This simulation study addressed with contracting and explained the concept of simulation, its conditions and applications in contracts, also their implications from it. The problem of the study was represented in how to organize the simulation contract to preserve the rights of the contracting parties and others; the importance of the study concluded from the fact that it addresses the legal effects resulting from the existence of two contracts, one of which is simulate and apparent to others, and the other is real and hidden from others, which may shake confidence in contracts. The study aimed to define the foundations on which simulation is based, and to know the conditions that shall be met in it; to achieve the objectives of the study, questions were raised, the most prominent of which were, what is the concept of simulation in contracting and its types? and what is the claim of the invalidity of the debtor’s actions in Omani law and Algerian law? To answer these questions, scientific necessity required the adoption of the descriptive method, the analytical method, and the comparative method in preparing this thesis. Accordingly, the study reached a number of conclusions, including that the claim of non-enforcement is merely a precautionary procedures that does not rise to the level of executive means, and that it does not provide sufficient protection for creditors in the event that the debtor's funds are insufficient to fulfill his rights, and its role is limited to protecting creditors from the actions of their debtor to protect them from hurting their rights; the study also recommended a number of recommendations, including the need to limit the outbreak of simulation contracts and the resulting loss of rights, especially if those were concluded for the purpose of circumventing the law. Keywords: Paper againstsimulation, claimOther, enforcement, warrantyFraud.