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As far as I remember the Sarbanes-Oxley Act itself and the implementing rule of the SEC remain silent on those issues. I think the PCAOB Auditing Standard No. 5 mentions the treament of associates. The SEC’s or the PCAOB’s Q and As may also mention those issues.
This is from the SEC FAQ on SOX -
Question 2
Q: Is a registrant required to evaluate the internal control over financial reporting of an equity method investment?
A: The accounts of an equity method investee are not consolidated on a line-by-line basis in the financial statements of the investor, and as such, controls over the recording of transactions into the investee’s accounts are not part of the registrant’s internal control structure. However, the registrant must have controls over the recording of amounts related to its investment that are recorded in the consolidated financial statements. Accordingly, a registrant would have to consider, among other things, the controls over: the selection of accounting methods for its investments, the recognition of equity method earnings and losses, its investment account balance, etc. For example, a registrant might require that, at least annually, its equity method investees provide audited financial statements as a control over the recognition of equity method earnings and losses. However, nothing precludes a registrant from evaluating the control over financial reporting of an equity method investment, and there may be circumstances where it is not only appropriate but also may be the most effective form of evaluation. For purposes of applying this guidance, we make no distinction between those equity method investments for which the registrant is required to file audited financial statements pursuant to Rule 3-09 of Regulation S-X and those where no such requirement is triggered.