Sustainability is a universal topic that has gained in significance during the last decade due to the increased risks for society as well as the environment itself. Therefore, a lot more attention is given to how companies disclose upon their impact on environment, society and governance. This paper aims to pick up on criticism to sustainability reporting regarding the variety of different frameworks surrounding this topic and investigate upon how companies use them to create their reports and if, in their opinion, unification can be reached in the nearby future. The second objective of this thesis is to explore upon and collect knowledge regarding the developing role of the new profession of the ESG/Sustainability controller. To reach the research objectives and collect sufficient data, semi-structured, qualitative interviews have been conducted with six companies and their respective sustainability reporting responsible. Previous research points out that the ‘arena’ of sustainability reporting frameworks has become too dense. This has led to companies firstly struggling to navigate through the enormous amount of regulations and guidelines, secondly adversely affected the implementation of harmonization within sustainability reporting and thirdly using their reports as marketing tools. These theoretical findings have been mostly supported by the results of this thesis. Almost all of the interviewed companies have adopted a common index, called GRI, that builds their sustainability disclosure base. However, the findings of this thesis point out that their efforts, to go beyond this reporting guideline, can be connected to motives that are either of external, operational, transparency or recruitment nature. Even though companies would wish for a common, unified reporting framework, such as the upcoming inclusion of CSRD in the future, and see potential advantages, there are some specific, current challenges that have to be overcome first regarding sustainability reporting. Nevertheless, from the data analyzed it is evident that companies are looking forward to this new, mandatory reporting regulation and prepare themselves adequately and intensively. The results of the qualitative study regarding the development of the new controller profession further suggests that the ESG/Sustainability controller has a broad post-graduate background, however, not only in business administration. One reason is that the tasks of this new profession vary by quite some margin from traditional controlling tasks and their responsibilities also go beyond merely preparing, analyzing financial reports and supporting management, but are dedicated to the sustainability reporting process and other sustainability projects.