India's National Stock Exchange (NSE) introduced a new closing auction mechanism which has led to pronounced volatility in the Nifty 50, particularly during weekly options expiry. On Monday, the Nifty 50 dropped 0.6% to 24,614.9 points by 3:35 p.m. when the closing auction window began, after being down 1.25% at 24,463.45 points at 3:15 p.m. This new 10-minute window, where institutional buy orders are concentrated, caused sharp price increases, turning seemingly worthless call options "in the money" and leading to unexpected losses for option writers.
The impact was particularly evident on Tuesday, coinciding with the weekly Nifty options expiry. Traders who believed their positions were safe at 3:15 p.m. found final settlement prices shifting dramatically during the auction, converting profits into losses or vice versa. The Nifty climbed nearly 150 points late on Tuesday, causing uncertainty for traders who previously relied on the 3:15 p.m. closing price as the expiry level. The Bombay Stock Exchange (BSE) Sensex, with lower institutional cash-market activity, has not experienced similar volatility, according to Josh Meena, head of research at Swastika Investmart.
Analysts have noted a significant divergence between the cash market and derivatives, with a synthetic August futures level calculated using Nifty call and put options at the 24,600 strike price implying a Nifty level of about 24,591.5. This was almost 183 points, or about 0.74%, below the Nifty’s official close of 24,774.30. This gap suggests that derivatives traders are not fully accepting the auction-driven price increases as a lasting repricing of the market, indicating a fault line between the cash and derivatives markets. The lack of visibility for retail investors into how prices would settle after normal trading hours remains a significant challenge.
