The investors' prospects on mandatory auditor rotation: evidence from Euronext Lisbon

The costs and benefits of mandatory auditor rotation (audit firm rotation and partner rotation) are far from being conclusive. This paper helps fill this gap in the literature by examining the relationship between mandatory auditor rotation and firms' stock market performance in the Portuguese context. Using a sample of listed companies in Portugal from 2009 to 2020, the main finding indicates that mandatory audit firm rotation is positively and significantly related to the firm's market performance. The evidence gathered suggests investors perceive mandatory audit firm rotation as a mechanism for improving audit quality. Controlling for the engagement partner rotation, we do not find that the rotation rule has a positive effect on firms' market performance. The net benefits of the mandatory audit rotation rule seem to be driven by the mandatory change of the audit firm, with improvements in market perceptions of earnings. Robustness tests suggest that the signal and significance of the association of firms' market performance and mandatory audit firm rotation holds in the presence of corporate governance mechanisms. Also, the audit experience of the departing and incoming partners does not interact with the relationship between mandatory partner rotation and firms' market performance.