What is a Call Auction session for illiquid stocks?

A Call Auction session is a special trading method used for illiquid stocks (stocks that meet specific illiquidity criteria specified by SEBI). Instead of continuous trading throughout the day, these stocks are traded in scheduled auction sessions. .

Why it’s done?

• To avoid price manipulation in low-volume stocks.
• To ensure fair price discovery when there are very few trades.
• To reduce volatility in illiquid stocks

How it works:

• There are six auction sessions in a trading day fo illiquid stocks
• Each session lasts one hour and is structured as follows:
• Order placement window: First 45 minutes of the session.
• Order matching window: Next 8 minutes where the system matches orders.
• Buffer period: Final ~7 minutes before the next session starts.
• Time schedule of sessions (in local market hours) is:
• Session 1: 09:30–10:15 (placement), 10:15–10:23 (matching), 10:24–10:30 (buffer)
• Session 2: 10:30–11:15 placement, 11:15–11:23 matching, 11:24–11:30 buffer
• Similarly for sessions 3, 4, 5, 6 with same pattern until ~15:30.
• During the auction, you might see bids/offers at ₹0 initially (in the “pre-market” segment) because order matching is delayed until the matching window.

👉 In short: Call Auction = batch trading system for illiquid stocks, done to ensure fair and transparent pricing.