Permanent establishment defined as fixed business presence; service and agency activities can create taxable nexus under treaty. A permanent establishment is a fixed place of business through which an enterprise's business is wholly or partly carried on, with specified examples and temporal thresholds converting construction sites or service provision by personnel into a permanent establishment. Preparatory or auxiliary activities are excluded from constituting a permanent establishment. Agency rules attribute a permanent establishment where a representative habitually concludes contracts, maintains delivery stock, or secures orders, while independent agents acting in the ordinary course do not create such a nexus. Insurance collection or insuring of risks through non-independent agents creates a permanent establishment. Mere corporate control between residents does not by itself create a permanent establishment.