Deficiencies in the data used or assumptions made may have a greater effect on some methods than others. In particular, the reliability of some methods is heavily dependent on the similarity of property or services involved in the controlled and uncontrolled transaction. For certain other methods, such as the resale price method, the analysis of the extent to which controlled and uncontrolled taxpayers undertake the same or similar functions, employ similar resources, and bear similar risks is particularly important. Finally, under other methods, such as the profit split method, defining the relevant business activity and appropriate allocation of costs, income, and assets may be of particular importance. Therefore, a difference between the controlled and uncontrolled transactions for which an accurate adjustment cannot be made may have a greater effect on the reliability of the results derived under one method than the results derived under another method. For example, differences in management efficiency may have a greater effect on a comparable profits method analysis than on a comparable uncontrolled price method analysis, while differences in product characteristics will ordinarily have a greater effect on a comparable uncontrolled price method analysis than on a comparable profits method analysis ...

All methods rely on certain assumptions. The reliability of the results derived from a method depends on the soundness of such assumptions. Some assumptions are relatively reliable. For example, adjustments for differences in payment terms between controlled and uncontrolled transactions may be based on the assumption that at arm’s length such differences would lead to price differences that reflect the time value of money. Although selection of the appropriate interest rate to use in making such adjustments involves some judgement, the economic analysis on which the assumption is based is relatively sound. Other assumptions may be less reliable. For example, the residual profit split method may be based on the assumption that capitalized intangible development expenses reflect the relative value of the intangible property contributed by each party. Because the costs of developing an intangible may not be related to its market value, the soundness of this assumption will affect the reliability of the results derived from this method ...

The completeness and accuracy of the data affects the ability to identify and quantify those factors that would affect the result under any particular method. For example, the completeness and accuracy of data will determine the extent to which it is possible to identify differences between the controlled and uncontrolled transactions, and the reliability of adjustments that are made to account for such differences. An analysis will be relatively more reliable as the completeness and accuracy of the data increases ...

Whether a method provides the most reliable measure of an arm’s length result also depends upon the completeness and accuracy of the underlying data, the reliability of the assumptions, and the sensitivity of the results to possible deficiencies in the data and assumptions. Such factors are particularly relevant in evaluating the degree of comparability between the controlled and uncontrolled transactions. These factors are discussed in paragraphs (c)(2)(ii) (A), (B), and (C) of this section ...

In applying the transactional net margin method, the selection of the most appropriate net profit indicator should follow the guidance at paragraphs 2.2 and 2.8 in relation to the selection of the most appropriate method to the circumstances of the case. It should take account of the respective strengths and weaknesses of the various possible indicators; the appropriateness of the indicator considered in view of the nature of the controlled transaction, determined in particular through a functional analysis; the availability of reliable information (in particular on uncontrolled comparables) needed to apply the transactional net margin method based on that indicator; and the degree of comparability between controlled and uncontrolled transactions, including the reliability of comparability adjustments that may be needed to eliminate differences between them, when applying the transactional net margin method based on that indicator. These factors are discussed below in relation to both the determination of the net profit and its weighting ...

In applying the transactional net margin method, the selection of the most appropriate net profit indicator should follow the guidance at paragraphs 2.2 and 2.8 in relation to the selection of the most appropriate method to the circumstances of the case. It should take account of the respective strengths and weaknesses of the various possible indicators; the appropriateness of the indicator considered in view of the nature of the controlled transaction, determined in particular through a functional analysis; the availability of reliable information (in particular on uncontrolled comparables) needed to apply the transactional net margin method based on that indicator; and the degree of comparability between controlled and uncontrolled transactions, including the reliability of comparability adjustments that may be needed to eliminate differences between them, when applying the transactional net margin method based on that indicator. These factors are discussed below in relation to both the determination of the net profit and its weighting ...