Article 20 of the KSA Value Added Tax Law addresses the determination of tax periods. This provision establishes the legal mandate for the Implementing Regulations to define the specific periods for tax calculation. It explicitly delegates the authority to stipulate the associated terms and conditions to these Regulations. Consequently, taxable persons must consult the Regulations to understand their compliance obligations regarding the frequency and timing of tax calculation and subsequent filing. The article itself does not specify these periods but provides the foundational legal authority for the subordinate legislation to do so, ensuring a structured framework for tax administration.