Registration liability requires state registration when aggregate turnover crosses prescribed thresholds, with specific exemptions and mandatory categories. Suppliers must register in the State where taxable supplies are made once aggregate turnover exceeds prescribed thresholds, with lower thresholds for specified special category States; aggregate turnover includes all supplies by the taxable person but excludes job-worker supplies treated as made by the principal. Persons exclusively supplying exempt/non-taxable goods and agriculturists are not liable. Transitional registration applies to those registered under prior laws, and transferees or successors on business transfer or corporate restructuring must register. Specific categories (inter State suppliers, casual/non-resident persons, reverse charge payers, deductors/collectors, agents, input service distributors, e commerce operators, overseas online suppliers and other notified classes) must register irrespective of threshold.