In this chapter, different definitions of accountancy are discussed. The broader meaning of accountancy comparing to accounting is emphasized. The difference between accountancy and accounting in an organization is deeply explained. To do this, the partial system approach is used. Accounting is defined as a part of information system with its information functions. Accountancy is discussed through tree partial systems and their connections. Some shortcomings of accounting theory are shown, especially its direction to external reporting and to mere process of accounting and neglecting its impact on socio-economic and political development. The main process of accounting (from data to information) is illustrated and deeply explained. Processes of accounting (book-keeping, forecasting, analyzing and controlling) are shown through their partial systems (operational, managerial and informational) and their connections are discussed.