The Securities and Exchange Board of India has comprehensively overhauled the operational framework governing the Closing Auction Session following sustained pushback from market participants. The capital market regulator initially introduced the closing auction mechanism earlier this year to ensure transparent and orderly price discovery for securities at the close of trading. However, active traders expressed sharp dissatisfaction over unpredictable price swings in benchmark indices and individual equities during the closing window. In response, the regulator reviewed public submissions from approximately 20,000 market participants across two consultation rounds before finalizing the revised guidelines. Under the updated timetable, the dedicated ten-minute closing auction session will run from 3:30 pm to 3:40 pm on all equity trading days. Continuous trading across stock and index derivative contracts will extend until 3:45 pm on regular days, whereas expiring index derivatives will halt at 3:30 pm on contract settlement dates.
During MSCI index rebalancing on August 31, 2026, closing auction turnover on the National Stock Exchange reached a historic peak of ₹39,718 crore, accounting for approximately 22 percent of total daily cash turnover.
Under the revised timings, CAS operates as a separate 10-minute session from 3:30 pm to 3:40 pm on all trading days, with the order-entry period closing randomly between 3:38 pm and 3:40 pm.
The restructured ten-minute closing auction session introduces three procedural phases to establish stable settlement benchmarks. During the opening minute from 3:30 pm to 3:31 pm, exchange systems will calculate reference prices and transfer eligible pending orders from the continuous trading book. In the final four minutes of the session, exchange engines will accept only limit orders, while existing market orders cannot be cancelled or modified.
In a pivotal structural adjustment, the regulator has restored the volume-weighted average price method for settling expiring derivatives contracts. Final settlement prices will be derived from continuous trading transactions executed during the concluding thirty minutes between 3:00 pm and 3:30 pm. For index derivatives, final settlement will reflect the weighted average of constituent shares, while stock derivatives will settle on the underlying equity price across exchanges. Stock exchanges will simultaneously publish live indicative index VWAP valuations throughout this half-hour window to maintain broad transparency. Unexecuted limit orders will migrate into the closing auction, excluding stop-loss instructions and bids placed outside permitted auction bands. Unfilled iceberg orders will convert automatically into fully disclosed limit orders within permitted bands unless traders opted out during submission. Orders carried forward from the continuous session will hold time priority over newly entered auction limit orders, though transferred iceberg orders rank below standard carried limit orders.
Stock exchanges and clearing corporations have been instructed to modify standard operating procedures in consultation with the regulator within seven days. The majority of the revised rules will take effect on December 7, 2026, while technical transitions for unexecuted limit and iceberg orders commence on February 8, 2027. SEBI Whole-Time Member KVR Murty stated that the regulator will monitor the revised mechanism for at least one year before contemplating additional revisions. Murty noted that the auction mechanism aligns with globally established market conventions and will evolve alongside domestic market requirements. Global brokerage Jefferies noted that the revised framework should reduce expiry-day volatility, supporting market participants whose order flows remained subdued. Capital market shares displayed mixed trading following the circular, with the NIFTY Capital Markets index falling 1.21 percent as BSE and Angel One declined.
