To implement a ERP, the companies call upon Consultancy Groups specialized for the training of the employees to the use of their future data-processing tool. This formation falls under a control of the change because the implementation of a ERP requires a major reorganization of the company. The control of the change is a fundamental stage towards a good implementation of a ERP. This is the result of an obvious lack of flexibility of the ERP which do not adapt completely to all the actors of the company in particular to the employees. This thus obliges the employees to make the effort adapt to the new tool and with the working methods what is in that is to say a disadvantage of size because the change in a company is very difficult.