This paper aims to identify the explanatory factors of mandatory disclosure (MD) and voluntary disclosure (VD) levels related to discount rates, based on disclosure theories. The size, leverage, profitability, and audit firms were selected from different theories, namely agency theory, signaling theory, positive accounting theory, including the political cost hypothesis, and the cost of capital theory. Furthermore, the materiality (weight of the items) and the relevance (nature) of the topic were also considered, based on the evidence already obtained in the literature. Research on disclosures related to discount rates has been assessed either as an incidental topic or from a limited-scope analysis, particularly with respect to MDs. This paper assesses this topic as its specific object of analysis for both MD and VD. The use of the discount rate has been assuming growing importance within financial reporting. Therefore, this topic should deserve particular attention from international standard-setting bodies. The understanding of the proper set of items to be disclosed and understanding the factors that explain its disclosure, aligned with the efforts to assure its compliance by legal authorities, may contribute to reducing asymmetries and increasing transparency in entities' financial reporting. This study uses the method of archival research and content analysis of consolidated reports and accounts for the year 2020 of listed entities in Euronext Lisboa. Regression models were used, having disclosure indices related to discount rates as dependent variables. This paper finds a positive association between disclosures related to discount rates and the entity’s size, as well as the materiality and the relevance, assessed by the weight of the items and the nature of the topic under assessment, respectively. It adds new explanatory factors on the VDs and MDs related to discount rates in a broader perspective of analysis.