Over the past three decades, the European Union has presented five energy packages that laid the foundations for the creation of a European integrated energy market. The adoption of directives and regulations, which initially encouraged the liberalization of the electricity and gas markets, was necessary in order to achieve an efficient market, fair market access and secure energy supply. In addition, the EU wants to achieve greater integration of member states’ markets and protect end consumers. Since the Republic of Croatia received the status of a candidate for membership in the European Union in 2004, it undertook to restructure the internal energy market according to the requirements of the energy packages adopted until then. The Government of the Republic of Croatia, according to the directives and regulations of the EU, passes its own set of laws defining the energy market and the regulation of that market. The Act on Regulation of Energy Activities established the Croatian Energy Regulatory Agency (CERA) as an independent legal entity with public authorities for the regulation of energy activities. For the purpose of regulating the energy market, CERA issued a Decision on the procedure and method of keeping separate accounting of energy entities at the end of 2018. The decision stipulates the obligation of specific financial reporting for entities in the energy sector. Companies that operate in the energy sector and perform two or more energy activities or perform some other activity in addition to energy activity in the Republic of Croatia are required to keep business ledgers and prepare financial statements separately for each energy activity, i.e. separately from other activities if the entity also performs other activities. The Decision's guidelines include accounting policy and financial reporting based on the principles of non-discrimination of system users, prevention of distortion of market competition, avoidance of bias and the segment of mutual subsidization between different energy activities. In addition, keeping separate accounting of energy entities enables the adoption of prices, tariff items and fees in accordance with the methodology and represents the basis for the proper calculation of fees for the performance of energy activity regulation.