Tax evasion can be considered as a systemic fraud in which different parties such as taxpayers, lawyers, banks, and multinational entities interact. Here, accountants are key agents owing to their legal liability in tax reporting and their knowledge on accounting rules. The present study analyzes the role that accountants play in firms tax evasion by presenting evidence from a randomized field experiment carried out with microenterprises in Ecuador’s tax system in early 2016. The article evaluates to what extent a notification of accountants is more effective in increasing tax reporting than a notification of taxpayers, through five different treatments. The results show that simultaneous persuasive notifications of both accountants and taxpayers were the unique treatment that significantly increased firms’ declared income tax. Furthermore, it was shown that penalty notifications of accountants, rather than taxpayers only, were the most significant treatment at reducing revenue underreporting.