The interlinking of competencies, the shared nature of many of the material competencies and the need to articulate joint policies to be developed throughout the territory have promoted the creation of different cooperation instruments that make possible the coherent and efficient operation of the territorial decentralization system. This system has been gradually developed and consolidated, taking into account the practice and needs detected at all times. Formally it can take two forms or possibilities: multilateral or sectoral cooperation, in which all local entities participate jointly; and bilateral cooperation, in which a single local entity participates.

To this end, the Law on the Legal Regime of the Public Sector articulates the relations of collaboration and cooperation through the provision of general principles and the promotion of voluntary instruments of cooperation, which are reinforced and complemented by the provision of obligatory coordination for those cases in which it is necessary to ensure the coherence of the action of public administrations.

For the effectiveness of this coordination, the Administrations of the State and the Autonomous Communities, on the one hand, and the Local Entities, on the other, must in their reciprocal relations:

• Respect the legitimate exercise by the other administrations of their competences and the consequences that derive from it for their own.
• To weigh, in the performance of their own competences, the totality of the public interests involved and, in particular, those whose management is entrusted to the other administrations.
• To provide the other Administrations with information on their own management that is relevant to the proper development by them of their tasks.
• To provide, at their own level, the active cooperation and assistance that the other Administrations may require for the effective fulfillment of their tasks.

In the case of Local Entities, the cooperation that is articulated through the Spanish Federation of Municipalities and Provinces (FEMP), in its condition of more representative association, is especially relevant, while special cooperation and for a specific municipal area, is usually carried out through the signing of agreements for the realization of joint actions.