The End of 3:30 PM Volatility, Closing Auction Session (CAS)
The End of 3:30 PM Volatility: How SEBI’s New Closing Auction Session (CAS) Stabilizes Your Portfolio The Securities and Exchange Board of India (SEBI) has fundamentally altered how the Indian equity market discovers its official closing prices. Effective August 3, 2026, the Closing Auction Session (CAS) replaced continuous trading during the final minutes of the day with a pooled, auction-based matching system for eligible Futures & Options (F&O) stocks. For retail investors focused on mutual funds and long-term asset allocation, this structural upgrade minimizes end-of-day price manipulation and ensures that your daily portfolio valuation reflects true market equilibrium. Here is a technical, step-by-step breakdown of how CAS operates, why it was introduced, and how it impacts your wealth creation journey at NUMMUS PROSPERITY LLP. Old Mechanism vs. New CAS Framework To appreciate the upgrade, we must compare the outgoing calculation methodology with the newly implemented auc...