13.17. Knowledge of compilers about the HS. It is good practice for compilers to have a close dialogue with customs on implementation of the HS, and familiarize themselves with the HS so that they can review, for statistical purposes, classification assignments made by customs and assign appropriate HS codes to commodities not labelled by customs.
13.18. Measures to ensure proper classification. Goods need to be properly classified in the HS, not only in order to ensure effective revenue collection, but also for the compilation of consistent international trade statistics. The HS, when incorporated in the national tariff, becomes a national law. Correct goods classification is a legal obligation of declarants and entering wrong codes in the goods declaration may entail legal consequences. It is good practice for compilers of trade statistics to cooperate with customs administrations in efforts to provide training and assistance to declarants in the business community, and to increase their awareness regarding their obligations and the importance of properly classifying goods for policy and analytical purposes.
13.19. Training and tools for customs officers and traders. Another important means of ensuring proper goods classification is organizing training for customs officers, traders and trade statisticians in the application of the HS. It is advised that statistical offices, in cooperation with customs, develop appropriate training programmes and conduct training seminars and workshops on a regular basis. It is also advised that trade data compilers periodically undertake special studies to assess the accuracy of the classification decisions and discuss their results with customs authorities. These studies may focus on the most frequently exported or imported goods or on traders with a significant share in total country exports or imports. Also, appropriate assistance and tools for assigning the appropriate HS code should be made available to customs officers and the business community.
13.20. WCO measures to improve the quality of classification decisions. As part of the technical assistance programme of its Nomenclature and Classification Sub-Directorate, WCO periodically conducts regional training seminars to enhance the classification skills of local customs personnel. At such seminars, classification principles are reviewed and practice is provided in classifying a sample of goods. Unresolved classification questions raised during such seminars may be forwarded to the Secretariat, which prepares an answer. If the contracting party does not agree with the answer, it can ask that the matter be referred to the Harmonized System Committee for resolution. WCO has also assisted customs offices in establishing customs laboratories to which goods may be sent when technical data are required for proper classification (see para. 13.21 below). In addition, representatives of intergovernmental and other international organizations are often invited to be present at Committee meetings, where they are able to make the Committee aware of the need for new elements in the classification, of industry practices that affect classification (e.g., the use of an unusual form of measurement, or a particular means of distinguishing quality, with regard to a given commodity) and of difficulties that traders experience in classifying certain goods.
13.21. Customs laboratories. One important measure that has been helpful in assisting declarants is the establishment of customs laboratories. The technical nature of classification work often demands laboratory analysis of certain products to enable their correct HS classification. Customs laboratories are able to establish an efficient system within which samples of goods for analysis are sent to the laboratory, where prompt and relevant analyses of such samples are performed and results are expeditiously reported. The WCO has prepared a “Customs laboratory guide” to serve as a practical handbook to establish or improve customs laboratories in developing countries.
 World Customs Organization (Brussels, September 2002).