A subject of the paper is a process diagram of entering data into IT system, as a tool for improving communication process inside enterprise. Observational study as well as reports of errors and missing data, created for administrator of computer production management system, conducted under real conditions of enterprise producing machine parts, provided knowledge about quality of communication between various organizational units (departments) within the enterprise, as well as, between the IT system users, in a process of entering data into computer production management system, hence the concept of using the diagram as a tool for improving communication process inside enterprise information system. The diagram presented in the paper, with clearly defined steps, defines methodology of filling the IT system with technological, planning, manufacturing, purchasing, cooperative and controlling data, improving this way an internal communication process. The diagram presents chronologically and logically organized activities, performed in the process. It shows the process structure and relationship between its components. There are two approaches to the diagram presented in the paper: diagnostic, describing an existing and applying under the real conditions the process of entering data into the IT system, and the second one, prognostic approach, treating the diagram as a tool for shaping communication system between units (departments) in the process. Visualization the chain of actions as the diagram process, allowed to understand better the essence of the process, also subject, functional and communication dependencies occurring between the IT system, as well as it realized an importance of the communication process. Analysis of the process of information transmission between enterprise units (departments, people) in a process of entering data, led to define a model of communication system as a hybrid model, which contains features of various literature communication models.