Article 58 of the VAT Implementing Regulations defines the tax period for taxable persons in Saudi Arabia. It mandates a monthly tax period for taxpayers whose annual taxable supplies exceed SAR 40 million, while all other taxpayers default to a three-month period. The article outlines the procedures for taxpayers to apply for a change in their tax period, subject to specific conditions and Authority approval. For instance, a person can switch to a monthly period voluntarily, or back to a quarterly period after two years if their supplies fall below the threshold. The Authority retains the right to assign a specific tax period.