Paytm's Rs 18,300-crore share sale via Initial Public Offering (IPO), the country's biggest ever, opened for subscription today. The company is planning to sell shares in the price band of Rs 2,080-2,150 per share and retail investors can bid for a minimum of one lot of six shares up to a maximum of 15 lots. At the upper price band one lot of Paytm shares will cost Rs 12,900.