prior to and during the discussion of SOX. However, because their study is focused
on the pre-SOX association between audit and tax fees, they provide limited evidence
as to whether separation of audit and tax services continued after the passage
of SOX or the extent to which that separation affected ETRs. On the basis of
one-year-ahead changes in ETRs and tax fees paid to auditors, they find that the
association between tax fees and reductions in annual ETRs weakened, at least initially,
during the period immediately following the passage of SOX.
We posit that separating audit and tax service providers reduces the association
between tax-planning investment and ETR changes between the third and
fourth quarters for two reasons. First, reducing tax fees paid to auditors without the
purchase of additional tax services from nonaudit providers (including in-house
tax departments) likely results in fewer tax-planning opportunities. Second,
although firms may replace auditor-provided tax services with tax services
acquired from other sources, those new providers are likely less knowledgeable
about firms’ tax opportunities in the short run. (We assume that in-house knowledge
is constant.) For these reasons, we expect that the returns to tax-planning
investments were initially lower in both scenarios.