Abstract. Online reputation mechanisms need honest feedback to function effectively. Self interested agents report the truth only when explicit rewards offset the cost of reporting and the potential gains that can be obtained from lying. Payment schemes (monetary rewards for submitted feedback) can make truth-telling rational based on the correlation between the reports of different clients. In this paper we use the idea of automated mechanism design to construct the best (i.e., budget minimizing) incentive-compatible payments that are also robust to some degree of private information.