This study examines the impacts of climate policy changes on business carbon performance in Australia as the country strives for climate neutrality. In this study, we analyse the carbon efficiency data of National Greenhouse and Energy Reporting (NGER) registrants—the largest emitters in Australia—from 2009 to 2020 to examine the carbon efficiency results of these top polluters against the significant climate policy changes over the decade, identifying patterns, challenges, and opportunities. The findings show that although over half of Australia’s top emitters improved their carbon efficiency, only a quarter were strong carbon-efficiency performers (i.e., improved both carbon and economic performance). Carbon efficiency developments were predominantly driven by economic performance, with few companies solely focusing on environmental performance (‘Green Stars’). However, companies also increasingly avoided being perceived as ‘dirty’ or as ‘Dirty Cash Cows’. Carbon performance improvement was more prominent among companies operating in less environmentally sensitive industries compared to highly sensitive industries. As economic performance rather than environmental improvement remained the main driver for carbon efficiency development, the carbon tax lowered carbon efficiency outcomes due to increased economic and compliance costs, while its repeal led to a slight improvement in carbon efficiency. However, the failure of the National Energy Guarantee and ongoing policy uncertainty regarding climate change significantly reduced carbon efficiency outcomes in more recent years.