Under the GST Act, any person or entity who is engaged in the supply of goods or services in India and whose turnover exceeds the threshold limit is required to register for GST. The threshold limit varies based on the type of business and the state of operation. As of 2021, the threshold limit for GST registration for businesses engaged in the supply of goods is INR 40 lakhs (INR 20 lakhs for some special category states), while for businesses engaged in the supply of services, it is INR 20 lakhs.

However, certain categories of businesses are mandatorily required to register for GST, irrespective of their turnover. These include inter-state suppliers, e-commerce operators, and businesses engaged in the supply of certain specified goods and services. It’s important to note that registration for GST is mandatory and failure to do so can result in penalties and legal consequences.