Article 7 falls within Chapter 3 of the Decree-Law, which deals with Tax Registration and Deregistration. It obliges a Registrant to apply to the Authority for Tax Deregistration where he is no longer liable for the Tax under Article 4 of the Decree-Law, the Article that identifies the Persons responsible for the Due Tax. The application must be made within the timeframe specified in the Executive Regulation of the Decree-Law. Deregistration is therefore triggered by the cessation of liability for Excise Tax, and the initiative rests with the Registrant, who must apply to the Authority rather than wait for it to act.