Generally a fixed place of business through which the business of an enterprise is wholly or partly carried on, including a place of management, a branch, an office, a factory or a workshop. This term usually arises in the context of double taxation treaties (www.practicallaw.com/A34913). The usual rule in a comprehensive double tax treaty is that only the country of residence can tax the profits of a trade or business, unless they arise from a permanent establishment in the other country.