Given the necessity of studying the mortgage of real estste and correcting the existing procedure in society, the present paper is examining the conditional sale as one of the legitimate mechanisms for such a mortgage, which is carried out for the purpose of turning a profit (istirbāh) as well as earning lawful incomes. After giving a literal definition of "option sale"–which in our old jurisprudence literature had been used as what is today called "conditional sale"–and referring to the semantic development of this literature from option sale to conditional sale, the author brings up the methods of conceiving "conditional option" and paying back the price, and then touches upon the objections raised to this issue and goes on to present the arguments for the authenticity and admissibility of option sale. He then proceeds with a brief look at the issue of the "fulfillment sale" in the Sunnī jurisprudence to find a way to adapt these two concepts to each other, and thereby to put to judgment the impression that the conditional sale can be taken into consideration as a substitute mechanism for what is today customarily carried on as mortgage of real estate.

Civil code identifies two rules which are similar to each other in writing. Article793 states that“, The pledger cannot enter into possession of the pledge in such a way as to be contrary to the rights of the creditors, except with the latter’, s permission. And article460 states that“, In a conditional sale, the purchaser may not perform any proprietary act regard to the object of sale which conflicts with the option, such as conveyance and the like”, . Both these articles indicate prohibition of proprietary. The rule of conveyor’, s act of proprietary is ambiguous in these two articles. The ambiguity in these articles creates some questions. What are the rules of sale of the pledge and sale of the object of conditional sale? Do the differences between these two articles lead to a different rule in these two contracts? Comparing juridical and legal viewpoints regarding this issue, it can be said that despite the differences in the writing of these two articles, these articles complement each other and follow the same principle and rule. The sale of these objects is voidable and observed until lapsing another’, s right. The present investigation aims at comparing the subject of sale in relation to the pledge and the object of conditional sale regarding to juridical and legal principles in order to provide solutions to remove ambiguity existing in these two articles. Finally, the proposed articles without the foregoing ambiguous are presented.

The extinguishment of options (Khiyār) through possession is generally accepted. However, the role of possession in the extinguishment of the option condition (Khiyār al-shart) differs from other options, because the option condition varies according to its types-namely, the option condition outside the framework of conditional sale and the option condition within the framework of conditional sale. This distinction is reflected not only in the jurists’ discourse but also in Articles 450, 451, and 460 of the Civil Code. The focus of this article is on one type of option condition, namely conditional sale, with a critical comparison to Article 460 of the Civil Code. The main question of the article is: What is the role of possession in a precarious contract during conditional sale, when critically examined in light of Article 460 of the Civil Code? Using a descriptive-analytical method, this study concludes that, according to some jurists -whose reasoning is also supported by evidence- possession by the buyer of the principal item (Muthamman) and by the seller of the price (Thaman) or, in other words, possession of the transferred subject by both parties in conditional sale, does not extinguish the option. From the perspective of the Civil Code, firstly Article 460 incompletely addresses the rules related to conditional sale, since this article explicitly addresses possession only with respect to the buyer’s possession of the sold item (Mabīʿ). Secondly, contrary to the jurisprudential view that possession does not absolutely extinguish the option condition, this article considers possession that leads to transfer of ownership or similar effects as extinguishing the option and also is silent regarding possession by the seller of the transferred subject and does not provide a ruling. Therefore, by suggesting a modification and rewording the article in a different manner, we have resolved these deficiencies.

Option sale, as a special type of sales contract, provides special conditions compared to ordinary sales by creating a right of termination for the parties and uncertainty in the ownership status of the sold item, which, if used correctly, can positive impact on the economy. This type of sale allows the seller to become the owner of the sold item again by returning the price if he is not satisfied with the transaction. On the other hand, there is also the possibility of terminating the transaction for the buyer and a third party. In French law, option sale is also one of the types of special purchase and sale contracts in which the seller acquires the right to repurchase the sold item within a certain period or according to specific conditions. This allows him to potentially regain his ownership, provided that he acts to repurchase within the agreed period. Therefore, this unique feature distinguishes the option sale from other purchase and sale contracts in French law, because in it, unlike ordinary sales, the seller retains part of his ownership rights until the time of redemption. As a result, the advantages of the option sale include greater flexibility in transactions and the possibility of returning to the previous situation in the event of disagreement. In this regard, the effects of the option sale as a complex legal entity require careful analysis and examination in the Iranian and French legal systems examined in this article.

Transfer of ownership and agreement between the parties is an important legal issue that has not received much attention in the comparative context. In this dissertation, an attempt is made to examine the agreement of the parties to the contract of sale in determining the time of transfer of ownership in Iranian law, the 1980 Vienna Convention on the International Sale of Goods and European law. The present dissertation is a descriptive-analytical study using the library method. The results of the treatise indicate that the 1980 Vienna Convention on the International Sale of Goods also referred the issue of transfer of ownership to national law. It should be noted that the task of this convention is to regulate uniformity for the international sale of goods. The enactment of those regulations was therefore intended to harmonize international trade law or a modern trade law. Regarding the possibility of agreeing on the time of transfer of ownership, it should be said that the contract of sale has more customary truth than sharia truth, so it is certain that the rules and regulations related to transactions are more signature And in principle has not established a rule or ruling. On this basis, it can be said that the agreement on changing the transfer of ownership through a contract of sale is not contrary to the general instructions.

Intellectual properties are a part of immaterial financial rights which are subject to numerous bargains these days. But the lack of explicit rules and provisions in this regard, causes plenty of disagreements in the course of explanation of nature of these agreements. While it is obvious that if we could explain these kinds of trades within an agreement such as sale that its nature, provisions and effects are clear in most legal systems, a major part of these disagreements would have been solved. By analyzing the elements of definition of sale agreements according to article 338 civil code and the definitions in religious jurisprudence from the perspective of object of sale, i.e. having the characteristics of properties, capability of acquisition in addition to notion of essence of the property on one hand and fundamental qualities of ownership, the nature of intellectual properties and quiddity of the relationship between the intellectual properties and its owner on the other hand, it can be concluded that transferring these properties within sale agreement is possible and is consistent with our legal system.

Leases are primarily concluded in the form of "mortgage or rent," in today common norm. Due to some legal objections govern on this type of contract s, jurists have raised suggestions including justification for the above contract in the form of conditions provided loans or conditions of loan and deposit on the rental contract. Among the solutions proposed in this regard, there is a method has been provided by some scholars such as Ayatollah Sistani and it will be remembered as a condition of sale and lease contracts. Meanwhile, the question that arises is about the legitimacy of this contract. What are the different forms of this type of contract? Can we attribute them to the accuracy of the transaction in all given forms. The authors also explain the various assumptions discussed in this study.

Background and Aim: One of the most common ways of buying and selling, especially among businessmen, is to conclude a contract in installments and in addition, the Iranian civil law has not provided a definition of it despite including this type of sale, nor has the 1980 Vienna Convention. He did not provide a definition of an installment contract, but according to Article 73, a contract in which "the delivery of goods is staged and frequent" is considered an installment contract and this opinion has been reflected in the opinions of the arbitration authorities to some extent. Method: This research is of a theoretical type and the research method is descriptive-analytical and the method of collecting information is library-based and was done by referring to documents, books and articles. Ethical Considerations: In this research, the principles of trustworthiness, honesty, impartiality and originality of the work have been observed. Results: In addition to examining the concept and theoretical foundations of installment sales, the present research has analyzed and compared it in Iran's law and the Vienna Convention, as well as the installment sales contract of the medical contract. Conclusion: Installment sales in Iranian law have different terms and conditions than the Vienna Convention and in some cases, the actions of the Vienna Convention regarding installment sales are against the regulations and rules accepted in Iran's legal system. However, this difference does not indicate the superiority of the provisions related to installment sale in Iranian law; in the general concept of the rules related to installment sale in Iranian law, it has ambiguities and the only way to benefit from the quality of installment sale is to remove its responsibility from the banking sector; Because the banking instructions regarding installment contracts are completely inconsistent with usury-free banking operations and in this field, except for a few installment contracts, they have been completely identical to usury operations. Please cite this article as: Taghizadeh E, Soltan Ahmadi J, Ebrahimi Y. A Comparative Study of the Principles and Types of Installment Sale in Iran and the Vienna Convention 1980. Medical Law Journal. 2024; 18: e19.