Options guide · Reviewed 27 September 2026
SPX and SPY both track the S&P 500. Their options settle, exercise, and trade in different ways.
SPY options are on an ETF that holds real shares. SPX options are on the index itself, with no shares to deliver. That single structural difference cascades into how each settles, when it can be exercised, and why SPX dominates same-day trading.
Cash settlement vs. share settlement
SPX is a calculated index value — there's no company, no issued shares, nothing to physically deliver. At expiration, an in-the-money SPX option settles by paying the cash difference between the index's settlement value and the strike price. SPY, by contrast, is a real exchange-traded fund holding the underlying index constituents; an exercised SPY option settles the same way a stock option does, by delivering or receiving 100 shares of the ETF. This is the root difference everything else on this page follows from.
European vs. American exercise
Because SPX has no shares to assign early, it's a European-style option: it can only be exercised at expiration, never before. As the early exercise mechanics guide covers in general, American-style options like SPY can be exercised on any trading day up to expiration — which means an SPY position, especially a short one that's deep in the money, carries a small but real risk of early assignment before you intended to close it. SPX carries no such risk at any point before its own expiration.
Contract size and notional exposure
SPY is priced at roughly one-tenth of the S&P 500 index level by design, so one SPY option contract (covering 100 shares) represents about one-tenth the notional exposure of one SPX contract. A trader who wants index-level exposure with SPX needs proportionally fewer contracts than with SPY to reach the same notional size — which also means SPX positions are harder to size in small increments than SPY, where each contract is a smaller, more granular unit.
Trading hours
SPX options trade on Cboe, which runs regular trading hours of 8:30am–3:15pm Chicago time (roughly 9:30am–4:15pm ET), plus Cboe's Global Trading Hours session extending from about 7:15pm to 8:25am Chicago time — close to 24 hours a day, five days a week, according to Cboe's own published SPX trading-hours schedule. That lets a position be adjusted around news that breaks well outside the regular US equity session. SPY options, listed on standard equity-options exchanges, trade during the regular market session alongside the ETF itself and don't have that extended overnight window. Always confirm current session times with your broker or Cboe directly, since exact windows can change and shift with Daylight Saving Time.
Why 0DTE activity concentrates on SPX
Both SPX and SPY list options expiring on every trading day, but same-day ("0DTE") trading volume skews heavily toward SPX for a few structural reasons: cash settlement removes any possibility of early or unexpected assignment on a position meant to expire worthless hours later, European exercise means there's nothing to manage before the close, and the larger per-contract notional lets a trader express a given dollar amount of exposure with fewer contracts and correspondingly less exposure to per-contract bid-ask spread. None of that makes 0DTE trading lower-risk in general — a same-day option's value can still move sharply on small index changes given how little time value remains — it just explains why SPX, specifically, is where that activity has concentrated.
Which one is "better"?
Neither is better in general — they suit different situations. SPX's cash settlement and European exercise remove a category of operational risk (early assignment) that some traders specifically want to avoid, and its tax treatment under Section 1256 differs from SPY's. SPY's smaller contract size makes it easier to size a position precisely, and its options market is typically the more liquid of the two at the retail level for standard, non-0DTE expirations. The choice depends on contract-size needs, sensitivity to early-assignment risk, and tax treatment — not on one product being structurally superior.
Price an option at any expiration ↗ Review early exercise mechanics ↗
Frequently asked questions
What's the difference between SPX and SPY options?
SPX options are on the S&P 500 index itself: they settle in cash, exercise only at expiration (European-style), and one contract represents roughly 10x the notional of one SPY contract. SPY options are on the SPY ETF, which holds the actual index constituents: they settle by delivering or receiving 100 shares of SPY, and can be exercised any time before expiration (American-style).
Can SPX options be exercised early?
No. SPX is a European-style option, which can only be exercised at expiration, not before. SPY is American-style, meaning it can technically be exercised on any trading day up to expiration, which introduces early-assignment risk that SPX doesn't have.
Why do SPX options settle in cash instead of shares?
SPX is a calculated index value, not a security with issued shares — there's nothing to deliver. At expiration, the difference between the index's settlement value and the strike price is paid in cash instead. SPY, by contrast, is an actual ETF holding real shares, so its options settle the normal way: by delivering or receiving 100 shares.
Why is 0DTE (zero days to expiration) trading concentrated in SPX?
SPX has expirations on every trading day (Monday through Friday) due to its weekly listing structure, cash settlement removes overnight assignment risk on an expiring contract, and its larger notional per contract appeals to traders sizing directional or hedging positions without needing many contracts. SPY also lists daily expirations, but SPX's cash settlement and European exercise make same-day positions simpler to manage since there's no possibility of early assignment before the position is closed.
Are SPX options taxed differently than SPY options?
In the US, SPX options are classified as Section 1256 contracts, which are taxed at a blended 60% long-term / 40% short-term capital gains rate regardless of how long the position was held. SPY options, as equity options, follow ordinary short-term or long-term capital gains rules based on the actual holding period. This is a general description, not tax advice — consult a tax professional for your specific situation.
Source note: Contract specifications described here (settlement, exercise style, multiplier, tax treatment) reflect standard, publicly documented terms for SPX and SPY options as defined by their listing exchanges and issuers, current as of this guide's review date — confirm current specifications with your broker or the listing exchange before trading. This is educational information, not investment or tax advice. Options involve substantial risk and are not suitable for all investors.