What is the difference between Mainboard IPO and SME IPO? What is the difference between Mainboard IPO and SME IPO? 58 businesses have so far listed on the exchange using the SME IPO method in 2022. Sayali Kotwal / Friday, August 26, 2022 / Article rating: 4.3 The process through which a privately held firm first sells shares to the public and becomes listed on stock exchanges is known as a Mainboard IPO (Initial Public Offer).