What triple witching is
Cboe's definition is the one to start from, because the exchange that lists the contracts has no reason to dramatize them. In its paper on the settlement of A.M.-settled S&P 500 options, Cboe writes that "Triple Witching" refers to "the simultaneous expiration of individual stock options, equity index options and equity index futures that occurs four times a year on third Fridays in March, June, September and December," and that on those days "there is often an observed increase in trading volume and market volatility as traders close, roll out or offset their expiring positions."
Three product classes, one session, four times a year. Four of the twelve monthly OPEX sessions are quarterly, and those four are the witching days. The OPEX calendar 2026 is the dated list. The "witching hour" is the final hour before the 4:00 p.m. ET close, when the single-stock side of the expiration and the index rebalances scheduled for the same close land together. The rest is plumbing: what settles, when, and which flows are mechanical.
Triple witching dates for 2026
The rule is the third Friday of each quarter-ending month. When that Friday is an exchange holiday, expiration moves to the preceding business day. For 2026 that gives:
- Friday, March 20, 2026
- Thursday, June 18, 2026, because NYSE was closed on Friday, June 19 for Juneteenth
- Friday, September 18, 2026, the next one on the calendar
- Friday, December 18, 2026
The June shift is not a quirk of one exchange. CME's rulebook for S&P 500 futures, Chapter 351 as filed with the CFTC, states that if the index "is not scheduled to be published on the third Friday of the contract delivery month," the final settlement price "shall be scheduled for determination on the first preceding Business Day." Listed options follow the same logic, which is why the Cboe 2026 expiration calendar is the document to trust over any third-Friday formula. The collision repeats next year: NYSE's calendar lists Friday, June 18, 2027 as the observed Juneteenth holiday, so expect the June 2027 session to move to a Thursday as well, and confirm it on the exchange calendar once published.
Triple or quadruple?
You will see both names for the same session. The "quadruple" label dates from November 2002, when OneChicago began trading single-stock futures on the same quarterly schedule, adding a fourth expiring product. OneChicago ceased operations on September 18, 2020, itself a triple witching day, and no U.S. exchange has listed single-stock futures since.
Two settlement windows, not one event
The detail most explainers skip is that triple witching settles in two separate windows, and the flows around each behave differently.
The morning window: index futures and standard SPX options
Quarterly S&P 500 futures do not trade into the closing bell on expiration day. Under CME Rule 351, the final settlement price "shall be a special opening quotation of the Index" that "shall be based on opening prices of the component stocks of the Index." Standard third-Friday SPX options settle the same way. Cboe's paper describes the exercise settlement value, published under the symbol SET, as "based on the opening trade price in the primary market of each constituent stock in the S&P 500 Index."
Two consequences follow. First, per Cboe's SPX contract specifications, "Trading in SPX options will ordinarily cease on the business day (usually a Thursday) preceding the day on which the exercise-settlement value (i.e., the expiration date) is calculated, 5:00 pm ET." Thursday's close is the last exit for a standard SPX position; on Friday morning it is settled for you. Second, the SOQ is assembled from 500 separate opening prints rather than from a continuous index value, so it can sit outside the range the index ever trades at. Cboe measured this across quarterly expirations from March 2009 through March 2024 and found the SOQ "fell outside the high and low range of the S&P 500 Index" on those dates "approximately 30% of the time, most often above the daily high." Our guide to SPX versus SPY options covers the practical differences.
The afternoon window: stock and ETF options
Single-stock and ETF options, including options on SPY, are P.M.-settled and trade through the 4:00 p.m. close. The pull toward heavily trafficked strikes described in our guide to pin risk and options expiration plays out into the final hour, and in-the-money contracts convert into share positions after the close.
That close is not a single print but an auction. Per the NYSE's guide to its closing auction, 3:50 p.m. is the cutoff for market-on-close and limit-on-close orders, and from that point the exchange publishes the order imbalance "every 1 second until auction is complete," with the auction itself running at 4:00 p.m. The last ten minutes are therefore unusually transparent: the mechanical flow is broadcast before it prices.
Why the volume is mechanical
Three flows account for most of the session, and none of them is a bet on direction.
Rolls. Anyone holding quarterly futures for ongoing exposure has to move from the expiring contract to the next one. Rolls are usually executed as spreads, selling the front and buying the deferred, so they add enormous volume without adding much net pressure on price.
Dealer hedge unwinds. Every expiring option on a market maker's book carries a hedge in stock or futures. As expiration arrives, the gamma exposure tied to that open interest vanishes, and the hedges attached to it are unwound or reset. Quarterly expirations retire more open interest at once than any other session, so this flow is proportionally larger. It is also the one to be careful with: open interest tells you a contract exists, not which side the dealer is on, so the direction of the unwind is an assumption rather than an observation.
Index rebalances. Index providers deliberately schedule their quarterly changes to the same close. The Nasdaq-100 methodology makes quarterly rebalances effective "at market open on the first trading day following the third Friday in March, June, September, and December," and S&P Dow Jones Indices' March 2026 announcement had its S&P 500 changes "take effect before the market opens on Monday, March 23, as part of the quarterly rebalance." Funds tracking those benchmarks trade the changes at Friday's close, which is why triple witching closes are among the largest auctions of the year. NYSE's own data puts the record on March 20, 2026, the year's first triple witching: 3.57 billion shares matched in the closing auction for $230.5 billion, against a first-quarter daily average of 605.5 million shares and about $43 billion.
One flow that is often confused with triple witching belongs to a different date. The JPM collar and other quarter-end hedges roll on the last business day of the quarter, one to two weeks after the third Friday. Both are mechanical; they are simply not the same session.
How large it has become
The headline number each quarter is notional exposure, and it keeps setting records. Ahead of the December 19, 2025 session, CNBC reported Goldman Sachs' estimate of "more than $7.1 trillion in notional options exposure" set to expire, "including roughly $5 trillion tied to the S&P 500 index and $880 billion linked to single stocks." Six months later, Yahoo Finance reported about $8.3 trillion set to expire in the June 18, 2026 session, which it described as 18% above December's record.
Read those figures for what they are. Notional is the face value of every open contract multiplied by the underlying price. Most of it expires worthless or has already been rolled, and only the hedges behind in-the-money and near-the-money contracts actually have to trade. The number measures how much positioning is being reset, not how much stock will change hands.
What the evidence says about price
The research record explains why the morning window exists at all. Hans Stoll and Robert Whaley's 1987 study in the Financial Analysts Journal, Program Trading and Expiration-Day Effects, examined the 1984 and 1985 expirations and found last-hour volume "substantially higher than normal," with an average price effect of "about 0.4 per cent of the closing index value at expiration" across the ten most recent quarterly expirations, falling to "about 0.15 per cent" once bid-ask bounce is accounted for. Their proposed mechanism was index arbitrage: cash-settled futures forced arbitrageurs to unwind stock positions at the same close.
The exchanges responded. In June 1987 the CME, NYSE and NYFE moved settlement of their S&P 500 and NYSE index contracts from the close to the open, and Stoll and Whaley's 1991 follow-up, Expiration-Day Effects: What Has Changed?, found that the disturbance moved with it. Volume and price reversals at the close shrank, "trading volume and price reversals increased significantly" at the open, and the price effect at the open was "somewhat smaller than the price effect observed at the close" before the change. Cboe completed the same transition for all standard SPX options in 1992. The morning settlement window that catches traders out today is a direct descendant of those findings.
On the single-stock side, Ni, Pearson and Poteshman's 2005 study of stock price clustering on option expiration dates found the returns of optionable stocks altered by "an average of at least 16.5 basis points" on expiration days, attributing the effect to both hedge rebalancing by option market makers and, in their words, "stock price manipulation by firm proprietary traders." None of these papers finds a reliable direction. The measured effects are volume, volatility and clustering, not a tendency to rise or fall.
Reading the session
A few habits keep the day legible:
- Check the exchange calendar, not the formula. June 2026 moved to a Thursday; June 2027 likely will too.
- Know which contracts stop on Thursday. Standard SPX options and quarterly futures settle to the opening print. Holding them through Thursday's close means accepting a settlement value you cannot trade against.
- Treat size as mechanical until proven otherwise. Rolls, hedge unwinds and rebalance orders dominate the tape. A large print is not a signal by itself.
- Watch the 3:50 p.m. imbalance. It is the closest thing the session offers to seeing the mechanical flow before it executes.
- Weigh levels by their record, not their story. Whatever anchoring the expiring open interest exerted disappears with it. Our SPX gamma page publishes the walls with the time they were captured and the settlement open interest behind them, and no hold rate, because the record that would justify one has to be counted on the days price actually reached the level. The SPX max pain level for each listed expiration shows where the retiring open interest is concentrated before it goes.
Triple witching is scheduled plumbing: two settlement windows, three mechanical flows, and a research record explaining why the day is built this way. The volume is real and the volatility is measured, but neither has ever been a direction.
Educational content, not financial advice. See our risk disclosure.