L'assetto federale e le forme di associazionismo intercomunale - This paper reviews main motivations behind the constitution of local councils partnerships as they serve to devise decentralization pitfalls in order to the optimal dimension of government. To this aim, the paper focuses on one of such partnership, namely Unione di Comune (UdC). Some stylized facts are derived with regard to dimension, functions and finalities of Italian UdC and structural characteristics of associated councils. The financing issue has been analyzed under the heading of both ensuring adequate funding to promote partnerships and avoiding pressure on the national government’s budget and public finance in general. Theoretical considerations and empirical experience from abroad, such as inter communality in France, show that the assignment of an autonomous tax proves to be more efficient compared to una tantum or annual transfer or tax sharing. Finally, the paper offers an insight into the way UdC provides administrative functions and public services by mean of the Marche Region case study.