Short answer. Yes. Article 1896 of the Civil Code is explicit: the agent owes interest on the sums he has applied to his own use from the day on which he did so. Interest runs from the very date of misappropriation — not from demand, not from a court judgment.
What the law says
The agent owes interest on the sums he has applied to his own use from the day on which he did so, and on those which he still owes after the extinguishment of the agency.
Civil Code, Article 1896 — Interest on Sums Applied to Own Use. Read the full provision →
Interest from the date of misappropriation
Article 1896 fixes the starting date of interest with unusual precision: from the day on which the agent applied the sums to his own use. There is no requirement that you made a demand, that you discovered the diversion, or that any court ruled on it. The moment the agent used your money for his own purposes, the interest clock started. This is a significant departure from the ordinary rule that interest runs from demand. The law treats misappropriation of an agent's entrusted funds as a wrong that generates immediate consequences, not one that ripens only after the principal complains.
Why this rule is strict
The strict starting date reflects the agent's fiduciary position. An agent who handles money for the principal holds it in a position of trust. Using that money for his own benefit — even temporarily, even with an intention to repay — is a breach of that trust from the moment it occurs. Allowing the agent a grace period before interest begins would mean the principal is unknowingly subsidizing the agent's use of the principal's own money. Article 1896 prevents this: the agent carries the cost of the misappropriation from day one.
Interest on balances remaining after the agency ends
Article 1896 also addresses a second situation: money the agent still owes after the extinguishment of the agency. Once the agency ends, the agent must account for and return everything belonging to the principal. If he does not, interest continues to accrue on the outstanding balance. The ending of the agency does not give the agent additional time to settle up without cost. The obligation to pay interest persists until the balance is actually paid.
Practical implications for your claim
If you are pursuing this claim, the key factual question is the date on which your agent first applied the funds to his own use. That date determines how much interest has accumulated. Gather records showing when the diversion occurred — bank statements, transaction logs, correspondence, or accounting records. The interest rate applicable will be determined by the applicable law and any agreement between you; if no rate was stipulated, the legal interest rate applies. A lawyer can help you calculate the total due and pursue recovery through the appropriate legal channel.