A contract is legally enforceable when five things line up: one party made a clear offer, the other accepted it, both exchanged something of value, both had the legal capacity to agree, and the purpose was lawful. Miss any one and a court has no basis to hold anyone to the deal. But those five elements are only the starting point. Whether the agreement had to be in writing, whether both sides truly consented, and whether you’re still inside the deadline to sue all decide whether the contract will actually hold up when you need it to.
The Five Elements a Court Looks For
A Clear Offer
An offer is a specific proposal to do something, or not do something, in exchange for something from the other side. It has to be definite enough that a reasonable person could tell what’s being proposed. Vague statements about future plans or casual expressions of interest don’t rise to the level of an offer.
Acceptance of That Offer
Acceptance has to match the offer. If the response changes any term, it isn’t acceptance at all — it’s a counteroffer, which wipes out the original and puts a new proposal on the table. The back-and-forth continues until both sides agree to the same terms. Lawyers sometimes call this a meeting of the minds.
Consideration
Each side has to give up something of legal value: money, a service, a promise to act, or even a promise not to do something they’d otherwise be free to do. Without an exchange, you have a gift or a favor, not a contract.
Courts care whether consideration exists, not whether the trade was fair. Someone who sells a $300,000 house for $1,000 has made a bad bargain, but the contract is still enforceable because value changed hands. The one hard limit: past consideration doesn’t count. If someone did the work before any agreement was discussed, a later promise to pay for it generally can’t be enforced, because nothing new was exchanged.
Legal Capacity
Both parties must be able, in the eyes of the law, to understand what they’re agreeing to. That generally means being of legal age (18 in most states) and having the mental capacity to grasp the terms. Contracts signed by minors are usually voidable at the minor’s option, though most states carve out exceptions for necessities like food, shelter, clothing, and medical care.
Lawful Purpose
The subject matter has to be legal. An agreement to do something illegal, or something that violates public policy, is void from the moment it’s made. No matter how carefully it was drafted, no court will enforce it.
When the Agreement Has to Be in Writing
A doctrine called the Statute of Frauds requires certain categories of agreement to be in writing and signed. Specifics vary by state, but the usual list includes:
- Real estate transactions, including sales, mortgages, leases, and easements.
- Contracts that can’t be fully performed within one year of being made. A two-year employment contract qualifies; a contract to finish a shed “sometime this year” generally doesn’t.
- Sales of goods worth $500 or more under the Uniform Commercial Code.1Legal Information Institute. Uniform Commercial Code 2-201 – Formal Requirements; Statute of Frauds
- Promises to pay someone else’s debt if they default.
- Agreements made in consideration of marriage, such as prenuptial agreements.
The writing doesn’t have to be a formal contract. A signed letter, email, or chain of text messages can satisfy the Statute of Frauds as long as it identifies the parties, describes the subject matter, and is signed or authenticated by the person being held to the deal.
The UCC also recognizes exceptions. If goods are custom-made for a specific buyer and unsuitable for resale, the writing requirement can drop away once the seller has substantially started production. Partial performance and court testimony admitting the contract existed can also override the writing requirement in some situations.
Oral and Implied Contracts Still Count
Outside the Statute of Frauds categories, oral contracts are generally enforceable. A verbal deal to paint a neighbor’s fence for $200 has every essential element and is legally binding. The problem with oral agreements isn’t legality, it’s proof. In a dispute, you’re arguing your word against theirs.
Implied contracts are enforceable too. Sitting down at a restaurant and ordering food creates one: nobody signs anything, but you owe for what you ordered and the restaurant owes you the meal. Conduct can form a contract just as reliably as words.
Electronic Signatures and Digital Contracts
Federal law treats electronic signatures and digital contracts as legally equivalent to paper. Under the Electronic Signatures in Global and National Commerce Act, a contract can’t be denied legal effect simply because it was formed electronically or signed electronically.2Office of the Law Revision Counsel. 15 USC 7001 – General Rule of Validity Every state has adopted either the Uniform Electronic Transactions Act or similar legislation recognizing electronic records and signatures.
What counts as an electronic signature is broad: a typed name in an email, a click on an “I agree” button, a stylus signature on a tablet, or a signature through a service like DocuSign. The key is intent. The person has to have meant the action as their signature. An auto-generated email footer probably doesn’t qualify because it wasn’t adopted deliberately for the specific agreement.
Things That Can Still Void a Contract That Looks Valid
A contract can check every element box and still fall apart if something went wrong during formation. Courts look hard at whether both sides genuinely, freely agreed.
Mutual Mistake
When both parties share the same false belief about a basic fact underlying the deal, the agreement may be voidable. Two people contract for the sale of a painting both believe is an original, and it turns out to be a copy. The mistake has to go to something fundamental, and the party trying to escape the contract can’t be the one who assumed the risk of that particular uncertainty.
Fraud
If one party deliberately lies about a material fact to get the other to sign, the deceived party can void the contract. A car seller who rolls back an odometer creates a contract tainted by fraud; the buyer never truly agreed to purchase a high-mileage vehicle.
Duress
A contract signed under threat isn’t a real agreement. Duress can be physical (“sign this or I’ll hurt you”) or economic, like threatening to destroy a business unless the other side agrees to unfavorable terms. The common thread is that the pressured party had no reasonable alternative. Ordinary hard bargaining doesn’t qualify.
Undue Influence
Undue influence is subtler. It typically arises in relationships where one person holds significant power or trust over another: a caregiver and an elderly patient, an attorney and a vulnerable client, a parent and an adult child. The stronger party uses that position to push the weaker party into a deal they wouldn’t have made on their own. Courts scrutinize these situations closely, especially when the resulting agreement overwhelmingly benefits the person in the power position.
Unconscionability
Even without fraud or coercion, a court can refuse to enforce terms that are so wildly unfair that doing so would offend basic fairness. Courts analyze this on two axes. Procedural unconscionability asks whether the formation process was fair: Did both sides have a meaningful choice? Were terms buried in fine print? Was there a huge gap in bargaining power? Substantive unconscionability looks at the terms themselves: Are they so lopsided that no reasonable person would agree voluntarily? Most courts expect some showing of both, though a strong case on one side can make up for a weaker case on the other.
Changing a Contract After It’s Been Signed
Modifications are trickier than most people realize. Under traditional contract law, any change needs new consideration. Simply promising to do what you were already obligated to do isn’t enough. This is the pre-existing duty rule. If a contractor is already under contract to remodel your kitchen for $30,000, a later demand for an extra $5,000 to finish the same work isn’t supported by new consideration, and you generally aren’t bound to pay it.
The UCC takes a more practical approach for the sale of goods. Under UCC § 2-209, modifications don’t require new consideration, only good faith.3Legal Information Institute. Uniform Commercial Code 2-209 – Modification, Rescission and Waiver If a supplier and buyer adjust delivery terms because of a materials shortage, that change is binding without either side offering something extra.
How Long You Have to Enforce It
Every breach of contract claim has a deadline. The statute of limitations starts running from the date the breach occurs, and if you miss it, the right to sue is gone regardless of how strong the case is. Deadlines vary by state. For written contracts, filing windows range from about 3 years to 10 years. Oral contracts get shorter deadlines, typically between 2 and 6 years.
The clock generally starts when the breach happens, not when you find out about it. If a contractor used substandard materials two years ago and you only noticed last month, most states measure the deadline from installation. Some states recognize a discovery rule for hidden defects, but it varies and shouldn’t be relied on without checking your state’s rules. If you believe a contract has been breached, don’t sit on it. Delays cost leverage, and they can cost the entire claim.