SPAXX vs FDRXX: what the expense gap costs after tax
Fidelity Government Money Market against Fidelity Government Cash Reserves, as filed for October 29, 2026. Not investment advice.
Example result
FDRXX after federal and California tax
2.65%
$1,324 a year kept on $1,815 of dividends
| Dividends before tax | $1,815 |
| Federal tax at 24.0% | −$436 |
| State tax at 9.30% $1,219 of the $1,815 is free of California tax | −$55 |
SPAXX after federal and California tax
2.60%
$1,301 a year kept on $1,775 of dividends
FDRXX leaves $23 more a year than SPAXX.
Yield reported by the fund for October 29, 2026; yields change daily. Estimate, not tax or investment advice. Nothing you type leaves your browser. How it is computed
A difference of cost, not of portfolio
Put the two holdings schedules next to each other and they read alike: Treasury bills and notes, floating-rate notes of the Federal Home Loan Banks and Farm Credit Banks, and repurchase agreements backed by Treasuries and agency securities. The yields do not read alike. The filings give each fund’s gross 7-day yield, what the portfolio earned before expenses, and the net yield of each share class. For SPAXX the gross was 3.97% and the net 3.55%; for FDRXX the gross was 3.97% and the net 3.63%. Expenses therefore took about 0.42% from SPAXX and 0.34% from FDRXX. On $100,000 the net yield gap is worth about $80 a year before tax, and roughly two thirds of that after federal and state tax for a typical reader, which the calculator above works out for your income.
Because both funds hold a similar share of exempt obligations, state tax hardly moves the comparison: whatever exemption one gets, the other gets nearly the same. The one place where they part is the quarter-end test of California, Connecticut and New York, where FDRXX sat closer to the 50% line than SPAXX. A fund that dips under it at a single quarter end loses the exemption for the year in those states.
SPAXX and FDRXX side by side
| SPAXX | FDRXX | |
|---|---|---|
| Type | Government | Government |
| 7-day net yield as filed | 3.55% | 3.63% |
| Gross 7-day yield of the fund | 3.97% | 3.97% |
| Expenses taken from the yield (expense drag) | 0.42% | 0.34% |
| State-tax-free part (U.S. government debt), last month end | 71.1% | 67.2% |
| U.S. government debt, June 30, 2026 | 61.0% | 58.1% |
| U.S. government debt, September 30, 2026 | 67.0% | 64.2% |
| Average days until holdings repay or reset their rate (weighted average maturity) | 39 days | 34 days |
| Average days until holdings are paid back in full (weighted average life) | 116 days | 108 days |
| Assets in the share class | $427.5 billion | $244.9 billion |
| Minimum initial investment on file | $1 | $1 |
| After tax, California | 2.60% | 2.65% |
| After tax, New York (outside NYC) | 2.64% | 2.69% |
| After tax, Texas | 2.70% | 2.76% |
The after-tax rows use one fixed example, the same in every side-by-side table on this site: a single filer with $120,000 of taxable income, and this site’s estimate of the state-tax-free part. Your own figures go in the calculator above.
Questions about this page
Tap a question to see the answer.
Is FDRXX the same fund as SPAXX?
No, they are two separate Fidelity funds, Government Money Market and Government Cash Reserves, filed by different trusts. Their holdings are similar: Treasuries, Federal Home Loan Bank and Farm Credit debt, and repo. Their expenses differ, which the filed gross and net yields measure at 0.42% and 0.34%.
Why is SPAXX the default in my Fidelity account?
Fidelity uses Government Money Market (SPAXX) as the core position of many brokerage accounts, where uninvested cash sits automatically. Other funds, FDRXX among them, can be bought with that cash like any other mutual fund. Which core options an account offers is set by Fidelity, not by the filing.
Do SPAXX and FDRXX pass the California 50% test?
Both did at the June and September quarter ends in the data: SPAXX held 61.0% and 67.0% in U.S. obligations, FDRXX 58.1% and 64.2%. FDRXX’s margin was thinner, so its December figure matters more, and the year-end letter settles the question for a return.
Other pages
Filings, rules and tax schedules behind this page
- Securities and Exchange Commission, Form N-MFP data sets (monthly, as filed)
- 17 CFR 270.2a-7, money market funds (rule 2a-7)
- California Franchise Tax Board, 2025 Schedule CA (540) instructions: funds with 50% of assets in U.S. or California obligations
- IRS Revenue Procedure 2025-32, 2026 tax rate tables
Compiled by Radif Partners
Independent publisher of money market fund yield and after-tax calculators built on Form N-MFP filings
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Fund data as filed for 2026, site checked on