SEBI has introduced the Closing Auction Session (CAS) in the Equity Cash Segment to bring greater transparency and fairness in determining the closing price of securities. This new framework replaces the existing method of calculating closing prices using the VWAP of the last 30 minutes of trading.
The move aligns Indian markets with global best practices by ensuring a structured, auction-based price discovery mechanism at market close.
⏰ How CAS Will Work
- Effective Date: Applicable in a phased manner from 6 August 2026
- Initially Applicable To: Securities with active F&O contracts
- Session Timing:
3:15 PM – 3:35 PM (20 minutes, divided into structured phases)
CAS Flow at a Glance:
- Reference price calculation: 3:15 – 3:20 PM
- Order entry (Limit & Market): 3:20 – 3:25 PM
- Limit orders only: 3:25 – 3:28 PM
- Random order closure: 3:28 – 3:30 PM
- Order matching: 3:30 – 3:35 PM
The closing price will be determined through an equilibrium price mechanism, ensuring minimum unmatched orders and reduced price manipulation.
🔄 Key Highlights You Should Note
- Price Band: ±3% from reference price
- Allowed Orders: Limit & Market orders
- Not Allowed: Iceberg & Stop-loss orders
- Market Orders: Given priority over limit orders
- F&O Segment: Continues till 3:40 PM
- Settlement Price: Based on closing prices of constituents across exchanges
SEBI has also aligned the Pre-Open Auction Session framework with CAS, effective 7 September 2026, introducing similar auction logic at market opening.
📈 Why This Matters
CAS enhances:
- Accurate price discovery
- Reduced volatility at close
- Stronger investor confidence
- Better alignment between cash and derivative markets
For brokers, intermediaries, and compliance teams, this change demands process readiness, system alignment, and regulatory awareness.
Stay ahead of regulatory changes.
Our compliance experts at Complisec help you interpret, implement, and stay fully aligned with SEBI’s evolving market frameworks.
👉 Connect with us today to ensure seamless CAS readiness.
