Article 73 mandates that each GCC Member State must implement local transitional provisions to manage the introduction of VAT. It establishes that tax becomes due on supplies and imports from the effective date of the local law. States are required to define registration timelines for persons obliged to register at inception. A key provision allows Member States to disregard the date of an invoice or payment if it precedes the VAT implementation or registration date, treating the actual date of supply as the tax due date. This principle extends to Intra-GCC supplies. For continuous supplies, VAT is not levied on the portion of the supply completed before the law's effective date or the supplier's registration.