조세소송의 소송물 ―흡수설과 병존설의 대립을 중심으로―

This study aims to critically analyze the Supreme Court's stance, which has adhered to the absorption theory regarding the relationship between the initial disposition (report) and the increased disposition, and to clarify whether the absorption theory can still function as a litigation theory under the current tax litigation structure. If not, it aims to identify a theory that provides more consistent logic while conforming to the reality of tax litigation. In this study, we first examine the general theory of litigation and tax litigation, and considering that various theories have been proposed regarding this issue, we comparatively analyze those theories. We also employ interpretation of the current legal system and comparative legal analysis to examine the superiority of the theory and its applicability in litigation practice. The absorption theory upheld by the Supreme Court has lost its function as a consistent theory due to the recognition of too many exceptions to avoid conflicts with current laws and existing Supreme Court rulings. Considering theoretical consistency, simplicity of tax litigation relations, and the relationship with general administrative theory, the coexistence theory is superior to the absorption theory. If preclusive effect arises for the initial disposition or the initial report, the absorption theory may be less protective of taxpayers' rights than the coexistence theory. However, this problem can be sufficiently overcome by recognizing the 'setoff defense' within the scope of the increased correction, as in U.S. case law. This study suggests that the Supreme Court's stance of adopting the absorption theory regarding the relationship between the initial disposition or initial report and the increased correction needs to change. By adopting the coexistence theory, a more consistent theory and operation of tax litigation can be achieved for this issue.