Compulsory registration requirement: specified suppliers and intermediaries must register for GST regardless of turnover threshold. Section 24 mandates compulsory registration for specified categories regardless of turnover threshold, including inter-State suppliers, casual taxable persons, persons liable under the reverse charge mechanism, non-resident taxable persons, persons paying tax under destination-based provisions, agents supplying on behalf of others, Input Service Distributors, tax deductors, electronic commerce operators required to collect tax at source, suppliers of online information and database access services, and persons supplying online money gaming from outside India; the Government may notify further classes for mandatory registration.