A collective obligation is an obligation directed to a group of agents so that the group, as a whole, is obliged to achieve a given task. The problem investigated here is to study the impact of collective obligations to individual obligations, i.e. obligations directed to single agents of the group. The groups we consider do not have any particular hierarchical structure nor have an institutionalized representative agent. In this case, we claim that the derivation of individual obligations from collective obligations depends on several parameters among which the ability of the agents (i.e. what they can do) and their own personal commitments (i.e. what they are determined to do). As for checking if these obligations are fulfilled or not, we need to know what are the actual actions performed by the agents. This present paper addresses these questions in the rather general case when the collective obligations are conditional ones
