Article 43 establishes a special mechanism for calculating tax on certain Taxable Supplies. It permits a Registrant to charge tax based on the profit margin earned from these supplies, rather than their full value. This option is available for any Tax Period, provided the Registrant notifies the relevant Authority of their choice to use this method. The article mandates that the specific conditions and requirements for implementing this profit margin scheme are to be detailed in the Executive Regulation of the governing Decree-Law, which will outline the precise circumstances under which this alternative calculation method is permissible.