Many regulators utilize self-reporting to enforce regulations in a variety of market
contexts. This paper studies the eectiveness of self-reporting within the context of
an oligopoly. We identify two important consequences of implementing self-reporting
(relative to non-reporting) for a welfare-maximizing regulator. First, when the regula-
tor can only control the audit probability and ne, then whether compliance rises or
falls upon implementing self-reporting, depends on the level of competition. Second,
if the regulator can also control the market size, then the welfare maximizing pol-
icy entails self-reporting but with more competition and lower compliance than under
no-reporting.