice.