GST Registration is mandatory for every business or corporation involved in buying and selling of goods or services. Those with an annual turnover of more than 20 lakh rupees for supply of services and 40 lakh rupees in case of supply of goods is the threshold limit. If a business is carried on without registering under GST, then it will be an offence under GST law. A casual taxable person/Non-Resident Taxable Person, e-commerce aggregator, agents of supplier and input service distributor etc. are required to register under GST.
https://taxring.com/service/gst-registration