Commissioned by the Directorate-General for Internal Market, Industry, Entrepreneurship and SMEs (DG GROW) of the European Commission, this study examines territorial supply constraints (TSCs) and their effects within the EU retail sector. Territorial supply constraints are limitations imposed by certain large manufacturers that make it very difficult or impossible for retailers to buy products in one member state and resell them in another. This harms cross-border business and breaks the promise of the single market to bring choice and price competition to the consumer. The study uses a broad range of data collection methods—literature reviews, stakeholder interviews, surveys, mystery shopping, and econometric analysis—to explore how suppliers may restrict wholesalers and retailers from sourcing or reselling products across Member States. Findings indicate that approximately half of retailers and wholesalers report encountering TSCs such as refusals to supply, destination obligations, and product differentiation in packaging and composition. The study highlights significant variations in product prices across the EU that cannot be fully explained by standard economic factors, suggesting the presence of TSCs as a contributing factor. With a degree of uncertainty, estimated consumer savings from the elimination of TSCs could amount to €14.1 billion annually.