Abstract
To reduce redundancies and increase efficiency in the evaluation of internal controls (PCAOB 2007, 402–403), professional standards encourage coordination between external auditors and their clients' internal audit function (IAF). Recent surveys of internal auditors find that a component of this coordination is external auditors' involvement in developing the IAF's audit plans. Nevertheless, it is not known how such involvement affects external auditors' reliance on the internal control test work of the IAF, either before or after a negative audit discovery. Based on an experiment with 107 experienced auditors, we find that external auditors involved in the development of the IAF's audit plan perceive the IAF as more objective and that both objectivity and involvement contribute to these auditors' placing more reliance on the IAF as compared to external auditors with no involvement. This initial reliance results in the involved auditors' proposing reductions to the audit budget and re-performing less of the IAF's work. Consistent with an anchoring bias, we find that involvement leads to external auditors' continuing to place greater reliance on the IAF's work, even after they become aware of a negative audit discovery that should not have occurred had the client's controls been effective.