Field and Aims: Although is the principle that after the renewal of the contract, the contractual Obligations are implemented, but the conditions for the implementation of a contract are not always ready and in some cases the implementation of a contract becomes impossible. This has been taken into consideration in both domestic and international regulations. Based on this, in this article, we are going to investigate what solutions are foreseen in Iranian law and international regulations in case of failure to execute the contract? Method: This research was carried out in terms of practical purpose and in terms of gathering information by documentary method and through the study of valid laws and sources, and the obtained information was analyzed in a descriptiveanalytical manner. Finding and Conclusion: Jurists and jurists have justified the nullity of a contract whose meaning is impossible to fulfill, in one of the following ways: firstly, the obligation of property, secondly, lack of taxation and the necessity of Gharrar, thirdly-consensus, fourthly-the necessity of the height of the contradictions and Fifth-It is the foundation of wisdom. Regarding the conditions for the fulfillment of the impossibility of performing the contract in Iranian law, it has been established that the defaulter is sentenced to pay damages when he cannot prove that the non-performance was due to an external cause that cannot be attributed to him. Regarding the impossibility of fulfilling Obligations, there are also provisions in the 1969 Vienna Convention. These cases include the termination and removal of the possibility of suspending the contract, the impossibility of fulfilling the Obligations under the rule of rebus, modifying or adjusting the Obligations, force majeure may also make it difficult to implement the contractual Obligations that oversee the hard slope.