Sebi revises CAS rules, changes derivatives expiry settlement methodology

Capital markets regulator Sebi has revised the framework for the closing auction session in the equity cash market, including changes to trading timings, the treatment of unexecuted orders and the calculation of settlement prices for derivatives contracts.Under the revised framework, the closing auction session (CAS) will run from 3.30 pm to 3.40 pm on all trading days. The changes will take effect from December 7, 2026, except for modifications governing the transition of unexecuted limit and iceberg orders from the continuous trading session, which will come into force on February 8, 2027.Sebi introduced the closing auction session to facilitate transparent and efficient price discovery for closing prices of securities. Following its implementation, the regulator reviewed aspects of the framework and sought public comments through a consultation paper issued on September 12.The revised schedule divides the 10-minute auction into three phases.