The focus of this diploma thesis is tax optimization and tax evasion of legal entities with emphasis on their impact on accounting and financial reporting. The first part of this thesis describes the relationship between accounting and tax, and the transformation of profit or loss from Income statement to tax base. The second chapter covers methods of tax optimization and the most used methods of tax evasion. This chapter also illustrates the role of international financial companies in tax avoidance. The third and last part of this thesis provides examples of measures used against tax evasion and accounting frauds.Diplomová práce se věnuje problematice daňové optimalizace a daňových úniků právnických osob a jejich vlivu na účetnictví a fin...