The three countries established a Benelux Trademarks Office and a Benelux Designs Office , both situated in The Hague . In 2005 , they concluded a treaty establishing a Benelux Organisation for Intellectual Property which replaced both offices upon its entry into force on September 1 , 2006 . The Treaty between the Benelux countries establishing the Benelux Economic Union was for a period of 50 years .