Institutional theory is used in literature to explain entrepreneurs' behaviours in forming new institutions or changing existing ones to overcome institutional voids in developing countries. Social entrepreneurs address these voids as opportunities serving their interests alongside other beneficiaries'. This article tackles the theoretical underpinning of social entrepreneurship, creating a venue for reviewing the formal market institutional voids that social entrepreneurs face in developing countries. Grounded theory is employed in five developing countries' contexts, studying twenty social entrepreneurs to address and develop operational definitions per market void. This research proposes a holistic categorisation for formal market institutions, as well as a context-related informal institutional one. Moreover, the research moves forward by projecting a taxonomy of strategies employed by social entrepreneurs to tackle the earlier voids addressed.