Article 160 grants taxpayers the right to object to any tax assessment, rectification, or revision within forty-five days of its service. The objection must be filed in writing to the Chairman, providing detailed reasons and claims. Failure to object within this window results in the assessment becoming final and legally binding. However, the Chairman has the discretion to accept late objections if emergent or unforeseen circumstances prevented timely filing. This provision is the first step in the Omani tax dispute process, allowing for an administrative review of the Authority's findings before escalating to higher bodies.