Compulsory GST registration requires specified suppliers and e commerce operators to register irrespective of threshold. Compulsory registration is required for persons making inter State taxable supplies, casual or non resident taxable persons, persons liable under reverse charge or under sub section (5) of section 9, persons supplying on behalf of others (including agents), persons required to deduct tax at source, Input Service Distributors, electronic commerce operators and persons supplying online information and database access services from outside India to unregistered persons; the Government may notify additional classes for compulsory registration.