Evaluating Corporate Carbon Emissions Reporting: Assessing Transparency and Completeness with the Carbon Integrity Index

Corporate carbon emissions reporting is central to climate accountability, yet significant gaps remain in transparency, completeness, and methodological rigor. This study introduces the Carbon Integrity Index (CIX), a structured framework for assessing disclosure quality through ten indicators covering Scopes 1, 2, and 3. Unlike existing standards focused on reporting requirements, the CIX evaluates how well emissions are reported, addressing methodological transparency, scope coverage, and treatment of uncertainty. Applied to 2022 sustainability reports from companies listed in Spain’s IBEX 35 index, the framework reveals an average score of 5.7/10, with 69% of firms achieving passing results. While Scope 2 reporting was generally robust (mean: 0.82), Scope 3 disclosures—often representing the majority of emissions—and uncertainty assessments were systematically weak (mean: 0.08). Findings provide empirical support for legitimacy and institutional theory, showing how formal compliance can mask performative compliance that limits meaningful accountability. Sectoral differences suggest that institutional pressures and operational complexity shape divergent transparency pathways, raising concerns that universal standards may entrench reporting disparities. The CIX offers regulators, investors, and companies a practical tool for distinguishing symbolic from substantive disclosure, enabling more informed decision-making and strengthening the role of reporting in driving the transition to net-zero business models.