In a constantly changing world marked by the omnipresence of technology, competences management has become a crucial element for the competitiveness and performance of companies. However, this management of competences has become a challenge due to the constant evolution of the company's activities, the complexity of the notion of competence and in particular that associated with cooperative activities. In this paper, we address this challenge by proposing a model of collective competence based on the activity. Unlike approaches based on the declaration of competences, we integrate their dynamic dimension due to their intrinsically iterative construction during the activity. We begin by defining a terminological specification for the concept of collective competence, describing the various key characteristics. Next, we present our activity-based collective competence model, which represents the competences used by a collective during a given activity. We put our model to the test with the instantiation of competences through a real activity within a company. Our main contribution concerns the understanding and specification of collective competence as a complex notion, i.e. with emergent properties, to ensure better management of it.