On August 26, 2026, India's Nifty 50 index experienced a sudden 271.4-point (1.11%) drop to 24005.5 within 30 seconds of the closing auction session (CAS) opening at 3:20 pm. This sharp decline from its 3:15 pm reference rate of 24276.9 was caused by a large bid placed for Bharti Airtel shares at 3% below its reference price, which was then matched by a seller, dragging down the stock and consequently the Nifty. The index later recovered, closing at 24207.75, only 0.28% below the reference rate, but the event caught market participants off-guard.
This incident mirrors similar volatility seen during the debut of the CAS on August 3, 2026, which replaced the volume-weighted average price system for determining end-of-day prices for derivatives-linked stocks. The new system has faced scrutiny and calls for rollback, though the regulator has affirmed its permanence. Traders are closely monitoring the new closing auction process, which some analysts suggest creates short-term volatility that can disadvantage retail investors.
The Securities and Exchange Board of India (SEBI) has been actively enforcing regulations around the new closing auction. On August 21, 2026, SEBI took action against Copthall Mauritius Investment and Mansi Share and Stock Broking for allegedly manipulating the Sensex close on August 13. They were accused of using aggressive trading to influence the benchmark and profit from options positions, with alleged wrongful gains estimated at about Rs 3.68 crore. This enforcement action highlights SEBI's vigilance in maintaining market integrity within the new system.
