The assurance of non-financial information (NFI) included in extended external reports (EERs) is a global activity that has far-reaching consequences for business, investors, other stakeholders, and society. EERs remain largely unregulated with few standards. Along with our companion paper (Krasodomska, Simnett, & Street, 2021, Journal of International Financial Management and Accounting, 25, 209), we contribute to the current discussion on EER assurance by providing an overview of the academic literature to inform the standard setting initiatives of the International Auditing and Assurance Standard Setting Board (IAASB), as well as the practice of assurance of EERs. We identify 121 articles on extended external reporting (EER) assurance published between 2009 and 2020 across 35 journals ranked A*, A, and B on the Australian Business Deans Council (ABDC) 2019 Journal Quality List. These articles cover archival, experimental, interviews, case studies, surveys, and content analysis research methods and serve as a possible input for standard setting activities. We document a rapid increase in this literature with almost half of the articles published in the last 3 years, 2018 to 2020. Finally, we offer ideas for future research directly linked to the proposed Guidance of the IAASB on EER assurance. We encourage researchers to engage in these and other issues of the IAASB’s Guidance to assist them with valuable input for their standard setting activities.