Background & Objective: Substitution of a different obligation is one of the important issues of civil rights, whose legal nature has always been the subject of debate. In this paper, an attempt is made to investigate the legal nature of entity of substitution of a different obligation in Iranian and Canadian laws.
On the other hand, it should be noted that substitution of a different obligation is a reciprocal contract. In Canadian law, the substitution of an obligation is referred to as a legal entity, and it refers to the substitution of an obligation with another obligation or the substitution of a person with a new person to create an agreement.
Conclusion: In both Iranian law and Canadian law, acceptance of the responsibility of a new obligor and acceptance of a new contract is the most important effect of the substitution of a different obligation. This means that in the case of concluding a contract of substitution of a different obligation, if this contract causes the substitution of any of the parties to the contract, the primary effect of this contract is the emergence of a new responsibility for the new obligor against the obligee, which is the result of a new contract. Therefore, the requirement for the emergence of this responsibility is the acceptance of a new contract between each of the parties to the contract and a third party.