This study examines the effect of voluntary disclosure in annual reports on tax avoidance activities. The agency theory of tax avoidance suggests that tax sheltering is associated with important agency costs, underlining the importance of corporate governance mechanisms such as voluntary disclosure in shaping tax planning. Using a sample of 3448 firm-year observations of French listed firms over 2007\textendash2013, the results show that voluntary disclosure is associated with lower tax avoidance activities, providing evidence that this disclosure can be seen as an effective monitoring tool that reduces the insiders' likelihood to engage in rent extraction through tax avoidance activities. The results also indicate that the negative effect of voluntary disclosure on tax avoidance is significant only when family control is below 40%, suggesting that the disciplinary role of voluntary disclosure is limited to firms with relatively low family control levels. Overall, our findings are consistent with the agency theory of tax avoidance and highlight the important role of corporate disclosure in improving corporate governance. \textcopyright 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.