Impossibility and Impracticability: When Contracts Cannot Be Performed

What Is the Doctrine of Impossibility in Contract Law?

Impossibility excuses a party from performing a contract when an unforeseen event makes performance objectively impossible–not merely difficult or expensive, but genuinely incapable of being accomplished. The doctrine reflects a core principle of contract law: parties should not be held liable for circumstances entirely beyond their control.

Courts apply a high standard before finding impossibility. The event must be truly unforeseen at the time of contract formation, and the impossibility must be objective rather than personal to the party claiming it. A party that simply lacks the financial resources to perform, for example, cannot claim impossibility–that is a subjective inability, not an objective one.

Three elements must be established to invoke impossibility as a defense:

1. Unforeseen event: An occurrence that neither party anticipated or could reasonably have anticipated when the contract was formed, such as a natural disaster, destruction of essential subject matter, or death or incapacity of a person essential to performance.
2. Objective impossibility: The event must make performance impossible for anyone, not just for the particular party seeking relief. If another party could perform the contract under the same circumstances, impossibility does not apply.
3. No fault: The party claiming impossibility must not have caused or contributed to the event that rendered performance impossible.

The doctrine balances the need for contractual stability with fairness in extraordinary situations. Courts do not apply it lightly because doing so releases parties from voluntarily assumed obligations, which could undermine confidence in the enforceability of contracts generally.

What Is Impracticability and How Does It Differ From Impossibility?

Impracticability addresses a broader range of situations than impossibility. Where impossibility requires that performance be literally incapable of accomplishment, impracticability applies when performance remains theoretically possible but has become so excessively burdensome that requiring it would be unreasonable and fundamentally unfair.

The Restatement (Second) of Contracts and the Uniform Commercial Code (UCC) both recognize impracticability as a defense. Under UCC Section 2-615, a seller’s delay or failure to deliver goods is excused when performance has been made impracticable by the occurrence of a contingency whose non-occurrence was a basic assumption on which the contract was made.

Four elements define an impracticability claim:

• The occurrence of an unforeseen event after contract formation
• A significant increase in cost or difficulty of performance far beyond what was contemplated
• The event was not caused by the fault of the party seeking relief
• The non-occurrence of the event was a basic assumption underlying the contract

The distinction between impossibility and impracticability matters in practice. Impossibility is an absolute defense–performance cannot occur. Impracticability is a relative defense–performance can occur but at a cost or difficulty so extreme that the contract’s fundamental purpose is defeated. Courts evaluating impracticability claims examine whether the increased burden is genuinely extraordinary or simply an ordinary business risk that the party should have anticipated and absorbed.

What Are Common Examples of Impossibility in Contracts?

Impossibility arises from events that eliminate the physical or legal possibility of performance. The most common categories include:

Destruction of subject matter: When the specific subject matter of the contract is destroyed without fault of either party, performance becomes impossible. A contract to sell a particular building that is destroyed by fire before closing cannot be performed, and the seller is excused.

Death or incapacity of an essential person: When performance depends on a specific individual–such as a commissioned artist, a named consultant, or a key performer–that person’s death or incapacitating illness excuses performance.

Force majeure events: Natural disasters such as hurricanes, earthquakes, floods, and pandemics can render performance impossible by destroying infrastructure, disrupting supply chains, or making physical performance unsafe. Government actions–including embargoes, lockdowns, and emergency orders–can similarly prevent performance by prohibiting the contracted activity outright.

Supervening illegality: When a change in law makes the contracted performance illegal after the contract was formed, impossibility applies. A contract to import specific goods becomes impossible if the government imposes a trade embargo on those goods. Similarly, licensing law changes may prohibit a party from performing services they were previously authorized to provide.

Each of these categories requires that the event was unforeseen and not caused by the party claiming impossibility. Courts will not excuse performance where the party assumed the risk of the event or could have reasonably anticipated it at the time of contracting. The party asserting impossibility bears the burden of proving that the event was genuinely unforeseeable and that no reasonable alternative means of performance existed. Courts also consider whether the party took all available steps to mitigate the impact of the event before concluding that performance was truly impossible.

What Are Common Examples of Impracticability in Contracts?

Impracticability claims arise from events that do not make performance impossible but make it unreasonably burdensome. Common scenarios include:

• Extreme cost increases: A supplier contracts to deliver materials at a fixed price, but a sudden commodity shortage causes the market price to increase tenfold. Performance is possible at the new price, but the cost is so far beyond what either party contemplated that enforcing the contract at the original price would be fundamentally unfair.
• Supply chain disruptions: Unforeseen shortages of critical materials–caused by natural disasters, trade restrictions, or industrial accidents–prevent timely procurement of components needed for performance, even though the materials exist somewhere in the market.
• Regulatory changes: New regulations do not prohibit performance outright but impose compliance requirements so extensive and costly that the nature of the obligation is fundamentally altered.
• Pandemic-related restrictions: Public health emergencies impose limitations on operations, gatherings, or travel that do not make performance absolutely impossible but render it impracticable under the circumstances. Event contracts, hospitality agreements, and construction timelines were all heavily affected during the COVID-19 pandemic.

Courts evaluate these claims by comparing the burden of performance against the baseline expectations of the parties at the time of contracting. A moderate cost increase or ordinary business disruption will not support an impracticability defense. The increase must be so severe that it goes well beyond the normal range of risk that the parties implicitly accepted.

The distinction between an ordinary business risk and an impracticability-level disruption is often the most heavily litigated issue in these cases. A cost increase of 10-20% is unlikely to qualify. An increase of 500-1000%–or a complete restructuring of the means of performance–is far more likely to meet the standard. Courts also consider whether the affected party could have obtained insurance against the risk, which may cut against finding impracticability if commercially reasonable insurance was available but not obtained.

What Are the Legal Consequences When Impossibility or Impracticability Applies?

When a court finds that impossibility or impracticability excuses performance, the primary consequence is discharge of the affected contractual duties. The party claiming the defense is released from the obligation to perform, and the other party generally cannot recover damages for the non-performance.

Discharge is not automatic or absolute. Several important principles apply:

Partial performance: If the affected party performed part of the contract before the excusing event occurred, equitable principles may require compensation for the value of work already completed. Courts may apply restitution or quantum meruit to prevent unjust enrichment.

Temporary versus permanent impossibility: If the impossibility is temporary, the obligation may be suspended rather than discharged entirely. When the excusing event ends, the duty to perform may revive, depending on whether the delay has fundamentally altered the contract’s value or purpose.

Burden of proof: The party claiming impossibility or impracticability bears the burden of proving each element–the unforeseen event, objective impossibility or extreme impracticability, absence of fault, and the basic assumption that the event would not occur. Courts require substantial evidence, not mere assertions of hardship.

Contractual risk allocation: If the contract itself allocates the risk of the event in question–through a force majeure clause, an assumption-of-risk provision, or other language–the contractual allocation typically controls over the common law defense. Parties that contractually assumed a risk cannot later claim impossibility or impracticability based on that same risk materializing.

Effect on related obligations: When impossibility or impracticability discharges one party’s performance obligation, the other party’s corresponding obligation–such as the duty to pay–is also typically discharged. The contract is unwound to the extent possible, with each party bearing its own losses up to the point of discharge unless the contract or equitable principles provide otherwise. This mutual discharge principle prevents one party from being left with an unperformed obligation while the other is excused.

Limitation to the affected obligation: Courts apply these doctrines narrowly to the specific obligation that has become impossible or impracticable. If only one aspect of a multi-part contract is affected, the remaining obligations may survive. A contract that includes both the sale of goods and the provision of services, for example, may be partially discharged if the goods component becomes impossible while the services component remains performable.

How Do Force Majeure Clauses Relate to Impossibility and Impracticability?

Force majeure clauses are contractual provisions that address impossibility and impracticability proactively rather than relying on common law defenses after the fact. These clauses define specific categories of events that excuse or delay performance, providing certainty that the common law doctrines may lack.

A well-drafted force majeure clause typically covers:

• Natural disasters (earthquakes, floods, hurricanes, wildfires)
• Government actions (embargoes, sanctions, lockdowns, regulatory changes)
• War, terrorism, or civil unrest
• Epidemics or pandemics
• Labor strikes or shortages beyond the parties’ control

The clause should specify the consequences of a qualifying event–whether performance is excused entirely, suspended for a defined period, or subject to renegotiation. It should also address notice requirements (how quickly the affected party must notify the other) and mitigation obligations (what steps the affected party must take to minimize the impact).

Force majeure clauses must be clearly defined to be enforceable. Vague language–such as “any event beyond the parties’ control”–may be interpreted narrowly by courts, while specific enumeration of covered events provides greater predictability. Many litigation disputes over force majeure arise not from whether the clause exists but from whether the specific event falls within its scope.

Invoking force majeure does not relieve a party from all responsibilities. The party must typically demonstrate that the event genuinely prevented or significantly impeded performance, that the party could not have avoided or overcome the event through reasonable efforts, and that the party provided timely notice as required by the clause.

How Should Parties Navigate Disputes Over Impossibility and Impracticability?

When a dispute arises over whether impossibility or impracticability excuses performance, the parties should take several steps before resorting to litigation.

Review the contract: Examine force majeure clauses, risk allocation provisions, and any other terms addressing unforeseen events. The contract’s own language often determines the outcome before common law doctrines come into play.

Communicate promptly: The party claiming impossibility or impracticability should notify the other party as soon as the excusing event occurs or becomes apparent. Delayed notice can weaken the defense and may violate specific contractual notice requirements.

Document everything: Maintain detailed records of the event, its impact on performance, the steps taken to mitigate, and all communications between the parties. These records form the evidentiary foundation for any claim or defense.

Consider alternative dispute resolution: Mediation or arbitration can resolve these disputes more efficiently than litigation, particularly where the relationship between the parties has ongoing value. A mediator can help the parties find a practical resolution–such as modified performance terms, partial payment, or contract termination with fair allocation of losses–that a court might not be positioned to craft.

Assess the strength of the claim: Not every disruption rises to the level of impossibility or impracticability. Parties should honestly evaluate whether the event meets the legal standard before asserting the defense, as an unsupported claim can damage credibility and increase litigation costs.

Explore modified performance: In many cases, the most practical resolution involves modifying the contract rather than terminating it entirely. The parties may agree to extend deadlines, adjust quantities, substitute materials, or revise pricing to reflect changed circumstances. A negotiated modification preserves the business relationship and avoids the cost and uncertainty of formal legal proceedings. Where the contract includes a renegotiation clause triggered by force majeure or changed circumstances, this path may already be contemplated by the agreement itself.

What Preventative Measures Should Be Included in Contract Drafting?

Careful contract drafting is the most effective tool for managing the risks of impossibility and impracticability. Three categories of provisions deserve particular attention:

Clear terms and conditions: Ambiguity in contract language creates disputes. Effective drafting should use precise, unambiguous terms; clearly define each party’s responsibilities and performance standards; specify consequences for non-performance, including available remedies; and maintain consistent terminology throughout the agreement. When both parties understand their obligations with specificity, the scope for disputes over impossibility narrows considerably.

Tailored force majeure clauses: Rather than relying on boilerplate language, force majeure clauses should be tailored to the specific risks relevant to the transaction. A construction contract may emphasize weather events and material shortages. An international supply agreement may focus on trade restrictions and currency controls. The clause should define notice requirements, mitigation obligations, and the consequences of prolonged force majeure events–including a termination right if the event extends beyond a specified period.

Dispute resolution provisions: Establishing structured methods for resolving conflicts reduces the cost and uncertainty of disputes. Effective provisions may include a negotiation period requiring good-faith discussion before formal proceedings, mediation as a mandatory step before arbitration or litigation, and clear rules for selecting arbitrators or determining jurisdiction if formal proceedings become necessary.

These preventative measures do not eliminate the risk of unforeseen events, but they provide a contractual framework for addressing those events efficiently and fairly when they occur.

Beyond specific contract provisions, businesses should integrate contract risk management into their broader operational planning. This includes maintaining awareness of industry-specific risks that could trigger impossibility or impracticability claims, building relationships with alternative suppliers or service providers who can step in if primary partners are unable to perform, and reviewing existing contracts periodically to ensure that risk allocation provisions remain appropriate as business conditions evolve. Organizations that treat contract risk as an ongoing management responsibility rather than a one-time drafting exercise are better positioned to respond effectively when unforeseen events occur.

For more on contract law topics, see the Contracts practice area.