The Closing Auction Session, or CAS, met the market on August 3. Within days, traders began complaining about sharp and unfamiliar movements around the close. Questions were raised about price discovery and the interaction between the cash and derivatives markets. SEBI has made it clear there will be no rollback and has asked brokers to educate investors about the new system. A campaign by traders on social media, calling for a one-day trading boycott, demonstrates their woes.

It would be premature to describe this as an industry-wide movement. But the fact that such a campaign has emerged within days of a major market structure change deserves attention. This is not an argument against CAS; it is an argument for asking whether a potentially good reform was adequately prepared before implementation.

There is little to dispute about the objective. SEBI has argued that a closing auction can aggregate market interest, improve price discovery, provide a more transparent closing price, facilitate large institutional orders, and help passive funds reduce tracking error. It has also pointed out that closing auctions are widely used in major international markets.

These are legitimate objectives and arguments. The difficulty lies in moving from objective to implementation.

SEBI did undertake a notional consultation process, with consultation papers in 2024 and 2025, followed by protocol deliberations in its Secondary Market Advisory Committee.

But consultation should mean more than inviting comments. For a change as consequential as altering the mechanism by which closing prices are discovered, the........

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