Revocation of registration: one-time opportunity to apply, subject to filing outstanding returns and meeting portal conditions. Clarifies that applicants seeking revocation of GST registration cancelled for failure to furnish returns must first furnish returns due up to the cancellation date and pay any amounts, and that returns for the period from cancellation to revocation must be filed within a prescribed short period; where cancellation is retrospective and the portal prevents past filing, an enabling proviso allows filing of revocation applications provided all returns for the retrospective period are filed within that same short compliance period after revocation.