Registration requirement under GST: mandatory timely registration, single registration norm with prescribed exceptions and verification. Every person liable to registration must apply within thirty days, with earlier application required for casual or non resident taxable persons, and supplies from territorial waters require coastal State registration. Single registration is standard, with possible separate registrations for distinct business verticals; voluntary registration is permitted. PAN is required for eligibility, subject to specified exceptions and alternative documents for non residents. The proper officer may register non compliant persons; certain international and notified entities may receive a Unique Identity Number. Registration decisions follow prescribed verification and timelines and are deemed granted if no deficiency is communicated within the prescribed period.