Redefining Financial Performance Reporting under IFRS 18: Evidence from Euronext 100 Listed Companies

This paper examines how the transition from IAS 1 to IFRS 18 may reshape financial reporting presentation, disclosure, and implementation readiness among Euronext 100 listed companies. The paper argues that IFRS 18 is not merely a technical replacement of IAS 1, but a substantive reform of the communication of financial performance. IFRS 18 is effective for annual reporting periods beginning on or after 1 January 2027, permits earlier application, and replaces IAS 1 as the main presentation standard while introducing new defined subtotals in the statement of profit or loss, disclosures on management-defined performance measures, and enhanced aggregation and disaggregation requirements. The Euronext 100 provides a relevant setting because, as of 31 March 2026, it is a large-cap but concentrated IFRS-based sample with a free-float market capitalization of €4,575.19 billion, top-ten concentration of 38.55%, and strong country and sector concentration. The manuscript therefore frames the study as a pre-adoption empirical assessment of IFRS 18 readiness in a concentrated pan-European reporting environment and proposes an operational coding design for firm-level analysis. JEL Codes: M41; G14; G38