VMFXX vs SPAXX vs SWVXX: Which Money Market Fund Wins in 2026?

If you hold a brokerage account at Vanguard, Fidelity, or Schwab, you've probably seen VMFXX, SPAXX, or SWVXX sitting in your account without fully knowing what it is. All three are government money market funds, low-risk vehicles that invest primarily in short-term U.S. Treasury securities, repurchase agreements, and government agency debt. They function as the "cash" position in a brokerage account, except unlike literal cash, they pay a real, competitive yield that tends to track closely with 4.20%, the top rate available on a standalone high-yield savings account.

The comparison people actually need isn't really "which fund pays more," since the three tend to move together and stay within a narrow band of each other. It's "am I actually earning the yield I think I'm earning, or is my cash sitting somewhere worse by default?" That second question has a genuinely different answer depending on which broker you use, and it's the part most cash-management guides skip.

VMFXX vs SPAXX vs SWVXX: The Default-Sweep Trap

Here's the detail that actually changes outcomes: not all three funds are automatically where your idle cash goes.

SPAXX at Fidelity is the default core position for most Fidelity brokerage accounts. When you deposit cash or a stock sale settles, it lands in SPAXX automatically, no action required. This is a genuine structural advantage of Fidelity's account design: you earn a money-market yield on idle cash by default, not by opting in.

VMFXX at Vanguard works similarly. It's Vanguard's default settlement fund for most brokerage account types, so uninvested cash lands there automatically as well.

SWVXX at Schwab is different, and this is the detail worth remembering from this entire comparison: SWVXX is not Schwab's default cash sweep. Schwab's default is the Schwab Bank Sweep program, which historically pays a meaningfully lower rate than SWVXX. To actually earn SWVXX's yield, a Schwab account holder generally has to manually purchase shares of the fund rather than relying on the account's default cash handling. If you've never checked this setting, there's a real chance your Schwab cash has been sitting in the lower-yielding default sweep the entire time.

This single structural fact is worth more to most readers than a side-by-side yield comparison, because the yield gap between the three funds themselves is usually small, while the gap between SWVXX and Schwab's default bank sweep can be substantial.

Operational Comparison: Sweep Status, Expense Ratio, and Holdings

Expense ratios and exact yields move over time, so treat any specific percentage as a snapshot rather than a permanent fact. What doesn't move as often is the structural relationship: Vanguard's money market lineup has a long-standing reputation for running lower expense ratios than most competitors, consistent with the firm's broader low-cost positioning. Check each fund's current fact sheet directly before assuming last year's numbers still hold.

State Tax Treatment: The Detail Most Comparisons Skip

All three funds can qualify for partial state income tax exemption, because a portion of their income comes from U.S. government obligations, which many states don't tax at the state level the way they tax ordinary bank interest. The catch is that the qualifying percentage changes every year and varies fund to fund, depending on exactly how much of that year's income came from Treasuries versus repurchase agreements (which often don't qualify for the same exemption).

Each fund publishes this percentage annually, usually as part of year-end tax documentation. If you live in a high-income-tax state, this detail can meaningfully change the after-tax comparison between a money market fund and a standard bank HYSA, since HYSA interest is fully taxable at both the federal and state level, while a portion of the fund's income may not be. Don't estimate this number from memory or from a prior year; pull the current year's disclosure from the fund provider directly.

Where VMFXX Wins (Pros)

• Historically low expense ratio. Vanguard's cost structure tends to keep more of the fund's gross yield in investors' pockets relative to competitors.
• Automatic default. No action needed to start earning the fund's yield on idle Vanguard brokerage cash.

Where SPAXX Wins (Pros)

• Automatic default at Fidelity. Like VMFXX at Vanguard, SPAXX requires no manual action to start earning yield on idle cash.
• Deep integration with Fidelity's broader cash management tools, including debit card and bill-pay features tied directly to the core position.

Where SWVXX Wins (Pros)

• Competitive yield once you're actually in it. SWVXX's yield is generally in line with SPAXX and VMFXX; the issue isn't the fund itself, it's whether your cash is actually invested in it.

Where SWVXX Falls Short (Cons)

• Not the default sweep. This is the single most important fact in this entire comparison. Schwab account holders who never manually buy SWVXX are very likely earning the lower Schwab Bank Sweep rate instead, without realizing it.
• Requires ongoing manual management. Because it isn't automatic, new cash deposits at Schwab may need to be manually swept into SWVXX repeatedly rather than happening by default.

How to Choose Between VMFXX, SPAXX, and SWVXX

1. Check which broker actually holds your account. For the vast majority of people, this question answers itself: use the fund native to your existing broker rather than trying to move assets between platforms just to chase a small yield difference.
2. If you're at Schwab, verify your cash isn't sitting in the default bank sweep. Log into your account and check whether your uninvested cash is in SWVXX or Schwab Bank Sweep. If it's the latter, you may be leaving real yield on the table.
3. Pull each fund's current 7-day yield and expense ratio directly from its fact sheet, since money market yields move with short-term rates and can shift within weeks.
4. Check the current year's state tax exemption percentage if you live in a state that taxes ordinary interest income, since it changes annually and affects the true after-tax comparison against a bank HYSA.

Decision Framework: Choose the Right Fund for Your Situation

Use VMFXX if:

• You hold a Vanguard brokerage account (it's your automatic default)
• You want the historically lowest-cost option among the three

Use SPAXX if:

• You hold a Fidelity brokerage account (it's your automatic default)
• You want deep integration with Fidelity's cash management and spending tools

Actively manage SWVXX if:

• You hold a Schwab account and want money-market yield instead of the lower default bank sweep
• You're comfortable manually purchasing the fund rather than relying on automatic sweep behavior

Methodology

SwitchWize compares brokerage money market funds on default sweep status, holdings composition, expense ratio, and state tax treatment, sourced directly from each fund's official fact sheet and prospectus. Because yields and expense ratios shift with short-term rates, we treat specific percentages as time-sensitive and direct readers to each fund's current disclosure rather than quoting a fixed historical number.

This is educational information, not personalized financial advice. Money market funds are not FDIC insured and, while considered very low risk, are not guaranteed against loss.

Quick answer

For most people, the VMFXX vs SPAXX vs SWVXX decision is really a "which broker do I already use" decision, since each fund is the natural cash vehicle at its own platform and their yields tend to move within a narrow band of each other. The one detail worth double-checking: SPAXX is Fidelity's automatic default, but SWVXX is not Schwab's default, so Schwab account holders should confirm their cash isn't sitting in the lower-yielding Schwab Bank Sweep by accident.

Decision guide

Sources

• SEC money market fund information explains how government money market funds are structured and their general risk profile relative to bank deposits.