The legal institution of operational splitting has been intensively examined by jurisprudence, literature, and tax authorities over the past decades. However, in this context, the focus has primarily been on questions of establishment and termination, as well as various configurations. Comparatively little attention has been given in the literature to the still significant question of the basis on which operational splitting rests and how its legitimacy can be derived. In cross-border cases, the fundamental issue of recognizing operational splitting is further complicated by additional cross-border peculiarities. This study aims to systematically examine operational splitting with the goal of finding a suitable justification basis that can also be applied cross-border. The significance of the justification basis of § 15 Abs. 2 EStG is the subject of investigation not only in national contexts but also in cross-border situations. The work differentiates between outbound and inbound cases. The presentation concludes with an examination of the consequences of terminating a cross-border operational splitting and in which constellations disentanglement criteria apply.