Financial accounting measures an enterprise's performance, but it does not show how this performance was realized. To support it, managerial accounting proposes to managers decision-making models relying on the theory elaborated by Simon. So, the accounting decision represents the process of rational choice of a line of action out of several possible, starting from real, clear, complete and relevant accounting information, on the one hand, and from previsions built based on it in order to obtain a maximum effect (performance) with a minimum effort (cost).
Decision making implies the asking of questions such as "What if...?" in which the kew word is relevance. The costs used in the decision-making process need to be made up only out of relevant costs. In this sense, a relevant
cost is: a future cost, which is going to be changed by a decision; an alternative cost, with influence on the issue of the choice of the adequate cost for a certain decision (Radu, 2010).
Relevant costs are studied in correlation to other categories of costs, and one will consider relevant only the variable and marginal costs. These costs need to be carefully analyzed as, under certain circumstances (initiation of a new project, determination of hourly tariff), they lose their relevance.
The costs'relevance is usually analyzed and identified on different resource structures accounting to table