This dissertation presents case study evidence on how possible gender stereotypes influence ratings in the appraisal system and the resulting bonus payments. The firm belongs to the metal and electrical industry in North Rhine-Westphalia and, thus, has to evaluate the performance of its more than 3,500 employees according to the collective agreement Entgeltrahmenabkommen (ERA). Based on more than 12,000 personnel records of the years 2011 to 2014, the results show that women benefit from formalization. Accordingly, within formalized appraisal systems, female employees receive better performance evaluations than otherwise equal male employees. Since the outcome of the evaluation is linked to employees remuneration, women do not only receive better ratings but also higher bonus payments than men. Conversely, when women choose a less formalized, subjective system of output appraisal, their performance will be evaluated worse than mens. Interviews with professionals provide a better understanding of the case study results and the general criticism concerning performance appraisals. The interviews reveal that the performance appraisals provide only a minor incentive for performance enhancement and are perceived as being rather subjective. By the combination of quantitative and qualitative research methods, the present dissertation provides important insights in order to design a more performance oriented appraisal system in the future.