It was common in the past for the network industry to be treated as natural monopolies. It is one of the reasons why network services providers were mainly state-owned enterprises. Until a few years ago, the industry had a structure in which the non-competitive component of the industry was vertically integrated with a potentially competitive component or activity. It is now generally accepted that the separation of activities (Eng. Unbundling) is of interest to the national economy. Unbundling of activities involves the reorganization of relations, liabilities and financial flows in a vertically integrated company. Separation of the network activities, as well as activities of natural monopolies, from the activities that can compete commercially, shall be ensured. It directly prevents conflicts of interest and the possibility of cross-subsidization in the performance of business activities and ultimately strengthens operational efficiency. In addition to the separation of activities, a fair and transparent access to the infrastructure that is essential to the development and effective action shall be ensured. The financial regulatory reports are based on the principle of accounting separation, which includes displaying the private business events in a way that shows separately costs and revenues for individual services. Accounting separation means the separation of the reports about the business infrastructure management from other parts of the integrated railway system. The regulatory financial reports shall be submitted to HAKOM until 30th of June for the previous year and shall contain the following data: Income Statement, Statement of total costs, report on the costs of the maintenance of the railway infrastructure and report on the costs of the traffic management, and the Report on the State Budget of the Republic of Croatia. One of the crucial reasons for Railway Services Market Regulation in the European Union is the need for monitoring the implementation of the principles and schemes for the calculation of fees for use of railway services. It is a multidisciplinary work that, in addition to economic analysis, includes the knowledge of technological processes and certain legal issues. By analysing the system of determining and establishing charges for the use of railway infrastructure in ten European railways, it was concluded that each of them has its own approach to the calculation of fees for access to the infrastructure containing specific respective railways, including the methodology for the calculation of the fee in the Republic of Croatia.