Securities and Exchange Board of India (SEBI) may partly reverse its Closing Auction Session rules, as sources cited by Reuters said that the market regulator may stop CAS usage for at least a year. The report added that CAS sessions may be stopped for calculating derivatives settlement prices. FinancialExpress.com has not verified this report. We are awaiting official announcement from SEBI. What is CAS? In August, SEBI introduced the Closing Auction Session (CAS) to make the market closing price more transparent and reduce the influence of large orders placed by the end of market closing. This measure was introduced for setting the closing price of key stocks and derivatives contracts.