Article 25 governs the stating of the Tax Registration Number. It requires the Taxable Person, or any other Person authorised in writing by the Taxable Person, to state the Tax Registration Number on all correspondence and dealings with the Authority, on Tax Returns, and on any document related to Tax. The obligation is drawn widely: it is not confined to returns or formal filings but extends to the whole of the Taxable Person's dealings with the Authority, and it follows the authority given in writing to any representative acting for him, ensuring that every excise document can be traced to the registered Person.