Under Goods and Services Tax (GST) in India, the following entities are required to register: 1. Businesses with Aggregate Turnover Above the Threshold Limit: Businesses with an aggregate turnover exceeding the prescribed threshold limit are required to register for GST. The threshold limit varies based on the type of business and the state in which the business operates. For Service Providers: The threshold limit is ₹20 lakhs for most states, and ₹10 lakhs for special category states (like Jammu & Kashmir, Himachal Pradesh, etc.). For Goods Suppliers: The threshold limit is ₹40 lakhs for most states, and ₹20 lakhs for special category states. For businesses engaged in both goods and services, the aggregate turnover limit is typically ₹40 lakhs. 2. Interstate Suppliers: Any business engaged in interstate supply of goods or services (i.e., supply across state borders) is required to register under GST, regardless of the turnover. This is to ensure the proper collection of Integrated GST (IGST) on interstate transactions. 3. E-commerce Operators and Sellers: E-commerce operators (marketplaces like Amazon, Flipkart, etc.) must register under GST. Sellers who are part of the e-commerce platform are required to register under GST if their turnover exceeds the prescribed limit or if they make interstate sales, irrespective of turnover. 4. Casual Taxable Persons: A casual taxable person is someone who occasionally conducts business in a state where they don’t have a fixed place of business. This can include temporary businesses like trade fairs, exhibitions, etc. Such persons are required to obtain GST registration even if their turnover is below the threshold limit. 5. Non-Residents: Non-resident taxable persons, who occasionally supply goods or services in India, are required to register for GST. 6. Input Service Distributors (ISD): An Input Service Distributor (ISD) is a business unit that distributes the credit of input services to other units or branches of the same business. Such units must register under GST. 7. Businesses with Voluntary Registration: Even if a business does not meet the mandatory threshold limit, it can voluntarily opt for GST registration. This allows businesses to avail of input tax credit and expand their operations. 8. Professionals and Freelancers: Professionals like doctors, lawyers, accountants, etc., need to register under GST if their aggregate turnover exceeds the prescribed limit for services (₹20 lakhs or ₹10 lakhs in special category states). 9. Specified Categories of Persons: Certain businesses, such as goods transport agencies, taxable persons engaged in the supply of specified goods (e.g., alcoholic beverages), and persons who supply through online platforms, are required to register based on specific criteria. 10. Reverse Charge Mechanism (RCM): Businesses that are liable to pay tax under the reverse charge mechanism (where the recipient, not the supplier, pays the tax) must also register under GST. Conclusion: GST registration is mandatory for businesses that meet the specified turnover thresholds, engage in interstate transactions, are e-commerce operators, or belong to other specified categories like casual taxable persons, non-resident taxable persons, and professionals. Businesses that do not fall under these categories may voluntarily register for GST.