The Activity Based Costing is a modern costing system and decision support instrument most commonly used in practice. Its innovativeness consists in setting new directions for development of management accounting, so far, predominated by traditional cost accounting. The main premises behind the Activity Based Costing is focus on activity as the cost generating factor. Costs only reflect the performed activities. This means that costs are not generated by the products, but by activities necessary to produce them. Activities define the size of resources used and thereby the costs of the resources used by the cost objects (e.g. products). Measurement of the size of the used and unused production capacity and management thereof constitutes the central point of the Activity Based Costing. Thus the ABC concept identifies and establishes the size of waste of resources in enterprises and, on that basis, it can be considered as a stock management concept. The ABC enables to control individual activities and plan their size thereby ensuring better cost management in the long-term perspective.