The Court of Cassation, with the sentence no. 21758/2010, specified that, during the trial period, the written form is required ad substantiam. This basic form requirement have to exist since the starting date of the employment relationship, without any chance to use other equivalent form or acts of indemnity. The parties are allowed to sign the agreement not at the same time before the execution of the contract, but the following documentation of the agreed orally provision through the signature, which was missing at the beginning, by one of the parties is not allowed, given that this will be the unlawful validation of a void act, with a substantial decrease of the employee’s tutelage.