The purpose of this study is to investigate the claims made basis civil liability insurance and the challenges of its practical application in the Portuguese legal system, namely in the context of environmental liability. The choice of this legal regime and the relevance of its analysis is due to the nature of claims and damages that may arise of environmental liability and the circumstances that characterize the consequent claim.

Our study is essentially focused in the the following topics: (i) the content of the claims made clause, (ii) the legality of its normative content, (iii) the impact of this clause in determining the concept of accident, (iv) the determination of the moment of claim and its objective and subjective scope and (v) practical hypotheses which allows us to prove our conclusions.

The main conclusions which were drawn after our investigation are the following: (i) according with Portuguese Law the normative content of the claims made clause should not have any legal censorship when this regime is applied to the environmental liability’s cases studied on this paper; (ii) the concept of accident is related with the exteriorization of facts of the insured for the insurer; (iii) the knowledge of the insurer and that the determination of the moment of the claim coincides with the insured's judicial citation in the case of the judicial claim.