How 2 cos allegedly manipulated Sensex in CAS

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Key points

• Top Trending Stocks: SBI Share Cost, Axis Bank Share Rate, HDFC Bank Share Cost, Infosys Share Rate, Wipro Share Cost, NTPC Share Rate.
• Everything seemed normal on Dalal Street as the stock market opened on Thursday, August 13.
• Explained: How a JP Morgan unit and a Mumbai-based stock broking firm allegedly manipulated Sensex during CAS.
• While Copthall's heavy purchase orders were allegedly creating enormous spikes in Sensex, another entity was heavily placing sell orders, pulling the index down.
• Sebi did not at this stage allege that Copthall and Mansi acted in concert.

Explained: How a JP Morgan unit and a Mumbai-based stock broking firm allegedly manipulated Sensex during CAS. ETMarkets.comLast Updated: Aug 20, 2026, 12: 36: 00 PM IST.

As the index's CAS closing cost moved to around 78, 080 from a 3: 15 pm reference of 77, 829.60, the regulator flagged three sharp Sensex spikes, including a 362-point jump in two seconds and a 405-point surge in 28 seconds.

Everything seemed normal on Dalal Street as the stock market opened on Thursday, August 13. Both Sensex and Nifty extended losses from the previous session even as oil rates eased, with traders bracing for some expiry-day volatility. Nevertheless, a sharp divergence emerged between the benchmark indices by the end of the session, with the market regulator raising eyebrows over unusual spikes seen in Sensex in a matter of few seconds. Sensex closed 114 points higher but Nifty concluded in the red after the closing auction session (CAS) on August 13. Abnormal spikes in the indicative equilibrium cost of Sensex during the CAS were noticed by the surveillance teams of Sebi. While the CAS-discovered closing rate stood at around 78, 080, the reference cost of Sensex was 77, 829.60 at 3.15 pm.

Notably, the market regulator in its latest order highlighted there were three sharp spikes in Sensex during the auction session. When Sensex surged 362 points from 77, 661.40 to 78, 023 in a matter of two seconds, the first spike came at around 3.20 pm. The second spike came at 3.24 pm when the benchmark index jumped 133 points. The third spike came at around 3.26 pm when Sensex rallied more than 405 points in just 28 seconds. Who was behind the sharp spikes in Sensex?

Such massive spikes in a matter of seconds must have been driven by heavy purchase orders at the fag end of the session. According to Sebi, Copthall Mauritius Investment. It is an entity owned by JPMorgan Chase, was the dominant buyer during the auction. It accounted for a whopping 86.6% of gross purchase value in Sensex constituents during CAS. But surprisingly, Copthall shortly cancelled most of its purchase orders that allegedly moved the index. Sebi remarked Copthall cancelled the highest number of purchase orders, cancelling 10.38 lakh shares out of 31.66 lakh shares ordered, or 32.79%. Live Events.

Let's break down how Copthall's purchase orders may have influenced Sensex. During the first 362 point surge that occurred at 3.20 pm, Copthall accounted for almost 100% of the overall Rs 67 crore purchase order value placed at that time. While other market participants placed orders below 2%, its 32 limit purchase orders were placed throughout all Sensex stocks at almost 3% above the reference rate. Sebi remarked this demonstrated an aggressive and index-wide cost impact. In practice, a similar pattern was observed during the second spike of 133 points at 3.24 pm, where Copthall accounted for 96% of the purchase orders. During the third spike, it accounted for 85% of the total order value. But why would Copthall place massive purchase orders that would move Sensex, only to cancel them afterwards? Sebi remarked Copthall had expiry-day Sensex option positions that would benefit from a higher Sensex closing value. It held net purchase call positions and net sell put positions at the 77, 500, 78, 000 and 78, 500 strike costs. Sebi flags manipulative trades during CAS on Sensex expiry day, fines two entities Who was placing heavy sell orders?

While Copthall's heavy purchase orders were allegedly creating enormous spikes in Sensex, another entity was heavily placing sell orders, pulling the index down. According to the market regulator, Mumbai-based Mansi Share and Stock Broking Private Limited allegedly placed sizeable sell orders at lower costs and then cancelled them. It placed sell orders worth Rs 145.65 crore between 3.21 pm and 3.26 pm throughout Sensex stocks and cancelled Rs 143.43 crore of those orders seconds afterwards. The same question arises for Mansi – why did it place such massive sell orders only to immediately cancel them? Sebi remarked Mansi had open put option positions on the expiry day, meaning that any downward movement in Sensex would have assisted those positions. Did Copthall and Mansi conspire together?

Sebi did not at this stage allege that Copthall and Mansi acted in concert. It remarked the two entities adopted opposite but aggressive price-impacting strategies during the same CAS session. Copthall's orders pushed the index up while Mansi's orders pushed it down temporarily until cancellation. The regulator calculated wrongful gains of Rs 2.96 crore for Copthall and Rs 71.64 lakh for Mansi, taking the total alleged wrongful gain to Rs 3.67 crore. Sebi barred Copthall Mauritius Investment and Mansi Share and Stock Broking from accessing the securities market and participating in the CAS, alleging the two entities manipulated the Sensex on the August 13 expiry day to benefit from their derivatives positions. Manipulation in CAS has serious market implications since the auction-discovered rate is applied for options settlement, mutual fund net asset value calculation and other market functions, the market regulator remarked in its order. It remarked such conduct, if allowed to continue, could damage fair rate discovery and harm investors who trade in derivatives or invest through mutual funds. Sebi bars two entities for 'manipulating' CAS (Disclaimer: Recommendations, suggestions, views and opinions given by the experts are their own. These do not represent the views of The Economic Times).

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For now, how 2 cos allegedly manipulated Sensex in CAS remains the part of the story worth watching, and further updates are likely as more details are confirmed.