Article 145 establishes the principle of aggregate assessment for foreign entities. It stipulates that if a person conducts business through more than one permanent establishment (PE) in Oman, the Tax Authority shall issue an assessment based on the combined taxable income of all such establishments. This prevents the taxpayer from cherry-picking results from individual branches and ensures that the total Omani-sourced profit of the foreign entity is subject to a single, unified tax calculation. It mirrors the filing obligation established in Article 136 for consolidated tax returns.