This monograph provides a detailed summary of how Australian firms report their financial performance. While applicable standards within Generally Accepted Accounting principles (GAAP) have increasingly restricted the ability to exclude certain components from the calculation of periodic income, we observe a consistent growth in the extent to which Australian firms promote alternative (i.e., non-GAAP) income measures. We show that this behaviour has increased significantly over the period we survey, and provide extensive descriptive evidence of how non-GAAP results differ from those that are reported in compliance with accounting standards. We also review the regulation of this practice, and provide a detailed discussion of the possible reasons for its increase, as well as the possible consequences. In doing so, we provide a detailed review of existing research examining the provision of non-GAAP income measures. Our over-riding conclusion is that there are competing objectives underlying these disclosures (i.e., self-interest versus better information for stakeholders), and the resulting consequences of these disclosures will also vary in line with the dominant motivation for their supply. We also highlight the manner in which non-GAAP reporting can be seen as a challenge to accounting standard setters and regulators of financial reporting, and contrast the direction of ‘top down’ standard setting with observations from practice.