We develop a dynamic model where people decide in the presence of moral constraints and test the predictions of the model through two experiments. Norm violations induce a temporal feeling of guilt that depreciates with time. Due to such fluctuations of guilt, people exhibit an endogenous temporal inconsistency in social preferences—a behavior we term conscience accounting. In our experiments people first have to make an ethical decision, and subsequently decide whether to donate to charity. We find that those who chose unethically were more likely to donate than those who did not. As predicted, donation rates were higher when the opportunity to donate came sooner after the unethical choice than later. Combined, our theoretical and empirical findings suggest a mechanism by which prosocial behavior is likely to occur within temporal brackets following an unethical choice.