FXAIX vs VOO: 7 Key Differences [2026 Update]

Choosing between FXAIX and VOO comes down to fractions — but those fractions compound over decades. Both funds track the S&P 500, yet subtle differences in expense ratios, tax treatment, and platform access can shift outcomes for long-term investors. Whether you're focused on expense tracking or simply growing your money, picking the right fund matters. Here's exactly how they compare.

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Summary Table

FXAIX vs VOO: 7 Key Differences [2026 Update]

Below you'll find detailed information about each option, including what makes them unique and their key benefits.

1. Performance Similarity

When comparing FXAIX vs VOO, historical returns have been nearly identical because both funds track the S&P 500 index. Over 1, 5, and 10-year periods, the two funds differ by just fractions of a percent annually, making performance alone an insufficient reason to choose one over the other.

Key facts:

• Both delivered ~26% returns in 2023 and closely match across all time horizons
• Minor differences stem from tracking error, not underlying strategy
• According to White Coat Investor, neither fund holds a meaningful performance edge

2. Expense Ratio

Cost is one of the few concrete differences in this S&P 500 fund comparison. FXAIX carries an expense ratio of 0.015%, while VOO charges 0.03% — making Fidelity's fund technically twice as cheap, though the real-dollar difference on a $10,000 investment is only about $1.50 per year.

Cost breakdown:

• FXAIX: 0.015% annual expense ratio
• VOO: 0.03% annual expense ratio
• Practical impact is negligible for most investors at typical portfolio sizes

3. Tax Efficiency

Tax efficiency is a meaningful differentiator between these two funds for taxable brokerage accounts. VOO, as an ETF, benefits from Vanguard's unique share-class patent structure, which historically allows it to avoid capital gains distributions more effectively than mutual funds like FXAIX. However, FXAIX has also managed to distribute zero capital gains in recent years, narrowing this gap considerably.

What investors should know:

• ETFs like VOO generally carry structural tax advantages in taxable accounts
• FXAIX held in a 401(k) or IRA makes tax efficiency a non-issue

4. Trading and Accessibility

When comparing FXAIX vs VOO, trading mechanics are a meaningful practical difference. FXAIX is a mutual fund that trades once daily at net asset value after market close, while VOO is an ETF that trades throughout the day like a stock, allowing limit orders and real-time pricing. This distinction matters if you want flexibility in entry timing or use a brokerage other than Fidelity.

Key differences:

• FXAIX: end-of-day pricing only, no intraday trades
• VOO: buy/sell anytime during market hours at live prices
• Both have $0 trading commissions at their respective home brokerages

5. Best for 2026 US Residents

For most US-based investors in 2026, the FXAIX vs VOO decision often comes down to your existing brokerage. Fidelity customers benefit from FXAIX's slightly lower expense ratio (0.015%) with no minimums and seamless automatic investing. Vanguard or Schwab users typically find VOO the more frictionless choice, since buying FXAIX outside Fidelity may involve transaction fees or restrictions.

Practical guidance:

• Fidelity account holders: FXAIX is the natural, cost-efficient pick
• All other brokerages: VOO trades commission-free nearly everywhere
• Tax-advantaged accounts (IRA/401k): performance difference is negligible for both

6. FXAIX

FXAIX is Fidelity's S&P 500 index mutual fund and one of the two primary subjects in the fxaix-vs-voo comparison. It tracks the same index as VOO but operates as a traditional mutual fund, meaning trades execute once daily at closing NAV rather than intraday. According to White Coat Investor, both funds are nearly identical in long-term performance.

Notable details:

• Expense ratio: 0.015% — slightly lower than VOO's 0.03%
• Fidelity-exclusive; not transferable as shares to other brokerages
• Best for: Fidelity account holders prioritizing simplicity and fractional investing

7. VOO

VOO is Vanguard's S&P 500 ETF and the competing fund in this head-to-head comparison. It tracks the same 500 large-cap U.S. companies as FXAIX but trades on exchanges throughout the day like a stock, offering more flexibility for active traders or investors using non-Fidelity brokerages. Its 0.03% expense ratio is slightly higher than FXAIX but still among the lowest available.

Key details:

• Expense ratio: 0.03% annually
• Available at virtually any brokerage, including Fidelity, Schwab, and Vanguard
• Best for: Investors wanting portability across brokerages or intraday trading flexibility

Final Words

Your best bet depends on whether you prioritize Fidelity's zero minimums or Vanguard's trusted ETF structure — both deliver near-identical S&P 500 exposure at rock-bottom costs. Use budget tracking tools to see which fits your portfolio goals.