The WCO developed a set of release/clearance procedures in early 1990 to assist both Customs and trade with expediting the clearance of large number of small or negligible value goods across borders that were primarily being carried by courier and express mail services. These Guidelines operated on the principle of information being provided by the operator to Customs in advance of the arrival of the goods. The Guidelines also provided categorization of goods. It also identified a set of data that was to be provided for grant of release of goods under these categories as well as procedures to be followed, including the conclusion of MOU's between the Customs and trade for the implementation of these Guidelines and the procedures contained in them.