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For an active trader, those differences can add up to thousands of dollars a year. This article breaks down what actually separates the two, using concrete dollar examples, and gives you a simple framework for choosing the right instrument for your account and your strategy. Underlying Asset Differences: Index vs. ETF Options SPX is the S&P 500 index itself. It is a statistical construct, not a security — there are no shares to buy or sell. You can only trade options (and futures) on it, and those options settle in cash. SPY is the SPDR S&P 500 ETF. It holds the actual 500 stocks, trades like any share, and its options settle by delivering shares. That single distinction — cash settlement versus physical share delivery — cascades into almost every practical difference that follows: exercise style, assignment risk, contract size, and even how the two are taxed. SPX vs SPY Option Contract Sizes and Capital Requirements SPY trades at about one-tenth the level of the SPX index. With SPX near 7,500 and SPY near $750, the notional exposure of each contract looks like this: SPX SPY Approx. level 7,500 $750 Multiplier $100 100 shares Notional per contract ~$750,000 ~$75,000 One SPX contract carries roughly the same market exposure as ten SPY contracts. For a trader putting on size, that means fewer contracts, fewer commissions, and less execution complexity. For a smaller account, it means SPX can be too coarse — you may only be able to hold one or two contracts where ten SPY contracts would let you scale in and out with precision. Settlement and exercise: European vs American SPX options are European-style. They can only be exercised at expiration, and they settle in cash. If you hold a long 5,900 call and SPX settles at 5,910, you simply receive $1,000 (10 points × the $100 multiplier). No shares ever change hands. SPY options are American-style. They can be exercised at any point before expiration, and in-the-money contracts result in shares being delivered or called away. For anyone trading multi-leg positions, this is bigger than it sounds. If you are short the body of an SPX iron condor or butterfly and the index blows through your strike intraday, nobody can exercise against you early — the position stays intact until expiration. With SPY, a short leg that goes deep in the money (especially around an ex-dividend date) can be assigned early, leaving you with an unwanted 100-share-per-contract stock position and a hedge that no longer lines up. Cash settlement removes that failure mode entirely. Section 1256 Tax Advantages of SPX Options This is where SPX earns its keep for active traders. SPX options are taxed more favorably than SPY options because they qualify as Section 1256 contracts. This subjects them to a 60% long-term and 40% short-term capital gains tax split, whereas SPY options are taxed at 100% short-term capital gains if held under a year. Even a 0DTE trade opened and closed in the same afternoon gets 60/40 treatment. Section 1256 positions are also marked to market at year-end, and wash-sale rules do not apply. SPY options are taxed like ordinary equity options. A trade held under a year is taxed 100% at your short-term (ordinary income) rate, and wash-sale rules do apply. Consider a trader with $20,000 of net options profit in a year, in a 32% marginal bracket with a 15% long-term rate: SPY (all short-term): $20,000 × 32% = $6,400 in tax. SPX (60/40): ($12,000 × 15%) + ($8,000 × 32%) = $1,800 + $2,560 = $4,360 in tax. Same trades, same market, roughly $2,000 saved — purely from the instrument you chose. For a high-volume premium seller, that gap compounds year after year. Tax treatment of options is complex and depends on your situation. Section 1256 generally applies to broad-based index options, but confirms applicability with a tax professional. Dividends: a wrinkle SPY carries and SPX doesn't SPY pays a quarterly dividend. Its price drops on the ex-dividend date, and market makers price that expected drop into the options — call premium tends to sag and put premium firms up ahead of the event. Deep in-the-money SPY calls also face elevated early-assignment risk right before the ex-dividend date, as holders exercise to capture the payout. SPX, being an index, pays no dividend and has no ex-dividend date. One less variable to track. Liquidity and spreads: it depends how you measure SPY options are the most actively traded options in the world. In absolute dollar terms they carry the tightest bid-ask spreads and offer the most granular strike selection, which suits smaller accounts and precise position sizing. SPX spreads look wider in dollar terms, but remember one SPX contract equals about ten SPY contracts — so on an apples-to-apples exposure basis the relative cost is competitive, and you are crossing the spread on one contract instead of ten. At-the-money SPX and SPXW strikes trade with deep liquidity and penny-wide markets during active sessions. A quick word on the ticker: SPX vs SPXW In your option chain you will see both SPX and SPXW. SPX (the classic monthly) is AM-settled — it stops trading Thursday and settles off Friday's opening prices, which introduces some overnight gap risk on the final day. SPXW covers the weekly and daily expirations and is PM-settled off the 4:00 PM close, so you can trade it right up to the bell. If you are trading 0DTE, you are in the SPXW chain. Both get identical Section 1256 tax treatment. XSP Options: The Mini-SPX Alternative to SPY XSP is the Mini-SPX option — it trades at one-tenth of the SPX level (comparable in size to SPY) but keeps SPX's cash settlement, European exercise, and Section 1256 tax treatment. In theory it is the best of both worlds for a smaller account that still wants the tax and assignment advantages. The catch is liquidity: XSP volume is far thinner than either SPX or SPY, so spreads are wider and fills are harder. Worth knowing about, worth checking the chain before you commit. How SPX and SPY Options Behave During a Flash Crash Everything above is theory until you watch it play out in a live position. On Friday, June 26, 2026 — during a jittery week in which JPMorgan (read more on that) had publicly warned of flash-crash risk in crowded AI names — the S&P 500 delivered a textbook demonstration of why the SPX-vs-SPY distinction matters. Right at the 4:00 PM close, a wave of sell orders hit thin liquidity. On a standard 1-minute line chart, nothing looked wrong: the line simply connects close-to-close, and the close held around 731 on SPY. But pull up the 1-minute candlestick chart for that final bar and the story changes completely — a tiny body around 731 with an enormous lower wick stabbing all the way down to 716.58, then recovering, all within a single closing minute. The volume bar on that candle dwarfed everything around it. That's the signature of a flash crash: a momentary liquidity air-pocket where a flood of orders blows through a thin book before buyers step back in and the close resolves. This is a closing-bell liquidity cascade — arguably the single most dangerous moment for this kind of event. At 4:00 PM, market-on-close imbalance orders execute, index rebalancing flows hit, and options-expiration settlement pressure peaks all at once. A large sell imbalance in that window can momentarily overwhelm the order book before the closing auction resolves. Here's where it gets instructive. That 716.58 print was SPY's worst individual tick. But the SPX cash index — pulled from live data — only printed down to about 7,336 in the same minute. At the roughly 10:1 ratio, SPY's 716.58 implies an SPX near 7,232, yet the actual index bottomed 100 points higher. Why the gap? During a flash crash, the ETF and the index decouple. SPY is a single instrument, so a market-sell order blows straight through its book and prints an extreme low. The SPX index, by contrast, is an average of all 500 constituents — and not every stock crashes to the same degree in the same instant. The index is "cushioned" by its own construction. The true dislocation sat somewhere between the two readings, with SPY overshooting to the downside. Now apply this to two hypothetical traders, each holding the same S&P 500 put spread going into that close: The SPY trader watched the ETF physically trade at 716.58 — potentially deep inside a danger zone — and, because SPY is American-style and physically settled, faced real assignment mechanics around any in-the-money strikes, plus the gut-punch of seeing the market trade through their level. The SPX trader settled off the official closing print near 7,354–7,357, determined by the closing auction — not the wick. Even the intraday SPX low of ~7,336 stayed above where an equivalent short strike would have sat. The terrifying wick, however real, never touched a cash-settled position that keys off the close. The lesson isn't that SPX is risk-free — that wick proves the market physically traded at a stressed level, and a stop-loss order resting in that zone would have been triggered, auction or not. The lesson is that cash settlement and European exercise changed the outcome. The same market event that could have been painful in SPY or in stock was, on a cash-settled SPX position, a non-event that expired off the official close. That is the structural edge described in the tax and settlement sections above, made concrete in a single closing minute. The decision framework Lean SPX if you: Trade meaningful size (one SPX replaces ten SPY, cutting commissions and complexity) Have enough capital and margin to handle the larger contract comfortably Run an active income strategy where the 60/40 tax treatment materially lowers your bill Want zero early-assignment risk on multi-leg structures Prefer the simplicity of cash settlement and no dividend exposure Lean SPY if you: Trade a smaller account and need granular position sizing Want the tightest absolute spreads and the widest strike selection Are building a strategy around actually holding shares (covered calls, cash-secured puts as accumulation) Are trading inside an IRA, where the Section 1256 tax edge is irrelevant Are newer to S&P 500 options and want to learn on a smaller, more familiar contract Consider XSP if you want SPX's tax and settlement benefits at a SPY-sized contract — and can live with thinner liquidity. The bottom line SPX and SPY track the same market, but they are not interchangeable. For a serious, active options trader — especially one selling premium or trading 0DTE at size — SPX's Section 1256 tax treatment, cash settlement, and freedom from early assignment give it a structural edge that compounds over time, in your fills and in your tax bill. SPY remains the better tool for smaller accounts, share-based strategies, and IRAs. Many experienced traders end up using both: SPX for tax-efficient premium selling at size, SPY for tactical trades and anything involving shares. The right answer isn't universal — it comes down to your account size, your tax situation, and the specific strategy in front of you. Choose the instrument that fits the trade, not the other way around. The examples above exclude commissions and fees and are for educational purposes only. Options trading involves substantial risk and is not suitable for every investor. Review the Characteristics and Risks of Standardized Options before trading.

Study Methodology Here are the specifics of the test: Time Period: January 2007 to Present Trade Setup: On each trading day, locate the standard expiration cycle with 30-45 days to expiration. If the front-month standard expiration cycle did not fall within that time frame, we simply did nothing and proceeded to the next trading day. When the front-month expiration cycle fell between 30-45 days to expiration, we “sold” the at-the-money put in that cycle. In the following standard expiration cycle, we purchased the put at the same strike price to complete the calendar spread. Position Tracking: Each position’s profit/loss as a percentage of the debit paid was tracked on each trading day until the day before settlement. We did this to avoid any unwanted outcomes as a result of the SPX settlement process. Overall, 1,200 SPX calendars were tracked. Once all of the profit/loss metrics were gathered, we filtered the trades into four buckets based on the VIX Index level at the time of entering the trade: VIX Below 15 VIX Between 15 to 20 VIX Between 20 and 25 VIX Above 25 Each bucket had a similar number of occurrences. The Results: Profit/Loss Frequencies for 30-45 DTE SPX Calendar Spreads Let’s take a look at the data! We’ll start with the percentage of calendar spreads that reached profit levels between 10-100% of the initial debit paid: There are some key findings from these results: Over 50% of the trades reached returns of 40% or more on the initial debit paid, with 75% of the positions reaching 10-20% returns on the debit paid. The low IV (VIX below 15) and high IV (VIX above 25) had the highest percentage of trades that reached each profit level. High IV calendar spreads in second place? How can that be? In super high IV environments, the VIX term structure (SPX volatility) goes into backwardation. As a result, the near-term expiration cycles trade with significantly higher implied volatility than longer-term expiration cycles. When volatility comes back down, the front-month implied volatility will fall with greater magnitude than the back-month implied volatility, which can lead to quick profits on a calendar spread if the underlying hasn’t moved too much. The only problem is that in high implied volatility environments, realized volatility tends to be high, which is not ideal for delta-neutral calendar spreads. So, in high IV, long calendar spreads become more of a term structure reversion trade, and less of a time decay trade. Let’s move on to the loss frequencies: In low IV environments, the SPX calendar spreads reached each loss level less frequently than in higher IV environments. Again, this is most likely due to the fact that realized volatility tends to be more significant in times of high implied volatility. When you compare the calendar spread profit frequencies to the loss frequencies, we can see that the biggest gap (profit frequency – loss frequency) is typically in the low IV (VIX below 15) trades. For example, in the low IV bucket, over 85% of positions reached a 10% profit, while 65% reached a 10% loss. In the 15-20 VIX trades, 75% of trades reached a 10% profit, while 85% reached a 10% loss. Of course, you’d like to see a large gap between the percentage of trades that hit each profit and loss level (more trades reach the profit level as opposed to the loss level). To visualize this, we simply subtracted the loss frequency from the profit frequency at each level: As we can see, the calendars entered when the VIX was between 15 and 25 reached the loss levels more frequently than the same profit level (resulting in a negative value). In the low (VIX below 15) and high (VIX above 25) volatility environments, the SPX calendar spreads reached the profit levels more often than the same loss level. Summary What can we learn from this calendar spread profit and loss data? First and foremost, calendar spreads typically perform very well in extremely low implied volatility environments, but they also have potential when front-month IV is inflated at a significant premium to the back-month IV. However, there are strategies that may be more suitable for time when implied volatility is high. Second, based on a positive spread between profit and loss frequencies, calendar spreads have historically had positive expectancy at each profit/loss level, as profits have occurred more often than losses of the same magnitude. On a final note, it’s important to keep in mind that this is a backtest based on closing values. As a result, it’s likely that there were trades that hit profit or loss levels intraday, but ended the day less than those levels. Additionally, these positions were not managed, which is the key to success when trading calendar spreads. At the very least, the data discussed in this post can help to guide management levels, and expectations for achieving certain profit/loss levels when trading SPX calendars. About the Author Chris Butler is the founder of projectoption, an options trading education and research website. Chris primarily trades non-directional options strategies in equity indices (SPX, RUT, /ES Options), but is also active in volatility-related ETNs (VIX Options, VXX, XIV).

And the same is true with determining which strikes to use when selling puts. As it turns out, over a relatively long period of time risk and reward are related, as we would expect. Below are the results of three backtests simulating the monthly sale of SPX put options from 2001-2017 at various delta levels (16, 30, and 50). Each test assumes you enter approximately one month from expiration and exit approximately 3 days prior to expiration (results have minimal variation if entries and exits are slightly modified). No active trade management is involved. My tests also assume no leverage is being used, with cash fully secured by 1 month T-bills. In other words, the returns of put selling can be thought of as the yield on cash plus the net results of the option trades. No commissions, slippage, or taxes are included, so real results would be slightly lower. Given the size of the SPX contract and its liquidity, this isn't a serious issue. The strategy passes the test of real world investability. Click on the image for greater clarity Several interesting observations can be seen: 1. All strikes deliver returns similar to the underlying asset (using SPY as a proxy). The at the money strike (50 delta) even slightly outperformed SPY. It should be noted that every backtest is sensitive to the start and end point, and if we started our test in 2009 SPY would substantially outperform. This is what we would expect given the limited profit potential of put selling. CBOE has data going back to 1986 showing that at the money put writing has delivered returns comparable to owning the underlying. 2. All strikes delivered less risk than the underlying asset, measured with standard deviation and max drawdown. This results in higher Sharpe Ratios. The Sharpe Ratio is one way to measure how well we are being compensated for the risk taken, and a higher number is better. Put selling having lower risk than owning the underlying asset is something that we can expect to persist in the future. This is often counter to the perception that many have about selling options being "risky". Leverage is what creates risk, not product/strategy. 3. The farther out of the money strikes deliver higher Sharpe Ratio's, with 16 delta options producing an extremely high 0.92 Sharpe. This could be noise in the data that may not be likely to continue out of sample, but many other researchers have found similar results on additional data and underlying assets leading us to believe it's not random. Those who believed this will continue to persist may choose to modestly lever their notional exposure to produce higher returns instead of selling strikes that are closer to the money. 4. If you look closely at the chart, you can see that put selling can make money even in a declining market (especially with further out of the money options, of course). For example, during the 2001-2002 bear market, 16 delta put selling was continuing to put in new equity highs. This was also the case during the first several months of 2008 where the market was declining, but not too far/too fast. When the crisis hit in the fourth quarter, the speed and magnitude of stock market losses was too great for any of the strikes to endure. No surprise there, as insurance must pay off from time to time to attract buyers. 5. After a crisis period like 2008, put selling recovered quickly as option premiums were substantial. SPY didn't reach a new high until 2013, while put selling recovered it's drawdowns in 2010. This is important given the nature of our human discomfort with losses and our ability to stick with a strategy. You may even draw additional conclusions of your own from this data. So with all this being said, which strike should you sell? I don't think a binary decision needs to be made here anymore than a binary decision on if you should sell puts or just buy the ETF directly. There are advantages and disadvantages of both, but hopefully this has made it clear that put selling is worthy of at least a partial allocation for a particular asset class like US large cap equity. Below I'll present one additional chart that is 50% SPY, and 50% put selling with equal allocation to our three strike levels (in other words, about 16.66% each), rebalanced monthly. Given the certainty of our uncertainty about which method will be best in the future, as well as the simplicity and tax efficiency of a traditional ETF allocation, this approach could be ideal for many sophisticated investors. Click on the image for greater clarity Jesse Blom is a licensed investment advisor and Vice President of Lorintine Capital, LP. He provides investment advice to clients all over the United States and around the world. Jesse has been in financial services since 2008 and is a CERTIFIED FINANCIAL PLANNER™ professional. Working with a CFP® professional represents the highest standard of financial planning advice. Jesse has a Bachelor of Science in Finance from Oral Roberts University. Jesse oversees the LC Diversified forum and contributes to the Steady Condors newsletter.

This year's sideways market has been very kind to calendar spread trades.We booked few very nice winners with SPX and RUT calendar spreads. When we opened another SPX calendar spread on August 5, I expected another nice winner. But the market had very different plans. The strike was 2100, which was right in the middle of the range for the big part of the year. Last Thursday, August 20 SPX was at 2061, and the trade was still in decent shape, down only 8%: However, as the selloff accelerated towards the end of the day, the trade was down around 20-25%. At this point I considered different adjustment options but didn't find an efficient and inexpensive hedge. So my plan was just to close the trade around 30% loss. I tested different adjustments and didn't find them too efficient, so considering the fact that we also had a butterfly trade that was expected to offset the loss, it was an acceptable result to me. However, SPX really collapsed at the last hour on Thursday, and the trade went through the stop loss in matter of minutes. I assume that most members wouldn't have time to act on the alert sent 5-10 minutes before the close. Spreads also became very wide, and I doubt we could close it anywhere near the mid. On Friday SPX gaped down another 20 points and the trade was down over 50%. By the end of the day the loss was 70%+. We used yesterday's rally to reduce the loss and closed the trade for 60% loss. To put things in perspective, SPX went down 130 points in 3 trading days. Last time it happened was 2011. So what could we do differently? In the wise words of one of our mentors, Dan Sheridan, "just buy a stinking put!" Dan survived on the floor of the CBOE trading options for over two decades, so he's experienced it. Lets see how things would be different with the put. When SPX went through our adjustment point, we could buy the 1750 put for just 0.75. This is how the P/L chart would look like with the put: As we can see, the chart looks much "smoother". But even more important, it significantly increases the vega, which helps in case SPX continues down and volatility increases. Fast forward to Friday morning: That's right. Instead of being down 50%+, we would be actually UP 41%. So what can we learn from this trade? The most important thing is "don't assume anything". Gaps happen and should be taken into consideration. If the market went down 60 points and became oversold, it doesn't mean it cannot go lower. Don't let your opinions impact your risk management. When in doubt, cut the loss or "just buy a stinking put!" This trade emphasizes once again the importance of position sizing. In our model portfolio, we recommend allocating 10% per trade. Which means that this trade had a 6% negative impact on the overall portfolio. Not pleasant but not catastrophic and allows us to leave another day. After closing 9 consecutive winners in August, we are still having a great month, while most major indexes are significantly down. Related posts: How We Made 23% on $QIHU Straddle in 4 Hours How Position Sizing Impacts Your Returns How we trade calendar spreads We invite you to join us and see how we manage our portfolio of non-directional strategies. Start Your Free Trial