Permanent establishment: definition and agency rules determine when cross-border business activities create taxable presence under a treaty. The Article defines permanent establishment as a fixed place of business and lists typical forms, including management, branches, offices, workshops, sales outlets, warehouses for storage services, agricultural and extraction sites, and construction projects subject to a temporal threshold. It excludes fixed places used solely for storage, display, delivery, processing by another enterprise, purchasing, information collection or preparatory or auxiliary activities. An enterprise is deemed to have a permanent establishment where a non-independent person habitually concludes contracts on its behalf, and insurance enterprises collecting premiums or insuring local risks through non-independent agents are likewise treated as having a permanent establishment, while independent agents acting in the ordinary course of business do not create one.