Concept and conditions of alternative performance of contractual obligations in Iranian and modern international documents

The approach of modern international documents such as DCFR, PELC, OHADA, UPICC, CISG in fulfilling the obligations is to increase the probability and chance of fulfilling the obligation by the obligor by accepting multiple obligations and the possibility of choosing one obligation by the obligee or the obligee to fulfill the obligation. In a function called the alternative performance of contractual obligations. But these multiple obligations are the same institution of voluntary obligation that has a long history in most European to Arab countries and is now emerging in new documents as an alternative performance. The alternative performance in Iranian civil is faced with the obstacle of invalidity in not determining and ambiguity of the transaction, which seems to have not been properly understood from these conditions. However, by analyzing the content and comparing it with a similar concept such as an alternative transaction and in terms of conditions such as the ability to diversity and plurality in the subject of the obligation and how to determine the authority in the implementation of the obligation can be achieved Regardless of the synchronicity of economics and law, this new look is necessary.