Revocation of cancellation of registration requires timely application and completion of pending returns and payment of dues to proceed. A person whose registration was cancelled may apply for revocation at the common portal within thirty days or extended time; if cancellation was for failure to furnish returns, revocation requires filing those returns and payment of tax, interest, penalty and late fee, and all returns from the cancellation effective date to revocation must be furnished within thirty days of revocation. The proper officer may revoke by FORM GST REG-22 or reject by FORM GST REG-05 after issuing a show cause notice in FORM GST REG-23 and receiving a reply in FORM GST REG-24, with specified disposal timeframes.