India’s stock markets are set for a major change with the introduction of the Closing Auction Session (CAS) for Futures and Options stocks from August 3, 2026. This new system will decide closing prices in a more transparent way and extend derivatives trading by ten minutes.
Earlier, the closing price of a stock was calculated using the volume‑weighted average price of trades during the last thirty minutes. Now, for eligible F&O stocks, continuous trading will stop at 3:15 pm. A special auction will then run until 3:35 pm. During this period, all buy and sell orders are collected and matched at a single price. That price becomes the official closing price.
The order entry will close randomly between 3:28 pm and 3:30 pm to prevent manipulation. This method is expected to improve price discovery and reduce volatility.
At the same time, equity derivatives trading will continue for ten minutes longer, ending at 3:40 pm instead of 3:30 pm. Non‑F&O stocks will still follow the old system, trading until 3:30 pm with closing prices based on average trades.
The Securities and Exchange Board of India believes these reforms will make markets more efficient and fairer. Investors and traders must now adjust to different closing times across segments, ensuring they remain alert to the new schedule.
