This report delves into contemporary accounting theory, focusing on Corporate Social Responsibility (CSR) and sustainability reporting. It explores the growing importance of CSR for firms with financial objectives, analyzes sustainability reporting in contrast to other reporting methods, and examines relevant theories such as legitimacy and institutional theory. The report then provides an in-depth analysis of IOOF Holding Limited, covering its history, ownership, governance, and financial performance. It further assesses IOOF's sustainability reporting practices and their quality, referencing the Global Reporting Initiative (GRI) guidelines. The report is structured into two main parts, addressing theoretical knowledge and a case study of IOOF, and concludes with a summary of findings and implications.