Companies are increasingly expected to provide comprehensive and reliable information on their
sustainability policies and the impacts of their operations. The EU’s Corporate Sustainability Reporting Directive makes sustainability reporting and assurance mandatory, fundamentally reshaping how companies construct legitimacy. We examine how regulation-based sustainability reporting and assurance influence corporate legitimacy, and to what extent they can advance the EU’s 2050 sustainability goals. Drawing on legitimacy theory, we focus on the tension between substantive and symbolic legitimacy. Based on document analysis and thematic interviews, our findings indicate that mandatory reporting can enhance the comparability, traceability, and fact-based quality of sustainability information, potentially strengthening companies’ substantive legitimacy. However, uneven preparedness, resource constraints, and reporting burdens may sustain symbolic, compliance-oriented reporting that fulfils minimum requirements without genuine sustainability impact. The CSR Directive is a promising but uncertain mechanism for advancing sustainability goals, and its actual effects can be assessed only once practices have stabilized.
