- SEBI has introduced the Closed Auction Session (CAS) as an auction-based mechanism to determine official closing prices for F&O stocks, replacing the earlier VWAP-based method.
- On August 3, 2026, the new CAS begins, ending continuous trading in F&O-eligible stocks at 3:15 pm and initiating a 20-minute Closing Auction Session from 3:15–3:35 pm to set the official close.
- During the auction window, Nifty surged about 185 points to close at 24,774.30, while Bank Nifty ended up 1.7% with a 500-point gain in the final minutes.
- Traders on X have flagged divergence between Nifty and Bank Nifty spot and futures prices, with an NSE source confirming that the displayed Nifty level was official and that some divergence was expected during the transition.
- The Closed Auction Session replaces the previous VWAP-based closing price discovery method for F&O stocks, aiming to improve price discovery and reduce end-of-day volatility.
India's new Closing Auction Session (CAS), introduced by SEBI, has sparked notable divergence in Nifty and Bank Nifty prices. On August 3, Nifty surged 185 points during the auction, closing at 24,774.30, while Bank Nifty gained 1.7% with over 500 points in the final minutes.134
The CAS, which replaces the previous volume-weighted average price method, halts continuous trading at 3:15 pm and matches buy/sell orders in a 20-minute auction to determine official closing prices. This transition has led to discrepancies, with traders noting a divergence between spot and futures prices.2
Siddhartha Khemka, head of research for wealth management at Motilal Oswal Financial Services, stated, “It appears to be a single, end-of-session price movement that has caused the divergence between the benchmarks.” A source familiar with the matter confirmed that the displayed Nifty level was the official closing level, indicating no trading glitch, but acknowledged that some divergence was expected during the transition.
The CAS aims to enhance price discovery and reduce end-of-day volatility, a shift that market participants are still adjusting to. As the market adapts, further clarifications from the NSE are anticipated regarding the observed anomalies.
“During the 20-minute auction, Nifty jumped about 185 points to close at 24,774.30, and Bank Nifty ended up 1.7%. An NSE source said the displayed level was the official close, with no glitch, and called the divergence expected during India's transition.”
