Registration requirement: liable persons must apply for GST registration; PAN/TAN eligibility and single-registration principles govern entitlement. Persons liable to registration must apply within prescribed time and manner; casual and non-resident taxable persons have an earlier filing requirement and territorial-waters supplies follow baseline-based State registration. Registration is generally single but may be separate for distinct business verticals; voluntary registration is permitted. PAN is required for registration, with TAN accepted for deductors and alternative documents for nonresidents. The proper officer may register defaulters; notified international bodies and other notified persons may receive a Unique Identity Number. Grant, rejection, issuance, deficiency communication and deemed grant follow prescribed verification and periods.