Every type of business activity must allow for a certain kind of uncertainty stemming from a variety of external and internal factors. Therefore, it is necessary to analyse the impact of the environment and all decisions with regard to the financial result. Proper planning makes it possible to make decisions which are rational from the standpoint of the company's profitability. On the one hand, it enables one to determine what resources an entrepreneur can use to put their projects into practice, at the same time providing information on the likely cost of these projects. On the other hand, it makes it possible to verify how possible decisions may impact the financial result.