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            Under Article 50 of the CISG, if the seller delivers a good that does not conform with the contract, the buyer may reduce the price in the same proportion as the value that the goods actually delivered had at the time of the delivery bears to the value that conforming goods would have had at that time. In this case, the buyer acts unilaterally and is not subject to his/her resort to the court and substantiating the lack of conformation before it, although, in any case, the convention provides remedy for the buyer resorting to an undue option. In some cases, in Imamia Jurisprudence and Iran Law, as where there is the claim for some portion of the object of sale belonging to the other and the buyer may be able based on option in sales unfulfilled in part to get some portion of the price and, in some places due to defect in the object of the sale, may cancel the sale or keep it at the price of getting compensation; they all can be legally considered as instances of price reduction. This paper attempts to compare the instances of price reduction in the 1890 Convention, Imamia Jurisprudence and Iran Law, and while putting the concept of price reduction in the Convention, examines its similarities and differences with the ones in Imamia Jurisprudence and Iran Law. In the end, it is discussed whether this option can be possibly applied as a rule in other transactions or not.      

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The "caveat emptor" rule, which has been introduced as one of the basic rules of contract law of traditional common law, does not hold the seller liable for defects in the goods or non-compliance with the terms of the contract, and holds the buyer responsible for inspecting the transaction. On the other hand, Islamic law considers the buyer to be entitled in such positions and gives him the option of defect or the option of incorrect description or the option of unfulfilled condition and the like.
In recent decades, with the emergence of many problems in implementing the "caveat emptor" and considering the violation of buyers' rights if this rule is applied, we face the emergence of the opposite rule called the "Caveat venditor" rule, which seeks to amend the previous rule and the main area of emergence That is the rules governing consumer rights.
In this article, while comparatively studying the institution of "caveat emptor" and similar Institution in Iranian law, we seek to explain the strengths of each of the two establishments and offer a correction proposal to correct the weaknesses of domestic law. However, in general, we will see that what has been achieved nowadays in the common law system, was explained concurrent with the formation of the independent legal system of Islam in the time of the Holy Prophet.