Like the methods described in §§ 1.482-3, 1.482-4, 1.482-5, and 1.482-9, the comparable profit split relies exclusively on external market benchmarks. As indicated in § 1.482-1(c)(2)(i), as the degree of comparability between the controlled and uncontrolled transactions increases, the relative weight accorded the analysis under this method will increase. In addition, the reliability of the analysis under this method may be enhanced by the fact that all parties to the controlled transaction are evaluated under the comparable profit split. However, the reliability of the results of an analysis based on information from all parties to a transaction is affected by the reliability of the data and the assumptions pertaining to each party to the controlled transaction. Thus, if the data and assumptions are significantly more reliable with respect to one of the parties than with respect to the others, a different method, focusing solely on the results of that party, may yield more reliable results ...

The reliability of the results derived from the comparable profit split is affected by the quality of the data and assumptions used to apply this method. In particular, the following factors must be considered – (1) The reliability of the allocation of costs, income, and assets between the relevant business activity and the participants’ other activities will affect the accuracy of the determination of combined operating profit and its allocation among the participants. If it is not possible to allocate costs, income, and assets directly based on factual relationships, a reasonable allocation formula may be used. To the extent direct allocations are not made, the reliability of the results derived from the application of this method is reduced relative to the results of a method that requires fewer allocations of costs, income, and assets. Similarly, the reliability of the results derived from the application of this method is affected by the extent to which it is possible to apply the method to the parties’ financial data that is related solely to the controlled transactions. For example, if the relevant business activity is the assembly of components purchased from both controlled and uncontrolled suppliers, it may not be possible to apply the method solely to financial data related to the controlled transactions. In such a case, the reliability of the results derived from the application of this method will be reduced. (2) The degree of consistency between the controlled and uncontrolled taxpayers in accounting practices that materially affect the items that determine the amount and allocation of operating profit affects the reliability of the result. Thus, for example, if differences in inventory and other cost accounting practices would materially affect operating profit, the ability to make reliable adjustments for such differences would affect the reliability of the results. Further, accounting consistency among the participants in the controlled transaction is required to ensure that the items determining the amount and allocation of operating profit are measured on a consistent basis ...

If there are differences between the controlled and uncontrolled taxpayers that would materially affect the division of operating profit, adjustments must be made according to the provisions of § 1.482-1(d)(2) ...

The degree of comparability between the controlled and uncontrolled taxpayers is determined by applying the comparability provisions of § 1.482-1(d). The comparable profit split compares the division of operating profits among the controlled taxpayers to the division of operating profits among uncontrolled taxpayers engaged in similar activities under similar circumstances. Although all of the factors described in § 1.482-1(d)(3) must be considered, comparability under this method is particularly dependent on the considerations described under the comparable profits method in § 1.482-5(c)(2) or § 1.482-9(f)(2)(iii) because this method is based on a comparison of the operating profit of the controlled and uncontrolled taxpayers. In addition, because the contractual terms of the relationship among the participants in the relevant business activity will be a principal determinant of the allocation of functions and risks among them, comparability under this method also depends particularly on the degree of similarity of the contractual terms of the controlled and uncontrolled taxpayers. Finally, the comparable profit split may not be used if the combined operating profit (as a percentage of the combined assets) of the uncontrolled comparables varies significantly from that earned by the controlled taxpayers ...

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Whether results derived from application of this method are the most reliable measure of the arm’s length result is determined using the factors described under the best method rule in § 1.482-1(c) ...