Customer value proposition” has become one of the most widely used terms in business markets in recent years. Yet our management-practice research reveals that there is no agreement as to what constitutes a customer value proposition—or what makes one persuasive. Moreover, we find that most value propositions make claims of savings and benefits to the customer without backing them up. An offering may actually provide superior value—but if the supplier doesn’t demonstrate and document that claim, a customer manager will likely dismiss it as marketing puffery. Customer managers, increasingly held accountable for reducing costs, don’t have the luxury of simply believing suppliers’ assertions.