An owner signs a mandat de vente (sale mandate, the written agency agreement a French estate agent must hold before marketing a property), then a notarised promise to sell her villa for €205,000. She then refuses to sign the deed, argues that she only intended to sell part of the property and accuses the estate agent of having undervalued it. On 19 September 2024, the Cour de cassation (the French supreme court for civil and commercial matters) upheld the order to complete the sale and dismissed the claim against the agent: the alleged undervaluation was not established. The ruling restates a useful truth: a value gap is proved, not asserted.
The facts
The owner had given a sale mandate to an agency, then, by a notarial deed of 22 May 2015, unilaterally promised to sell a house to two beneficiaries. The promise contained a condition precedent of obtaining a loan and insurance before 7 August 2015, stipulated in the exclusive interest of the beneficiaries, and provided for the deed to be signed before 7 September 2015. By letters of 7 August 2015, the seller claimed the promise had lapsed and refused to sign.
She sued the beneficiaries for a declaration that the promise had lapsed and for compensation; they asked for the sale to be enforced. She joined the agency to the proceedings, seeking the annulment of the mandate and compensation. The mandate described the property as a “T3/T4 villa of 70 m² on a plot of 442 m²” (translated from the French); according to the seller, that wording could refer to the flat alone and not to the whole, and the price of €205,000 was in her view closer to that of a flat than of a house.
The Toulouse Court of Appeal, on 8 November 2022, dismissed all her claims and ordered her to pay €20,000 in damages to the beneficiaries.
The decision
The appeal was dismissed (Cass. 3e civ., 19 September 2024, appeal no. 23-10.585).
On the mandate, the Court of Appeal had found, within its sovereign power of interpretation, that it was unambiguous: it referred to the whole villa, with both floors vacant, and to the cadastral references of the entire plot.
On the agent’s liability, the seller argued that a professional bound by a duty to inform and advise must prove that he performed it, and that the Court of Appeal had reversed the burden of proof by rejecting the breach concerning the price on the ground that the undervaluation was not demonstrated. The Cour de cassation approved the Court of Appeal for holding that the terms of the mandate and the price were unambiguous, that the promise had been signed before a notaire (French civil-law notary) without any restriction as to area, and that the alleged undervaluation was not established, the property being located in a flood zone near the Garonne embankment. The Court of Appeal was entitled to conclude, “without reversing the burden of proof” (translated from the French), that as no breach was established, the claims for compensation could not succeed.
A reminder: once the agent’s fault is established, it is compensated in full
Conversely, when the estate agent’s fault is proved, the First Civil Chamber draws all the consequences. In a case concerning the sale of a light leisure dwelling with a commercial lease, annulled for fraud, it held, on the basis of article 1240 of the Civil Code, that “the seller whose fraud caused the annulment of the sale and the estate agent whose fault contributed to the nullity of the sale are bound to make good all the harmful consequences for the buyer” (translated from the French), and that the agent “whose fault contributed, at least in part, to the annulment of the deed may be ordered to guarantee payment in the event of the seller’s proven insolvency” (Cass. 1re civ., 28 June 2023, appeal no. 21-21.181, reported decision).
What the expert takes from it
Undervaluation is a fact to be proved, at the date of the sale. Saying that a price is too low is not enough; the value of the property on the day of the promise must be established. That is a retrospective valuation: comparable sales from the same period, condition of the property at that date, local market at the time. The report presents the market value within the meaning of the Charte de l’expertise en évaluation immobilière (the French property valuation charter, 6th edition, November 2025, Title III, § 1.1) and of EVS 1 of the European Valuation Standards 2025, then the gap with the agreed price. Without that quantified gap, no loss can be measured.
Site constraints are part of the value. The decisive argument was the location in a flood zone, near an embankment. A risk prevention plan, an easement, an agricultural zone or a poor DPE (energy performance certificate) reduce value, and a price that looks low against the town’s averages may be in line with the market once these constraints are taken into account. The expert identifies them in the planning documents and during the visit, and translates them into documented deductions.
The mandate defines the object; the report fixes the value of that object. The dispute arose from a disagreement over what was being sold, the whole villa or a flat. A valuation describes precisely what is valued: plot, areas, floors, occupation. That description protects the seller as much as the buyer, and the agent, before signature. When fault is subsequently found, as in the 2023 ruling, the recoverable loss includes all the consequences of the transaction, which makes the initial valuation all the more important.
Further reading
The Market value page describes the valuation of a property at a past date, the timescale and the fee. On the same theme: Selling below value in France: the seller is deemed to know and Cancelling a property sale in France for a price far too low?. The rulings are available on Légifrance: 19 September 2024 and 28 June 2023.
What next
You think you sold, or bought, at a price far from the value?
I establish the market value of the property at the date of the sale, with verifiable comparables and taking into account the constraints of the site. The report measures the gap, if there is one, and gives your lawyer a basis to pursue or rule out a liability claim.
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