Short answer. A usufructuary who has not given security must invest the collected capital at interest — first by agreement with the owner, and if no agreement is reached, then with judicial authorization. In every case, the investment must be covered by security sufficient to preserve the integrity of the capital.
What the law says
The usufructuary who has not given security shall invest the said capital at interest upon agreement with the owner; in default of such agreement, with judicial authorization; and, in every case, with security sufficient to preserve the integrity of the capital in usufruct.
Civil Code, Article 599 — Collecting Credits That Form Part of the Usufruct. Read the full provision →
How security status affects the right to collect credits
Article 599 of the Civil Code draws a clear line between two types of usufructuaries. A usufructuary who has given the proper security may independently claim matured credits that form part of the usufruct and may then use the collected capital in any manner the usufructuary chooses. A usufructuary who has not given security — whether excused from doing so, unable to do so, or whose security was insufficient — faces two additional restrictions: needing the owner's or the court's authorization even to collect, and being prohibited from freely using the capital once collected.
The obligation to invest at interest
Once a usufructuary without security has collected capital from matured credits, the law does not permit spending, consuming, or keeping it as a deposit. Article 599 requires investment at interest. The rationale is that the capital itself is not the usufructuary's property — the right extends only to the fruits of the thing in usufruct, which in the case of credits means the interest they generate. Requiring interest-bearing investment ensures the usufructuary receives the fruits (the income) while the underlying capital is preserved for the owner.
Agreement with the owner comes first
The Civil Code's preferred mechanism for deciding where to invest the capital is agreement between the usufructuary and the owner. Both parties choose together where and how the funds will be placed. This gives the owner some say in protecting the capital's integrity while allowing the usufructuary and owner to tailor the arrangement to the specific circumstances — the available investment options, prevailing interest rates, and the remaining duration of the usufruct. Only when no agreement can be reached does the law provide a fallback.
Court authorization when agreement fails
If the usufructuary and owner cannot agree on how the capital should be invested, Article 599 allows the usufructuary to seek judicial authorization. The court steps in to approve a suitable investment in place of the agreement the parties could not reach. In every case — whether the investment was settled by agreement or by court order — the law imposes one non-negotiable requirement: there must be security sufficient to preserve the integrity of the capital. This security protects the owner's interest in recovering the principal when the usufruct eventually ends.