You have found the flat in the Marais or the stone house in the Luberon, the estate agent is pressing you to sign, and the document on the table is neither a reservation nor the final deed but a promesse unilatérale de vente (unilateral promise of sale). For a foreign buyer, this is the most misunderstood contract in the French purchase process: you pay a substantial sum on signing, you believe the property is secured, and yet the legal mechanics are the exact opposite of what most British or American buyers expect. Only the seller is bound. You, the buyer, are free to walk away — but walking away usually costs you the money you paid upfront. And if the seller tries to walk away, the outcome depends on rules that the Cour de cassation (France’s supreme court for civil matters) has rewritten twice in the last five years. This article explains, for non-resident buyers, how the unilateral promise works, what happens to your deposit if you miss the option deadline or if a condition fails, and what remedies exist when the seller backs out. For an overview of how our firm assists international clients with French property transactions, see our Paris real estate law practice.
I. What the unilateral promise is, and why foreign buyers sign one
A. One seller bound, one buyer free: the mechanics and the money
The unilateral promise is defined by the Civil Code itself. Article 1124 of the Civil Code provides: « La promesse unilatérale est le contrat par lequel une partie, le promettant, accorde à l’autre, le bénéficiaire, le droit d’opter pour la conclusion d’un contrat dont les éléments essentiels sont déterminés, et pour la formation duquel ne manque que le consentement du bénéficiaire. » In plain English: the seller (promettant, the promisor) grants the buyer (bénéficiaire, the beneficiary) the right to choose, for an agreed period, whether to buy a precisely described property at a fixed price, and the only thing missing for the sale to exist is the buyer’s yes. During the option period (délai d’option, the time left to the buyer to decide), the seller cannot sell to anyone else and cannot change the price; the buyer, by contrast, has a pure freedom to decide.
This asymmetry is exactly why the contract appeals to foreign buyers. You secure the property while you arrange the mortgage from London or New York, commission surveys, or wait for the French planning searches to come back, and you keep the right to walk away if the financing collapses or the surveys are bad. But that freedom has a price, literally: the indemnité d’immobilisation (lock-in payment, typically 5 to 10% of the price, very often 10%). It compensates the seller for taking the property off the market. It is usually paid on signing into the hands of the notaire (the French public officer who authenticates the final deed) acting as séquestre (escrow holder). If you lift the option, the sum counts toward the purchase price. If you let the deadline pass without lifting it, the seller keeps it. If the sale falls through for a reason that is the seller’s fault, for example because a condition the seller was supposed to fulfil never materialises, the buyer gets it back, as a 2020 ruling of the Third Civil Chamber confirms and as this article explains below.
Foreign buyers constantly confuse this payment with two neighbouring institutions, and the confusion is expensive. First, the compromis de vente (bilateral preliminary agreement), which is the contract most French residential sales actually use. Under Article 1589 of the Civil Code: « La promesse de vente vaut vente, lorsqu’il y a consentement réciproque des deux parties sur la chose et sur le prix. » In other words, a bilateral promise counts as a sale as soon as both sides agree on the property and the price: both parties are bound, and either side can be forced to complete. A unilateral promise is the mirror image — one party bound, one party free — so read the heading of your contract before assuming you can force the seller to complete, or before assuming you can walk away cheaply.
Second, the arrhes (earnest money with a mutual right to withdraw), governed by Article 1590 of the Civil Code: « Si la promesse de vendre a été faite avec des arrhes chacun des contractants est maître de s’en départir, Celui qui les a données, en les perdant, Et celui qui les a reçues, en restituant le double. » Where a promise is made with earnest money, each party may withdraw, the giver by losing what was paid and the receiver by returning double. The lock-in payment of a unilateral promise works nothing like that: the buyer cannot force the seller to pay double, and the seller cannot simply buy its freedom by returning double either. Since the 2016 contract reform, a seller who revokes the promise during the option period does not prevent the sale from forming at all, as the second paragraph of Article 1124 of the Civil Code states: « La révocation de la promesse pendant le temps laissé au bénéficiaire pour opter n’empêche pas la formation du contrat promis. » Revoking the promise while the buyer still has time to decide does not stop the promised contract from being formed. Before you sign, therefore, check three lines with your lawyer: the exact expiry date of the option, the precise form required to lift it (registered letter, service by commissaire de justice, appearance before the notaire), and the legal label of the sum you are paying.
B. The conditions that decide everything: loan, planning and your own sale
Almost every unilateral promise signed by a foreign buyer contains conditions suspensives (conditions precedent): events that must occur for the sale to become final. The classic trio is the mortgage (condition suspensive d’obtention de prêt, loan condition), the planning position (urbanisme, confirmation that the property may lawfully be used as intended), and sometimes the sale of the buyer’s own home abroad. The general mechanism is stated in Article 1304 of the Civil Code: « L’obligation est conditionnelle lorsqu’elle dépend d’un événement futur et incertain. » An obligation is conditional when it depends on a future and uncertain event. And the same article continues: « La condition est suspensive lorsque son accomplissement rend l’obligation pure et simple. » A condition is precedent (suspensive) when its fulfilment turns the obligation into a final one. In practice this means that lifting the option and satisfying the conditions are two different steps: you can lift the option while a condition is still pending, and the sale will then depend on whether the condition is fulfilled.
That two-step structure is where foreign buyers lose money, and the Third Civil Chamber illustrated it in a ruling of 5 March 2020 (nos. 19-13.386 and 19-13.717, reported by legal press Lextenso). By a notarised deed of 8 April 2016, sellers had granted a buyer a unilateral promise over a building, subject to several conditions including one on the sellers themselves: obtaining authorisation to change the building’s permitted use to residential. The buyer lifted the option on 7 June 2016 but postponed completion to 30 September 2016; on 2 August 2016 he withdrew because the change-of-use authorisation had never been obtained for the whole floor area. The sellers argued that lifting the option had created a perfect sale and that the buyer could not then walk away and reclaim the lock-in payment. The Cour de cassation rejected the argument and approved the appeal court’s reasoning that the lifting of the option, explained by correspondence showing the sellers had never applied for the authorisation over the full surface, could not be read as the buyer waiving the condition, still less as proof that the condition had been met. The court concluded, in the holding quoted by the commentator: « la vente ne s’étant pas réalisée par leur fait, les promettants devaient restituer l’indemnité d’immobilisation », meaning that since the sale had failed through the sellers’ own doing, they had to return the lock-in payment (Cass. 3e civ., 5 March 2020, nos. 19-13.386 and 19-13.717, see also Actu-Juridique analysis of the ruling).
Three practical lessons follow for a non-resident buyer. First, identify who bears each condition: a loan condition is on you, a change-of-use or planning condition is usually on the seller, and the fate of your deposit turns on that allocation. Second, never draft or accept a lifting letter that could be read as waiving a condition in your favour; state expressly that the option is lifted subject to (sous réserve de) the pending conditions. Third, remember the safety valve of Article 1304-4 of the Civil Code: « Une partie est libre de renoncer à la condition stipulée dans son intérêt exclusif, tant que celle-ci n’est pas accomplie ou n’a pas défailli. » A party may freely waive a condition agreed solely in its own interest, so long as the condition has neither been fulfilled nor failed. You can therefore deliberately waive your own loan condition late in the process if your financing is secure and you want to force completion — but you can never waive a condition stipulated in the seller’s interest, and no one can waive a condition after it has definitively failed. Calendar every condition with its documentary proof: the loan condition typically requires you to apply to a bank within days of signing and to produce written refusals, not oral ones, and foreign buyers should assume French courts will examine whether applications were serious and timely.
II. When things go wrong: missed deadlines, retraction and who keeps the money
A. Missing the deadline or walking away: the buyer pays, and the agent may lose too
The harshest rule of the unilateral promise is also the simplest: the option deadline is strict. If the délai d’option expires on 30 June and your lifting letter reaches the seller on 1 July, there is no sale, however close you were, and the seller keeps the indemnité d’immobilisation. No grace period is implied, and courts do not rewrite the date because your bank was slow or because you were abroad. For a buyer in another time zone, this means organising the lifting mechanics before travelling: give your French lawyer a written authority (pouvoir) to lift the option on your behalf, agree in advance the exact channel the contract requires, and keep proof of dispatch and receipt. A lifting letter sent by ordinary email when the contract demands a registered letter with acknowledgment of receipt (lettre recommandée avec accusé de réception) or service by commissaire de justice (court officer) is a classic way to lose both the property and the deposit.
Voluntarily walking away has the same financial result: the buyer who decides not to buy forfeits the lock-in payment, which is its contractual function, not a penalty for fault. That is the price of the freedom the contract gave you. Note the contrast with the seller’s position developed in the next section: since 2016, the seller has no mirror-image freedom, and a buyer who lifts the option in time can force the sale even if the seller has changed its mind. This asymmetry should shape your negotiation. If you are unsure about the property, a unilateral promise with a realistic option period and a 5% lock-in payment is a cheaper reservation than a bilateral compromis from which you cannot freely withdraw. If you are certain and want maximum security, the compromis binds the seller from day one without depending on a later act of will on your part — but it also binds you.
There is one more loser when the option is never lifted: the estate agent. Foreign buyers often assume the agent’s commission is earned once the promise is signed, especially where the agent introduced the parties. The Third Civil Chamber said no in a ruling of 26 March 2026 (no. 24-13.838), a decision every buyer using an agent should know. An agency held a search mandate and a non-exclusive sale mandate, each providing 5% commission; it introduced the seller and the buyer, who signed an authentic unilateral promise for 4.1 million euros over land, with several conditions including a building permit with a completion guarantee. The promise was extended to 24 April 2018 but the sale was never concluded, the land later being sold to a developer, and the agency sued for its commission. The Court of Appeal rejected the claim, and the Cour de cassation upheld that rejection: « Ayant constaté que la promesse était une promesse unilatérale de vente et que, l’option n’ayant pas été levée dans le délai par la bénéficiaire, la vente n’avait pas été conclue », the appeal court had correctly deduced the consequence, « l’agence immobilière n’était pas fondée à réclamer la rémunération convenue », meaning that since the promise was unilateral and the buyer had never lifted the option in time so no sale was concluded, the agency was not entitled to the agreed fee (Cass. 3e civ., 26 March 2026, no. 24-13.838). The principle behind the ruling is the statute governing agents, which requires the transaction to have been actually concluded and recorded in a single written act before any commission is due. For a foreign buyer this has a direct practical use: if your agent demands commission after a promise that never turned into a sale, the answer is no, and any clause in the mandate promising otherwise must be checked against the statute with your lawyer. Conversely, if you are the one who prevented completion in bad faith to deprive the agent of its fee, expect a fraud (fraude) claim, which is the only door the ruling leaves open.
B. The seller backs out: forced sale under the new law and the recent reversals
What if the seller finds a better offer during your option period and tells you the deal is off? For promises signed since 1 October 2016, the answer is now clear and buyer-friendly: the seller’s retraction changes nothing, and a buyer who lifts the option in time can obtain a court order forcing the sale (vente forcée, forced sale). The statutory anchor is the second paragraph of Article 1124, quoted above: revocation during the option period does not prevent formation of the promised contract. The leading illustration is a ruling of the Third Civil Chamber of 11 September 2025 (no. 24-13.774), which applied the new law to facts close to an ordinary residential purchase. By an authentic deed of 21 November 2016, several co-owning sellers had granted a company a unilateral promise over a house for 720,000 euros, initially expiring 21 February 2018 and extended to 30 June 2018, with the notaire convening the parties to sign the final deed on 29 June 2018. The building could not be vacated in time, the notaire postponed completion to 26 November 2018, seven sellers failed to attend, and the buyer sued for forced sale. The Court of Appeal rejected the claim under the old Article 1134, reasoning that the sellers’ renunciation before the lifting of the option had made the promise lapse. The Cour de cassation quashed that reasoning: the promise dated 21 November 2016 fell under the post-reform law, under which « la révocation de la promesse unilatérale de vente pendant le temps laissé au bénéficiaire pour opter n’empêche pas la formation du contrat promis », so a revocation during the option period cannot stop the promised sale from forming (Cass. 3e civ., 11 Sept. 2025, no. 24-13.774). For a foreign buyer, the message is concrete: if the seller gets cold feet after you have signed, do not accept the lapse — lift the option within the period, in the required form, and sue for completion.
The same protection now extends even to promises signed before the 2016 reform, thanks to two reversals (revirements de jurisprudence, overrulings) that rewrote decades of case law. For years, the rule was that lifting the option after the seller’s retraction produced no meeting of minds and no forced sale. The Third Civil Chamber abandoned that position on 23 June 2021 (no. 20-17.554) and 20 October 2021 (no. 20-18.514): the promisor is definitively bound from the preliminary contract and cannot retract, absent a clause to the contrary. In the October 2021 case, owners had sold quarry land with a promise to re-sell it back after extraction, then retracted; the appeal court held the retraction blocked the re-sale for want of exchanged consent, and the Cour de cassation quashed, holding: « le promettant signataire d’une promesse unilatérale de vente s’oblige définitivement à vendre dès la conclusion de l’avant-contrat, sans possibilité de rétractation, sauf stipulation contraire », meaning the promisor is definitively bound to sell from the preliminary contract with no right to retract, unless otherwise agreed (Cass. 3e civ., 20 Oct. 2021, no. 20-18.514). The Commercial Chamber then aligned the other chambers on 15 March 2023 (no. 21-20.399) in a share-sale promise dispute: retraction on 8 March 2016, option lifted 28 June 2016, appeal court refused forced sale under the old law, and the Cour de cassation quashed, stating the new principle in terms that now govern all promises: « le promettant signataire d’une promesse unilatérale de vente s’oblige définitivement à vendre dès cette promesse et ne peut pas se rétracter, même avant l’ouverture du délai d’option offert au bénéficiaire, sauf stipulation contraire », so the promisor is bound from the promise and cannot retract even before the option period opens, unless the contract says otherwise (Cass. com., 15 March 2023, no. 21-20.399). Note the reservation that ends both holdings — sauf stipulation contraire (unless otherwise agreed): parties can still contractually allow retraction, so check whether your promise contains such a clause before relying on the forced-sale remedy.
In practice, a foreign buyer facing a retracting seller should move fast and in the right order. First, lift the option within the contractual period even if the seller says the deal is dead; without that act there is nothing to enforce. Second, have your lawyer put the seller on formal notice (mise en demeure) to attend the notaire’s office on a fixed date. Third, if the seller still refuses, petition the court for forced sale plus damages for delay, and register your claim where possible so the property cannot quietly be sold to a third party in the meantime. Buyers who need counsel to manage the timetable, the lifting formalities and the court application from abroad can instruct a firm handling cross-border property disputes, such as our Paris real estate litigation team. Time limits for court action (prescription) run from the breach, so do not let months pass while negotiating informally from abroad.
Conclusion
The unilateral promise of sale is a powerful tool for a foreign buyer who uses it with open eyes: it reserves the property while you organise finance and checks, and it now binds the seller almost absolutely, before and after the 2016 reform, unless the contract expressly says otherwise. But its three traps catch a buyer every week in our experience: treating the lock-in payment as refundable goodwill money when it is forfeited if you simply walk away; lifting the option late or in the wrong form and discovering there is no sale to enforce; and signing a lifting letter that waives, by clumsy wording, the very conditions that would have entitled you to your money back. Protect yourself with four reflexes: calendar the option deadline with a safety margin and a written proxy for lifting it; allocate each condition to the right party and demand documentary proof of fulfilment; lift the option expressly subject to pending conditions; and if the seller retracts, lift first and litigate second. Done properly, the promise gives you time without giving the seller freedom — which is exactly what a buyer purchasing from three thousand miles away needs.
Need a quick opinion on your case
If you are buying French property under a unilateral promise of sale, you can request a telephone consultation within 48 hours to review your option deadline and deposit position. Call +33 6 46 60 58 22 or write via our contact page.