NSE New Rule From Today: Closing Auction Session Begins for F&O Stocks; Check New Closing Price Rules

From August 3, however, the process changes for F&O stocks. These shares will now trade normally only until 3:15 pm. After that, they will enter the newly introduced Closing Auction Session, which will continue until 3:35 pm. During this period, investors can place buy and sell orders, and the exchange will use these orders to determine a single official closing price.

How New NSE CAS System Will Work

The Closing Auction Session works differently from normal trading. Instead of orders being matched instantly throughout the session, the exchange collects all buy and sell orders submitted during the auction window. It then identifies one price at which the maximum number of shares can be traded. That price becomes the stock's official closing price for the day.

This means the closing price will no longer depend on the average of trades made during the final 30 minutes. Instead, it will reflect the point where buying and selling interest is best matched at the end of the trading session.

The closing price is much more than the final traded value of a stock. It serves as the benchmark for calculating daily gains and losses and is widely used by mutual funds, exchange-traded funds (ETFs), institutional investors and index providers while valuing portfolios and calculating benchmark indices.

A more reliable closing price helps ensure that investment portfolios, index values and fund performances reflect actual market conditions more accurately.

Changes in Stock Market Timings from Today

Although the market opening time remains unchanged, investors should be aware of the revised closing schedule. Continuous trading for F&O stocks will now end at 3:15 pm, followed by the Closing Auction Session until 3:35 pm. Stocks outside the F&O segment will continue trading normally until 3:30 pm, while stock and index derivatives will remain open until 3:40 pm.

As a result, different segments of the market will now have different closing times. The new framework also changes auto square-off timings for intraday traders using MIS (Margin Intraday Square-off) facilities.

For stocks covered under the Closing Auction Session, intraday positions will now be automatically squared off at 3:10 pm. For stocks outside the CAS framework, the auto square-off time will remain 3:20 pm. Meanwhile, stock and index Futures & Options positions will now be squared off automatically at 3:25 pm.

Traders who rely on intraday leverage should keep these revised timings in mind to avoid unexpected position closures before the end of the trading session.

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