This article examines why two fatwa bodies operating under the same organisational roof, the Fatwa Commission of the Indonesian Ulama Council (MUI) and the National Sharia Board (DSN-MUI), arrive at substantially different legal formulations when they confront the identical question of riba in financial transactions. The study adopts a qualitative design with a comparative-descriptive approach, drawing on documentary study and content analysis of fatwa texts alongside relevant usul al-fiqh literature. The findings indicate that the MUI Fatwa Commission relies predominantly on a textual-formal mode of reasoning, in which direct qiyas and takhayyur prevail, producing an absolute ruling that bank interest constitutes riba and is therefore unconditionally forbidden. The DSN-MUI, by contrast, follows a contextual-maqasidi path that combines istihsan, istislah, talfiq, and maqasid al-shari’ah, yielding technical rulings tailored to individual Islamic financial products. Three conditions account for this divergence: the differing composition of each body’s membership, the varying degree to which practical applicability is required, and the underlying paradigm of muamalah each body adopts. Viewed through comparative usul al-fiqh, the two approaches are better understood as complementary rather than contradictory, together forming a coherent and responsive structure of Islamic law.