A bid-lot is the predetermined number of shares that have to be applied for by an investor. It is different for each issue. There is a minimum lot size that is pre-decided by the company and mentioned in the application form. Eg: Suppose minimum bid lot in IPO of XYZ co. is 10 or multiples of 10, and Price Band is 100-120. It means that a retail investor cannot apply for less than 10 shares in that particular issue. The application for more than 10 shares has to be in multiples of 10 like 20, 30, 40, etc.