The paper delves into two rudimentary concepts of the EU competition law, namely single economic unit doctrine and probatio diabolica whereby the EU enforcers and court are able to impute liability to parent companies whenever subsidiaries perpetrate anticompetitive delict. This topic is elaborated with reference to the CJEU case law. Moreover, seminal Directive 1/2019 is included. A range of aspects of the single economic unit doctrine are examined in order to double check whether this incumbent concept is truly valid. The observations are carried out through the prism of legal requirement, responsive corporate governance and regulatory expectations. Thereby the public and private facets are dissected. The paper’s insights capture managers’ perspective as well. Final part provides proposals to the law or its interpretations that are addressed to lawmakers and agencies/courts as well as recommendations for the companies to ensure alignment with the current state of this fragment of competition law.