<p>This paper reviews the literature on trade-in programs, which have become increasingly common across various industries. A trade-in program offers consumers a rebate when they return used products and purchase new ones. These programs serve dual purposes: a marketing objective of promoting sales of new products, and an operational purpose of leveraging returned items for remanufacturing, refurbishing, or recycling, in order to generate additional revenue. Trade-in programs have been studied in the literature using models in monopoly and duopoly settings, as well as within supply chains. The review also covers contributions that explore the possibility of reselling purchased products in secondary markets, including peer-to-peer consumer transactions.</p>