Fairness norms and resulting behaviors are an important prerequisite for cooperation in human societies. At the same time, financial incentives are commonly used to motivate social behaviors, yet it remains unclear how financial incentives affect fairness-based behaviors. Combining a decision paradigm from behavioral economics with hierarchical drift-diffusion modeling, we investigate in this registered report (https://osf.io/bgka8/) the effect of different financial incentives on two types of fairness-based decisions in four experimental groups. Two groups of participants divide points between themselves and a disadvantaged person, inciting fairness-based compensation behavior and two other groups of participants divide points between themselves and a fairness violator, inciting fairness-based punishment behavior. In addition, each group will either receive financial incentives that are aligned or in conflict with the respective fairness-based behavior. This design allows us to directly investigate how different incentives shape the cognitive mechanism of fairness-based decisions and whether these effects are comparable across different fairness domains (punishment-based vs compensation-based fairness). Besides specifying how the interaction between financial incentives and fairness affect the computation of social decisions, the findings will clarify the conditions under which incentives undermine and enhance fairness and are thus potentially relevant for developing incentive schemes. Results will be ready to be presented at the conference as data collection is nearly completed.