Retail Traders Call For August 12 Trading Boycott Over New CAS Mechanism

Several retail traders on X have called for a one-day trading boycott on Wednesday, demanding that the new CAS mechanism be withdrawn. The campaign follows the first week of the new closing process, which has drawn complaints from traders over sharp moves between the 3:15 pm market price and the official closing price.
The proposed boycott is a social media-led protest and does not involve any suspension of trading by the exchanges.

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Traders Rally Around CAS Rollback Demand

Posts supporting the August 12 boycott have asked day traders to avoid taking positions during the session and, in some cases, share screenshots of their empty order books.

One trader urged others to stay out of the market to demonstrate their opposition to CAS. Other users said they would also refrain from trading on the day, arguing that a noticeable fall in market activity could bring greater attention to their demand for a rollback.

The campaign has gained visibility among retail participants who trade in the cash and derivatives segments.

New Closing Process Began On August 3

SEBI introduced CAS on August 3 for stocks eligible for futures and options trading. The move replaced the earlier 30-minute VWAP-based method used to calculate closing prices.

With CAS, orders placed during the auction are matched to arrive at the final price for the trading day. The system is intended to improve price discovery and reduce the possibility of unusual price movements near the end of the regular trading session.

The change also brings the Indian market structure closer to closing auction systems used in several other major markets.

Early Sessions Trigger Price Concerns

The rollout has produced instances in which a stock’s price around 3:15 pm differed considerably from its final official close. Such moves have drawn particular attention from derivatives traders because the official closing price is used for settlement purposes.

The difference has also raised questions among retail traders about how existing trading strategies may work under the new system, particularly for positions held close to the end of the session.

The initial response has come as exchanges and market participants adjust to the revised process.

Liquidity To Be Closely Watched

CAS relies on orders coming into the auction before the final price is established. As more participants become familiar with the process, the level of activity during the auction will determine how smoothly prices are formed.

Regulators have maintained that the mechanism is aimed at making closing prices more dependable and limiting end-of-day distortions. Retail traders opposing the change, however, are seeking a reversal of the system.

The August 12 campaign remains an informal protest organised through social media. Trading is expected to continue normally, while the market adjusts to the new closing mechanism and participants assess its impact on prices and derivatives settlements.