The bidding window is the period during which investors can submit, revise or cancel their bids in an IPO. For most mainboard and SME issues it runs for three working days, from the opening date to the closing date, and bidding is open between 10:00 in the morning and 5:00 in the afternoon on most days, with the last day closing earlier for some categories. The dates are announced in the price band advertisement and the Red Herring Prospectus, and can be extended in some cases, for example when the price band is revised. During the window the exchanges publish subscription figures through the day, and you can see how many times each category has been subscribed. Retail applications made with UPI must also be approved by you in the UPI app before the window closes, otherwise the application will not be counted. Many large institutions bid only on the last day, so the day-three subscription figures often change sharply in the last hours. Once the window closes, no further bids can be placed, and the process moves on to finalising the price and the basis of allotment.
Example: An IPO opens on Monday and closes on Wednesday. You can place your bid on any of the three days, change the quantity on Tuesday, and approve the UPI mandate before the closing time on Wednesday.