In a taxable brokerage account, VOO is the more tax-efficient way to hold the S&P 500 than SWPPX, but the SWPPX vs VOO tax efficiency gap is narrower in practice than the structural difference suggests. Both funds hold nearly the same stocks and pay nearly the same dividends. What separates them is how each vehicle handles its own internal trading, and whether that trading can generate a tax bill you didn’t ask for.
Why the ETF Structure Wins on Paper
SWPPX is a traditional mutual fund. When shareholders cash out, the fund manager sometimes has to sell stocks from the portfolio to raise the money, and those internal sales can produce capital gains inside the fund even though you personally didn’t sell anything. Federal tax law then requires the fund to pass those gains through to shareholders each year, or face a fund-level tax.1Office of the Law Revision Counsel. 26 U.S. Code 852 – Taxation of Regulated Investment Companies and Their Shareholders You’ll see the distributions on a Form 1099-DIV at tax time, and you owe tax on them whether you took the cash or reinvested it.2Internal Revenue Service. Instructions for Form 1099-DIV
VOO uses a mechanism SWPPX can’t. Instead of selling stocks to meet redemptions, the ETF swaps baskets of actual shares with large institutional players called authorized participants. The fund hands over its most appreciated stocks and receives ETF shares back for cancellation. Because no cash changes hands, the IRS doesn’t treat this as a sale, and the fund gets to purge its lowest-cost-basis shares without creating a taxable event for anyone.3Office of the Law Revision Counsel. 26 U.S. Code 852 – Taxation of Regulated Investment Companies and Their Shareholders
The result: VOO has never distributed a capital gain to shareholders, going back to its inception. Every dollar of price growth stays unrealized until you personally decide to sell.
What SWPPX Has Actually Distributed
SWPPX’s real-world record is better than the mutual fund format suggests. The fund distributed zero capital gains from 2022 through 2025. Its last long-term capital gains distribution was just $0.0678 per share in December 2021, and earlier distributions were similarly small.4Schwab Asset Management. Schwab S&P 500 Index Fund S&P 500 index funds have low turnover to begin with, and heavy inflows over the past decade have meant Schwab has rarely needed to sell holdings to cover redemptions.
So while VOO’s tax advantage is real and permanent, SWPPX’s tax drag from capital gains distributions has been close to nothing lately. If you’re evaluating the two funds based on the last few tax years, they’ve looked essentially the same.
When the Gap Actually Bites
Two situations sharpen the difference.
The first is a prolonged bear market. If enough SWPPX shareholders redeem at once and inflows aren’t there to offset them, Schwab may have to sell appreciated holdings to raise cash. That can produce capital gains distributions to remaining shareholders even as account values are falling. VOO shareholders won’t see this, because the in-kind redemption mechanism keeps functioning regardless of market direction.
The second is high income. The 3.8% net investment income tax applies to dividends, capital gains, and interest above these thresholds, which are not indexed for inflation:5Office of the Law Revision Counsel. 26 U.S. Code 1411 – Imposition of Tax
- $250,000 for married filing jointly
- $200,000 for single or head of household
- $125,000 for married filing separately
For someone above these thresholds, an unwanted capital gains distribution from a mutual fund gets taxed at the regular capital gains rate plus the 3.8% surtax. VOO’s ability to defer that income until you choose to sell is worth more when the marginal cost of receiving it is higher.
At the other end, a single filer with taxable income up to $49,450 in 2026 sits in the 0% long-term capital gains bracket. In that case, capital gains distributions from SWPPX cost nothing in federal tax, and the ETF advantage effectively disappears.
What’s the Same Either Way
Dividends are a wash. Both funds hold the same S&P 500 stocks, collect the same dividends, and pass them through on similar schedules. Most of these are qualified dividends taxed at the preferential long-term capital gains rates, provided the fund meets the required holding period around the ex-dividend date.6Legal Information Institute. 26 U.S. Code 1 – Tax Imposed Whichever fund you own, the dividend tax bill is the same.
The tax on your own sale is the same too. Shares held more than a year qualify for long-term capital gains rates; shares held a year or less are taxed as ordinary income, which runs up to 37% federal in 2026.7Internal Revenue Service. Topic No. 409, Capital Gains and Losses Your broker reports the sale on Form 1099-B with the acquisition date and proceeds.8Internal Revenue Service. Instructions for Form 1099-B
Expense ratios are close enough to ignore. SWPPX charges about 0.02% and VOO charges 0.03%. On $100,000, the gap is $10 a year, well below the potential tax drag it might have to offset.
Cost Basis Defaults Differ
When you do sell, one quiet difference is worth checking before you place the order. Most brokerages default mutual funds like SWPPX to the average cost method, which blends every share you’ve ever bought into a single per-share basis. ETFs like VOO typically default to first-in, first-out, which treats your oldest shares as sold first. Neither default is automatically better — it depends on the prices you paid over time.
You can change it. Most brokerages let you pick highest-cost-first to minimize the gain on each sale, or specific identification to pick exactly which lots go. Do it before you sell; switching after a transaction settles is restricted for some methods.
Owning Both to Harvest Losses
Holding SWPPX and VOO alongside each other opens up tax-loss harvesting. If one drops, you can sell it at a loss, immediately buy the other, and keep nearly identical S&P 500 exposure while claiming the loss on your return. The wash sale rule blocks the deduction if you buy “substantially identical” securities within 30 days on either side of the sale.9Office of the Law Revision Counsel. 26 U.S. Code 1091 – Loss From Wash Sales of Stock or Securities
The IRS has never formally ruled on whether two S&P 500 funds from different providers count as substantially identical. The statute uses the phrase without a bright-line definition. Most tax professionals treat funds from different companies as distinct securities for this purpose, pointing to differences in management, expense ratios, and tracking methodology, and the IRS has not publicly challenged that view. The risk isn’t zero, though. For large harvests, it’s worth running the trade past a tax professional.
When None of This Matters
Everything above applies only to taxable brokerage accounts. Inside a traditional IRA, Roth IRA, or 401(k), capital gains distributions aren’t taxed when they occur. The retirement wrapper neutralizes the entire structural advantage of the ETF format, and SWPPX and VOO become functionally identical from a tax perspective. If your only accounts are retirement accounts, pick whichever your plan offers or whichever is easier to buy. Save the VOO preference for money in a regular brokerage account where every distribution shows up on a 1099.