Registration under GST is mandatory for all businesses whose annual turnover exceeds Rs 40 lakhs in a financial year. This threshold is Rs 20 lakhs for special category states such as Arunachal Pradesh, Assam, Meghalaya, Manipur, Mizoram, Nagaland, Sikkim, Tripura, Himachal Pradesh and Uttarakhand.
Compulsory registration under GST is done through the GST Common Portal. It is a web-based platform allowing businesses to register and file their tax returns. Companies can also use the portal to track their GST payments and check their refunds.