SPX is the S&P 500 index itself, a number that tracks the value of 500 large U.S. companies. SPY is an exchange-traded fund (ETF) that holds shares of those same companies so you can buy and sell it like a stock. Both give you exposure to the S&P 500, but they work very differently in practice, especially when it comes to options trading, taxes, costs, and how settlement works.
What Each One Actually Is
SPX is a price index maintained by S&P Dow Jones Indices. You cannot buy shares of SPX because it is not a tradable security. It is simply a calculated number that reflects the combined market value of roughly 500 large-cap U.S. stocks. When people talk about “the S&P 500 being up 1% today,” they are talking about SPX.
SPY is the SPDR S&P 500 ETF Trust, managed by State Street Global Advisors. It holds actual shares of the companies in the S&P 500 index and trades on the stock exchange throughout the day. You can buy one share of SPY the same way you would buy a share of Apple or Microsoft. SPY trades at roughly one-tenth the value of SPX, so if the index is at 5,500, SPY trades near $550 per share. SPY has a gross expense ratio of 0.0945%, meaning you pay about 95 cents per year for every $1,000 invested.
Options: The Biggest Practical Difference
Most people comparing SPX and SPY are interested in options trading, and this is where the differences matter most.
SPX options use European-style exercise, which means they can only be exercised at expiration. They settle in cash. If you bought SPX calls for $150 and they are worth $200 at expiration, you simply receive a $50 credit in your account. You never own shares of anything, and you are never at risk of being assigned stock you did not want.
SPY options use American-style exercise, meaning they can be exercised at any time before expiration. They settle in physical shares. If you hold in-the-money SPY calls through expiration, you will automatically buy SPY shares at the strike price. If you hold in-the-money puts, you will be assigned a short position in SPY. This means SPY options require you to manage the possibility of early assignment and the capital needed to take delivery of shares.
Because SPX trades at roughly 10 times the price of SPY, a single SPX option contract controls about 10 times the notional value of a single SPY option contract. Traders who want smaller position sizes often prefer SPY options. Traders who want larger exposure with fewer contracts, or who want to avoid the complications of physical delivery, tend to use SPX.
Tax Treatment
SPX options qualify as Section 1256 contracts under the tax code, which gives them a favorable blended rate: 60% of any gain is taxed as a long-term capital gain and 40% as a short-term capital gain, regardless of how long you held the position. For someone in a high tax bracket, that 60/40 split can meaningfully reduce the tax bill compared to short-term trading gains taxed entirely at ordinary income rates.
Section 1256 contracts also come with two other benefits. First, they are generally not subject to wash sale rules, which restrict you from claiming a loss if you buy a substantially identical position within 30 days. Second, if you have a net loss on Section 1256 contracts, you may be able to carry that loss back up to three years to offset gains from prior tax years. These contracts are reported on Form 6781.
SPY shares and SPY options follow standard capital gains rules. Hold a position for a year or less, and gains are taxed as ordinary income. Hold for more than a year, and gains qualify for long-term capital gains rates ranging from 0% to 20%. Wash sale rules apply normally. Gains and losses are reported on Schedule D and Form 8949.
Dividends and Income
SPX is a price index, so it does not pay dividends. Its value reflects only the stock prices of its components, not the income those stocks generate.
SPY holds the actual stocks, so it collects and distributes dividends to shareholders. The fund’s recent distribution yield is about 1.04%. If you own SPY shares in a taxable account, you will receive quarterly dividend payments that are taxable in the year you receive them. In a retirement account, those dividends reinvest without an immediate tax impact.
Trading Hours
SPY trades during regular stock market hours and during pre-market and after-hours sessions on stock exchanges. SPX options, however, offer global trading hours on the Cboe from 8:15 p.m. to 9:25 a.m. ET in addition to regular session hours. This gives SPX options traders the ability to react to overnight news from international markets before SPY opens for trading.
Which One to Use
If you want to invest in the S&P 500 by owning shares of a fund that tracks it, SPY is your tool. You buy shares, collect dividends, and sell when you are ready. It is straightforward and works in any brokerage account.
If you are trading options on the S&P 500, the choice between SPX and SPY depends on your priorities. SPX options offer cash settlement (no risk of unwanted share assignment), potential tax advantages through the 60/40 rule, and extended trading hours. SPY options offer smaller contract sizes, American-style flexibility to exercise early, and the familiarity of trading an ETF that behaves like a stock.
Many active options traders use SPX for larger or tax-sensitive strategies and SPY for smaller, more flexible positions. The two products track the same underlying index, so price movements are nearly identical. The differences come down to mechanics: how they settle, how they are taxed, and how much capital each contract requires.