This chapter examines the issue of imputing liability in the context of the private enforcement of competition law. It focuses specifically on the notion of imputing liability to a legal person for the EU competition law violation committed by another legal person within the same corporate group. The chapter thus evaluates the rules that National Courts in the EU Member States must follow with respect to subsidiary liability, parental liability, and sister liability when ruling on antitrust damages actions for breaches of Article 101 or 102 TFEU. It argues that, whilst EU-level jurisprudence has recently provided some clarification on imputation in private antitrust enforcement, as well as an explicit, useful legal foundation for the analysis of the applicability of these forms of liability, an evident lack of clarity remains with respect to some key issues.