VMFXX vs HYSA: Vanguard's Biggest Money Market Fund vs Savings in 2026

VMFXX (Vanguard Federal Money Market Fund) is the largest money market fund in the country by assets, mostly because it's Vanguard's automatic settlement fund for uninvested brokerage cash. If you've ever sold a stock at Vanguard and left the proceeds sitting, there's a good chance they landed in VMFXX without you choosing it. That makes it worth understanding on its own terms, not just as "the Vanguard version of SGOV."

VMFXX holds a mix of U.S. government agency securities and repurchase agreements rather than direct Treasuries alone, which matters for one specific reason: state tax. Interest from direct U.S. government obligations is exempt from state and local tax, but VMFXX's mixed holdings mean its qualifying percentage is less consistent than a Treasury-only fund like Vanguard's own VUSXX. This guide compares VMFXX against a high-yield savings account, and against VUSXX, so you know which Vanguard cash option (if any) actually fits your situation.

Quick answer

If VMFXX is already your Vanguard default and your balance is modest or you live in a no-income-tax state, there's little reason to change anything, it's safe, liquid, and fee-light at 0.11%. If you pay meaningful state income tax and can clear VUSXX's $3,000 minimum, VUSXX (or the ETF equivalent, SGOV) offers a more reliable state-tax exemption for the same underlying safety. If you'd rather skip brokerage settlement mechanics altogether, a top HYSA gives you FDIC insurance and same-day access with $0 minimum and $0 fee.

VMFXX vs HYSA: Side-by-Side Comparison

VMFXX vs VUSXX: The Choice Vanguard Customers Actually Face

For most Vanguard customers, the real decision isn't VMFXX versus a HYSA, it's VMFXX versus VUSXX, Vanguard's Treasury-only fund. The two differ in exactly two ways that matter: minimum investment and state-tax reliability.

VMFXX has no minimum, so it's accessible to every account regardless of balance. VUSXX requires $3,000 to open. On tax treatment, VUSXX wins clearly: its holdings are concentrated in direct Treasury bills, notes, and Treasury-collateralized repos, which have historically cleared the roughly 50% government-obligation threshold that states like California, New York, and Connecticut require before any state exemption applies. VMFXX's mix of agency securities alongside Treasuries has historically produced a lower and less consistent qualifying percentage, meaning its state-tax benefit is real some years and marginal in others.

The practical rule: if you have $3,000-plus and pay meaningful state tax, move to VUSXX (or SGOV, which has no minimum and the same tax profile). If you don't clear that bar, VMFXX remains a reasonable, low-fee place to park brokerage cash, just don't assume it comes with the same guaranteed tax break.

How the State-Tax Math Plays Out

Interest from direct U.S. government obligations is exempt from state and local tax under 31 U.S.C. § 3124, but only in proportion to the fund's reported qualifying percentage, published annually. For a fund like VMFXX whose qualifying percentage moves year to year and isn't guaranteed to clear the 50% state threshold, the practical exemption can range from meaningful to negligible depending on the year and your state's specific rules.

Ranges reflect the uncertainty in VMFXX's annual qualifying percentage. Check Vanguard's current tax supplement before relying on a specific figure. A Treasury-only fund like VUSXX or SGOV removes most of this uncertainty.

Where VMFXX Wins (Pros)

• No minimum, unlike VUSXX's $3,000 floor.
• Low fee (0.11%), far below SPAXX-style funds at other brokerages.
• Automatic and frictionless if you already hold a Vanguard account.
• Highly liquid, as the largest money market fund in the country.

Where VMFXX Falls Short (Cons)

• Less reliable state-tax exemption than a Treasury-only fund.
• Not FDIC-insured, unlike a bank savings account.
• Slightly higher fee than VUSXX (0.11% vs 0.09%), though the gap is minor.
• Still requires a brokerage account, unlike a HYSA.

How to Decide

Keep VMFXX if it's already your default, your balance is under $3,000, or you live in a no-income-tax state where the exemption question doesn't matter.

Switch to VUSXX if you can clear the $3,000 minimum and pay meaningful state income tax, for a more reliable exemption at nearly the same fee.

Choose SGOV instead if you want VUSXX's tax profile without any minimum, on any brokerage.

Choose a HYSA if you want FDIC insurance, same-day access, and zero fee, with no brokerage account required. See our emergency fund guide for how to size that layer alongside a money market fund.

Sources

• Vanguard Federal Money Market Fund (VMFXX) fund page
• 31 U.S.C. § 3124
• FDIC: understanding deposit insurance

Yields, fees, and government-obligation percentages change; verify current figures on Vanguard's site before acting.

Methodology

SwitchWize compares money market fund structure, fees, and minimums against issuer fund pages and cross-references savings APYs against institution disclosures, verified weekly. Rankings are never influenced by advertiser compensation. For full details, see our methodology.

This is educational information, not personalized financial advice.