Today, August 6, marks the first weekly Sensex expiry conducted using India’s new Closing Auction System, a move aimed at improving price discovery.
Traders have entered the session with caution rather than conviction, wary of how the new system will play out.
The session was tinged with unease after Tuesday’s Nifty expiry, when the index jumped over 150 points during the closing auction.
Another worry is the thin cash market during the auction window, which could make the final settlement price easier to influence.
Sensex call option implied volatility rose sharply ahead of expiry, signalling that traders expect more uncertainty and a possible late‑session move.
Under CAS, the exchange collects buy and sell orders during the auction window, then sets a single equilibrium price that matches the maximum number of orders.
While NSE participation has been improving, Sensex auction volumes remain much thinner, widening the gap between spot and futures prices.
Chandan Taparia, Head of Technical and Derivatives Research at Motilal Oswal, warned that low liquidity could lead to a spike, especially if aggressive bids hit the 3% limit, which equals 600‑700 points in Sensex.
Palviya added that operators could use the same tactics as high‑frequency traders, buying in the cash market and profiting from option books, as even a 0.4‑0.9% move in a heavy‑weight stock could shift Sensex by about half a percent.
Hitesh Rathi of Angel One and Hitesh Tailor of Choice Broking argue that low volumes alone do not guarantee price manipulation and that the system is already used worldwide; they expect the market to adapt and see steadier behavior once liquidity improves.
A family office official said traders will likely watch closely before committing, with most activity expected between 2.30 pm and 3.15 pm, and many will square off positions before the auction.
Despite concerns, analysts believe any volatility from CAS will be temporary as spot and futures prices converge, signalling a more efficient price discovery process.
All eyes will remain on this first expiry to see whether traders embrace the evolving market or if the new system will prove a stumbling block.