Permanent establishment: fixed place or dependent agent activity can create tax nexus under treaty rules affecting business presence. Permanent establishment is defined as a fixed place of business through which an enterprise wholly or partly carries on business, with examples such as management offices, branches, factories, workshops, extraction sites and construction projects that exceed a specified duration. Exclusions include facilities used solely for storage, display, delivery, certain stocks, purchasing, information collection, and preparatory or auxiliary activities; a dependent agent habitually concluding contracts creates a permanent establishment unless limited to excluded activities; independent agents acting in the ordinary course do not create a permanent establishment; mere control or ownership links are not dispositive.