A contract becomes impossible to perform when an unforeseeable event, outside either party’s control, makes the promised performance something no one could carry out — not merely something one party finds harder or more expensive. Courts treat this as a narrow defense. The event must genuinely prevent performance, it must not have been something the parties could reasonably have anticipated when they signed, and the impossibility must be objective rather than personal to one side. A handful of specific situations qualify: the destruction of an irreplaceable item the contract depends on, the death or incapacity of a person whose individual skill was the point of the deal, and a new law that makes the required activity illegal. Everything else — rising costs, supply problems, changed business plans — almost always stays the obligated party’s problem.
The Objective Standard
The threshold question in any impossibility claim is whether the performance is objectively impossible or just subjectively impossible for this particular party. Only the first counts.
Objective impossibility means no one on earth could do what the contract requires. Subjective impossibility means this specific party can’t do it, even though someone else theoretically could. Courts excuse the first and ignore the second.
A farmer who contracted to deliver 100 bushels of apples and lost his crop to blight has a subjective problem. Apples still exist in the world; he can buy them elsewhere to satisfy the contract. His hardship is real, but it isn’t impossibility. Change the facts so the contract required apples from one specific tree that disease destroyed, and the analysis flips. No one can produce apples from a tree that no longer exists. That performance has become objectively impossible, and the duty is discharged.
Most impossibility arguments die at this line. “I can no longer do this profitably” and “my circumstances changed” are not the same as “this literally cannot be done,” and courts are unsympathetic when parties blur them.
Situations Courts Recognize as Impossible
Destruction of the Thing the Contract Depends On
When a contract turns on a specific, irreplaceable item and that item is destroyed through no one’s fault, performance is excused. Both parties built the agreement on the assumption that the thing would still exist; when it doesn’t, the foundation of the deal is gone.
The defense only works if the destroyed item was the actual subject of the contract — not a general commodity. A fire that destroys the specific vintage car you agreed to sell discharges your duty. If you simply agreed to sell “a 1967 Mustang” without identifying a particular vehicle, you’re expected to find another. The more unique and specifically identified the item, the stronger the defense.
Death or Incapacity in a Personal Service Contract
When a contract depends on a specific person’s skill, talent, or judgment, that person’s death or serious incapacity ends the obligation. A portrait commissioned from a particular artist is the textbook case. If the artist dies or can no longer paint, no one else can step in, because the whole point was that individual’s work.
This only applies where the person is genuinely irreplaceable. If a homeowner hires a large painting company and the assigned worker gets sick, the company still owes performance — it can send someone else. The question courts ask is whether the contract’s value depends on a particular human being or just on getting the job done.
A New Law That Prohibits Performance
A contract that was legal when signed can become impossible if a later law, regulation, or government order makes the required activity illegal. The change has to come after formation, and it has to directly prohibit the performance, not just raise its cost or add paperwork.
A company that contracted to import a specific electronic component is excused if the federal government imposes a trade embargo on that product before shipment. The same logic applies to local changes: a property owner who contracted to run a particular business on a site may be excused if the area is rezoned to prohibit that use. A regulation that simply makes compliance more expensive doesn’t qualify.
When the Impossibility Is Only Temporary
Not every impossibility is permanent. A disaster might block delivery routes for weeks. A government order might shut down operations for a defined period. In those situations, the obligation doesn’t disappear — it pauses. The duty is suspended while the impossibility lasts, and performance resumes once conditions return to normal.
There’s an important exception. If performing after the delay would be fundamentally more burdensome than the original deal contemplated, a court may discharge the obligation entirely rather than force a party into what is effectively a different contract. A two-week delay on a shipment is one thing; a two-year delay on a time-sensitive construction project is another, because by the time the obstacle lifts, materials, labor, and project economics may have shifted so far that holding the party to the original terms would be unfair.
One practical point parties routinely overlook: when the temporary impossibility ends, you’re expected to perform promptly, not sit back and wait to see if conditions improve further. Notice requirements that were excused during the disruption come due at the earliest opportunity once things clear. Courts have little patience for parties who use a lifted obstacle as cover to delay further.
The Foreseeability Trap
Every impossibility defense lives or dies on foreseeability. If the disrupting event was something the parties could reasonably have anticipated when they signed, the defense fails. The reasoning is that a foreseeable risk is one the parties could have addressed in the contract itself, and if they chose not to, they implicitly accepted it.
Courts measure foreseeability against what a reasonable person in the same industry and setting would have expected. A shipping company that ignores the possibility of port closures during hurricane season will struggle to claim impossibility when a hurricane shuts the port. A construction firm working in a known seismic zone can’t easily claim it after an earthquake.
This is where the defense most often collapses. The COVID-19 pandemic produced a wave of impossibility claims, and courts largely rejected them, particularly for commercial leases. When a restaurant’s lease didn’t limit it to dine-in service, courts found takeout remained possible and impossibility didn’t apply. Sophisticated commercial parties who hadn’t included pandemic-related provisions were generally held to their deals. The lesson is unavoidable: if a risk is identifiable at signing, address it in the contract, because the common law defense is not a safety net for omitted terms.
When a Force Majeure Clause Changes the Analysis
Many contracts handle these events through a force majeure clause rather than relying on the common law. Those clauses list the specific types of events — wars, natural disasters, government actions, pandemics, and similar disruptions — that excuse or delay performance. When a contract has one, it typically supersedes the common law doctrines of impossibility, impracticability, and frustration of purpose. Courts treat it as the parties’ own negotiated allocation of risk and apply it in preference to the default rules.
Force majeure clauses are read narrowly. Relief is limited to the events the clause actually lists. If yours mentions “natural disasters, war, and government action” but not “pandemic” or “epidemic,” a court may refuse to apply it to a disease-related shutdown, no matter how severe. Broad catch-all phrases like “any event beyond the parties’ control” help but don’t guarantee coverage.
Nearly every force majeure clause requires the affected party to give prompt written notice describing the event and its expected duration. Missing that notice can forfeit the protection even when the underlying event clearly qualifies. Some clauses also set a maximum duration, after which either party may terminate. Before invoking the clause, read it carefully and follow its procedures exactly. Getting the process wrong is as costly as being wrong on the substance.
Impracticability and Frustration of Purpose
If literal impossibility doesn’t fit, two related doctrines sometimes do.
Commercial impracticability is the more flexible cousin. It doesn’t require that performance be impossible, only that an unforeseen event has made it so unreasonably difficult or expensive that forcing compliance would be unjust. For contracts involving the sale of goods, this defense is codified in Section 2-615 of the Uniform Commercial Code, which excuses a seller’s delay or non-delivery when performance becomes impracticable due to an event both parties assumed would not occur.1Legal Information Institute. UCC 2-615 Excuse by Failure of Presupposed Conditions The bar is still high. A price increase doesn’t qualify, even a substantial one, because that’s a business risk baked into any fixed-price contract. The cost spike must come from an unforeseen event that fundamentally changes what performance involves, not from ordinary market swings.
Frustration of purpose handles a different problem. Performance is still possible — nothing physically prevents either side from doing what they promised — but an unforeseen event has destroyed the entire reason one party entered the contract, leaving the deal worthless to them. A rented apartment along a canceled parade route is the classic illustration: the renter can still take the apartment, the landlord can still provide it, but the point of the agreement is gone. The same foreseeability requirement applies, and the destroyed purpose has to be the principal reason for the contract, not an incidental benefit. A company that leases office space and later prefers remote work can’t invoke frustration, because the lease still delivers what it promised.
Getting Your Money Back After Discharge
When a contract is discharged, both parties walk away from future obligations. That doesn’t resolve what already happened. If one side paid a deposit, delivered partial work, or shipped some goods before the impossibility arose, the law doesn’t let the other side keep those benefits for free.
Under the principle of restitution, a party whose duty is discharged can recover the reasonable value of any benefit it already provided. A deposit paid before the contract became impossible is refundable. Half the goods shipped before a government ban cut off further delivery are compensable at fair value. The point is to prevent one side from being unjustly enriched because circumstances intervened.
The other side gets credits too. Any benefit the recovering party received — use of property, services rendered, materials consumed — is offset against what’s owed. Courts aim for a fair unwinding, not a windfall. This gets complicated quickly when both sides have partially performed over long periods, which is one reason a well-drafted force majeure clause that spells out how costs and payments are handled during a disruption is worth the effort to negotiate upfront. That work costs far less than litigating restitution after the fact.