Self-service technologies have been gaining increasing importance in public and private organizations over recent years. One of the predominant responsibilities of the customers in the context of self-service is to enter their data on their own. Self-service for data entry can help organizations to further enhance the efficiency of their processes and to make customer experience smoother. However, as self-service for data entry is intended to be handled without intensive employee assistance, inexperienced data entry can lead to data quality problems. Although academic research has explored several effects of self-service technologies, there is still a lack of research investigating the effect of self-service data entry on data quality. Thus, in an in-depth case study in cooperation with the German Federal Employment Agency we analyzed how customer self-service for data entry affects data quality and found that assisted self-service data entry leads to highest data quality.