Here, the elementary postulates and foundations of modern accounting, as an information system, are discussed in detail. All the most important accounting methods and techniques used today in business communication and financial reporting are considered. The subject is specifically focused on accounting as an information system. These methods and techniques are scientifically based, legally regulated and generally accepted through positive accounting professional regulations. The basic assumptions from which we proceed are focused on the fact that accounting can be formed as an information system at the level of business entities. Within the framework of the basic hypothesis set out in this way, accounting, as a system, has developed by following changes, adapting to socio-economic systems. As an auxiliary hypothesis, it was taken that accounting, in its essence as an information system, takes data, which it presents in the form of information through financial statements. Therefore, the accounting system has a feedback loop between data related to balance accounts and data related to profit and loss accounts. Accounting as an information system takes the account or bill as the basic functional unit of its system.