Didactic Unit 3, is devoted to subsystem accounting information in the business. Accounting is a management tool that provides information on the economic and financial situation of the company as well as the causes that have led to this situation, being therefore essential for further efficient management. The unit, which is basic and fundamental to understanding the following teaching unit is divided into four themes. In the first scenario, the concept of heritage is explained, and the masses and constituent assets (item 3.1). The second (item 3.2) is devoted to the study of the income and therefore the quantification of business income in a financial year. The following item (item 3.3) affects the accounting information system and the register of economic events as regulatory agreement and the completion of a full accounting cycle and preparation of financial statements for year end. The accounting policies in its most basic aspects is referred to in the last issue of the unit (item 3.4).