This paper examines the effect of two Australian environmental regulatory changes, specifically the Clean Energy Act (CEA) 2011 and the National Greenhouse and Energy Reporting (NGER) Act 2007 with reference to voluntary corporate carbon disclosure practices. In doing so, it describes the brief history of this carbon-related regulatory change, its scope, enforcement criteria and corporations’ disclosures. This is a longitudinal analysis of 219 annual reports of 73 listed corporations in Australia which were subjected to carbon tax and report carbon emissions as per the CEA 2011 and NGER Act 2007 accordingly. Any corporation or facility that emitted scope 1 emissions of 25,000 tonnes of carbon dioxide equivalent (CO2-e) or more were liable for a carbon tax in accordance with CEA 2011. Drawing on stakeholder theory and legitimacy theory, this study uses content analysis to examine corporate carbon disclosure. The findings suggest there is a considerable increase in the number of carbon-related disclosures following these regulations being enacted as law. In addition, carbon-specific communication has become much more prevalent and accounts for a larger proportion of the sampled organisations’ reported environmental information. The results of this study enrich the validity of the hypothesis that organisations would seek to legitimise their operations to stakeholders by increasing their environment-related declarations. The evidence presented in the analysis confirms the assertion that government environmental legislation/regulation has a positive impact on corporate behaviour and accountability. These findings have significant consequences for the government, decision-makers and the accounting profession, indicating that regulatory guidance enhances both mandatory and voluntary disclosure. It also offers key insights into the possible impacts of the carbon regulatory change for future research to consider.