ZATCA’s economic-activity guideline links VAT registration thresholds, ISIC-style activity codes, input VAT recovery, invoicing, and return filing obligations for taxable persons in Saudi Arabia. Controllers use it when onboarding new CR activities on Meras, enabling FATOORA e-invoicing, and mapping ERP tax codes. Verify Arabic circulars and portal messages before registration or deregistration because thresholds and exceptions change.