Aadhaar authentication requirement for GST registration: failure or non opt triggers physical/document verification or deemed approval on nonaction. Aadhaar authentication is made the primary verification mechanism for GST registration; where applicants (other than statutorily exempt persons) fail or do not opt for Aadhaar authentication, registration requires physical verification of the business in the applicant's presence, although a proper officer-with written reasons and senior approval-may instead verify documents. The amendments set distinct timelines for officer action and provide that failure to act within those periods results in deemed approval of the registration application.