At what point does the auditor have an obligation to review the audit reports that have been previously issued and issue corrections -- or withdraw its statements as to their accuracy?

The credit card charges aren't material by themselves, but I wonder whether the combination of this and other budgeting and reporting errors create questions as to whether the district has complied with state-mandated generally accepted government accounting principles.

(Of course, the Board should be asking an auditor to conduct a full audit of its accounting practices.)