What is Closing Auction Session (CAS) ?

---

NSE has introduced a Closing Auction Session (CAS) framework in the equity cash segment for securities where derivatives are available. Alongside this, equity derivatives market timings will be extended till 3:40 PM to align with the revised closing process from 03 August 2026.

 

• Initially, CAS will apply only to cash-market securities where derivative contracts are available.
• Non-F&O securities will continue to follow the existing closing mechanism.

 

Futures & Options market timings will be extended to 3:40 PM; this is applicable for Stock & index Futures & options.

 

The closing price in the cash segment for eligible securities will now be determined through the Closing Auction Session (CAS) instead of the earlier methodology.

However, F&O closing price calculation remains unchanged and will continue based on VWAP of the last half hour (3:10 PM – 3:40 PM)

 

Order restrictions

 

• No order entry allowed between 3:15 PM and 3:20 PM (transition period).
• Market & limit orders are allowed between 3:20 PM and 3:25 PM.
• Only limit orders can be modified/cancelled from 3:25 PM till random market closure.
• IOC orders are not allowed during CAS.
• Stop-loss & disclosed quantity orders will be cancelled if ineligible

Please refer to the table below for the timings and operational guidelines effective from 3 August for CAS-listed stocks.

TIME	MARKET ACTIVITY
9:15 AM to 3:15 PM	Regular trading session.
3:15 PM to 3:20 PM	Transition Period  • No new orders can be placed during this period.  • The exchange calculates the Reference Price.  • Orders submitted before 3:15 PM cannot be modified or cancelled.
3:20 PM to 3:25 PM	Order Entry and Modification Window  • Market and Limit Orders may be placed, modified, or cancelled.  • Order prices must be within ±3% of the Reference Price.  • The ±3% price band also applies to Futures contracts.
3:25 PM to Random Close (between 3:28 PM and 3:30 PM)	Limit Order Session  • Only Limit Orders may be placed, modified, or cancelled.  • Market Orders cannot be placed, modified, or cancelled during this period.
3:30 PM to 3:35 PM	Order Matching and Closing Price Determination  • Orders are matched to determine the official closing price.  • No new orders can be entered during this session.
3:40 PM	The F&O trading session concludes.