Permanent establishment defined by fixed place plus MLI rules limiting preparatory exemptions and certain agent arrangements. Permanent establishment is a fixed place of business through which an enterprise's business is carried on, including management, branch, office, factory, warehouse, sales outlet, and extraction or installation sites that meet specified duration or charge-related thresholds. Preparatory or auxiliary activities (storage, display, stock maintenance, purchasing, information collection, advertising, research) are excluded, but the MLI narrows these exemptions where combined activities are not preparatory or auxiliary or where related enterprises carry on complementary functions at the same place. The MLI also treats certain agent arrangements that habitually conclude or effect contracts as creating a permanent establishment unless the agent is independent and acts in the ordinary course of business.