Registration requirement for taxable persons: single or vertical-specific registration, PAN/TAN eligibility, and Unique Identity Number regime. Every person liable under the Act must apply for registration within a short period from becoming liable, with casual and non-resident taxable persons required to apply prior to commencement of business. A single registration is normally issued, subject to separate registrations for distinct business verticals. Eligibility requires a Permanent Account Number or, for deductors, a Tax Deduction and Collection Account Number; non-resident persons may use prescribed alternative documents. The proper officer may register non-compliant persons, and special international or notified entities may receive a Unique Identity Number. Registration is granted or deemed granted following prescribed verification and timelines and is evidenced by a certificate.