Compulsory registration required for specified supply roles, converting inter state, reverse charge and e commerce activities into registration triggers. Compulsory registration is mandated for specified categories irrespective of the ordinary threshold: inter State suppliers, casual and non resident taxable persons, persons liable under reverse charge or other specified tax provisions, persons required to deduct tax, agents making supplies on behalf of others, Input Service Distributors, electronic commerce operators, suppliers using e commerce operators who collect tax at source, providers of online information and database access from outside India to unregistered recipients, and other classes as notified by the Government.