Finally, we examine both the earnings management and the tax-planning
explanations for ETR changes between the third and fourth quarters in the context
of SOX. Two main provisions of SOX apply. First, section 201 states that, while a
public accounting firm may perform nonaudit services, including tax services,
these services must be approved in advance by the audit committee. Section 202
creates a de minimis exception for this approval if the aggregate amount of all nonaudit
services does not exceed 5 percent of the total revenues paid to the auditor.
Assuming that most firms do not qualify for this de minimis exception, SOX may
motivate audit committees to reduce or eliminate the tax fees paid to auditors in
order to preserve or bolster their auditors’ appearance of independence. Omer et al.
(2006) suggest that firms were separating their audit and tax service providers