Various studies argue that non-financial information is particularly relevant for business stakeholders. To reduce the risks related to information asymmetries and "window dressing" practices and to enhance the credibility of non-financial information, the need for assurance has arisen.
In recent years, scientific and professional interest in the issues related to the assurance of non-financial information has increased. Up to now, there have been very few studies on the evolution of non-financial disclosure (NFD) assurance, nor have scholars addressed the possible gaps and future research perspectives in this field. A systematic review is developed with the following aims: first, to explore the evolution of the NFD assurance literature by systematising academic studies (i.e., papers published in scientific journals) and professional contributions (i.e., papers published in non-scientific sources) from the auditing field, and second, to understand whether theory and practice have influenced each other in the field of NFD assurance, i.e., whether a bridge between theory and practice can be identified within this discourse. The main findings are the following: firstly, four stages can be identified in the evolution of the study of NFD assurance, and secondly, there is virtually no interaction between theory and practice, as practically no scientific papers are mentioned in professional papers, while academic scholars consider professional publications only as empirical data sources.
Keywords: non-financial information, assurance, sustainability, integrated reporting, influence, professional literature, literature review.
Jel Code: M42, M49, Q56