In this paper, the author describes the impact of accounting policies and estimates on the reporting system in controlling. Their impact on individual positions in the company's financial statements and their impact on the calculation of key performance indicators of the company are investigated and analyzed. The key indicators of the company today in business are the scoreboard through which the company's management monitors the success and stability of the company's operations. Today, as accounting standards become more comprehensive and demanding to apply, and many accounting valuation procedures are future-oriented and require a large number of information that needs to be processed and anticipated in order to be properly applied, they pose an increasing challenge for company management. The controller, as the person in charge of calculating and presenting key business indicators, must be continuously acquainted with the accounting policies and estimates applied by the company in order to be able to accurately and timely quantify their impact on key business indicators. The paper analyzes how different accounting policies and estimates can influence the calculation and results of key business indicators through various practical examples. Successful monitoring of the impact of various applications of accounting policies and assessments by controllers will provide the company's management with better information for timely and efficient business decisions.