Aadhaar authentication required for specified GST registrant representatives, with alternate ID methods where Aadhaar is unavailable. The notification requires Aadhaar authentication for GST registration eligibility of the authorised signatory, managing and authorised partners of partnership firms, and the Karta of a Hindu undivided family; where Aadhaar is not assigned, alternate and viable means of identification specified in the rules must be offered, and the notification fixes the operative date for this requirement.