Permanent establishment: fixed place or dependent agent activity can create cross border tax presence under treaty rules. The text defines permanent establishment as a fixed place of business through which an enterprise's business is carried on, lists typical examples and extends PE to building sites, construction, assembly or installation projects and to service provision through personnel when activities exceed specified aggregate durations. It sets out exclusions for preparatory or auxiliary activities, while MLI modifications prevent artificial avoidance of PE status, aggregate connected activities across related enterprises, and treat dependent agents who habitually conclude contracts or secure orders as creating a PE; independent agents acting in the ordinary course do not, unless acting almost exclusively for the enterprise.