US Contract Law Basics — Formation & Doctrine

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The US common-law contract framework — state common law, Restatement (Second), UCC overlay, Statute of Frauds, mutual assent, consideration, ESIGN / UETA.

United States contract law is, in the first place, state law. There is no federal contract code, no central civil code in the continental tradition, and no single set of statutes uniformly binding across the fifty jurisdictions. A contract dispute is governed by the common law of one state — or by the Uniform Commercial Code as enacted in that state — and the elementary doctrines of offer, acceptance, consideration, capacity, and legality vary modestly but persistently from one jurisdiction to another. The American Law Institute’s Restatement (Second) of Contracts (“R2K”) is the most influential synthesis of those state common laws, but it is persuasive rather than binding authority: courts cite it for its scholarly weight, not because they must. The principal federal overlay is the Federal Arbitration Act, 9 USC §§ 1-307, which preempts state-law hostility to arbitration agreements, and the ESIGN Act, 15 USC §§ 7001-7031, which validates electronic signatures and records for transactions in interstate commerce. Beyond those carve-outs and a handful of regulated subject-matter regimes (consumer credit, securities, antitrust), the default position is that the law of some state answers every contract question and parties should plan accordingly. This page is the cross-handbook reference for the doctrinal architecture; see UCC Article 2 for the goods-sale regime that displaces parts of this default, and standard boilerplate clauses for the recurring contractual choices that route around it.

Sources of US Contract Law

Five sources frame every analysis.

First, the common law of the fifty states. Each state’s appellate decisions, applied by trial courts in that state, are the binding authority for contracts whose centre of gravity sits within the state. New York and Delaware are the most heavily litigated commercial-contract jurisdictions and produce the densest body of doctrinal authority; California’s Civil Code §§ 1549-1701 is unusual in having a partial statutory codification of contract law (a legacy of David Dudley Field’s 1872 codification project), but the bulk of California contract doctrine is still judge-made and tracks the wider common-law pattern. Substantive variations matter: the parol evidence rule’s reach, the consideration doctrine’s tolerance for nominal consideration, the standards for unconscionability and for excuse on grounds of impracticability, the rules on agreement to disagree and on liquidated damages — each splits along state lines in ways that occasionally decide outcomes.

Second, the Restatement (Second) of Contracts. Promulgated by the American Law Institute in 1981 as successor to the 1932 First Restatement, R2K is the leading academic synthesis of US contract law. It is persuasive authority — frequently cited, occasionally adopted by name, but never binding in the sense that a code is binding in a civil-law system. The Restatement is most influential where it adopts a “majority rule” with clarity (e.g., R2K § 71’s bargain theory of consideration), and least useful where state common law is sharply split and the Restatement takes one side (e.g., R2K § 90 on promissory estoppel, where state attitudes range from enthusiastic adoption to formal scepticism). A careful US contract analysis cites the Restatement and the state law that the Restatement purports to summarise.

Third, the Uniform Commercial Code. The UCC is the most successful uniform-law project in US history. Article 2 governs the sale of goods and is enacted in every state except Louisiana; Article 9 governs secured transactions in personal property; Article 3 governs negotiable instruments; and Article 1 carries general definitions and good-faith obligations that apply throughout. Article 2 displaces common-law contract doctrine for transactions in goods and reorients large parts of the analysis — its battle-of-the-forms section at § 2-207, its sale-of-goods Statute of Frauds at § 2-201, and its implied warranties at §§ 2-314 and 2-315 are all common-law departures. The UCC is technically a model code drafted by the Uniform Law Commission and the American Law Institute jointly; each state enacts its own version, with occasional non-uniform amendments. The federal government cannot enact the UCC, but federal courts apply it under Erie when sitting in diversity. See UCC Article 2 for the goods-specific analysis.

Fourth, federal statutes that occupy particular subject matters. The Federal Arbitration Act preempts state-law hostility to arbitration agreements (AT&T Mobility v. Concepcion, 563 U.S. 333 (2011)). The ESIGN Act validates electronic signatures and records for interstate-commerce transactions. The Truth in Lending Act, the Fair Credit Reporting Act, and a portfolio of consumer-protection statutes regulate disclosures and substantive terms in consumer credit. The Defend Trade Secrets Act of 2016 (18 USC § 1836) federalises trade-secret misappropriation. Each operates as a partial overlay; outside the regulated zone, state contract law continues to apply.

Fifth, international treaty law in the narrow case where it applies. The United Nations Convention on Contracts for the International Sale of Goods (CISG), ratified by the US in 1988, governs international sale-of-goods contracts between parties in different signatory states unless the parties expressly opt out. The CISG displaces UCC Article 2 in its scope and adopts conspicuously different rules — no Statute of Frauds, a relaxed approach to acceptance and battle-of-the-forms, and a different mistake regime. Most US commercial-contract drafters opt the CISG out by express clause; the international-trade lawyers who do not so opt out have a different and legitimate set of reasons for the choice.

Formation: Offer, Acceptance, Consideration

The objective theory of mutual assent is the working analytic frame. Lucy v. Zehmer, 196 Va. 493 (1954) is the canonical instance: Zehmer wrote a sale-of-farm contract on the back of a restaurant check, his wife signed, and Lucy paid five dollars deposit; Zehmer’s later claim that he meant the entire thing as a joke was rejected because the objective manifestations — the written terms, the signatures, the discussion of price — were those of a person making a serious offer. What a party meant matters far less than what a reasonable counterparty would have understood from the outward signs.

R2K § 24 defines an offer as “the manifestation of willingness to enter into a bargain, so made as to justify another person in understanding that his assent to that bargain is invited and will conclude it.” Two doctrinal points repay attention. First, advertisements and price lists are ordinarily not offers but invitations to treat, subject to the well-known exception of Lefkowitz v. Great Minneapolis Surplus Store, 251 Minn. 188 (1957) — “clear, definite, and explicit” advertisements with no terms left open can be offers. Second, the offeror remains “master of the offer” and can specify the manner of acceptance: a phrase like “acceptance by signing and returning this document” forecloses acceptance by performance or by oral statement.

Acceptance is governed by R2K §§ 50-70. The common-law mirror-image rule requires acceptance to match the offer’s terms exactly; any deviation operates as rejection and counteroffer. UCC § 2-207 famously departs from this for sale-of-goods contracts and is treated separately in the UCC Article 2 reference. The mailbox rule (R2K § 63) deems an acceptance effective on dispatch, not on receipt — but only for acceptances, not rejections or counteroffers, and only where the offer does not specify a contrary rule. Modern e-commerce drafting often displaces the mailbox rule by express terms; absent such terms, federal and state courts have applied analogous “click-effective” rules to electronic communications.

Consideration sits at the heart of the bargain theory codified in R2K § 71. Consideration is a bargained-for exchange of legal value: each party must give the other something the other has a right to receive but did not previously have. The 1891 New York Court of Appeals decision in Hamer v. Sidway, 124 N.Y. 538, is the canonical case — an uncle promised his nephew $5,000 if the nephew abstained from drinking, smoking, swearing, and playing cards or billiards for money until the nephew turned twenty-one. The nephew so abstained; the executor of the uncle’s estate refused to pay; the court held the contract enforceable because the nephew’s giving up of legal liberties was a bargained-for forbearance and therefore consideration. Pre-existing-duty rule cases (a promise to do what one is already legally obligated to do is no consideration; see Stilk v. Myrick (1809) 6 Esp 129 for the English root) and nominal-consideration cases (a peppercorn or a dollar may suffice if genuinely bargained for, but recital of consideration that is not actually exchanged is treated sceptically by most US courts) bookend the doctrine.

The bargain theory’s principal alternative is promissory estoppel under R2K § 90: a promise foreseeably and reasonably inducing detrimental reliance is enforceable to the extent justice requires. The doctrine bridges the gap between consideration-supported contracts and unenforceable gratuitous promises, and is most powerful in employment promises (offers of “at-will” employment that the recipient relied on to move cities), construction subcontractor bids (Drennan v. Star Paving, 51 Cal. 2d 409 (1958)), and charitable subscriptions. Recovery is generally limited to reliance damages — putting the promisee back in the position they would have been in had no promise been made — rather than full expectation damages.

Capacity (R2K §§ 12-16) and legality (R2K §§ 178-199) round out the formation analysis. Minors generally lack capacity to bind themselves contractually before age 18 (the age of majority in most states; Mississippi sets it at 21), and a minor’s contract is voidable at the minor’s election except for “necessaries” (food, lodging, medical care) for which the minor is liable on a quasi-contract basis. Persons of unsound mind, persons under guardianship, and persons intoxicated at the time of contracting may lack capacity in different and fact-specific ways. Public-policy unenforceability spans gambling debts (where prohibited), agreements in restraint of trade exceeding statutory or common-law limits, contracts inducing the commission of crime or tort, and certain exculpatory clauses (an attempt to release a counterparty from liability for gross negligence is unenforceable in most states; for ordinary negligence in non-consumer contexts it usually stands).

Statute of Frauds

The Statute of Frauds traces its lineage to the English statute of 1677, 29 Car. 2, c. 3, and is now embodied in every US state’s law in some form. R2K § 110 lists the categories of contract that require a signed writing to be enforceable: contracts of an executor or administrator to answer for a duty of the decedent; contracts to answer for the duty of another (suretyship); contracts made upon consideration of marriage; contracts for the sale of an interest in land; contracts that by their terms cannot be performed within one year from the making; and, by virtue of UCC § 2-201, contracts for the sale of goods for the price of $500 or more.

The writing requirement is interpreted flexibly. A confirmation memorandum, an email exchange, a series of correspondence, a check with terms scribbled on the back, a tweet — any of these can satisfy the statute if it (i) identifies the parties, (ii) describes the subject matter sufficiently to be ascertained, (iii) states essential terms (which under UCC § 2-201 reduces to a quantity term), and (iv) bears the signature of “the party to be charged” — i.e., the party against whom enforcement is sought. The signature is broadly read; a typed name, a printed letterhead, a “/s/” recital, an electronic signature within the meaning of ESIGN, and even an initialled fax cover sheet have been held sufficient in particular cases.

The doctrinal carve-outs are extensive. The part-performance exception cures missing writing in land-sale contracts where the buyer has paid part of the price and taken possession or made improvements. The merchant-memo exception of UCC § 2-201(2) binds a merchant who receives a writing confirming an oral sale-of-goods contract from another merchant if the recipient does not object within ten days. The specially manufactured goods exception of UCC § 2-201(3)(a) excuses missing writing for goods manufactured to the buyer’s specifications and not suitable for resale to others. The judicial admission exception of UCC § 2-201(3)(b) holds that admissions in pleadings, testimony, or other court process satisfy the statute for the quantity admitted. Promissory estoppel under R2K § 139 can defeat a Statute of Frauds defence where the promisee’s reasonable reliance would make non-enforcement unjust — though some states still resist this overlay in land-contract cases.

Two categories deserve particular emphasis because they recur in commercial drafting. The one-year clause applies only where it is impossible for performance to be completed within one year from the making of the contract: a contract for “lifetime employment” can be performed within one year if the employee dies, and is therefore not within the statute under the majority rule; a contract to build a house in eighteen months is within the statute. The suretyship clause applies only to promises to answer for the primary obligation of another; a promise made principally to advance the promisor’s own economic interest, even if it incidentally discharges another’s obligation, falls under the main-purpose (or leading-object) exception. Both categories are vehicles for state-by-state variation that materially affects outcomes.

Parol Evidence Rule

The parol evidence rule sits in R2K §§ 209-218 and at UCC § 2-202 for sale-of-goods contracts. The rule bars admission of extrinsic evidence — prior or contemporaneous agreements, oral or written — to contradict the terms of a final written contract. Two preconditions: (i) the writing must be integrated, meaning intended as a final expression of the agreement on those terms it contains, and (ii) the writing must be fully integrated for the rule to bar evidence of additional consistent terms, as opposed to merely partially integrated for the rule to bar contradictory terms. A merger or integration clause — “this Agreement constitutes the entire understanding of the parties and supersedes all prior negotiations” — creates a strong presumption of full integration but is not always conclusive.

A pivotal state-by-state split divides the Williston and Corbin schools. The Williston view (followed in New York, Florida, and many traditional jurisdictions) reads the four corners of the writing first and admits extrinsic evidence only if the writing is ambiguous on its face. The Corbin view (followed in California after Pacific Gas & Electric Co. v. G.W. Thomas Drayage, 69 Cal. 2d 33 (1968) and in many jurisdictions following its lead) admits extrinsic evidence to determine whether the writing is ambiguous in the first place — meaning evidence comes in much more freely under Corbin. The choice of state-law governs the choice of approach, and that choice can be outcome-determinative. UCC § 2-202 is broadly Corbin-flavoured and admits course-of-dealing, course-of-performance, and trade-usage evidence freely (UCC § 1-303), reserving its bar for evidence that would contradict the writing’s express terms.

Several extrinsic-evidence categories sit outside the rule’s reach altogether. Evidence of fraud, duress, undue influence, or mistake in the making of the contract is admissible regardless of integration; the rule is about interpretation of valid contracts, not about whether a contract was validly formed. Evidence of subsequent modifications (after the writing) is also outside the rule — which is why no-oral-modification clauses are themselves needed (see below at standard clauses). Evidence offered to interpret (as opposed to contradict) ambiguous terms is admissible under both Williston and Corbin, though their tolerance for what counts as “ambiguous” differs sharply.

Defences: Mistake, Duress, Undue Influence, Fraud

A contract validly formed in the formation sense (offer + acceptance + consideration + capacity + legality) is nevertheless unenforceable if procurally defective. Five defences recur in modern litigation.

Mutual mistake (R2K § 152): a mistake by both parties at the time of contracting about a fact basic to the assumption on which the contract was made renders the contract voidable by the adversely affected party, unless that party bore the risk of the mistake. Sherwood v. Walker, 66 Mich. 568 (1887) is the textbook case — sale of a cow believed barren that turned out to be pregnant; the parties’ shared mistake about a basic assumption of the deal made the contract avoidable.

Unilateral mistake (R2K § 153): a mistake by only one party is harder to invoke. The mistaken party must show that the mistake was about a basic assumption, that enforcement would be unconscionable, and either that the other party had reason to know of the mistake or that the other party’s fault caused it. Pure clerical errors detected before reliance often qualify; ambitious-bid cases sometimes do.

Duress (R2K §§ 174-176): a contract induced by an improper threat depriving the other party of a reasonable alternative is voidable. The doctrine has expanded from physical duress (R2K § 174 — wholly void contract) to economic duress (R2K § 175 — voidable), with the latter requiring an improper threat and the absence of a reasonable alternative. “Take it or leave it” terms in adhesion contracts do not in themselves constitute duress; the test is whether the threat was improper and whether the recipient had a meaningful choice.

Undue influence (R2K § 177): persuasion that overcomes the will of a person under a domination or in a relationship of trust voids the contract at the disadvantaged party’s election. Most common in elder-care and family-trust contexts; rare in arms-length commercial transactions.

Fraud and misrepresentation (R2K §§ 159-173): a contract induced by a fraudulent misrepresentation (knowing or reckless falsehood) is voidable; a contract induced by an innocent material misrepresentation is also voidable, though punitive damages do not lie for innocent misrepresentation. The reliance must be justifiable (mere “puffing” does not support reliance) and the misrepresentation must have been material.

Unconscionability (R2K § 208; UCC § 2-302) overlays all of the above. Procedural unconscionability — surprise, deception, lack of meaningful choice — combined with substantive unconscionability — overly harsh terms — voids the offending clause or the entire contract at the court’s discretion. Williams v. Walker-Thomas Furniture Co., 350 F.2d 445 (D.C. Cir. 1965) is the modern foundational case: a “cross-collateral” clause that allowed a furniture seller to repossess all previously purchased items if the buyer defaulted on a single subsequent purchase was deemed procedurally unconscionable (buried in fine print, sold to indigent consumers without explanation) and substantively unconscionable (no benefit to buyer, severe consequence on minor default). Federal and state unconscionability doctrine has expanded since Williams to cover one-sided arbitration clauses, class-action waivers in some contexts, and aggressive limitation-of-liability terms — though the AT&T Mobility v. Concepcion, 563 U.S. 333 (2011) decision sharply curtailed unconscionability challenges to class-action waivers in consumer arbitration clauses on FAA-preemption grounds.

Public-Policy Unenforceability

R2K §§ 178-199 frames the limits of party freedom. A contract is unenforceable on public-policy grounds if (a) legislation provides that it is, or (b) the interest in its enforcement is clearly outweighed in the circumstances by a public policy against its enforcement. The doctrine catches contracts to commit crimes or torts, contracts that impair government processes (bribery, political-influence contracts, jury-tampering), contracts to obstruct litigation or marriage, gambling-debt contracts where prohibited by state law, and agreements in restraint of trade that exceed reasonableness. Employment non-compete agreements are the most heavily litigated example in this category — California’s Business & Professions Code § 16600 voids them outright (with narrow exceptions for sale-of-business and partnership-dissolution settings), while most other states enforce them subject to reasonableness review of scope, duration, and geographic reach. The FTC’s 2024 ban on most non-competes is in litigation as of 2026; pending its outcome, state law continues to govern.

Exculpatory clauses — clauses by which one party releases the other from future liability — are enforceable for ordinary negligence in most non-consumer contexts but are typically void for gross negligence, recklessness, intentional misconduct, and for personal injury in consumer contexts. The rule reflects the public’s interest in not being asked to assume protection from another’s serious wrongdoing.

Choice of Law and Choice of Forum

Because US contract law is state law, the threshold question in every cross-state dispute is which state’s law applies. The two organising authorities are Restatement (Second) Conflict of Laws § 187 and each state’s own choice-of-law statute or judicial doctrine. R2K Conflicts § 187 honours the parties’ choice of law if (1) the chosen state has a substantial relationship to the parties or the transaction or there is another reasonable basis for the choice, and (2) application of the chosen state’s law would not be contrary to a fundamental public policy of a state with a materially greater interest. The “fundamental public policy” exception is narrow; most consumer-protection statutes have been read to express such a policy in their home state, with the consequence that a choice-of-law clause pointing away from the consumer’s home state is often unenforced against consumer-protection claims.

Two states have adopted statutory frameworks that displace the substantial-relationship test for large commercial contracts. California Civil Code § 1646.5 and New York General Obligations Law § 5-1401 both uphold party choice for contracts of $250,000 or more (NY) and for any contract relating to a transaction covering more than $250,000 (CA), regardless of substantial relationship. The choice of New York or California law is therefore broadly enforceable for sophisticated commercial contracts even where the only nexus to the chosen state is the parties’ selection itself.

Forum-selection clauses operate parallel to but distinct from choice-of-law clauses. The Supreme Court’s decision in M/S Bremen v. Zapata Off-Shore Co., 407 U.S. 1 (1972) established the federal rule that forum-selection clauses are presumptively valid and enforceable unless unreasonable under the circumstances. Atlantic Marine Constr. Co. v. U.S. Dist. Court, 571 U.S. 49 (2013) tightened the federal rule still further: in a transfer-of-venue analysis under 28 USC § 1404(a), a court must give the parties’ valid forum-selection clause controlling weight, may not consider the parties’ private interests (which are deemed waived by agreeing to the clause), and may deny transfer only in extraordinary public-interest circumstances. State courts vary in their enforcement of forum-selection clauses, with the majority following Bremen reasonableness and a minority applying more sceptical review.

E-Signatures: ESIGN and UETA

The ESIGN Act, 15 USC §§ 7001-7031, enacted in 2000, validates electronic signatures and records for transactions in interstate commerce. The headline rule at 15 USC § 7001(a) is unambiguous: a signature, contract, or other record relating to such a transaction may not be denied legal effect, validity, or enforceability solely because it is in electronic form. A contract relating to such a transaction may not be denied legal effect solely because an electronic signature or electronic record was used in its formation. The parallel state-law framework is the Uniform Electronic Transactions Act (UETA), promulgated by the Uniform Law Commission in 1999 and adopted in 49 states and the District of Columbia.

New York is the lone hold-out: it never adopted UETA, applying instead the Electronic Signatures and Records Act (ESRA), New York State Technology Law §§ 301-309, with parallel substantive effect. ESIGN’s federal-preemption provision at 15 USC § 7002 establishes the framework: state law operates instead of ESIGN to the extent the state has adopted UETA in its original form (with limited authorised modifications), and ESIGN otherwise governs for interstate-commerce transactions.

The carve-outs at 15 USC § 7003 are important. ESIGN does not apply to: wills, codicils, and testamentary trusts; family-law matters (adoptions, divorces); court orders, official court documents, notices, and notices to be served by a court; notices of cancellation or termination of utility services; notices of default, acceleration, repossession, foreclosure, eviction, or the right to cure under a credit agreement or lease for an individual’s primary residence; notices of cancellation or termination of life insurance or health insurance benefits (excluding annuities); notices of recall of a product or a material failure of a product that risks endangering health or safety; and certain UCC documents (excluding the sale-of-goods documents themselves, which are within ESIGN’s scope). For these excluded matters, traditional paper-and-ink signature requirements continue to apply.

Consumer transactions carry additional ESIGN § 7001(c) consent requirements: before a record required by law to be provided to a consumer can be delivered electronically, the consumer must (i) affirmatively consent in a manner that reasonably demonstrates that the consumer can access information in the electronic form, (ii) be provided with a clear statement of the right to receive paper records and any conditions, consequences, or fees, and (iii) be informed of the hardware and software requirements. The “reasonable demonstration” requirement was the subject of the FDIC’s 2007 advisory letter on E-SIGN compliance and remains a friction point in consumer e-disclosure design.

For commercial contracts (B2B), the consent layer is largely absent: parties can simply agree to use electronic signatures, and a counterparty clause confirming the agreement and intent to be bound electronically is sufficient. A signature delivered by DocuSign, by typed name in an email reply, by clicking a button in a web flow, or by drawing in a signature pad is each a valid “electronic signature” within the meaning of ESIGN and UETA. The choice between these forms is a matter of evidentiary quality, not legal effect.

The interaction between ESIGN/UETA and the Statute of Frauds is the practitioner’s principal touchstone. ESIGN § 7001(a)(2) provides that any law requiring a contract to be in writing is satisfied by an electronic record; ESIGN § 7001(a)(1) provides that any law requiring a signature is satisfied by an electronic signature. The combined effect is that every Statute of Frauds category — sale of land, contracts not performable within one year, suretyship, marriage contracts, executor promises, and UCC § 2-201 sale-of-goods contracts of $500 or more — can now be satisfied by electronic record and signature, subject to the carve-outs at § 7003 noted above. See the Chaindoc blog on legal strength of e-signatures for the evidentiary architecture that ensures a particular e-signature withstands later challenge.

Federal Preemption: Narrow but Real

The default of state contract law yields to federal law in a small number of subject-matter areas. The Federal Arbitration Act preempts state-law hostility to arbitration agreements, as confirmed in AT&T Mobility v. Concepcion and extended to employment contracts in Epic Systems Corp. v. Lewis, 138 S. Ct. 1612 (2018). ERISA preempts state contract law for employee-benefit-plan claims under 29 USC § 1144. The Copyright Act preempts state contract law for certain copyright-equivalent rights under 17 USC § 301, though courts have been notably reluctant to apply this preemption to most commercial licensing terms. The federal Bankruptcy Code reorganises contract rights through executory-contract treatment under 11 USC § 365. Outside these and a handful of analogous preemption zones (securities, antitrust, certain telecommunications and labour-law topics), state contract law governs.

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Disclaimer: This content is informational, not legal advice. Last verified: 2026-05-10. Always consult licensed counsel for binding decisions.

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