Informal store credit, recorded in the shopkeeper’s ledger and known across much of India as udhaar or the khata, has long served as a decentralized system of consumer finance for households that formal banks reach poorly or not at all. Its operation has depended on a particular transactional moment: the face-to-face, cash-mediated encounter in which a purchase is made, a debt is inscribed, and a relationship is renewed. The rapid displacement of cash by instant account-to-account settlement, exemplified by India’s Unified Payments Interface (UPI), removes that moment. This article asks how the diffusion of instant digital payment reconfigures the informal credit institution that the cash economy sustained. Drawing on economic sociology, the article argues that the ledger did more than record debt; it bundled four functions that had no reason to travel together except that a single physical routine carried them all: liquidity provision, relational earmarking, reputational collateral, and co-present monitoring. Instant payment unbundles them. The article develops a conceptual model of this unbundling and derives six propositions concerning credit availability, the norms that govern repayment, and the social meaning of the shopkeeper–customer tie. Because the phenomenon is emergent and under-theorized, the article specifies an exploratory, dyadic, constructivist grounded-theory design, pairing interviews with vendors and their customers across contrasting retail settings and supported by analysis of ledger artifacts, with explicit criteria for trustworthiness. The article reframes a question that adoption-centred fintech research has largely bypassed and offers a Global South vantage on how payment infrastructure remakes, rather than merely digitizes, everyday economic relationships....