Chapter 2 adopts a managerial perspective to explore the role of materiality in sustainability reporting. Building on the definitional tensions outlined in Chap. 1, it examines financial, impact, and double materiality approaches, highlighting their implications for performance management and strategic integration. The concept of internal materiality is introduced as a strategic construct that influences resource allocation, stakeholder engagement, and control system design, reframing materiality not merely as a reporting filter but as a driver of organisational change. The chapter presents the theoretical foundations of sustainability reporting, distinguishing between internal and external orientations and analysing how materiality assessments reflect broader strategic intentions. It discusses how misalignments between internal processes and external expectations can generate greenwashing activities, which can undermine stakeholder trust. A systemic vision is developed, in which corporate sustainability performance is compared with stakeholder expectations, forming a dynamic benchmark for assessing sustainability. The degree to which these expectations are met generates repercussions in both impact and financial dimensions, closing the sustainability reporting cycle. This systemic view is further elaborated in Chap. 3 through System Dynamics modelling, which captures feedback loops between materiality assessment, performance communication, stakeholders’ satisfaction, and financial outcomes, offering a dynamic lens for understanding sustainability integration.