@pcunniff
Here is the exact wording from AU-C 402.A44:
“when the user auditor expresses a modified opinion because of a modified
opinion in a service auditor's report, the user auditor is not precluded from
referring to the service auditor's report if such reference assists in explaining
the reason for the user auditor's modified opinion. In such circumstances, the
user auditor need not identify the service auditor by name and may need the
consent of the service auditor before making such a reference.”
examples of modification: maybe the service auditor's report has a modified opinion, and I believe it will materially affect the F/S of my client, therefore, I need to modify my report too.. Modifying the report should be the auditor's own judgment, there isn't a concrete rule says you must modify your report if service auditor report is modified.