Due to increased interest in sustainability from non-governmental organizations (NGO), investors, and other stakeholders, many companies prepare sustainability reports, sometimes with third-party assurance as to the veracity of their claims. This instructional case provides a challenging and enriching experience for students in which the provision of assurance services on nonfinancial sustainability reporting is addressed. The case involves determining the procedures necessary to provide assurance on a sustainability report where procedures are non-standard and may vary substantially from client to client. To arrive at a solution, students are required to familiarize themselves with sustainability reporting in general and use judgment in deciding the most appropriate type of assurance and related procedures to provide. Students are also asked to discuss a number of related topics including the need for assurance in this area and auditor independence issues. This instructional resource provides students with an opportunity to gain an understanding of sustainability reporting and assurance. The case is appropriate for upper-division undergraduate and graduate auditing courses in which assurance services other than audits are discussed and can be assigned on an individual or group basis for out-of-class preparation, followed by in-class discussion.