OECD member countries continue to endorse the arm’s length principle as embodied in the OECD Model Tax Convention (and in the bilateral conventions that legally bind treaty partners in this respect) and in the 1979 Report. These Guidelines focus on the application of the arm’s length principle to evaluate the transfer pricing of associated enterprises. The Guidelines are intended to help tax administrations (of both OECD member countries and non-member countries) and MNEs by indicating ways to find mutually satisfactory solutions to transfer pricing cases, thereby minimising conflict among tax administrations and between tax administrations and MNEs and avoiding costly litigation. The Guidelines analyse the methods for evaluating whether the conditions of commercial and financial relations within an MNE satisfy the arm’s length principle and discuss the practical application of those methods. They also include a discussion of global formulary apportionment.