If a union member repeatedly arrives late, you should...

Reporting the union member to management is the most appropriate action in this scenario, as it addresses the issue in a formal and constructive manner. This approach ensures that the problem is documented and allows for proper procedures to be followed within the organization's framework. It also allows management to address the lateness appropriately, potentially through interventions or disciplinary measures, which can benefit both the employee and the overall team environment.

Taking no action, like making a note of the late arrivals or simply ignoring the behavior, can lead to further issues down the line, such as decreased productivity or morale among other team members. Additionally, firing the member or forgetting the issue altogether would not only be premature but could also create an inconsistent approach to workplace behavior and expectations. Reporting to management creates an opportunity for intervention, communication, and improvement.