A contract is a legally enforceable agreement between two or more parties that creates binding obligations one side can ask a court to enforce against the other. To qualify as a contract rather than a casual promise, an agreement needs three things: an offer, an acceptance of that offer, and an exchange of something of value on both sides. Those elements are what separate a deal a judge will back from a conversation you simply hope the other person honors.
The Three Elements That Make an Agreement a Contract
Every enforceable contract starts with an offer. One party proposes specific terms and signals a willingness to be bound if the other side agrees. The offer has to be clear enough that a reasonable person would understand they are being invited into a deal, not just a discussion. Vague statements like “I might sell you my car someday” do not qualify. The offer needs enough detail about price, subject matter, and timing that the other party can simply say “yes” and create a binding agreement.
Acceptance is that “yes.” The accepting party must agree to the terms as proposed, without changing them. Respond by tweaking the price or adding conditions and you have not accepted; you have made a counteroffer, which the original offeror is free to accept or reject. Both sides need to reach what courts call a meeting of the minds, meaning they share the same understanding of what they are agreeing to.
Consideration is the element that trips people up. Each side must give up something of value: money, services, property, or even a promise to refrain from doing something they have a legal right to do. A promise to give someone $5,000 with nothing expected in return is a gift, not a contract. A promise to pay $5,000 in exchange for painting your house creates consideration on both sides — money for labor. Without that mutual exchange, courts generally will not enforce the agreement.
When a Promise Can Bind Without Consideration
There is one notable exception. If someone makes a promise they should reasonably expect another person to rely on, and that person does rely on it to their detriment, a court can enforce the promise even without traditional consideration. This doctrine, called promissory estoppel, exists to prevent injustice. Picture an employer who promises an applicant a job; the applicant quits their current position and relocates; then the employer rescinds the offer. A court could enforce that promise because the applicant changed their life based on it. The remedy may be limited to what fairness requires rather than full contract damages, but the principle keeps people from walking away from serious promises others have built plans around.
Who Is Legally Able to Enter a Contract
Even a perfectly structured agreement falls apart if one party lacks the legal capacity to enter it. Capacity issues come up in three main situations: age, mental state, and organizational authority.
Minors, meaning anyone under eighteen in most states, can enter contracts, but those contracts are generally voidable at the minor’s option. The minor can walk away; the adult on the other side cannot. Once the minor turns eighteen, they can ratify the agreement, which makes it fully binding going forward. There is a practical exception for necessities like food, clothing, shelter, and medical care — a minor generally cannot avoid paying for those.
Adults who are mentally incapacitated or severely intoxicated at the time of signing may also have the right to void a contract. The question courts ask is whether the person understood the nature and consequences of what they were agreeing to. If they did not, the contract is voidable at their discretion.
When dealing with a business rather than an individual, capacity depends on whether the person signing actually has authority to bind the organization. Corporations typically delegate signing authority through board resolutions that specify who can execute contracts and up to what dollar amount. If someone signs without proper authorization, the company may later argue the agreement is not enforceable. Before entering a significant deal with a business, confirm that the person across the table has the authority to commit it.
The Subject Matter Has to Be Legal
A contract’s subject matter has to be lawful. Courts will not enforce an agreement that requires either party to break the law or that violates public policy. A deal to distribute controlled substances or evade tax obligations is void from the start, not just unenforceable but treated as though it never existed. The same applies to agreements that restrict rights the law protects, such as a contract requiring an employee to waive all workplace safety protections. Illegality voids the entire agreement, and courts will not sort out who owes what under a deal that should never have been made.
Does a Contract Have to Be in Writing
A handshake deal is more enforceable than most people think. Oral contracts are valid and binding for many types of transactions. The challenge is proving what was agreed to; without a written record, disputes come down to conflicting testimony and whatever circumstantial evidence exists. That is why written agreements matter even when they are not legally required.
Contracts That Must Be in Writing
Certain categories of contracts must be in writing to be enforceable. This requirement, known as the Statute of Frauds, applies to transactions where the stakes are high enough that oral testimony alone creates too much risk of fraud. The categories that typically require a written record include:
- Contracts for the sale or transfer of land or an interest in land.
- Agreements that by their terms cannot be fully performed within twelve months from the date they are made.
- Contracts for the sale of goods worth $500 or more, which under the Uniform Commercial Code need a writing signed by the party being held to the deal.1Legal Information Institute. Uniform Commercial Code 2-201 – Formal Requirements; Statute of Frauds
- Promises to pay someone else’s debt, such as a guarantee of another person’s obligation.
- Contracts made in consideration of marriage, including prenuptial agreements.
The writing does not need to be a polished document. A signed email, a letter, or even a note on a napkin can satisfy the requirement as long as it identifies the parties, describes the subject matter, and is signed by the person being held to the contract.
Electronic Signatures Count
Federal law treats electronic signatures and records the same as their paper equivalents. Under the E-SIGN Act, a contract cannot be denied legal effect solely because it was formed using electronic signatures or stored as an electronic record.2Office of the Law Revision Counsel. 15 USC 7001 – General Rule of Validity Clicking “I agree,” typing your name in a signature field, or using a platform like DocuSign creates the same legal obligation as a pen-and-ink signature. The law does not force anyone to accept electronic signatures, but it prevents courts from rejecting a contract just because the signatures are digital.
Common Types of Contracts
Bilateral and Unilateral
Most contracts are bilateral: both parties make promises to each other. You agree to pay rent; the landlord agrees to provide a habitable apartment. Both sides are bound from the moment the agreement is made. Bilateral contracts dominate commercial life because businesses need the certainty of knowing both parties are committed.
Unilateral contracts work differently. Only one party makes a promise, and that promise becomes binding only when the other party performs a specific act. The classic example is a reward: someone posts a flyer offering $500 for the return of a lost dog. Nobody is obligated to go looking, but anyone who finds and returns the dog is entitled to the payment. The obligation runs one direction and only kicks in upon performance.
Express and Implied
Express contracts are what most people picture. The terms are spelled out, whether in writing or spoken aloud. You negotiate a price, agree on a delivery date, and shake hands or sign a document. There is no ambiguity about whether a deal exists.
Implied contracts form through conduct rather than words. Sit down at a restaurant and order a meal, and you have not signed an agreement to pay, but your behavior creates an implied-in-fact contract. The restaurant provides food; you are expected to pay. Courts look at the circumstances and the parties’ actions to determine whether both sides behaved as though they had an agreement.
Courts also recognize what are sometimes called quasi-contracts, which are not true contracts at all. When one party receives a benefit that would be unjust to keep without paying for it, a court can impose an obligation to compensate the other side even though no agreement existed. A contractor who mistakenly improves the wrong property, for instance, might recover the value of the work under a quasi-contract theory. The goal is preventing unjust enrichment rather than enforcing a deal that was actually made.
What Happens When Someone Breaks a Contract
A breach of contract occurs when one party fails to perform their obligations. Not all breaches are created equal, and the distinction between a material breach and a minor one determines what the other side can do about it.
A material breach goes to the heart of the agreement. It is serious enough that the non-breaching party did not get what they bargained for. If a homebuilder constructs your house with the wrong foundation, that is material. The non-breaching party can typically stop performing their own obligations, treat the contract as terminated, and sue for damages. A minor breach is a deviation that does not undermine the overall deal. If the builder uses a slightly different shade of interior paint, you can recover the cost of repainting, but you cannot refuse to pay for the entire house. This is where people get into trouble: overreacting to a minor breach by walking away from your own obligations can make you the one liable for breach.
What You Can Recover
The default remedy is compensatory damages — money intended to put the non-breaching party in the position they would have been in if the contract had been fully performed. Courts calculate this as the difference between what was promised and what was actually delivered, plus any additional losses that flowed naturally from the breach.
When money is not enough, a court may order specific performance, requiring the breaching party to actually do what they promised. This remedy is reserved for situations where the subject matter is unique. Real estate is the most common example, since every piece of land is one of a kind. Courts rarely order specific performance for ordinary goods or services because the non-breaching party can usually buy a substitute and recover the price difference as damages.
The non-breaching party also has a duty to mitigate. You cannot sit back, watch your losses pile up, and hand the bill to the other side. If a vendor fails to deliver supplies, you are expected to find a reasonable alternative. Any losses you could have avoided through reasonable effort will not be recoverable.
Defenses That Can Undo a Signed Contract
Sometimes an agreement that looks valid on its face can still be challenged. Courts recognize several defenses that can make an otherwise binding contract voidable or void.
A contract signed under threat or coercion is not a product of free will. Duress involves threats, intimidation, or other pressure that leaves a party with no real choice but to agree. The threat does not have to be physical. Economic duress, like threatening to breach an existing contract at a critical moment unless the other party agrees to new terms, can also qualify. Undue influence is subtler: it arises when one party holds a position of trust or authority over another and exploits that relationship to push through a one-sided agreement, such as a caretaker pressuring an elderly person into signing over assets.
When both parties share the same false belief about a basic fact at the time of contracting, the adversely affected party may be able to rescind the agreement. The mistake has to be about something fundamental — not a bad prediction about future market conditions, but a factual error like both parties believing a painting is an original when it is actually a reproduction. If you knew your knowledge was limited but chose to proceed anyway, you bear the risk of being wrong.
Courts can also refuse to enforce a contract, or strike individual clauses, if the terms are so unfair they shock the conscience. Under the UCC, a court that finds a contract or clause unconscionable at the time it was made can void it entirely, enforce the rest of the contract without the offending clause, or limit how the clause applies.3Legal Information Institute. Uniform Commercial Code 2-302 – Unconscionable Contract or Clause Courts look at both whether the bargaining process was fundamentally unfair and whether the terms themselves are unreasonably one-sided. A contract is most vulnerable when both problems are present.
How a Contract Ends
The simplest and most common way a contract ends is through full performance: both sides do what they promised, and the obligations are discharged. The parties can also agree to terminate. A mutual rescission effectively undoes the contract, returning both sides to their pre-agreement positions. They can modify the original terms by mutual consent, replacing old obligations with new ones.
When an unforeseen event makes performance genuinely impossible, the obligated party may be excused. Agree to renovate a building and it burns down through no fault of yours, and the contract is discharged because its subject matter no longer exists. The impossibility must be objective: the task itself must be impossible, not just harder or more expensive than expected. Frustration of purpose is a related concept. Performance is still technically possible, but an unforeseen event has destroyed the entire reason the contract existed. Courts apply this defense narrowly and only when the frustrated purpose was understood by both parties as the foundation of the deal.
Many commercial contracts include force majeure clauses that allocate risk for extraordinary events like natural disasters, wars, or pandemics. Courts in many jurisdictions interpret these clauses narrowly, excusing performance only when the triggering event matches what the clause actually describes. Garden-variety business difficulties like economic downturns generally do not qualify. If your contract includes a force majeure clause, read it carefully. The protection is only as strong as the specific language.