Permanent establishment rules define when a foreign enterprise is taxable through fixed business presence and agency authority. Permanent establishment is defined as a fixed place of business including management, branch, office, factory, workshop, extraction sites, agricultural sites, and construction or assembly projects continuing beyond a specified duration. Exclusions cover facilities used solely for storage, display or delivery, stocks held for storage or processing by others, places maintained only for purchasing or information gathering, and preparatory or auxiliary advertising, information or scientific research activities. A person (other than an independent agent) who habitually has authority to conclude contracts on behalf of an enterprise creates a permanent establishment, whereas independent agents acting in the ordinary course do not unless they work almost exclusively for the enterprise.