Short answer

You can trade IPO-listed stocks from 10:00 AM to 3:30 PM on their listing day. However, there is a pre-open session between 9:00 AM and 10:00 AM, during which the following activities take place:

You can place, modify, or cancel only limit orders. The system will randomly close all pending orders at any time between 9:35 AM and 9:45 AM.

Orders are executed immediately when the order entry period closes. For example, if the system closes pending orders at 9:40 AM, your order will be executed around 9:40 to 9:41 AM and will not wait until 9:45 AM for execution.

You can refer to BSE circular for more information. For more details about normal trading hours, visit the stock market timing page.