New Delhi, Aug. 4 -- If you invest in index funds, exchange-traded funds (ETFs) or arbitrage funds, you need to understand a key change in stock market closing rules that came into effect from 3 August 2026.

While the market opening time remains unchanged at 9:15 AM, the closing process is no longer the same for all stocks and contracts. Earlier, all equity stocks and F&O contracts followed a common closing time of 3:30 PM, with the official closing price calculated using the volume-weighted average price (VWAP) of trades during the last 30 minutes.

Under the new system, stocks with active F&O contracts stop regular trading at 3:15 PM and move to a Closing Auction Session (CAS), where the final closing price is determined through order ...