About $7 trillion in U.S. options contracts reached expiration on September 18, 2026, in an event Citadel Securities ranked as the second-largest in recorded history. The newer account describes the event as triple witching, involving S&P 500 index options and individual equity options, while the existing record classified it as quadruple witching involving four derivative categories. The expiration followed the Federal Reserve's 25-basis-point rate increase to 3.75%-4.00% and coincided with a Bank of Japan policy meeting. Citadel's Scott Rubner said 60% of the volume arrived at the market open. The S&P 500 had rallied after the Fed decision, helped by a weaker U.S. Dollar Index and short covering, while positive dealer gamma positioning around SPY provided potential downside support. SPY traded near 762.70, with a gamma flip at 761.34 and options-related resistance near 765. Analysts still point to restrictive monetary policy, energy-driven inflation and September's historically weak seasonality as risks; about 75% of September triple-witching events from 2000 through 2026 were followed by lower prices five sessions later.