In German law, 285 BGB plays the same role as Art. 1186 CC in Spanish law, but there it was already accepted from its enactment that the commodum can also be demanded when the supervening failure of performance is imputable to the debtor. Even more, soon after the BGB's entry into force, it was even accepted that the commodum ex negotiatione, i.e. the price the debtor gets for negotiating with the due thing, can also be demanded. At present, the interpretation of the said paragraph poses new challenges, such as its aplication to obligations to do or to obligations not to do, and offers the new insights advanced by legal writers to justify these proposals. The present study briefly describes the different ways of understanding and justifying 285 BGB, to thereby explore the adequate interpretation of our Art. 1186 CC: What function is intended to fulfill the claim for the commodum ex negotiatione? Would it be reasonable to incorporate it into our legal system? And, if so, to what cases should it be applied?

Some court decisions affirm the subsidiarity of the unjustified enrichment action, but some others deny it. Likewise, some legal writers think that subsidiarity is a requirement of those actions, but others do not. The present paper tries to solve this contradiction. For this purpose, it emphasizes that there are different conflicts that arise around subsidiarity and that, depending on the issue that is to be solved in each case, each of them deserves an independent treatment: A concurrence of rules, a concurrence of claims, the need to integrate the legal system through analogy or, in the fourth place, the search for solutions to the problems of indirect enrichment taking into account that it implies central principles of the general theory of obligations (relativity of contracts, preference of credits). The paper insists on the idea that it is better to dispense once for all with the general principle of unjustified enrichment understood as a principle suitable for coherently solving all restitution problems that may arise regardless of the conflict of interests that takes place in each case. Therefore, the paper concludes that it is also preferable to dispense with subsidiarity as a requirement of the unjustified enrichment action.