Registration requirement: timely GST registration triggers single registration rule, PAN eligibility, and Unique Identity Number provisions. Every person liable to register must apply within prescribed timeframes, with casual and non resident taxable persons requiring earlier notice; supplies from territorial waters are registered in the State nearest the baseline. A single registration is the norm, subject to separate registrations for distinct business verticals; voluntary registration is permitted. Registration eligibility requires a Permanent Account Number or, where applicable, a Tax Deduction and Collection Account Number, and non residents may use other prescribed documents. The proper officer may register defaults, certain international entities may obtain a Unique Identity Number, and registration or UIN is subject to prescribed verification and deemed grant rules.