This work deals with the topic of optimal income taxation of top earners which has been a topic of numerous academic pieces of work in the past forty years. For instance, a result attracting attention is the zero marginal tax rate for top earners. In the past years, the debate has continued. As a result, the need to summarize the work and discussion on the most relevant aspects of income taxation has emerged. Therefore in this paper, the essential informational background is given and then the two main models, linear and non-linear, are explained. Then, the debate is summarized and more advanced topics are tackled. Such a paper is needed to provide not only a solid understanding of the topic, but also suggestions for further work in the field to achieve a consensus.