brokerage commission

Yes. Mandatory for commission income.

sub broker is providing services both to the broker and the investor on behalf of the broker, the sub broker would be duly covered within the definition of ‘agent’ as provided in Section 2(5) of the CGST Act, and needs to compulsorily register themselves under GST without the threshold exemption under Section 24(vii) of the CGST Act, 2017.

Yes it is COVERED under compulsory registration provision