Article 8 establishes the primary legal duty of the Principal Officer. It mandates that the Principal Officer of an establishment, Omani company, or permanent establishment is the individual personally responsible for discharging all obligations imposed on that entity under the Income Tax Law. This responsibility applies unless the Law expressly provides otherwise for specific matters. By centralising accountability, this Article facilitates enforcement and ensures that the Tax Authority can hold a specific individual liable for the entity's failure to file returns, pay taxes, or maintain required documentation.