Permanent establishment: fixed-place, agency and activity-based tests determine when an enterprise is treated as having taxable presence under the treaty. Permanent establishment is a fixed place of business through which an enterprise's business is wholly or partly carried on, including management, branch, office, factory, workshop, sales outlet, warehouse for others, agricultural sites and resource extraction points; construction or assembly projects qualify only after a sustained duration. Exclusions cover facilities used solely for storage, display, delivery, purchasing, information collection or other preparatory or auxiliary activities. A non-independent agent habitually concluding contracts, maintaining delivery stock, or securing orders can create a permanent establishment, as can insurance activities conducted through non-independent persons; independent agents acting in their ordinary course do not.