Who are required for registration under GST?

1. Any business whose turnover exceeds the threshold limit of Rs. 20 lakhs (Rs 10 lakhs for North Eastern and hill states) will have to register under GST. 
2. Businesses were already registered under any of the laws: VAT, Excise/Service Tax are required  to be registered under GST by default.
3. Apart from above there are few persons that have to register for GST whether  their turnover.are below 20 lakhs or 10 lakhs.the list of such persons are as follows:

• Anyone who drives inter-state supply of goods
• Casual taxable person
• Non-Resident taxable person
• Agents of a supplier
• Those paying tax under the reverse charge mechanism
• Input service distributor
• E-commerce operator or aggregator
• Person who supplies via e-commerce aggregator
• Person supplying online information and database access or retrieval services from a place outside India to a person in India, other than a registered taxable person