Tools · Money Market Comparison
Money market funds.
After-tax yield comparison.
Compare SPAXX, FZFXX, FDLXX, HYSAs, T-bills, and CDs on an after-tax basis given your federal and state tax brackets. The right choice depends on your state.
US-only. Yields and state-tax exemption rules are US-specific.
WORKED EXAMPLE
At a 9.3% California state rate, a $50,000 balance for 12 months. SPAXX at 3.30% gross with 60% state-exempt: after-tax yield approximately 3.12%, interest earned approximately $1,560. FZFXX at 3.20% gross with 100% state-exempt: after-tax yield approximately 3.20%, interest earned approximately $1,600. FZFXX wins by $40 on this balance. The advantage grows with higher state rates and larger balances.
YOUR SITUATION
CURRENT YIELDS (EDIT TO MATCH TODAY) verify×DON'T TRUST, VERIFYClaim: Yields update weekly. Defaults are approximate as of April 2026.Verify at: SPAXX ↗ · TreasuryDirect ↗ · Bankrate ↗Update each input with the current rate before relying on the after-tax comparison.
SPAXX (Gov MMF)
FZFXX (Treasury MMF)
FDLXX (Treasury Only)
HYSA (FDICFederal Deposit Insurance Corporation (FDIC)The US agency that insures bank deposits up to $250,000 per depositor if a bank fails. bank)
T-bill (4-week)
CD (12-month)
(Yield %)YIELD %STATE-EXEMPT %
AFTER-TAX RANKING
| OPTION | GROSS | AFTER-TAX | INTEREST EARNED |
|---|
HIGHEST AFTER-TAX YIELD
Enter your numbers above.
What this tool assumes
- after-tax yield = gross × (1 - federalRate - stateRate × (1 - stateExemptPct/100)).
- State-tax exemption applies only to the portion of yield from US Treasury obligations. SPAXX is partially exempt because it holds repurchase agreements alongside Treasuries; FZFXX is fully exempt because it holds Treasuries only; HYSAs and CDs are bank products with no state-tax exemption.
- Interest is treated as ordinary income at your federal marginal rate. State tax applies only to the non-exempt portion.
- FDIC vs SIPCSecurities Investor Protection Corporation (SIPC)A nonprofit that pays back customers up to $500,000 if a stock brokerage firm goes bankrupt and loses their shares. It protects against the firm failing, not against your investments dropping in value.: HYSAs are FDIC-insured up to $250,000. Government money market funds (SPAXX, FZFXX) are SIPC-protected as securities and hold US-government instruments, which are considered extremely safe but not FDIC-insured.