Contract

Definition

A contract is a legally binding agreement between two or more parties that creates mutual obligations enforceable by law. Contract law governs the formation, performance, enforcement, and remedies for breach of agreements. The maxim pacta sunt servanda—agreements must be kept—is its foundational principle.

Contract law enables private ordering. It allows individuals and businesses to plan their affairs with confidence that their agreements will be enforced. It facilitates economic exchange by providing a legal framework for transactions. It protects the reasonable expectations of parties who rely on promises. Without contract law, commercial activity would be riskier, costlier, and less efficient.

Formation Requirements

Valid contract formation requires six elements: (1) offer—a clear expression of willingness to contract on specified terms; (2) acceptance—unconditional agreement to the offer’s terms; (3) consideration—something of value exchanged between the parties (in common law systems); (4) capacity—legal competence of the parties to contract; (5) legality—lawful purpose; and (6) intention to create legal relations.

The objective test determines whether a reasonable person would believe the parties intended to contract. Courts ask not what the parties subjectively intended but what their words and conduct would lead a reasonable person to believe. This objective approach promotes certainty and protects reasonable expectations.

An offer is a definite proposal communicated to the offeree. It must be distinguished from an invitation to treat (an invitation to make an offer, such as displaying goods in a shop). Acceptance must match the offer’s terms exactly—the mirror image rule. Any variation constitutes a counter-offer, which rejects the original offer. Modern commercial practice modifies this rule through standard terms and battle-of-the-forms analysis.

Consideration

Consideration is a distinctive feature of common law contract. Each party must give, promise, or forbear something of value. Consideration must be sufficient (legally recognisable) but need not be adequate (fair market value). A peppercorn can be sufficient consideration. The requirement distinguishes bargains from gifts: promises made without consideration are generally unenforceable.

The pre-existing duty rule provides that promising to do what one already must do is not good consideration. If a contractor already owes a duty to complete a building, a promise of extra payment for completing on time is not binding. Exceptions exist for practical benefits, unforeseen circumstances, and settlements of disputed claims.

Civil law systems generally require cause (causa) rather than consideration—the reason or motive for undertaking the obligation. The French Civil Code requires a lawful cause; the German BGB requires that contracts not violate good morals. While functionally similar to consideration, cause is more flexible and focuses on the transaction’s underlying purpose.

Terms and Interpretation

Contractual terms may be express (explicitly stated, orally or in writing) or implied (inferred by law or custom). Implied terms fill gaps in incomplete contracts, reflecting what the parties would have agreed had they considered the matter. Terms may be implied by fact (necessary to give business efficacy), by law (statutory requirements), or by custom (trade usage).

Courts interpret contracts objectively, asking what a reasonable person in the parties’ position would have understood. The parol evidence rule limits extrinsic evidence when the contract appears complete, though exceptions exist for ambiguity, fraud, and collateral agreements. In civil law, the principle of good faith (bona fides) governs contractual performance and interpretation throughout the life of the contract, requiring parties to cooperate and act fairly.

Standard form contracts present distinctive interpretive issues. The contra proferentem rule construes ambiguous terms against the drafter. Exclusion clauses must be clearly communicated and may be subject to statutory control. Unfair terms legislation, particularly in consumer contexts, invalidates terms that create significant imbalance between the parties’ rights.

Breach and Remedies

Breach occurs when a party fails to perform as promised. Material breach (or fundamental breach) justifies the innocent party’s termination and damages; minor breach entitles damages but not termination. The distinction turns on the importance of the term breached and the consequences of breach.

Remedies include: damages (expectation, reliance, or restitution); specific performance (court-ordered performance); injunctions (restraining breach); and liquidated damages (pre-agreed sums). The measure of damages aims to place the innocent party in the position they would have occupied had the contract been performed (expectation interest). Alternatively, the plaintiff may recover expenditures made in reliance on the contract (reliance interest) or the defendant’s unjust enrichment (restitution interest).

The duty to mitigate requires the innocent party to take reasonable steps to reduce their losses. Failure to mitigate limits recovery to the losses that would have been sustained even with reasonable mitigation. This duty reflects the principle that contract law seeks efficient outcomes, not punishment.

Vitiating Factors

Certain defects render a contract void, voidable, or unenforceable. Misrepresentation (a false statement inducing the contract) entitles rescission and damages. Mistake (fundamental misunderstanding) may void the contract if both parties were mistaken about a fundamental fact.

Duress (coercion) and undue influence (improper pressure) vitiate consent, making the contract voidable. Undue influence is presumed in certain relationships (parent-child, solicitor-client, doctor-patient) and must be disproved by the dominant party. Illegality (unlawful purpose) renders the contract unenforceable. The court will not assist a party to enforce an illegal transaction.

Unconscionability and unfair terms legislation protect weaker parties from exploitation. Courts may refuse to enforce terms that are grossly unfair or that were imposed through inequality of bargaining power. Consumer protection statutes provide additional safeguards, invalidating terms that create significant imbalance.

Comparative Contract Law

Contract law diverges between common law and civil law traditions. Civil law codifications such as the French Civil Code and German BGB structure contract law within broader codes of obligations. French law emphasizes consent, cause, and good faith; German law distinguishes between obligation-creating contracts and performance.

The UNIDROIT Principles of International Commercial Contracts and the CISG (UN Convention on Contracts for the International Sale of Goods) harmonize international commercial contract law. The CISG governs international sales between parties in contracting states, providing uniform rules for formation, performance, and remedies. It has been adopted by over 90 countries.

Despite differences, convergence around good faith, reasonableness, and party autonomy reflects a shared understanding of contract as the primary vehicle for voluntary economic exchange. Contract law enables individuals to create binding obligations, plan their affairs, and pursue their purposes through cooperation with others. It is the legal infrastructure of a market economy and a free society.