Revocation of registration cancellation allows late applications if outstanding returns are filed and dues paid; no further extensions. Registered persons whose registration was cancelled under clause (b) or (c) of section 29(2) and who failed to apply for revocation within section 30's time limit may apply within the notified special window only after furnishing returns up to the effective date of cancellation and paying tax along with any applicable interest, penalty and late fee; no further extension of the filing period is available. Persons whose appeals under section 107 were rejected for time bar under section 30(1) are included.