In the context of statutory, corporate or voluntary representation, self-contracting occurs where the same person participates in a legal transaction in two distinct and potentially opposing capacities, either acting simultaneously on his or her own behalf and on behalf of another person, or representing both parties to the transaction.

In practice, this occurs, for example, where, in a contract of sale, a person acts as buyer and at the same time represents the seller, or where the same person simultaneously represents both buyer and seller.

Self-contracting may give rise to a conflict of interests, since a person acting simultaneously in two different capacities may be required to protect opposing interests.

Spanish law does not contain a general prohibition on self-contracting, but it lays down various limitations designed to protect the interests of persons who are represented. Thus, for example, Article 1459 of the Civil Code prohibits persons acting as guardians or exercising support functions from purchasing property belonging to the persons they represent, and agents from purchasing property whose administration or disposal has been entrusted to them.

Outside cases in which there is a statutory prohibition, self-contracting may be permitted where the person represented has specifically authorised it or where, in the particular circumstances of the transaction, the existence of a genuine conflict of interests can be excluded.

For this reason, when a power of attorney is granted, it may be advisable to consider whether the powers conferred should allow the agent to enter into transactions on both sides or to act in situations involving a conflict of interests and, where legally permissible, to include an express authorisation to that effect.