"This study analyzes the concept of 'tax gap', which is one of the most fundamental structural problems of modern financial systems, within the framework of theoretical foundations, measurement methodologies and strategic reform areas specific to Turkey. In the work, the tax gap, which expresses the difference between tax capacity and actual collection, is discussed with an interdisciplinary approach through elements such as tax evasion, tax avoidance and informal economy. Focusing especially on current projections such as global tax management, predictive analytical methods in digital audit and green tax reform, the study offers structural solution suggestions to increase Turkey's tax revenues. It aims to fill the theoretical and empirical gap in the literature.