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CISG Article 79 exempts a party from damages for non-performance when an impediment beyond its control, unforeseeable at contracting and unavoidable in effect, causes the failure. The exemption lasts while the impediment persists, requires prompt notice, and blocks only damages claims. Courts remain divided on whether economic hardship qualifies as an impediment.
The question matters more than ever. Tariff swings, sanctions, and raw-material shortages keep upsetting the math of long-term supply deals. Therefore, businesses selling across borders should understand when the Vienna Sales Convention excuses a failure, and when it leaves them exposed. This guide covers the elements, the notice rules, the hardship debate, and the drafting answers.
What Does CISG Article 79 Require?
The United Nations Convention on Contracts for the International Sale of Goods governs many cross-border sales by default. It currently binds 97 states, according to the UNCITRAL status table for the Vienna Sales Convention. Its exemption rule sets three conditions, and all of them must be met. First, an impediment beyond the party’s control must cause the failure. Second, the party could not reasonably have taken the impediment into account when it signed. Third, the party could not reasonably avoid or overcome the impediment or its consequences.
The failing party bears the burden on every element. Moreover, a seller who blames a supplier faces a stricter double test, because the provision’s second paragraph demands that both the seller and the third party qualify for the exemption. Typical qualifying events include war, export bans, embargoes, and natural disasters. In contrast, ordinary market movements almost never qualify.
Notice, Duration, and the Damages-Only Limit
Three mechanics decide most disputes under this rule. First, the exemption runs only while the impediment exists; performance duties revive when it ends. Second, the affected party must notify the other side within a reasonable time after it knew or should have known of the impediment. Late notice creates liability for the damages the silence caused.
Third, the exemption blocks only damages claims. As a result, the other party may still avoid the contract, reduce the price, or claim interest. Buyers should also remember their separate duties when goods arrive defective; we explain them in our guide to notice rules for defective goods.
Does Hardship Count as an Impediment? The Scafom Case
The treaty never mentions hardship, which arises when performance stays possible but becomes excessively burdensome. The leading case says CISG Article 79 can still apply. In Scafom International BV v. Lorraine Tubes S.A.S., steel prices rose about 70% after the parties fixed their price. On 19 June 2009, the Belgian Court of Cassation held that an unforeseeable price surge may qualify as an impediment. Furthermore, the court filled the treaty’s gap with general principles and recognized a duty to renegotiate the price. A summary appears in the Unilex case database.
Scholars pushed back. The CISG Advisory Council’s Opinion No. 20 accepts that hardship can fall within the exemption, yet it rejects any duty to renegotiate and denies courts the power to adapt or terminate the contract. Consequently, the law remains in flux, and outcomes vary by forum. Parties who want renegotiation rights cannot rely on the Convention alone.
Drafting Around Article 79: Force Majeure and Hardship Clauses
The Convention lets parties derogate from its provisions, so careful drafting beats litigation. Most international contracts therefore pair two provisions. A force majeure clause handles impossibility: it lists qualifying events, requires notice, suspends performance, and allows termination after a set period. A hardship clause handles profitability: it triggers renegotiation when set thresholds are crossed, such as a cost rise beyond a stated share.
The International Chamber of Commerce publishes balanced model texts for both in the ICC’s March 2020 model clauses. Under the ICC hardship text, failed talks lead to one of three outcomes picked at drafting: the affected party may end the contract; a judge or arbitrator may adapt it or end it; or the judge or arbitrator may end it, without power to adapt. For the impossibility side of the line, read our guide to excusing non-performance in global trade contracts.
For fixed-price supply deals, an escalator mechanism can prevent the problem entirely by adjusting the price against a published index. We compared these tools in our analysis of price-inflation defenses in fixed-price deals. For broader contract-planning support, see our international sales practice overview.
How Tribunals Apply the Article 79 Exemption
Arbitral tribunals and courts apply the exemption strictly. The affected party must prove causation between the impediment and the failure, so a seller already in breach before the event rarely succeeds. Tribunals also police mitigation, and they expect evidence of alternative sourcing efforts, even at higher cost. In fact, several decisions have denied relief because the seller could still buy the goods elsewhere.
Records often decide these cases. Timely notices, letters, and notes from the talks carry real weight. Businesses that treat CISG Article 79 as a managed procedure, rather than a last-minute excuse, enter any later arbitration with the stronger file.
Frequently Asked Questions
Sometimes. The Belgian Supreme Court’s Scafom decision treated a roughly 70% price surge as a qualifying impediment, while the CISG Advisory Council accepts hardship only in exceptional cases and rejects any renegotiation duty. Outcomes therefore depend heavily on the forum and the facts.
The failing party must notify the other side of the impediment and its effects within a reasonable time after learning of it. Otherwise, it owes damages caused by the missing notice, even when the impediment itself qualifies. Prompt written notice with updates remains the safe practice.
Yes. The Convention expressly allows parties to derogate from or vary its provisions. Consequently, most cross-border contracts add tailored force majeure and hardship clauses that define events, notice deadlines, and remedies with more precision than the default rule provides.
Conclusion
CISG Article 79 offers a narrow exemption, not a general escape. The defense demands an external impediment, true unforeseeability, causation, mitigation, and prompt notice, and it blocks only damages. Because the hardship question remains contested, the drafting stage is the only reliable place to secure renegotiation rights and clear risk allocation. A well-built force majeure clause, a hardship clause, or an escalator clause turns an economic shock into a managed process.
Our attorneys help businesses draft, invoke, and respond to these provisions in cross-border sales and arbitration. Schedule a consultation with our team to discuss protections tailored to your contracts and supply chain.
