Revocation of cancellation of registration - one time application allowed, subject to furnishing outstanding returns and post revocation filings. A Removal of Difficulty Order grants a one time opportunity to apply for revocation of cancellation of registration for affected persons, subject to furnishing all outstanding returns and payment before filing the application; additionally, returns for the period from cancellation to revocation must be filed within thirty days of the revocation order. Where cancellation is retrospective and portal filing is blocked, a proviso permits filing the revocation application provided post revocation returns for the retrospective period are furnished within thirty days.