VMFXX is not tax-exempt. Dividends from the Vanguard Federal Money Market Fund are fully taxable on your federal return as ordinary income, and only a portion escapes state and local tax, specifically the share of the fund’s income that comes from direct U.S. government obligations. The word “Federal” in the fund’s name describes the securities it holds, not any special tax status.
Federal Tax Treatment
The IRS treats money market fund payouts as dividends rather than interest, even though the fund earns its money from short-term debt like Treasury bills.1Internal Revenue Service. Publication 550 – Investment Income and Expenses Vanguard reports the total in Box 1a of Form 1099-DIV, and you include it in your ordinary income for the year.2Internal Revenue Service. About Form 1099-DIV, Dividends and Distributions
Those dividends are taxed at your regular federal income tax rate, which runs from 10% to 37% depending on your total taxable income.3Internal Revenue Service. Federal Income Tax Rates and Brackets They do not qualify for the lower rates that apply to long-term capital gains or qualified dividends. The income is ordinary, and the IRS taxes it that way.
The Net Investment Income Tax
If your modified adjusted gross income exceeds certain thresholds, VMFXX dividends can also trigger the net investment income tax, an added 3.8% on top of your regular rate. The thresholds are $200,000 for single filers and heads of household, $250,000 for married couples filing jointly, and $125,000 for married filing separately.
The 3.8% applies to whichever is smaller: your total net investment income or the amount by which your modified AGI exceeds the threshold.4Office of the Law Revision Counsel. 26 U.S.C. 1411 – Imposition of Tax VMFXX dividends count as net investment income because they are ordinary dividends, not tax-exempt interest.5Internal Revenue Service. Instructions for Form 8960 Net Investment Income Tax For someone in the 37% bracket who also owes the surtax, the effective federal rate on VMFXX income reaches 40.8%.
The Partial State and Local Exemption
Federal law prohibits states from taxing interest earned on direct obligations of the U.S. government, such as Treasury bills and notes.6Office of the Law Revision Counsel. 31 U.S.C. 3124 – Exemption From Taxation Because VMFXX invests heavily in these securities, a portion of its dividends qualifies for the state tax exemption. The key word is portion.
For the 2024 tax year, Vanguard reported that 59.87% of VMFXX’s income came from direct U.S. government obligations.7Vanguard. U.S. Government Obligations Income Information That percentage shifts each year with the fund’s portfolio mix. Only that qualifying slice can be subtracted from state taxable income. The remaining roughly 40% is subject to whatever state and local income taxes apply where you live.
The exemption is worth the most to investors in high-tax states. Someone earning $5,000 in VMFXX dividends with a 60% qualifying percentage could exclude about $3,000 from state taxable income. At a state rate around 9% to 13%, that saves roughly $270 to $390.
Why It Isn’t 100%
The reason VMFXX falls short of full state exemption comes down to repurchase agreements. These are short-term lending arrangements in which the fund loans cash to a counterparty, typically a bank, and receives government securities as collateral. Even though Treasuries back the transaction, courts have consistently ruled that income from a repurchase agreement is interest on a private loan, not interest on a government obligation.6Office of the Law Revision Counsel. 31 U.S.C. 3124 – Exemption From Taxation The fund isn’t earning a coupon from a Treasury bill. It’s earning interest on a cash loan that happens to be collateralized by one.
Repurchase agreements make up a substantial share of VMFXX’s portfolio because they help the fund maintain liquidity and a stable $1.00 share price. That flexibility costs some state tax efficiency.
Calculating Your State-Exempt Amount
Vanguard publishes a document each year called “U.S. government obligations income information” on its tax resources page.8Vanguard. Tax Information for Vanguard Funds It lists the qualifying percentage for every Vanguard fund, including VMFXX, and typically becomes available in the first few months of the year, covering the prior tax year.
The math is simple. Take the ordinary dividends shown in Box 1a of your Form 1099-DIV and multiply by the percentage listed for VMFXX. If your 1099-DIV shows $4,000 in ordinary dividends and the qualifying percentage is 60%, then $2,400 is potentially exempt from state income tax. Where and how you report the deduction varies by state. Some states provide a specific line for U.S. obligation income; others require a manual adjustment.
Keep a copy of both your 1099-DIV and Vanguard’s government obligations report with your tax records. If your state’s revenue department questions the deduction, those two documents together establish how much of your income came from exempt sources.
States With Minimum Holding Rules
Not every state automatically grants the exemption on whatever percentage Vanguard reports. A handful of states, including some of the highest-tax ones, require that a fund hold at least a minimum percentage of its assets in government securities, typically around 50%, measured at the end of each quarter. If the fund dips below that threshold in any quarter, the state may deny the exemption entirely for that year.
VMFXX’s government obligation percentage has hovered near 60% in recent years, which clears a 50% floor without a wide margin. If the fund’s managers shift more assets into repurchase agreements during a given quarter, the percentage could drop. Check your state’s specific rules and Vanguard’s annual report before claiming the exemption.
VMFXX in Retirement Accounts
Many investors encounter VMFXX as the default settlement fund in a Vanguard brokerage IRA or 401(k). The state tax exemption discussion above doesn’t apply inside those accounts. In a traditional IRA or 401(k), dividends aren’t taxed when earned; you pay ordinary income tax on the full amount when you withdraw it, regardless of what the underlying fund held. In a Roth IRA, qualified withdrawals are tax-free at both federal and state levels, so there’s nothing to allocate. The partial state exemption only matters when you’re receiving VMFXX dividends in a regular taxable brokerage account.
How VMFXX Compares to Treasury-Only and Municipal Funds
If state tax efficiency is a priority, Vanguard’s Treasury Money Market Fund (VUSXX) is a useful comparison. VUSXX invests exclusively in Treasury securities and reported 100% of its 2024 income as derived from direct U.S. government obligations, versus VMFXX’s 59.87%.7Vanguard. U.S. Government Obligations Income Information Every dollar of VUSXX dividends qualifies for the state exemption. The trade-off is usually yield; VMFXX’s broader mandate can produce a slightly higher pre-tax return. Whether that extra yield survives after state taxes depends on your state’s rate and the current spread between the funds. For investors in states with no income tax, the distinction is irrelevant.
Municipal money market funds work differently again. They invest in debt issued by state and local governments, and the interest on those bonds is generally excluded from federal gross income altogether.9Office of the Law Revision Counsel. 26 U.S.C. 103 – Interest on State and Local Bonds VMFXX offers no federal break at all. Municipal yields tend to be lower because tax-exempt income commands a premium. For investors in the highest brackets in high-tax states, a municipal fund sometimes wins on an after-tax basis despite the lower headline yield. For most others, VMFXX’s higher gross yield combined with the partial state exemption comes out ahead.