The subject of the paper presented the business organization, ie the organization of the banking system in legal transactions and the ways of management and business on the practical example of Zagrebačka banka d. d. The paper will present the basic concepts of business organization of the banking system, banking operations in legal transactions, methods of management and operation of types and divisions and the factors that affect the banking system and the practical example of Zagrebačka banka d.d. The aim of this paper is to point out the positive legislation of banking operations and its importance. The structure of business organizations is important for the operation of financial markets. Financial institutions, such as banks, are present in every aspect and way of life today and they must be in step with the times and the development of technologies. It is necessary for the business organizational bank to improve in order to satisfy both its own and the needs of its clients. The paper also presents the history of the Bank and its model of organization and operations today. In the conclusion, a review of the business organization of the banking system in Croatia and positive legislation on banking operations is presented.