SEBI’s Closing Auction: Volatility & Manipulation Concerns

The Securities and Exchange Board of India (SEBI) is facing intense scrutiny over its recently implemented Closing Auction Session (CAS) mechanism, which critics argue has introduced significant instability into the Indian stock market. The system, intended to reduce tracking errors for global passive funds, is instead being labeled a “CASino” due to its detrimental impact.

Key issues highlighted include extreme volatility in closing prices, instances of the same stock having two different official closing prices across separate exchanges, and clear evidence of market manipulation. These problems undermine market integrity, causing concern among stakeholders.

Understanding the Market Impact

Several incidents illustrate the disruptive nature of the new CAS mechanism. Market movements during these sessions have shown unprecedented swings, affecting investor confidence.

• The Sensex experienced a fall of over 2,100 points, only to recover nearly 2,000 points within minutes during a single closing auction.
• The Nifty Bank index recorded more movement in the final five minutes of CAS than it did during the preceding six hours of continuous trading.
• Adani group shares saw a substantial ₹1.4 trillion (approximately $15 billion) decline on an MSCI rebalancing day, an event the CAS mechanism was supposedly designed to manage smoothly.

Mechanism Flaws and Manipulation Concerns

Unlike established international practices, India’s CAS operates two separate auctions across two distinct exchanges. This fragmented approach is identified as a core flaw in the system’s design.

Splitting liquidity across two platforms makes the market vulnerable to manipulation. An example cited involves a JPMorgan Chase unit’s buy orders, which reportedly exerted significant influence over the Sensex during an auction period.

Calls for Immediate Suspension and Reform

Critics are urging SEBI to immediately suspend the CAS mechanism and revert to the previous Volume Weighted Average Price (VWAP) system. They argue that the current implementation is deeply flawed and detrimental to Indian shareholders.

Recommendations for a more robust future system include building a single, unified closing auction with adequate depth, establishing clear participation thresholds, and incorporating strong safeguards. These measures are seen as essential before any such mechanism is made compulsory, ensuring market credibility is prioritized over defending a problematic implementation.