Permanent establishment: taxable presence hinges on fixed place, agent authority, and specified functional exclusions. The provision defines permanent establishment as a fixed place of business including management, branch, office, factory, workshop, sites for extraction and construction projects subject to a duration threshold; lists exclusions for storage, display, delivery, stock maintenance, purchasing, information gathering, and preparatory or auxiliary activities; and treats as a permanent establishment an agent habitually authorized to conclude contracts on behalf of the enterprise unless the agent's activities fall within those exclusions, while ownership or control between related companies does not alone create a permanent establishment.