Article 79 establishes the mandatory requirement for a Taxable Person, or their authorised representative, to state the Tax Registration Number on all official communications and documents related to tax. This provision specifies that the number must be included on every Tax Return, notification, Tax Invoice, and Tax Credit Note. The obligation also extends to any other tax-related correspondence or documentation required under the provisions of the governing Decree-Law. The original referenced procedural law, Federal Law No. 7 of 2017, has since been repealed and replaced by Federal Law No. 28 of 2022, effective from 1 March 2023.