The Legal Entity Identifier and Legacy Systems: Harmonisation, Interoperability, and Balance in Digital Governance

Abstract This article examines the Legal Entity Identifier (LEI) as a cornerstone of contemporary digitalised governance. Originally introduced in response to the 2008 financial crisis to address systemic opacity in financial markets, the LEI has since evolved into a global public-good infrastructure that enables interoperability, transparency, and accountability across jurisdictions and sectors. This study investigates the extent to which the LEI can be effectively implemented in Poland and the European Union, and what legal, institutional, and economic barriers constrain its universal adoption. The research employs a multi-method design, combining doctrinal and comparative analysis with empirical evidence from European supervisory projects (the EIOPA, ESMA, ECB, and EBA) and a Polish case study conducted under an NCN project on tax administration. Findings confirm that the LEI strengthens systemic risk monitoring, audit quality, and SME participation in global trade, but also reveal persistent barriers, including renewal costs, administrative burdens, and fragmented domestic identifiers. The analysis identifies four pillars of reform – universality, interoperability, continuity, and public co-financing – necessary to embed the LEI within governance systems. Comparative lessons from the United States and Japan demonstrate that statutory identifiers can extend beyond finance and support innovation while oversight is maintained. The article concludes that only by recognising the LEI as a structural component of digitalised governance can its transformative potential for transparent, resilient, and inclusive public administration be fully realised.