SWTXX vs SWOXX: Which Fund is Best?

Schwab offers several municipal (muni) money market mutual funds including the Schwab Municipal Money Fund Ultra Shares (SWOXX) and the Schwab Municipal Money Fund Investor Shares (SWTXX). Many investors ask about the differences between these two funds since they are two of the largest muni money market mutual funds in the market today. When comparing SWOXX vs SWTXX, it is clear which fund is best for most investors.

The Short Answer

SWOXX and SWTXX are two share classes of the exact same fund! There is no need to compare SWOXX vs SWTXX because the only difference is the minimum initial investment amount and the expense ratio. Investors who can make an initial purchase of $1M or more will get a higher yield with SWOXX.

SWOXX vs SWTXX Historical Performance

Since its inception, SWOXX has outperformed SWTXX by .12% on an annualized basis. This has compounded to a 2.89% cumulative difference over the past 20 years, which is relatively small. Currently the yield difference is about .15% however, so future performance may deviate further.

Current Yields for SWTXX & SWOXX

The current 7 day yield is a standardized yield metric for money market mutual funds and the 7 day yields for both SWOXX and SWTXX can be found on the fund’s webpages. See here for SWTXX and here for SWOXX.

What rate is SWOXX & SWTXX paying?

The current interest rate for SWOXX, SWTXX, and other Schwab money markets can be found on Schwab’s money market page.


The expense ratio is .34% for the SWTXX investor shares and .19% for the SWOXX ultra shares. Since the funds are just different share classes of the same portfolio, this difference in expenses is what accounts for the differences in yield and performance. Neither fund charges a load or 12b-1 fees.

SWTXX has no minimum investment and investors can invest as little as one cent, while SWOXX has a minimum investment of $1 million. My observation is that investors can keep SWOXX even if they sell and their balance falls below $1 million. The $1 million minimum seems to only apply to the initial purchase.

I have not checked every brokerage, but SWOXX and SWTXX is generally only available to clients of Charles Schwab.

Like most money market mutual funds, investors can sell SWOXX or SWTXX at any time.


Hypothetically, an investor could lose money with SWOXX or SWTXX, but I personally do not think that is a realistic risk as I believe the fund sponsor or the federal government would intervene if that were about to happen. Technically, it is possible to lose money in SWTXX or SWOXX though.

As of June 30, 2023, the fund was composed of approximately $3.7 billion in the investor shares and $11.4 billion in ultra shares.


No, neither SWTXX nor SWOXX are FDIC insured.


The two funds are share classes of the same portfolio, so the holdings are identical. The funds own 61% variable rate demand obligations (VRDNs), 17% tender auction bonds, and 11.6% commercial paper, and some smaller asset classes. 89.4% of the funds’ holdings have an effective maturity of less than one week.

High Balances

Investors allocating more than $1 million may want to consider the “ultra” share class of the fund, whose symbol is SWOXX.

Tax Considerations

SWTXX and SWOXX are municipal funds which means that they only invest in municipal-related securities. However, investors who are not in the highest marginal tax rates may be better off investing in a non-muni money market fund.

Muni Money Market Funds

Investors subject to higher tax rates may consider municipal (muni) money market funds due to the fact the interest is typically exempt from federal income tax (and often from state tax too!). To the extent that an investor is subject to the “alternative minimum tax,” they may want to consider an AMT-free money market (such as SWWXX or SCTXX).

The caveat with muni money market funds though is that the yields can move up and down A LOT. Therefore, the stated yield that an investor looks up on any given day is not necessarily indicative of the future return. To understand why, read my post on muni money market yields.

Rather than expecting a muni money market fund’s stated yield, I encourage investors to expect the trailing average yield (over the past few weeks). Generally speaking, the after tax returns of munis will only be higher than non-muni money markets for those in the highest tax brackets.

Which is Best? SWOXX or SWTXX?

Overall, SWTXX is a good investment for many situations. Those investing more than $1 million should generally go with SWOXX for the higher yield. Investors who are not subject to the highest tax rates may want to consider other funds though.

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