Registration revocation applications require all outstanding returns filed; retrospective cancellations permit revocation if returns filed within 30 days. Where cancellation for non furnishing of returns has occurred, no application for revocation may be filed unless all returns due up to the date of cancellation are furnished and tax paid; if cancellation is effective from the cancellation order date, returns for the period from that date until revocation must be furnished within thirty days of the revocation order. For retrospective cancellations where the portal prevents post cancellation filing, a proviso permits revocation applications provided returns for the period from the effective cancellation date to revocation are filed within thirty days of the revocation order.