GST registration rules require registration for inter state supplies and significant turnover, shaping reverse charge and registration obligations. Registration is mandatory for inter State suppliers and persons exceeding turnover thresholds; aggregate turnover excludes inward supplies taxed under reverse charge but includes outward supplies where the recipient pays tax. Provisional GSTINs require conversion to final within ninety days. Suppliers exclusively making exempt supplies need not register. Reverse charge liabilities are to be discharged by recipients with self invoicing and reporting in returns; de minimis relief applies for small daily receipts from unregistered suppliers. ITC is subject to STATE specific utilization rules, transition credit is available for duty paid closing stock under prescribed conditions, and SEZ supplies are zero rated.