Under Section 7(1)(aa) of the CGST Act, any supply of goods or services by an unincorporated association to its members is legally treated as a taxable supply. However, mandatory registration is only required if the association's aggregate turnover exceeds the prescribed threshold limits (e.g., ₹20/40 Lakhs) or if it engages in activities requiring compulsory registration under Section 24 (such as making inter-state taxable supplies of goods).