Knowledge Base

Periodic call auction is a special trading mechanism where stocks trade in scheduled auction sessions instead of continuous trading throughout the day. SEBI introduced this to reduce volatility in illiquid stocks.

Which stocks move to this category?

Stocks that meet specific illiquidity criteria are moved to periodic call auction, including those with fewer than 50 average daily trades and daily trading volume below 10,000 shares.

How it works

The exchange conducts six one-hour auction sessions throughout the day, starting at 9:30 AM. Each session has three parts:

Session	Order placement	Order matching	Buffer period
1	9:30 AM – 10:15 AM	10:15 AM – 10:23 AM	10:24 AM – 10:30 AM
2	10:30 AM – 11:15 AM	11:15 AM – 11:23 AM	11:24 AM – 11:30 AM
3	11:30 AM – 12:15 PM	12:15 PM – 12:23 PM	12:24 PM – 12:30 PM
4	12:30 PM – 1:15 PM	1:15 PM – 1:23 PM	1:24 PM – 1:30 PM
5	1:30 PM – 2:15 PM	2:15 PM – 2:23 PM	2:24 PM – 2:30 PM
6	2:30 PM – 3:15 PM	3:15 PM – 3:23 PM	3:24 PM – 3:30 PM

You place your order during the first 45 minutes. The session then closes at a random point within the last minute so you can’t time the exact cutoff. After that, the system takes 8 minutes to match all orders and confirm trades. A 7-minute buffer follows before the next session starts.

You may sometimes see bids and offers showing ₹0 during the session this is normal. It happens because the system initially prices market orders at zero, similar to how the pre-market session works for regular stocks.

How to place orders

You can place, modify, and cancel orders during the 45-minute order entry window. Only limit and market orders are allowed and stop-loss, IOC, and GTT orders are not permitted for stocks in this category.

To buy or sell a stock in periodic call auction:

1. Place your order within the first 45 minutes of any session
2. Wait for order matching during the eight-minute matching window
3. Your order executes based on successful matching with other orders

If your order remains unexecuted in a session, the system automatically retries in subsequent sessions throughout the day.