The Impact of Usage and Practice in Determining Sellers Obligations in Convention on Contracts for The International Sale of Goods Approved in 1980 with Comparative Study in Iranian law

The Contract of Sale as one of the most exchanged contracts requires each parties to perform The Obligations against the other Party. According to the Vienna Convention, the Seller is required to perform the Obligations against the Buyer. The question is that whether Usage is effective in determining of The Obligations of the Seller based on the Convention on the International Sale of Goods? Parties to the contract are not required to predict and specify all details of the contract, It is sufficient to reach an agreement on the elements of the subject matter of the contract and Usage and Supplementary law determine other details and the effects of contract (specifying the rights and obligations of the parties about it). Article 220 and 225 of the Civil Code confirms this claim. Usage also have an important role based on the Vienna Convention 1980, because, in the Convention on the International Sale, in addition to being, the parties are bound by any usage to which they have agreed and by any practices which they have established between themselves, are considered, unless otherwise agreed, to have impliedly made applicable to their contract or its formation a usage of which the parties knew or ought to have known and which in international trade is widely known to, and regularly observed by, parties to contracts of the type involved in the particular trade concerned. In this Research will examine the effect of Usage and Practice in determining the Obligations of the Seller. By induction under the provisions of the Convention, we get the general result that, in the assumption of the absence of an agreement on the determination of sellers obligations, according to Article 9 of the Convention, Usage and Practice will undoubtedly determine the sellers obligations.Therefore, in the absence of an agreement between the parties on the commitment to certain Usages and the lack of Practice among them regarding the Sellers obligations, if the conditions of the Usages referred to in paragraph 2 of Article 9 of the Convention exist, the seller will be obliged to comply with it. Finally, in the absence of decisive rules, the Seller is bound to fulfill its obligations, In accordance with the Supplementary Provisions of the Convention. The same situation exists in the Iranian law.