Compliance rarely happens in isolation. This chapter explains how to map complex supply chains, craft flow-down clauses, and conduct supplier audits so that every tier meets EU requirements. It also covers constructive engagement with national authorities and notified bodies, the value of cross-border R&D consortia, and contractual mechanisms that allocate liability, data-sharing duties, and incident-reporting responsibilities. Communication strategies, internal and external around the guidance, fostering transparency and trust across stakeholder groups.