This digital document is a journal article from Journal of Environmental Economics and Management, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.Description: In a market where firms with different characteristics decide upon both the level of emissions and their reports, we study the optimal audit policy for an enforcement agency whose objective is to minimize the level of emissions. We show that it is optimal to devote the resources primarily to the easiest-to-monitor firms and to those firms that value pollution the less. Moreover, unless the budget for monitoring is very large, there are always firms that do not comply with the environmental objective and others that do comply; but all of them evade the environmental taxes.