Taxable person definition: registration, supply characterisation and input tax credit rules shape GST compliance requirements. Core definitions establish the GST regime's substantive and compliance foundations: broad business scope; aggregation rules for aggregate turnover and turnover in State; definitions of taxable supply, exempt and non taxable supply; and the concepts of input tax and input tax credit. The Act distinguishes categories of persons and registration status, and fixes territorial and establishment rules through place of supply, location of supplier, location of recipient and place of business, while supply classifications (composite, mixed, continuous) and documentary terms frame transactional treatment and compliance.