Short answer. When both parties made the same mistake in a written contract, Civil Code Article 1368 allows either party — or their successors in interest — to petition for reformation. If only one party was injured by a mistake or fraud, only that party, or their heirs and assigns, may seek it.
What the law says
Reformation may be ordered at the instance of either party or his successors in interest, if the mistake was mutual; otherwise, upon petition of the injured party, or his heirs and assigns.
Civil Code, Article 1368 — Who May Seek Reformation. Read the full provision →
What reformation is and why it matters
Reformation is a remedy that asks a court to correct a written contract that does not accurately reflect what the parties actually agreed to. The agreement is valid; the written document is the problem. Rather than voiding the transaction entirely, the court rewrites or corrects the document so it matches the true intent. Article 1368 determines who has the right to initiate this process, and the answer depends on whether the mistake was shared by both parties or suffered by only one.
Mutual mistake: either party can ask
When the mistake in the written contract was mutual — both parties misunderstood or both signed a document that did not reflect what they agreed on — Article 1368 gives either party the right to seek reformation. Since both were equally mistaken, neither has an exclusive grievance. Either side can bring the petition, and so can their successors in interest — the heirs, assignees, or others who have stepped into a party's position. This makes practical sense: both parties share the same interest in correcting a document that neither intended to sign in its flawed form.
One-sided mistake or fraud: only the injured party
When only one party is hurt — through a unilateral mistake that the other exploited, or through fraud, inequitable conduct, or accident — Article 1368 limits the right to petition to the injured party, or that party's heirs and assigns. The party who benefited from the error cannot turn around and seek reformation on those grounds; they have nothing to complain about. The remedy belongs to the person who was harmed by the discrepancy between what was agreed and what was written.
Successors in interest can continue what the original party started
Article 1368 expressly includes successors in interest — in both the mutual and unilateral scenarios. This means a reformation claim does not die with the original contracting party. If the party who had standing to seek reformation dies before doing so, their heirs or assigns inherit that right and can petition the court in their own names. This is particularly relevant in estate proceedings where a defective deed or agreement surfaces after the contracting party's death and the heirs need to clean up the documentary record to properly settle the estate.