GST revocation applications require filing within thirty days and full return filing plus payment of dues before revocation. Form GST REG-21 and instructions require applicants to provide registration and cancellation details and supporting documents, and to file revocation applications within thirty days on the Common Portal. Applications for revocation are not allowed where cancellation resulted from non-filing of returns unless the outstanding returns are filed and all tax, interest, penalty and late fees are paid. Changes to authorised signatory contact details require online verification; application status is trackable and no fee is payable.