When Polish companies met the ESEF Taxonomy. The correctness of XBRL tags in the first year of the ESMA ESEF mandate

Purpose: The article presents the results of a study on the use of XBRL (eXtensible Business Re-porting Language) tags in the consolidated financial statements of Polish listed companies for 2020. The study: 1) verified the correctness of the classification of substantive errors, first published by Kobiela-Pionnier (2023); 2) analyzed the frequency of occurrence of particular types of errors related to the type of primary financial statement; 3) analyzed the occurrence frequency of extensions, their validity, and the correctness of anchoring. Methodology/approach: The research method used was a detailed analysis of all XBRL tags used by 50 companies listed on the Warsaw Stock Exchange in their first consolidated annual financial statements in the European Single Electronic Format (ESEF) format. This sample covers all Polish listed companies (excluding banks and insurers) whose consolidated financial statements for 2020 are available in the data-base filings.xbrl.org. The authors examined a total of 5,980 tags from the core ESMA ESEF taxonomy (5,626 used to tag rows in primary financial statements and 354 used to tag columns in statements of changes in equity) and 510 extensions. Findings: The verified classification was found to be generally correct, although one new type of error was revealed. The most common errors in companies҆ taxonomies concerned the selection of tags that are too general, unauthorized extensions, and selecting anchors that were too wide in meaning. Most errors occurred in cash flow statements, while the fewest were found in the statements of comprehensive income. At the same time, the cash flow statements and the statement of financial situation contained the most extensions, which was one of the significant sources of substantive errors. Research limitations/implications: The results will be useful both for issuers of financial statements using XBRL tags and statutory auditors, who are required to verify the correctness of the tags used as part of their audit obligation. Additionally, the article will be of interest to regulators developing guidelines for the use of XBRL tags. Originality/value: This article provides evidence that the main source of errors in tagging primary financial statements in the first year of the ESEF Regulation is insufficient knowledge and understanding of the ESEF taxonomy, in particular, creating and anchoring extensions.