Experimental evidence on external auditor reliance on the internal audit

With the revised version of ISA 610 (revised 2013), external auditors now face both requirements and guidance addressing their responsibilities when relying on the internal audit function (IAF). The reliance decision of an external auditor has important economic consequences and implications for the efficiency and effectiveness of the annual audit. Using an experimental design, we explore how German external auditors’ reliance decisions regarding the IAF are affected by varying levels of environmental factors, like client business risk, effectiveness of the internal control system, and quality of the corporate governance. Furthermore, the experiences of external auditors in collaborating with an IAF are taken into consideration. The results indicate main effects for each factor and a two-way interaction between the effectiveness of the internal control system and the quality of corporate governance. Specifically, a strong internal control system can compensate for weaknesses in corporate governance with respect to the confidence of external auditors in the IAF. Also, the type of audit procedure influences the willingness of auditors to rely on the IAF, and the inherent risk of the examined transaction strengthens the negative impact of client business risk on the reliance decision. Moreover, past experiences of external auditors with an IAF have a significant impact on their reliance decision. Overall, the findings suggest that organizations can foster internal–external auditor coordination by enhancing corporate governance effectiveness and strengthening the internal control system.