The implementation of ESEF requirements by companies of the sWIG80

Purpose: The article presents the results of research on the implementation of the Eu-ropean Single Electronic Format (ESEF) by companies listed on the Warsaw Stock Exchange's (WSE) sWIG80. Methodology/approach: The research was based on the analysis of financial state-ments of companies listed on the WSE in terms of:  changes in the presentation of items in the statement of financial position (balance sheet) and the statement of comprehensive income in order to adjust them to the model structure of the ESEF (core taxonomy),  the degree of use of extensions that allow tags to be adapted to the specifics of the company. The analysis concerned consolidated financial statements published between January 1, 2021 and April 30, 2022, in which the companies implemented the ESEF requirements for the first time. The basis for the formulation of the research hypothesis was the neo-institutional theory. Findings: The study verified the research hypothesis that listed companies included in the sWIG80 tried to adjust the presentation of data in financial statements to the core taxonomy more than they applied extensions and extension taxonomy. Research limitations/implications: The results concern only companies included in the sWIG80 as of December 31, 2021. Therefore, extending the findings to the entire population of companies listed on the WSE is unjustified. Originality/value: The research is the first empirical study of this type in Poland conducted in relation to smaller companies listed on the Warsaw Stock Exchange. There-fore, they illustrate the behavior of entities in the context of financial data reporting obligations under the ESEF format.