Contract law is the branch of law governing agreements that create legally enforceable obligations. It determines when an agreement becomes binding, what its terms mean, how obligations must be performed, and what remedies follow non-performance. Contracts are not necessarily written documents: depending on the applicable legal system and transaction, obligations may arise from spoken words, exchanged communications, or conduct. Although legal systems share many contractual concepts, their requirements for formation, validity, and enforcement differ. (law.cornell.edu)
Scope and legal sources
Contract law supplies both general rules and rules for particular transactions. General rules address matters such as consent, interpretation, and breach; special regimes govern transactions such as sales of goods. A contractual relationship may therefore be governed by several overlapping bodies of law rather than by a single comprehensive statute. The French Civil Code, for example, expressly makes general contractual rules subject to rules particular to specific contracts. (justice.gouv.fr)
In common-law jurisdictions, judicial decisions and legal precedent provide an important part of contract law, alongside legislation. In the United States, much general contract law is state law rather than federal law. The Uniform Commercial Code provides a statutory framework for commercial transactions; Article 2 governs sales of goods through the versions enacted by individual jurisdictions. The model code itself is not federal legislation. (law.cornell.edu)
In civil-law systems, contractual rules are commonly organized in civil codes. The French Civil Code, for instance, defines a contract as an agreement of wills intended to create, modify, transfer, or extinguish obligations. This formulation illustrates why a contract should not universally be defined as an exchange of promises: some systems recognize gratuitous contracts or contracts imposing obligations on only one party. (justice.gouv.fr)
Freedom of contract and its limits
Freedom of contract generally includes freedom to decide whether to contract, to select a counterparty, and to determine contractual terms. Its counterpart is the binding force of an agreement lawfully made. These principles allow parties to organize transactions and allocate responsibilities, costs, and risks. They operate within legal limits, however: private agreement cannot necessarily override mandatory legislation or rules of public policy. (justice.gouv.fr)
Contract law consequently distinguishes default rules, which apply unless the parties agree otherwise, from mandatory rules, which cannot be displaced by agreement. International commercial instruments such as the UNIDROIT Principles preserve contractual freedom while recognizing the overriding operation of applicable mandatory rules. Consumer legislation may impose additional restrictions on terms that disadvantage the protected party. (unidroit.org)
Good faith also qualifies contractual freedom, although its scope depends on the governing law. Article 1104 of the French Civil Code requires good faith in negotiation, formation, and performance. The UNIDROIT Principles impose good faith and fair dealing in international trade and do not permit the parties to exclude that duty. These provisions should not be treated as proof that every jurisdiction recognizes an identical general obligation. (justice.gouv.fr)
Formation
The central formation question is whether the parties have reached an agreement that the law recognizes as binding. Offer and acceptance provide a common framework: one party proposes sufficiently definite terms with an intention to be bound, and the other assents. But the framework is not exhaustive. The UNIDROIT Principles also recognize formation through conduct sufficient to demonstrate agreement, including transactions in which no discrete offer-and-acceptance sequence can be identified. (unidroit.org)
Agreement need not settle every possible detail. Under some rules, missing minor terms can be supplied without preventing formation. Conversely, where a party makes agreement on a particular matter or execution in a specified form a condition of being bound, satisfying that condition may be necessary before a contract exists. This distinction is important in negotiations that produce preliminary agreements before a final document. (unidroit.org)
In many common-law settings, ordinary contractual promises also require consideration: a bargained-for exchange of a promise, act, or forbearance. Consideration need not consist of money, and courts do not ordinarily require the exchanged benefits to have equal economic value. A promise to pay for work in exchange for the work, for example, can satisfy the requirement. (law.cornell.edu)
Consideration is not a universal condition of contractual liability. The UNIDROIT Principles treat agreement itself as sufficient for formation, while the French Civil Code recognizes gratuitous contracts. An analysis that presents consideration as indispensable to every contract therefore mistakes a jurisdiction-specific doctrine for a worldwide rule. (unidroit.org)
Formal requirements are another separate issue. Some contracts can be concluded informally, while others require prescribed documentation or procedures. The international sales convention generally permits freedom of form, but allows states to make declarations affecting that freedom. Whether a signature or written record is required must therefore be determined from the applicable rules, not from the everyday assumption that a contract is a signed document. (justice.gouv.fr)
Capacity, consent, and validity
Formation does not establish that an agreement is valid or enforceable in every respect. Legal systems also examine the parties’ capacity, the lawfulness of the transaction, and defects in consent. Legal capacity concerns whether a person can undertake binding obligations; rules may give special treatment to minors or persons lacking the legally required ability to understand the transaction. (law.cornell.edu)
Mistake, fraudulent misrepresentation, duress, and undue influence may provide grounds for setting an agreement aside, depending on the governing law and circumstances. These grounds address different problems: an erroneous understanding, deception, coercion, or improper influence. They do not establish that any disappointment or imbalance in a bargain automatically invalidates it. (law.cornell.edu)
The consequences of invalidity must also be distinguished. An agreement that never acquired legal effect is not necessarily treated like an agreement that binds the parties until a protected party avoids it. The grounds and procedures for rescission, and the availability of restoration of benefits, vary between jurisdictions. (law.cornell.edu)
Terms and interpretation
Contractual obligations depend on more than the existence of agreement: their content must be established. Express terms identify matters such as the promised performance, price, timing, and allocation of risk. Where the parties leave a gap, applicable rules may supply an implied term rather than treat the entire agreement as incomplete. (unidroit.org)
Interpretation determines the meaning of the parties’ words and conduct. Under the UNIDROIT Principles, the parties’ common intention takes priority; if it cannot be established, the agreement is interpreted according to the understanding of reasonable persons of the same kind in the same circumstances. Terms are read in the context of the whole contract rather than in isolation. These rules illustrate an interpretive approach, not a formula applied identically by every court. (unidroit.org)
Standard-form contracts introduce additional difficulties because their terms are prepared in advance rather than individually negotiated. Businesses may exchange purchase orders and acknowledgments containing inconsistent conditions—a problem known as the battle of forms. The legal questions are whether a contract nevertheless exists and which terms become part of it. Under the UNIDROIT approach, agreement on essential terms can produce a contract incorporating terms common in substance, subject to qualifications concerning a party’s insistence on its own conditions. (unidroit.org)
Performance and non-performance
Performance is the fulfillment of contractual obligations. For a sale of goods, this may include delivery of conforming goods and associated documents, payment of the price, and acceptance of delivery. Breach of contract, or non-performance, occurs when an obligation is not fulfilled as required. The applicable rules determine whether the injured party can demand performance, obtain damages, or end the contractual relationship. (uncitral.un.org)
Not all non-performance immediately justifies termination. International sales rules distinguish fundamental breach from lesser failures. Other contractual regimes may provide opportunities to cure defective performance, and accepting a proper cure can affect the injured party’s available remedies without eliminating compensation for harm already sustained. (uncitral.un.org)
Changed circumstances raise a different question: whether performance remains legally required despite disruption. Hardship concerns a fundamental alteration of the contractual equilibrium rather than merely a less profitable bargain. Under the UNIDROIT Principles, qualifying hardship can support a request for renegotiation and, in appropriate circumstances, judicial adaptation or termination. An ordinary change in circumstances does not by itself discharge the duty to perform. (unidroit.org)
Remedies
Contractual remedies address the consequences of non-performance. Their availability depends on the applicable law, the seriousness of the breach, the nature of the promised performance, and the loss established. The principal categories include monetary compensation, an order to perform, and termination or avoidance of the agreement. (uncitral.un.org)
Damages are a monetary remedy. A central compensatory approach seeks to place the injured party in the position it would have occupied had the contract been performed. Recoverable harm may include lost gains as well as incurred loss, but compensation is subject to restrictions such as causation, foreseeability, certainty, and mitigation. Savings resulting from non-performance may also need to be deducted. (law.cornell.edu)
Specific performance requires the promised performance rather than a monetary substitute. In common-law practice it is generally more restricted than damages, particularly where money can adequately compensate the injured party. Transactions involving unique assets, including particular parcels of land, are an important setting in which this remedy may be available. (law.cornell.edu)
Parties may specify a payment for breach through a liquidated damages clause. Such provisions can reduce the difficulty of establishing loss after a breach, but their enforceability is not unlimited. Under relevant common-law rules, a clause functioning as an impermissible penalty or containing unconscionable terms may not be enforced. (law.cornell.edu)
Standard terms and consumer protection
Contract law does not always enforce a term merely because it appears in an agreed document. Consumer protection legislation can make unfair terms non-binding and regulate attempts to exclude legal obligations. Section 62 of the United Kingdom’s Consumer Rights Act 2015, for example, uses a fairness test involving good faith and a significant imbalance in contractual rights and obligations to the consumer’s detriment. (legislation.gov.uk)
This creates a distinction between consenting to a transaction and the enforceability of each of its provisions. Standardization and unequal bargaining power do not automatically invalidate every contract, but they can trigger scrutiny of the terms and the circumstances in which assent was obtained. (law.cornell.edu)
International contracts
Cross-border transactions introduce questions about the applicable legal rules. Private international law helps determine which jurisdiction’s law governs, while international instruments can supply uniform substantive rules for particular transactions. A harmonized regime does not necessarily govern every issue arising from the contract. (uncitral.un.org)
The United Nations Convention on Contracts for the International Sale of Goods was adopted on April 11, 1980, and entered into force on January 1, 1988. It governs qualifying international sales, including formation, the parties’ obligations, and remedies. Consumer sales and contracts predominantly for services fall outside its scope; it also generally leaves contract validity and the proprietary effects of the sale to other applicable law. Parties may exclude its application. (uncitral.un.org)
The UNIDROIT Principles of International Commercial Contracts provide a broader, non-treaty framework covering formation, interpretation, performance, non-performance, and other contractual matters. They are used in contractual arrangements, interpretation, and law reform, but do not automatically replace national law simply because a transaction is international. (unidroit.org)
Electronic and automated contracting
Electronic commerce changes the medium through which agreement is expressed rather than dispensing with contractual rules. International electronic-commerce instruments use principles of non-discrimination, technological neutrality, and functional equivalence: electronic communications should not be denied legal effect solely because they are electronic, and they can satisfy writing or signature requirements when the specified conditions are met. (uncitral.un.org)
The United Nations Electronic Communications Convention also recognizes contracts formed through automated message systems, even when no person reviews each individual action. That recognition does not make every automated transaction valid regardless of consent, error, or other applicable rules. UNCITRAL’s Model Law on Automated Contracting, adopted in 2024, further addresses contracting through automated systems, including systems using artificial intelligence. As a model law, it supplies a legislative framework rather than universally applicable law. (uncitral.un.org)
References
- Contract — Wex, Legal Information Institutelaw.cornell.edu
- Consideration — Wex, Legal Information Institutelaw.cornell.edu
- Breach of Contract — Wex, Legal Information Institutelaw.cornell.edu
- Rescind — Wex, Legal Information Institutelaw.cornell.edu
- Translation revised 2018 final — French Ministry of Justicejustice.gouv.fr
- Uniform Commercial Code — Uniform Law Commissionuniformlaws.org
- Consumer Rights Act 2015 — Fairness of Contract Terms and Noticeslegislation.gov.uk