Existing studies have relied on the notion of developmentalism to explain key aspects of the tax policies in Japan and Korea. However, limited efforts have been made to explore these cases from a comparative perspective based on relevant evidence. Far fewer studies have been conducted for examining the contemporary evolution of the tax policies following major reforms since the 1990s. This article seeks to fill these gaps in the research. Employing an analytic framework of tax structure, it provides key definitions of the old and new tax models in Japan and Korea in a way that is comparable with other OECD cases. “Residualism” and “constrained activism,” two heuristic models drawn from low-tax OECD countries, provide useful references for this comparative task. To validate key assessments, the author utilizes and replicates extensive tax data that operationalize important aspects of the tax structure from the 1980s to 2018.