Under the Agreement, the customs authorities can only add to the transaction value of something – other additions are not allowed: 2. Where the customs value cannot be determined in accordance with Article 1, a consultation procedure should normally be conducted between the customs administration and the importer in order to arrive at a value base in accordance with Articles 2 or 3. For example, the importer may have information on the customs value of identical or similar imported goods that are not immediately available to the customs administration of the port of importation. On the other hand, the customs administration may have information on the customs value of identical or similar imported goods which are not easily accessible to the importer. A consultation process between the two parties will allow for the exchange of information while respecting business secrecy in order to establish an appropriate basis for customs valuation. Upon written request, the importer has the right to declare in writing by the customs administration of the importing country how the customs value of the imported goods has been determined. The agreement allows the laws of importing countries to include or exclude from customs valuation: customs valuation is the process by which customs authorities assign a monetary value to a good or service for import or export purposes. In general, the authorities are involved in this process to protect tariff concessions, collect revenue for the government agency, implement trade policy, and protect public health and safety. Tariffs and the need for customs valuation have existed for thousands of years in different cultures, with evidence of their use in the Roman Empire, Han Dynasty and Indian subcontinent. The first documented tariff dates back to 136 in Palmyra, an oasis city in the Syrian desert.  Beginning in the late 20th century, customs valuation procedures used worldwide were codified in the Agreement on Implementation of Article VII of the General Agreement on Tariffs and Trade (GATT) 1994.  Recognising that customs valuation should be based on simple and fair criteria consistent with commercial practices and that valuation procedures should have general application without distinction between sources of supply; 2.
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