Short answer. Your share of the estate is reduced by the amount you already received as a donation. Article 1073 of the Civil Code provides that the donee's share shall be reduced by what was already received, and the co-heirs shall receive an equivalent in property of the same nature, class, and quality where possible.
What the law says
The donee's share of the estate shall be reduced by an amount equal to that already received by him; and his co-heirs shall receive an equivalent, as much as possible, in property of the same nature, class and quality.
Civil Code, Article 1073 — Reducing the Donee's Share. Read the full provision →
How collation reduces your share
Article 1073 of the Civil Code implements the practical consequence of collation: "The donee's share of the estate shall be reduced by an amount equal to that already received by him." If you are a compulsory heir and you received a donation from the decedent during their lifetime, that donation is treated as an advance on your share. When the estate is divided, you receive correspondingly less from what remains. The law does not let you collect a full share of the residual estate as though the prior gift never happened.
How co-heirs are compensated
The second sentence of Article 1073 protects the co-heirs' interests: "his co-heirs shall receive an equivalent, as much as possible, in property of the same nature, class and quality." If your donation reduced your share of the residual estate, the estate property that would otherwise have gone to you is instead distributed to the other heirs who did not receive equivalent advance gifts. The law tries to give those co-heirs comparable property — land for land, movables for movables — rather than forcing them to accept cash or unrelated assets as compensation.
The underlying purpose of collation
Collation exists to prevent a parent from favoring one child during life and then leaving that child a full share of the estate anyway. Without it, a recipient of a large lifetime gift would also inherit equally at death, while siblings who received nothing were effectively left with a smaller combined share. Article 1073 puts the mechanism in concrete terms: the donee gets credit for what was already received, the co-heirs get the equivalent of what was not given to them. The goal is rough parity among compulsory heirs, accounting for what was given before death.
When this does not apply
Not every donation triggers collation. Article 1073 applies specifically to donations that are subject to collation under the Civil Code — typically, donations made to compulsory heirs that the donor did not expressly exempt. If the decedent made a donation expressly exempting it from collation, or if the donation was made to a stranger who is not an heir, Article 1073's reduction mechanism does not apply to that heir's share. Knowing whether a specific donation is subject to collation — and what its value was at the time it was made — is the essential first step in applying this rule.