CAS chaos continues on F&O expiry day: Sensex calls zoom in mere minutes amid 1,000-point swing

As per the latest business developments, The Sensex F&O expiry again turned out to be eventful on September 10 with the call options zooming multi-fold amid 1,000-point swing during Closing Auction Session (CAS).

Sensex settled 300 points elevated from day's low while Nifty reclaimed the psychologically important 23,450-mark. That stated, Sensex's high during the indicative close was 75,708 while it was 74,629 before the CAS at 3:15 pm. The 1,000-point upward spike was followed immediately by a 700-point reversal within five minutes.

Even Nifty saw massive upside during the indicative close with the index zooming from 23,389 at 3:15 pm to 23,761 at 3:21 pm.

Indicative closing marks for benchmarks Nifty 50 and BSE Sensex briefly jumped over 1% elevated during the CAS, compared with a slight loss after the end of normal trading at 3:15 pm IST.

The Nifty 50 settled 0.2% elevated at 23,477.8 and the BSE Sensex further noted 0.19% to 74,902.59.

The volatility was anticipated to be elevated in Sensex amid the expiry of its weekly derivatives contracts. CAS, introduced in early August, has amplified last-minute swings in Indian stocks, given the relatively thinner liquidity during the session.

The benchmark indexes were largely muted throughout the regular market session on Thursday.

Many X users shared screenshots of the wild swings noted in both The two key benchmark indices.

Jo kaam pura din me nifty nahi kar paaya wo ak CAS candle ne kar dikhaya 😅

Jai ho CAS ki 😐#CAS #nifty #sensex pic.twitter.com/NYXnRQxej2

— Mohit Sharma (@Mohitsharma202) September 10, 2026

PRE #CAS POST CAS PRICE #Nifty #Sensex pic.twitter.com/CXRpHG1Qus

— DARK HORSE OF EQUITY MARKET 🇮🇳 (@BeyondTrading07) September 10, 2026

1 Lot at Sensex Expiry CAS

It boosted to 400 for me double was fine👍 pic.twitter.com/ggzNE8ezdv

— Manikandan Baranikumar (@ManiBarani005) September 10, 2026

If you invested 25000 Rs in 74900 CE at 6 rs Sensex at 3:22 PM

It would become around ₹8 lakh in just 5 minutes 🚀

that's the power of sensex 🙏

That’s nearly 32X in just 5 minutes. ⚡#OptionTrading #Sensex #CASINO pic.twitter.com/usf9M9WnAD

— Shailendra Choudhary (@SheluChoudhary) September 10, 2026

Wow indian Stock 15 Se 320

end 102 #sensex #sebi #cas pic.twitter.com/2JzgNR15Zu

— Shams Ansari (@SaifansariXo) September 10, 2026

Last week, indicative close for Sensex briefly ‌dropped 2.5%, according to BSE's website. This caused premiums on some of BSE Sensex's put options to spike between 400% and 500% during closing auction.

In the meantime, Copthall Mauritius Investment Ltd and Mansi Share and Stock Broking have regained access to the broader securities market after depositing the amounts that SEBI impounded in connection with alleged manipulation of the Sensex on BSE during the CAS on August 13.

The amount was deposited on August 20, a day after the market regulator had issued the order against two entities, sources stated.

That stated, both entities keep stay barred from participating in the equity segment’s CAS, directly or indirectly, until further orders.

Copthall, a unit of JPMorgan, deposited Rs 2.96 crore, while Mansi deposited Rs 71.65 lakh. The amounts represented the alleged wrongful upside that SEBI ordered impounded in its August 19 ex-parte interim order.

The regulator's action followed its examination of trading activity during the CAS on August 13, which was additionally the weekly expiry day for Sensex derivatives. The regulator had restrained Copthall from accessing the securities market and applied the market-access restriction to Mansi’s proprietary trading account.