In this study, we conducted two experiments to examine the effect of relationship commitment on the reaction of shoppers to receiving too much change, controlling for the amount of excess change. Hypotheses based on equity theory, opportunism and guilt were set up and tested. The first study showed that, when the less committed consumer is confronted with a large excess of change, he/she is less likely to report this mistake, compared with a small excess. Conversely, consumers with a high commitment towards the retailer are more likely to tell when they receive too much change, especially when the amount is large. The second experiment provided an explanation for these findings: the less committed consumer is driven by opportunism, whereas guilt-related feelings play an important role in a high commitment relationship. These results have several implications for both retail management and future research.