A sharp and sudden movement in the Sensex during Thursday's closing session has sparked a debate among traders, with one trader claiming that a Rs 1 lakh investment in a Sensex put option could have turned into Rs 44 lakh in just five minutes.
The claim, shared on X, was based on a hypothetical trade. According to the trader, if an investor had bought Sensex 76,500 put options worth Rs 1 lakh at 3.15 pm and sold them at 3.20 pm, the position could have yielded a profit of around Rs 44 lakh. However, the original post appears to contain a typo, mentioning 3:15 AM instead of 3:15 pm.
The claim came after the Sensex witnessed an extraordinary swing during the Closing Auction Session (CAS) on the monthly derivatives expiry day.
if you have invested 1L in Sensex option
— Vibhor Varshney (@nakulvibhor) August 27, 2026
76500 PE at 3:15 AM and exited at 3:20 PM you would have made 44 lakhs
44 times in just 5 min
Power of CAS 💪🏻
According to The Economic Times, the Sensex saw a sharp late-session swing, moving from around 77,200 at 3:17 pm to about 74,983 at 3:23 pm, a move of more than 2,000 points in just a few minutes.It then recovered nearly 2,000 points in the next seven minutes, between 3.23pm and 3.30pm.
The index eventually closed at 76,934, down 539 points from Wednesday's close.
The sudden moves were not limited to the index. Reliance Industries, the stock with the highest weight in the Sensex, fell from around Rs 1,289 to Rs 1,250 in just seven minutes, before recovering sharply to close at Rs 1,286.
HDFC Bank, ITC and Bharti Airtel also saw large price movements during the closing period.
The volatility has raised questions about the impact of the new Closing Auction Session on trading near the market close. The Bombay Stock Exchange introduced CAS on August 3 as a new method for determining closing prices, with the aim of reducing the possibility of price manipulation.
The system now applies to around 200 stocks on which equity derivatives are traded. Other stocks continue to use the earlier volume-weighted average price method.
Since CAS was introduced, both the Sensex and Nifty have seen unusually large price movements between 3.15pm, just before the auction begins, and 3.30pm, when the market closes.
The latest episode has also attracted attention because of recent regulatory action. A week earlier, Sebi took action against Copthall Mauritius, a JP Morgan-linked entity, over alleged manipulation involving the Sensex and its constituent stocks. Sebi also alleged similar manipulation by Mansi Stock & Share Broking.
The regulator has barred the two entities from the market in the relevant trading activities and ordered them to give up nearly Rs 3.8 crore in alleged illegal gains.
The Rs 1 lakh to Rs 44 lakh example has therefore added to the discussion around the sharp swings. However, it is important to note that the figure is a trader's hypothetical calculation based on the price movement. It does not mean that an actual trader made Rs 44 lakh from such a trade.
