Tax avoidance activities are complex, and the effective planning of these activities requires a mix of functional knowledge in business and a good understanding of a firm's operations. Armed with hands-on experience of running their firms' business and experience of other firms through their outside directorship appointments, certified inside directors (CIDs) are able to structure and execute tax avoidance activities for their firms. This study finds that firms with CIDs on their boards avoid more taxes. At the same time, only CIDs with no more than three outside directorships help firm save taxes. This study also supports that CIDs in complex firms and firms with bad environmental corporate social responsibility (CSR) avoid more taxes. This research extends the literature on corporate governance in general and inside directors in particular by examining whether CIDs can help firms save taxes.