The relevance of the study is related to changes in legislation and the growing need for transparency of financial statements, which obliges companies to comply with accounting principles and improve the reliability of the data provided. The purpose of the study is to study the role of reserves and estimated liabilities in accounting, analyze their regulatory regulation, as well as identify the opportunities and risks of using them to manipulate financial indicators. The key accounting principles, such as the principle of prudence, as well as their impact on the formation of reserves and liabilities are considered. The features of the formation and reflection of estimated reserves and liabilities based on Russian accounting standards and tax legislation are studied. The types of reserves and methods of their application for correcting financial data, including reserves for reducing the value of assets, debts and costs, are disclosed. The advantages and possible negative consequences of using reserves in companies' reporting have been identified, including artificial reduction or increase in assets to improve investment attractiveness. The conclusion emphasizes the need for strict adherence to accounting principles to ensure transparency and reliability of financial information.