Short answer. As soon as you learn of the testator's death. Article 876 requires a purely potestative condition — one that depends entirely on your own act — to be fulfilled as soon as you know the testator has died. The exception is where you have already complied and the act cannot be done again.
What the law says
Any purely potestative condition imposed upon an heir must be fulfilled by him as soon as he learns of the testator's death. This rule shall not apply when the condition, already complied with, cannot be fulfilled again.
Civil Code, Article 876 — Purely Potestative Conditions. Read the full provision →
What Article 876 requires
Article 876 provides that any purely potestative condition imposed upon an heir must be fulfilled by him as soon as he learns of the testator's death. This rule shall not apply when the condition, already complied with, cannot be fulfilled again. A purely potestative condition is one whose fulfilment lies entirely within the heir's own will — something he simply chooses to do, like taking a particular action or making a specified undertaking. Because it depends on nobody and nothing but him, the law sets a clear moment for performance: the point at which he learns the testator has died.
What 'purely potestative' means, and why timing is tied to death
'Purely potestative' distinguishes these conditions from ones that hang on chance or on another person's act. If the condition depends on an outside event, the heir waits for it; but if it depends solely on his own decision, there is nothing to wait for. So the trigger is knowledge of the death — the moment the inheritance is on offer, the heir who wants it must do the thing the will asks. The rule prevents a beneficiary from holding a conditional gift open indefinitely while declining to perform the very act the testator required as the price of it.
The exception for a condition already fulfilled
The second sentence carves out a sensible exception: the duty to perform on learning of the death shall not apply when the condition, already complied with, cannot be fulfilled again. If the heir happened to do the required act before the testator died, and it is the kind of act that cannot be repeated, the law does not make him do the impossible over again. The condition counts as satisfied by the earlier performance. This matters where the will attaches a condition the heir has, by chance or design, already met — he is not disqualified merely because he cannot perform a second time.
What to do when you learn of the death
If you are an heir under a will you suspect carries such a condition, read it promptly once the testator has died, and identify exactly what the condition asks and whether it depends purely on your own act. If it does, act on it without sitting on the gift, and keep proof that you did and when. Where it is one you already satisfied earlier and cannot repeat, gather the evidence of that earlier compliance. If the nature of the condition is unclear — whether purely potestative or mixed with some outside event — that distinction decides your deadline and is worth resolving early.