To be flawless of the goods is a condition that is hidden in the silence of the parties in the agreement. The seller is aware of this obligation and customer considers himself as the rightful of this obligation. In the Convention on the International Sale of Goods approved in1980, if the goods are not in accordance with the contract, the seller is obliged to repair the goods. This right is recognized in paragraph 3 of article 46 in that convention with conditions. Such a right has not been raised either in jurisprudence or in the civil law and there is a difference of opinion among jurists regarding its legitimacy. According to Article 422 of the Civil Code the buyer has only the option of obtaining compensation or a rescission of the transaction; Regarding the fact that the Civil Code is silent on the issue of performance guarantee and has not mentioned the right to oblige to repair, it should be said that the primary ruling in is the absence of such a right. It is worth mentioning that in the assumption that the goods is a unspecified, there is basically no need to identify that right for the customer, and the seller must submit the substitute product; But if the goods is certain, there is a possibility of loss. In the latter assumption, based on the rule of "The necessity to compensation of the loss", the ruling on the obligation of the seller to repair the goods is justified.