The European Union’s Level(s) framework represents a significant step toward standardized sustainability assessments in the built environment, yet its implementation, particularly at Level 3—faces challenges due to fragmented tools, lack of interoperability, and insufficient real-time data integration. This study addresses these gaps by developing a collaborative digital platform (CDP) that leverages Building Information Modeling (BIM), Internet of Things (IoT), Digital Twins (DT), and Artificial Intelligence (AI) to enable real-time monitoring, predictive analytics, and stakeholder engagement for Level 3 compliance. Adopting a Design Science Research (DSR) methodology, the study conceptualizes, designs, and prototypes a CDP that enables real-time monitoring, predictive analytics, and multi-stakeholder collaboration for Level 3 reporting. A case study involving a tutorial digital model of a small residential building demonstrates the CDS’s ability to integrate static BIM data with dynamic sensor inputs, visualize performance indicators, and support compliance with Level 3 KPIs related to operational energy use, carbon emissions, and indoor environmental quality (IEQ). CDP employs open BIM standards to ensure interoperability and feature an interactive dashboard involving AI chatbot for multi-stakeholder collaboration. The study concludes that such a CDP can enhance data-driven decision-making, regulatory compliance, and sustainability outcomes in the built environment. This research contributes to the digital transformation of sustainable building management, offering a scalable solution to advance the EU’s green transition and harmonize lifecycle performance assessments within the concept of Level 3 for circularity