GST registration requirement: timely application, unique identity number, PAN requirement, verification governs eligibility and issuance. Persons liable to tax must apply for registration within the prescribed period; casual and non-resident taxable persons have earlier filing requirements and territorial-water supplies link registration to the nearest baseline. Single registration is standard, with separate registrations permitted for business verticals; voluntary registration is allowed. Multiple registrations and out-of-State establishments are treated as distinct persons. A Permanent Account Number is required for eligibility, with limited substitution and alternative documents for non-residents. Proper officers may register defaulters, certain international or notified persons may obtain a Unique Identity Number, and registration is granted, rejected or deemed granted following prescribed verification.