국내 미등록특허 사용료소득의 소득원천지국 : 대법원 2025. 9. 18. 선고 2021두59908 전원합의체 판결-반대의견의 주요논거에 관한 검토를 중심으로

The en banc decision of the Supreme Court of Korea rendered on September 18, 2025 (2021Du59908) marks an important turning point in the long-standing debate on how to determine the source country of royalty income derived from foreign patents that are not registered in Korea. By holding that royalties for patented technology that is in fact used in Korea may constitute Korean-source income, the Court departed from the approach adopted in its previous precedents. This article aims to examine the validity of the principal arguments advanced in the dissenting opinion. To this end, the article first summarizes the factual background of the case and the reasoning of the majority opinion. It then analyzes the key issues raised in the dissenting opinion, focusing on the meaning of the principle of patent territoriality, the interpretation of the concept of “use of a patent” under the Korea–U.S. tax treaty, the meaning and function of “context” under Article 2(2) of the treaty, and issues concerning the allocation of royalty income and the burden of proof. In this regard, the study also reviews the negotiation process of the U.S.–Japan tax treaty as well as the relevant domestic tax laws, administrative interpretations, and judicial precedents in order to examine whether the principle of patent territoriality should be regarded as a self-evident premise in the interpretation of tax treaties. The analysis shows that it is difficult to conclude that the Korea–U.S. tax treaty explicitly presupposes the principle of patent territoriality, and that the concept of “context” in Article 2(2) of the treaty cannot readily be interpreted as a basis for entirely excluding the application of the latter part of the proviso to subparagraph 8 of Article 93 of the former Korean Corporate Tax Act. Nevertheless, despite the change in precedent, it remains possible that the outcome of individual cases will not differ substantially in practice, due to issues relating to the allocation of royalty income between domestic and foreign sources and the burden of proof. The decision is significant in that it clarifies the debate over the determination of the source of royalty income from unregistered patents in Korea, particularly as it provides an important reference point for future treaty interpretation by engaging in a substantive discussion of the meaning and function of “context” in tax treaty interpretation.