The public persons have the contractual freedom. They can choose freely tou outsource their action by resorting to contracts to mobilize the know-how and de financing which are lacking to them. The contract so constitutes a process of the public action and particularly a mode of gestion of the public utilities. The public persons are going to appreciate the opportunity of the various public contracts considering their needs and considering an optimization of the public spending and will be forced by the respect for the rules of signing and for the legal regime of execution of the contract which they will have chosen to conclude. The judge will be competent to control the legal qualification of this contract as well as the respect for the application of the rules of his legal regime. Although being a fundamental characteristic of the public contracts, the object of a contract is not any more a criterion exclusive and appropriate for every contract. An erroneous qualification of contracts with a contentious incidence can result from it. The appeal to the method of payment of the cocontracting party is going to allow to confirm the identification of the contract or to distinguish him it from the other one. Beforehand, it will be a question of demonstrating that the payment for the cocontracting party of a public person is an operational financial criterion contributing to the qualification of the public contracts