What Do We Know About Sustainability Reporting Assurance Quality?

The assurance of sustainability and CSR reporting has emerged as an important mechanism for enhancing the credibility and reliability of non-financial disclosures. Although assurance practices have expanded rapidly, academic evidence regarding their quality, determinants, and consequences remains fragmented and is still evolving. This paper synthesizes the historical development of CSR assurance, outlines its core objectives, evaluates existing evidence on assurance quality, and identifies key gaps and avenues for future research. In doing so, we offer a critical assessment of what is known and what remains unknown about CSR assurance as it gains prominence in corporate accountability and the functioning of capital markets.