The methods of assessing customs in descending order are: the evaluation methods mentioned above must be used in hierarchical order. Customs assessment is the regime by which customs authorities assign a monetary value to a good or service for import or export. In general, the authorities participate in this process to protect tariff concessions, collect revenue for government authority, implement trade policies and protect public health and safety. Tariffs and the need for tariff assessment have existed for thousands of years between different cultures, with evidence of their use in the Roman Empire, the Han dynasty and the Indian subcontinent. The first registered tariff was from 136 in Palmyra, an oasis city in the Syrian desert.  Beginning at the end of the 20th century, customs assessment procedures in most parts of the world were codified in the 1994 agreement on the implementation of Article VII of the General Agreement on Tariffs and Trade (GATT).  The full text of the agreement is available on the WTO website. More information on the agreement and its application is also available on the WTO website in the Trade Topics category. The agreement gives customs authorities the right to request additional information from importers when they have reason to doubt the accuracy of the reported value of imported products. If, in spite of any additional information, the administration retains reasonable doubts, it can be considered that the customs value of the imported goods cannot be determined on the basis of the declared value and that the duty should determine the value taking into account the provisions of the agreement.  The agreement consists of four main parts, a preamble and three annexes.
Part I contains substantive rules for the valuation of goods. Part II provides for the international administration of the agreement and the settlement of disputes. Part III provides for special and differentiated treatment of developing countries and Part IV contains the so-called final provisions on issues such as the adoption and accession of the agreement, reservations and maintenance of the agreement. [Customs Assessment Rules – Corrections (complements and exclusions) of the transaction value covered by Section 1] The agreement aims to establish a uniform system that is fair, uniform and neutral for the valuation of goods imported for customs purposes, that is in accordance with commercial conditions and that prohibits the use of arbitrary or fictitious customs values.