<p>The objectives of our study are twofold. Firstly, it is to assess the extent to which Indonesian corporate annual reports conform to the elements of the International Integrated Reporting Framework (IIRF). Secondly, the objective is to explore what factors determine the level of its disclosure. We use Indonesia, a developing country, for our study setting where the implementation of integrated reporting is voluntary, offering a unique context to explore disclosure factors without regulatory mandates. We conduct a thorough examination of 165 annual reports (55 companies listed on Kompas100) over a period of 2020–2022. In the first step, we use a comprehensive checklist developed based on IIRF as a framework for our gap analysis. We find that the overall IIRF disclosures elements of our sample are at 34%. This result indicates that corporate reporting practices in Indonesia are still limited and far behind in the implementation of integrated reporting. In the second step, using the results from the first step, we investigate whether corporate governance attributes are associated with the level of corporate disclosure. We find that the disclosure levels are positively associated with board nationality diversity, sustainability report, foreign ownership, and state ownership. Our study enhances our understanding of corporate reporting practices in developing countries, specifically regarding disclosure policies. Furthermore, it provides regulators and practitioners with useful insights into the current state of corporate reporting disclosure practices and empirical evidence on the factors affecting these disclosure levels. This knowledge may motivate them to take action in promoting integrated reporting adoption.</p>