La norme ESRS S1 de la CSRD: quels impacts sur l'audit extra-financier?

Abstract

The Corporate Sustainability Reporting Directive (CSRD) represents a major shift in corporate transparency, requiring large companies to publish structured, standardised, and externally verified sustainability reports. At the heart of this transformation lies the adoption of the European Sustainability Reporting Standards (ESRS), including ESRS S1, which focuses on own workforce-related disclosures. This standard imposes comprehensive reporting obligations on companies regarding working conditions, diversity, training, social dialogue, and employee well-being. This thesis investigates the concrete implications of ESRS S1 for sustainability assurance practices. While sustainability assurance is still an emerging field, the introduction of ESRS S1 reveals specific challenges for auditors: the qualitative nature of many social indicators, the lack of structured internal control systems, and the insufficient maturity of data collection and documentation processes. The study adopts a qualitative approach, based on nine semi-structured interviews with sustainability assurance professionals, both in strategic and operational roles. Their insights shed light on the methodological, organisational, and ethical transformations currently reshaping the profession. A key finding is the growing tension between regulatory ambition and practical feasibility. The recent adoption of the Omnibus Amendment has significantly altered the scope of the CSRD, introducing uncertainty regarding the reporting timetable, the level of assurance expected, and the precise boundaries of what must be disclosed. This has created considerable ambiguity for companies and auditors alike, who must navigate moving targets while attempting to prepare robust reporting and assurance frameworks. Despite this uncertainty, the results underline a strong trend toward the formalisation of ESG assurance. Auditors are expected to integrate new skills, develop interdisciplinary teams, and align with evolving international standards such as ISSA 5000, which aims to provide a dedicated framework for sustainability assurance engagements. The application of the double materiality principle further complicates the audit process, especially when it comes to setting thresholds and validating qualitative indicators. Ultimately, this research highlights the major implications for auditors, which are immediately linked to the level of preparation of companies and the clarity of guidance provided by legislators. Auditors must strengthen their methodologies and address the lack of audit trails for social indicators; companies must build reliable data systems; and regulators must urgently clarify expectations and provide operational tools to ensure consistency and credibility across the EU. In this transitional phase, the role of assurance is more critical than ever to support the legitimacy and comparability of sustainability reporting under the CSRD.