A nullity declared four years after signing erases the contract, never the investments made in reliance on it: a defect of consent is dealt with at the time of the negotiation, not at the time the writ is issued. Between July 2024 and July 2026, the Cour de cassation handed down five decisions published in the Bulletin that have shifted this area of law more decisively than any legislative reform since the 2016 ordinance: duress has become more objective and is now made out without any scene of coercion, the excessive-advantage test has been relativised and now requires a two-sided assessment, and proof is now built from evidence created after signing. Six points determine, in every case, whether a contract survives a nullity action.
1. Duress no longer requires conduct
Since a ruling of 4 June 2026, the Third Civil Chamber has held that “it is not necessary to establish the existence of positive acts of threat or pressure” to characterise abuse of dependence, and that a state of dependence “may result from a state of vulnerability, known to the other contracting party, of which it takes advantage when concluding the contract” (Cass. 3e civ., 4 June 2026, no. 24-15.070, published in the Bulletin). A claimant no longer has to recount a scene: it is enough to establish a situation, the other party’s knowledge of it, and a price imbalance. Dependence ceases to be an economic power relationship and becomes a state, which may stem from age, illness, isolation or impaired judgment, provided the other contracting party knew of it and took advantage of it. The ruling does not, however, create any presumption: the four conditions of Article 1143 remain cumulative and rest on the claimant.
2. But the excessive advantage is now weighed from both sides
The counterweight came sixteen months earlier, and it is just as firm as the opening: “in a synallagmatic contract, obtaining a manifestly excessive advantage within the meaning of Articles 1141 and 1143 of the Civil Code must also be assessed in light of the advantages obtained by the other party” (Cass. 1re civ., 29 January 2025, no. 23-21.150, published in the Bulletin). Comparing the price paid to the market price is therefore no longer enough: the complete balance sheet of the transaction must be produced, including reciprocal concessions, securities obtained and risks avoided. In the case decided, an apparent advantage of several million euros disappeared entirely once the agreement was compared with what the beneficiary would have obtained without it. This is a heavy burden of proof, and it rests entirely on the claimant.
3. The court is entitled to look at what happened after signing
The defect is assessed as of the date the contract was formed, but it is proven with evidence from afterwards. The Commercial Chamber upheld a court of appeal that had relied on an amendment signed on the very day of the sale to rule out abuse of dependence, holding that it “could rely on evidence concomitant with or subsequent to the date the contract was formed” (Cass. com., 10 July 2024, no. 22-21.947, published in the Bulletin). Everything the parties do in the days following signing enters the file, including a thank-you email or a clarifying amendment. For the drafter, the consequence is direct: the safeguarding file does not stop at signing, it continues in the weeks that follow.
4. Silence about value stays free; silence about anything else is very costly
A buyer, even a professional one, owes no duty to disclose the value of the asset being purchased (Cass. 1re civ., 3 May 2000, no. 98-11.381; Cass. 3e civ., 17 January 2007, no. 06-10.442), and Article 1112-1 of the Civil Code expressly excludes the valuation of the price of the performance from the duty of disclosure. By contrast, an employee who conceals from his employer the competing venture he is preparing vitiates that employer’s consent: the mutually agreed termination then annulled produces the effects of a resignation, and it is the employee who owes the notice indemnity (Cass. soc., 19 June 2024, no. 23-10.817, published in the Bulletin). Fraud has no side: it can come from the stronger party as much as the weaker one, and the sanction follows the same severity in both directions. Staying silent about value is lawful; lying about what determines it is not.
5. Lesion is not a defect of consent, the two must not be confused
“A lack of equivalence between the parties’ performance is not a ground for nullity of the contract, unless the law provides otherwise” (Civil Code, Art. 1168). The most common mistake since the ruling of 4 June 2026 is to treat Article 1143 as a rescission for lesion applicable to all contracts. It is not: the manifestly excessive advantage is only one of the four cumulative conditions of duress by abuse of dependence, alongside the state of dependence, its abuse and the decisive character of the undertaking, and it can no longer be measured in isolation since 29 January 2025. An unbalanced contract entered into between sophisticated professionals, each of them advised, after several weeks of documented negotiation, remains valid, whatever price gap is found after the fact.
6. The timetable is shorter than people think, and it can be forced shut
The five-year limitation period runs, in the case of mistake or fraud, only from the day of discovery and, in the case of duress, only from the day it ceased (Civil Code, Art. 1144 and Art. 2224); voluntary performance of the contract with knowledge of the ground for nullity amounts to confirmation (Art. 1182). Above all, a party who fears a claim may give the other contracting party written notice to either confirm the contract or bring a nullity action within six months, on pain of forfeiture (Art. 1183). This is the most effective tool in this area of law, and the least used in the whole of contract law: used well, it turns a five-year exposure into a six-month one. It has its place in any family transfer, partner buy-out or transaction where an apparent imbalance leaves open a risk of challenge.
Guyader Avocat handles the full range of disputes over defects of consent: an audit of contract-safeguarding measures ahead of a sale or acquisition, bringing or defending a nullity action, using the interpellatory notice of Article 1183, and damages claims distinct from nullity.
For assistance with a business law matter, see our page on business law, as well as those on business acquisition and sale and shareholder disputes.
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Further reading: Duty of vigilance: the six points that decide whether your plan survives a formal notice.