The internal audit function is increasingly recognised as an important internal governance mechanism and consequently factors that contribute to its effectiveness are now an area of great interest to researchers and practitioners. This study draws on signalling theory to fill a gap in the internal audit effectiveness (IAE) literature by investigating which IAE signals are sent by large South African companies in their company reports. Using a self-developed IAE signalling frame, a content analysis was performed on the integrated reports and other annual reports of the top 100 listed companies in South Africa over a five-year period. Thereafter a multiple correspondence analysis was used to extract IAE signals. The results revealed that IAE disclosure patterns of South African listed companies follow the normative dictates of the King Code and the Companies Act. The study also discovered a low average IAE disclosure rate linked to non-mandatory disclosure requirements. Disclosing more detail on IAE represents a missed opportunity to signal superiority through voluntary communication of the IAE signals especially on internal aspects such as management support for internal audit recommendations and the continuous professional development of internal auditors.

内部审计职能越来越被认为是一种重要的内部治理机制，因此有助于其有效性的因素现在是研究人员和从业人员非常感兴趣的领域。本研究利用信号理论通过调查大型南非公司在其公司报告中发送的 IAE 信号来填补内部审计有效性 (IAE) 文献中的空白。使用自主研发的IAE信令框架，对南非上市公司前100强的5年综合报告及其他年报进行内容分析。此后，使用多重对应分析来提取 IAE 信号。结果显示，南非上市公司的 IAE 披露模式遵循国王法典和公司法的规范要求。该研究还发现，与非强制性披露要求相关的 IAE 平均披露率较低。披露有关 IAE 的更多细节意味着错失了通过自愿交流 IAE 信号来表明优势的机会，尤其是在内部方面，例如管理层对内部审计建议的支持和内部审计师的持续专业发展。