Article 79 of the KSA VAT Implementing Regulations establishes crucial transitional provisions for the introduction and rate modification of Value Added Tax. It outlines rules for supplies straddling the VAT implementation date, requiring additional invoices for tax due. The Article details conditions for zero-rating specific contracts entered into before 30 May 2017. It also sets initial mandatory registration deadlines (20 December 2017) and provides a temporary registration exemption until 2019 for certain businesses. Furthermore, it addresses the treatment of GCC Member States and specifies rules for the 2020 VAT rate increase.