GST registration requirement: liable persons must apply within prescribed timeframe; PAN/TAN and unique identity rules govern eligibility. Registration requires liable persons to apply within prescribed periods; casual and non-resident taxable persons have earlier application timing. A single registration is standard, with optional separate registrations for distinct business verticals. Voluntary registration carries full statutory obligations. PAN is required for eligibility, with a tax deduction account number accepted where applicable and alternative documents for non-resident taxable persons. Proper officers may register defaulters, and certain notified international entities may receive a Unique Identity Number. Grant, rejection or deemed grant follow prescribed verification and timelines and a certificate of registration is issued in prescribed form.