This PhD is an exploratory study examining the current cost accounting systems and key indicators in SMEs in Germany. The study is based on a survey and interviews with SME managers. Data are collected that provide information on the extent to which SME managers use their cost accounting and key indicators to obtain sound facts as the basis for their business decisions. On the one hand, this is about determining the current situation in German SMEs. On the other hand, the collected data should shed light on what information SME managers would like to have to support their work. In addition, it is being examined whether the target group of SMEs in the development of cost accounting and performance indicator systems is clearly addressed in economics. The aim of the research is to develop key indicators and a cost accounting system that is tailored to the specific needs of SMEs in Germany. In addition, the current scientific state of these two areas will be examined in a Literature Review. It also provides information on the extent to which SMEs are different from large companies, and whether these types of businesses are so different that a specialized cost accounting and key indicator system is justified and necessary for SMEs. For the development of a special system of cost accounting and the individual key figures, both quantitative and qualitative data are collected and analyzed. The results show that the way SMEs and large companies work differs significantly. Different levels of technology, different financing options on the capital market or the concentration of many tasks on a small number of employees in SMEs require different strategies than in large companies. A clear reference to the target group of SMEs often lacks in economics. In addition, research often lacks suggestions as to how the theoretical models can actually be put into practice. This is an access barrier for many SME managers, even though they are aware of the importance of tools that help them in planning, management and monitoring. The data collected has resulted in a cost accounting system and a set of indicators that can map the most pressing needs of SMEs managers, but at the same time, it is kept to a minimum so as not to overburden SME managers when implementing and running the system.