The purpose of this study is to validate the drivers of voluntary audit in small companies identified in previous research and uncover additional determinants related to agency conflicts with owners. For our research we use the German institutional setting, documented in the literature as being very different from its Anglo-Saxon equivalent. Based on a random sample of 405 small companies responding to a postal questionnaire survey, we find that the proportion of owners not involved in management, the subsidiary status of a company, a company's legal form, and the importance of financial statements' information to management activities all increase the likelihood of voluntary audit. In contrast, firms that outsource accounting tasks to an external expert are less likely to opt for voluntary audit, suggesting that an external expert's involvement substitutes for an external audit. In addition, owing to the absence of a statutory audit history for small companies in Germany, we find that voluntary audits are less common compared with findings from previous studies.