In the first two parts of this article (1 World Tax Journal 1 (2009), p. 67 and 2 World Tax Journal 1 (2010), p. 65) the author has laid out basic elements of an international world order for the taxation of business profits. Under the assumption that no general principles (ability-to-pay or benefit principle) preordain the allocation of taxing rights among countries, this framework should take into account the mechanics of tax competition among jurisdictions, as well as the internal business model of internationally active corporations. Insofar, the article pleads for a “continuity approach” which tries to avoid sudden switches of tax treatment which might prevent efficient allocation of resources within a business framework. In particular he proposes international tax allocation on a “sales and services” basis exceeding the traditional permanent establishment threshold, he compares treatment for incorporated and non-incorporated establishments and advocates equal treatment of controlling and portfolio shareholdings. Source taxation of interest and royalties may contribute to the “continuity approach” in order to keep all kinds of business income within the same tax treatment, but this is not advisable as far as tax competition goes. In this third part of the article, the choice of business organization by multinational enterprises is the object of the analysis. The starting point is the current “arm’s length vs. formulary apportionment” debate. The author pleads for an extended version of the arm’s length standard which he sees to be in line with the “continuity approach” as it interferes as little as possible with business decisions such as “make or buy”, “integrate or non-integrate” or the choice between a corporate group and a unitary enterprise. Nevertheless, while the allocation of income to the corporate entities within a multinational group should follow the contractual arrangements between the parties at arm’s length, this should not be the last word: the non-resident related party should be taxed on “synergy rents” it derives from the group structure, in particular the use of intangibles and other production factors relying on sunk specific investment. Insofar, the personal allocation of income and the territorial allocation of revenue should not automatically correspond; it is up to the source state to tax rents derived by the non-resident party as far as tax competition allows such a move.