The Securities and Exchange Board of India (SEBI) has initiated interim proceedings against two entities, Copthall Mauritius Investment Limited and Mansi Share and Stock Broking Private Limited, citing prima facie manipulative trading during the Sensex Closing Auction Session (CAS) on August 13, 2026. The regulator has ordered the impounding of ₹3.68 crore in alleged wrongful gains and has barred both firms from accessing securities markets.
Allegations of Price Manipulation
SEBI's investigation revealed significant price movements within short durations during the CAS on the BSE Sensex weekly expiry day. Three distinct spikes in the Sensex Indicative Equilibrium Price (IEP) were observed:
- A 362.02-point rise between 15:20:41 and 15:20:43.
- A 132.67-point increase between 15:24:08 and 15:24:20.
- A 405.08-point jump between 15:25:49 and 15:26:17.
These upward movements interrupted a general downward trend in the Sensex during the session, according to the regulator.
Roles of the Entities
Copthall Mauritius Investment Limited
SEBI found that Copthall was responsible for a substantial 86.6% of the gross buy value in Sensex constituents during the CAS, totaling ₹191.29 crore in gross purchases. During the first price spike, Copthall's buy orders accounted for 99.91% of the total buy value, placing 32 limit buy orders at 3% above the reference price across all Sensex components. Similar patterns were observed in subsequent spikes, with Copthall's buy orders dominating the market. SEBI concluded that these aggressive orders likely influenced the Sensex IEP and were connected to Copthall’s outstanding long call and short put options positions.
Mansi Share and Stock Broking Private Limited
Mansi's actions were also scrutinized, with SEBI noting that the firm placed aggressive sell orders across eight Sensex constituents, aggregating 12.65 lakh shares, between 15:21:03 and 15:24:59. Approximately 7.05 lakh of these shares were placed at prices 2.5% below the reference price. All 12.65 lakh shares were subsequently canceled within a brief period between 15:26:02 and 15:26:05. The regulator believes this activity temporarily suppressed the Sensex IEP, benefiting Mansi’s expiry-day put option positions.
Wrongful Gains and Regulatory Action
SEBI has estimated prima facie wrongful gains of ₹2.96 crore for Copthall and ₹71.65 lakh for Mansi, bringing the total to ₹3.68 crore. As a result, both entities have been restrained from accessing the securities markets and are prohibited from participating in the equity CAS until further orders are issued.
The regulator emphasized the critical importance of protecting the integrity of the Closing Auction Session, as the closing price determined through this mechanism is vital for options settlement and the calculation of mutual fund Net Asset Values (NAVs). SEBI also highlighted that the new CAS framework provides enhanced capabilities for identifying potential manipulation compared to the previous Volume Weighted Average Price (VWAP) system.