Abstract Social impact bonds (SIBs) are one of the most important financial instruments within the social finance market. The concept of SIBs has evolved in parallel with impact investing (Mulgan et al., 2011). It is considered as the most innovative method of financing social services programs and welfare (Nicholls & Tomkinson, 2015). The SIB structure is based on a set of contracts among actors with the aim of improving social outcomes. The first SIB was issued in 2010 in the United Kingdom (UK), and during the last 12 years, several transformations have been made in the SIBs model. The study aims to highlight challenges and present suggestions in this ever-evolving research field to guide future research studies regarding the conceptual structure of SIB. Moreover, this study provides a concrete understanding to policymakers, impact investors, and researchers regarding the contemporary issues within the SIBs market and proposes some innovative solutions that could enhance social outcomes and build a more sustainable future.