The author has taken an in-depth look at the notion of associated enterprises at both the tax treaty and domestic level. The function of Article 9 of the OECD Model Convention can only be effectively used, if its definition of associated enterprises is consistent with the domestic definitions of this, or a comparable, concept. The conclusion of the author is that there are remarkable differences in the domestic definitions of this concept. A worthwhile finding is also that a mismatch between the domestic concept and the one used in Article 9 of the OECD Model Convention may lead to unresolved economic double taxation.