Yes, you have to apply in lots in an IPO. You cannot apply for any amount you wish. Suppose the price of a share in an IPO is Rs 100. The lot size is 200 shares. So you have to apply for at least 1 lot and your application amount would be Rs 200 X 100= Rs 20,000. You cannot apply with Rs 10, 000 or Rs 15,000 or even Rs 30,000. If you want to invest more than 1 lot then you have to apply for 2 lots by paying Rs 40,000, 3 lots by paying Rs 60,000 and so on.