CLOSING AUCTION SESSION
We imported the auction, but we left out the brakes
India’s Closing Auction Session (CAS) was introduced to improve price discovery, but recent sharp swings have exposed gaps in its safeguards. Jimeet Modi argues that allowing order cancellations until the auction ends can leave markets vulnerable to manipulation, calling for stronger controls, deeper liquidity and better protection around index-level settlement prices.
Indian bank stocks show widest exchange price gap in decades
Indian bank stocks saw unusually wide price gaps between the NSE and BSE during Thursday’s closing auction, with IndusInd Bank recording its widest exchange price difference in more than two decades. The divergence has intensified scrutiny of the new auction system amid thin liquidity, monthly expiry pressures and concerns over market manipulation.
No room for CASual volatility
The recent Closing Auction Session has led to dramatic swings in the market, resulting in major losses for investors. While the intention behind the new system was to enhance mutual fund assessments, it has instead spiraled into chaos. Regulators have taken action against those found manipulating the session and acknowledged systemic flaws, emphasizing the need for a robust securities lending framework to stabilize future sessions.
Was Sensex’s 2,000-point expiry crash a one-off? Here's what Friday's close hints about CAS
Sensex stayed relatively calm during Friday’s closing auction, a day after a 2,000-point plunge during the monthly expiry raised fresh concerns over CAS. The subdued move suggests Thursday’s sharp swings may have been an expiry-driven anomaly rather than a persistent issue with the new closing-price mechanism, experts said.
Sensex rises 330 points, Nifty closes above 24,150 as IT rally helps market snap 2-day losing streak. What’s ahead?
Indian markets rebounded on Friday after two sessions of losses, with Sensex rising 331 points and Nifty gaining 85 points. Heavyweight IT stocks TCS, Infosys, Tech Mahindra and HCL Technologies led the rally. Nifty IT surged 3.5%, while broader markets advanced and India VIX fell over 4%, signalling easing volatility.
CAS chaos: How did Sensex crash 2,000 points in 6 minutes while Nifty stayed stable on monthly expiry?
Sensex plunged over 2,000 points during Thursday’s closing auction session before recovering some losses, while Nifty remained comparatively stable. Market experts attributed the sharp divergence largely to thin trading volumes on BSE. The episode has renewed scrutiny of the new CAS mechanism, particularly around monthly expiry and its impact on price discovery.
4,000% options surge in 15 mins highlights India’s wild closing auction system
India’s new closing-auction system is triggering extreme volatility in the options market, with prices swinging sharply within minutes. During the first monthly expiry under the new system at BSE, a Bankex put option surged nearly 4,000% from Rs 1.70 to Rs 68.55 before crashing to zero, all within 15 minutes, highlighting the risks of compressed end-of-day trading.
Bankex put sees a dramatic surge of 14,700% on expiry day
Bankex options saw a significant surge during Thursday's expiry session. This unusual spike occurred within minutes, causing considerable trader reaction. Indicative closing levels briefly showed a steeper Sensex decline than expected. Several Bankex put options experienced sharp premium jumps, impacting sellers. The Sensex and Bankex closed lower, while Nifty and Bank Nifty saw smaller declines.
Sebi chief Tuhin Kanta Pandey clarifies on CAS changes after big Sensex expiry-day swing
Sebi Chairman Tuhin Kanta Pandey said the regulator has no plans to change the Closing Auction Session despite sharp expiry-day swings. Sebi expects participation and understanding to improve, while monitoring liquidity concerns and alleged manipulation. NSE IPO approval is also nearing.
Monthly Expiry shock: Did CAS fail its biggest test after Sensex loses 2,000 points in 6 minutes?
The Sensex witnessed a sharp late-session swing of over 2,000 points in six minutes on Thursday, raising fresh questions about the Closing Auction Session (CAS) on its first monthly derivatives expiry. The Nifty also ended lower as thin auction-window liquidity amplified volatility and drew renewed regulatory scrutiny.
Sensex sharply tumbles 500 points on first monthly expiry after CAS, Nifty closes below 24,100. What lies ahead?
Indian equities fell sharply on Thursday, erasing gains during the first monthly expiry under the new closing auction session. Sensex dropped 539 points, or 0.7%, while Nifty declined 117 points, or 0.48%. HDFC Bank and NTPC led losses, while Kotak Mahindra Bank, ICICI Bank and Tech Mahindra gained.
Ahead of Market: 10 things that will decide stock market action on Wednesday
Sensex and Nifty reversed morning losses to close higher on Tuesday, amid sharp volatility on the first expiry day after the closing auction session launch. Healthcare and financial stocks gained, while broader market breadth remained mixed and cautious.
Sensex rises 287 points, Nifty closes above 24,300 as market swings into green on first monthly expiry after CAS
The Indian stock market ended higher on Tuesday after a volatile session, with Sensex gaining 287 points and Nifty rising 115 points. Pharma, PSU banks and consumer durables led sectoral gains, while private banks and metals declined. IndiGo, Adani Ports, Infosys and Trent gained, while Eternal and HCLTech fell.
Closing Auction System braces for its first monthly expiry test
India’s derivatives market is set for its first monthly expiry under the new auction-based closing price system, marking a crucial test for the mechanism after concerns over sharp price swings and alleged manipulation. Introduced on August 3, the system has so far handled regular sessions and a weekly expiry. Tuesday’s monthly expiry will bring stock futures and options into play.
CAS chaos triggers liquidity spiral: Nuvama says higher participation needed to break cycle
BSE’s new Closing Auction Session has faced weak participation, with Nuvama reporting sharp declines in option premium volumes and contracts. Thin liquidity is creating a self-reinforcing cycle, while early confusion, retail concerns and alleged CAS manipulation have further intensified scrutiny of the new closing-price mechanism.
Rs 30,000 cr loss in 3 months: Why BSE stock is failing investors and should you buy now?
The BSE stock has witnessed a pronounced decrease in market value recently, attributed to the introduction of new auction regulations and diminished option trading activity. Additionally, the stricter bank guarantee requirements for brokers have raised alarm among investors. As a result, analysts have revised down their earnings expectations and stock projections, posing challenges for the exchange in maintaining its present valuation.
Sebi flags manipulative trades during CAS on Sensex expiry day, fines two entities
Sebi issued an interim order against Copthall Mauritius and Mansi Share and Stock Broking for manipulative trading during the August 13, 2026, Closing Auction Session. The regulator impounded Rs 3.67 crore in alleged wrongful gains from these two entities.
Getting used to CAS for auction delivery
Sebi's new closing auction session will determine stock prices. This new method improves price discovery and reduces manipulation risks. Options traders accustomed to old methods are experiencing initial friction. The regulator is open to feedback for fine-tuning the system. This new mechanism is intended to promote market stability and efficiency.
Sebi chief Tuhin Kanta Pandey says CAS here to stay, will study concerns over rollout
Sebi Chairman Tuhin Kanta Pandey says the closing auction session (CAS) is here to stay, even as the regulator reviews concerns over its implementation. Launched on August 3, CAS has triggered sharp moves in the final minutes of trading and raised concerns over legacy systems, order placement and derivative positions. While Sebi has found no evidence of manipulation, Bernstein expects near-term pressure on index-options volumes.
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