U.S. transfer pricing rules require U.S. taxpayers to report arm's length results on their U.S. federal income tax returns. The reported results of transactions with related parties must be consistent with the results that would have been realized by uncontrolled taxpayers in similar circumstances. In practice, U.S. taxpayers commonly demonstrate compliance with this requirement by showing that their profitability on transactions with related parties is consistent with the profitability of comparable companies engaging in comparable transactions. For example, a U.S. distributor of imported goods might benchmark its operating margin for a tax year against the operating margins of independent distributors, with such information being obtained from public financial disclosures.
Transfer Pricing 就是美国公司（US taxpayer）和一个子公司（related party）虚构一个arm's length transaction。规定是只要母公司和海外子公司的交易对比母公司与其他公司交易，只要profitability类似就可以。
那么太好搞了，大家都从中国进口，买给美国公司们都是一个价，也就是说，大家都避税，那么避税做法就是基准线。
挑战是什么？
The introduction of unanticipated costs into a supply chain can have significant implications for transfer pricing purposes. An immediate issue is determining which affiliate – the U.S. distributor, a foreign manufacturer, a foreign principal company, or some combination – should bear the cost to the extent it is not passed on to customers. Under the arm's length standard, that depends on, among other things, the allocation of risk among the parties, as evidenced from intercompany agreements and course of conduct, and relative bargaining position. Another issue is how to implement changes to transfer prices to ensure arm's length results.
在关税下面，到底是美国公司，海外工厂，还是海外子公司负担关税问题，如何分配关税负担而符合arm's length transaction，是一个税务挑战。
但是，不要担心，总会有办法的。
