Article 39 of this Decree-Law stipulates that the value of a supply, for tax calculation purposes, shall be reduced to account for any discounts or subsidies. This provision applies to discounts granted either before or after the supply date and also includes subsidies provided to the supplier by the State for that specific supply. The value must be reduced in direct proportion to the discount or subsidy amount. The article further mandates that the specific conditions and controls for calculating the tax impact of such discounts will be detailed within the Executive Regulation of this Decree-Law.