You just signed a contract — or maybe you’re about to — and a nagging question crosses your mind: is this thing actually legal? Whether it’s a freelance agreement, a gym membership, or a terms-of-service page you clicked through at midnight, understanding what makes a contract enforceable is one of the most practical legal skills you can have.
The short answer is that most contracts you encounter in daily life are technically valid. But there are important exceptions, and knowing them can save you money, stress, and legal headaches.
The Six Elements of a Valid Contract
For a contract to be legally binding in the United States, it generally needs to satisfy six core requirements. If any one of these is missing, the entire agreement may be unenforceable.
1. Offer
One party must make a clear, definite proposal to enter into an agreement. This isn’t just a casual suggestion — it must be specific enough that the other party can accept it without negotiation. “I’ll sell you my car” is vague. “I’ll sell you my 2022 Honda Civic for $18,000” is an offer.
An offer can be revoked at any time before it’s accepted, unless the offeror has promised to keep it open for a certain period (known as an option contract).
2. Acceptance
The other party must agree to the exact terms of the offer. This is called the “mirror image rule” — the acceptance has to match the offer. If someone changes a term while accepting, that’s actually a counteroffer, not an acceptance, and the original offer is effectively rejected.
In the digital age, acceptance often looks like clicking “I Agree” or signing electronically. Courts have generally upheld these as valid forms of acceptance, though there have been challenges around “browsewrap” agreements (where terms are available via a hyperlink but you never have to click to agree).
3. Consideration
Both parties must exchange something of value. This is what separates a contract from a gift. Consideration can be money, services, goods, a promise to do something, or even a promise not to do something.
The law generally doesn’t care whether the exchange is “fair.” Selling a $50,000 car for $1 is technically valid consideration, though an extreme imbalance might raise red flags about duress or fraud.
4. Capacity
Both parties must have the legal ability to enter into a contract. This means they must be:
- Of legal age: In most states, that’s 18. Contracts with minors are generally voidable — the minor can choose to honor the agreement or walk away from it. (There are exceptions for necessities like food, clothing, and shelter.)
- Of sound mind: Someone who is mentally incapacitated — whether due to cognitive disability, intoxication, or other impairment — may lack the capacity to consent to a contract.
- Not under undue influence: If one party holds a position of power or trust over the other (a caregiver, a financial advisor, a family member), any contract between them may be scrutinized more carefully.
5. Legality
The subject matter of the contract must be legal. You cannot enforce a contract for illegal goods, illegal services, or anything that violates public policy. A contract to sell stolen property is void. A contract that requires someone to commit a crime is void. An agreement that violates anti-discrimination laws is void.
This seems obvious, but it comes up in subtler ways. For example, non-compete agreements that are too restrictive may be deemed unenforceable because they violate public policy around the right to earn a living. Certain types of penalty clauses may be thrown out as unconscionable.
6. Mutual Assent (Meeting of the Minds)
Both parties must genuinely understand and agree to the essential terms. If there’s a fundamental misunderstanding about what the contract covers — say, one party thinks they’re buying a painting and the other thinks they’re licensing a reproduction — there’s no mutual assent.
Fraud, misrepresentation, and mistakes can all undermine mutual assent. If someone lied to you about a material fact to get you to sign, the contract may be voidable.
What Makes a Contract Unenforceable?
Even if a contract checks all six boxes at the time of signing, certain conditions can render it unenforceable after the fact.
Unconscionability
A court can refuse to enforce a contract — or specific clauses within it — if the terms are so one-sided that they “shock the conscience.” There are two types of unconscionability:
- Procedural unconscionability relates to the process: Was the contract presented on a take-it-or-leave-it basis with no opportunity to negotiate? Was the language so complex that a reasonable person couldn’t understand it? Was the disadvantaged party under pressure?
- Substantive unconscionability relates to the terms themselves: Does one party give up nearly all their rights? Are the penalties wildly disproportionate? Is there a massive imbalance in obligations?
Many consumer contracts — cell phone agreements, software licenses, rental agreements — contain individual clauses that could be challenged as unconscionable. Courts often strike the offending clause while keeping the rest of the contract intact.
Duress and Undue Influence
If you signed a contract because someone threatened you — physically, financially, or otherwise — the contract is voidable. Duress doesn’t require a gun to your head. Economic duress counts too: “Sign this or I’ll destroy your business” can be enough.
Undue influence is subtler. It happens when someone in a position of trust or authority manipulates you into an agreement that benefits them. Think of an elderly person pressured by a caretaker into signing over assets.
Fraud and Misrepresentation
If one party intentionally lied about a material fact, or concealed important information, the contract can be voided by the deceived party. This applies even if the lie wasn’t in the contract itself — verbal misrepresentations during negotiation count.
There’s an important distinction between fraud (intentional deception) and innocent misrepresentation (someone genuinely believed what they said was true). Both can make a contract voidable, but fraud can also lead to additional damages.
Mistake
If both parties were mistaken about a fundamental fact at the time the contract was formed (a “mutual mistake”), the contract may be voidable. For example, if you contract to buy a specific piece of land and both parties believe it’s 10 acres but it’s actually 2 acres, that’s a mutual mistake.
A unilateral mistake (only one party was wrong) is harder to use as grounds for voiding a contract, unless the other party knew about the mistake and took advantage of it.
Impossibility and Impracticability
If circumstances change so dramatically that performance becomes literally impossible — the subject of the contract is destroyed, a new law makes the activity illegal, or a key person dies — the contract may be discharged. The COVID-19 pandemic created a wave of impossibility and impracticability claims as businesses couldn’t fulfill their contractual obligations.
Common Contracts That Might Not Be Enforceable
Here are a few everyday situations where enforceability is frequently challenged:
Contracts with Minors
As mentioned, these are almost always voidable at the minor’s option. If your 17-year-old signs up for a $200/month subscription service, they (or you, as their guardian) can likely void it. However, once the minor turns 18, they may “ratify” the contract by continuing to accept its benefits.
Clickwrap and Browsewrap Agreements
Courts generally uphold “clickwrap” agreements where you must actively click “I Agree.” They’re more skeptical of “browsewrap” agreements where terms are buried in a footer link and you’re assumed to have agreed just by using the website. If the terms weren’t reasonably conspicuous, they may not hold up.
Non-Compete Agreements
These are increasingly under fire. The FTC has pushed to limit non-competes, and many states (California being the most notable) refuse to enforce them altogether. Even in states that allow them, overly broad non-competes — covering too wide a geographic area, lasting too long, or restricting too many activities — are frequently struck down. For more on this, see our guide on non-compete agreement red flags.
Contracts of Adhesion
A “contract of adhesion” is a take-it-or-leave-it agreement drafted entirely by one party with superior bargaining power. Think insurance policies, rental agreements, or software licenses. These are generally enforceable, but courts are more willing to strike individual clauses that are unconscionable because the weaker party had no ability to negotiate.
How to Check if Your Contract Is Legally Sound
If you’re unsure about a contract, here are practical steps you can take:
Read Every Word
This sounds obvious, but most people don’t do it. Pay special attention to sections on termination, penalties, liability limitations, arbitration clauses, and automatic renewals. These are where the most problematic terms tend to hide. Our article on apartment lease red flags covers many of the common traps in rental agreements.
Look for Red Flag Language
Watch for phrases like:
- “Waive any and all claims”
- “Sole discretion”
- “Liquidated damages” (especially when the amount seems disproportionate)
- “Binding arbitration” with “class action waiver”
- “Non-refundable” (especially for deposits)
- “Indemnify and hold harmless” (if it’s entirely one-sided)
If you want a deeper understanding of indemnification language, check out our plain-English guide to indemnification.
Ask Questions Before Signing
If something is unclear, ask. If the other party refuses to explain a term or pressures you to sign immediately, that’s a red flag. Legitimate businesses are usually willing to walk you through their contracts.
Use Technology to Your Advantage
You don’t need to be a lawyer to understand a contract. AI-powered tools like Fineprint can scan your contract in seconds and highlight clauses that could be problematic — from one-sided liability waivers to hidden auto-renewal terms. Getting a plain-English breakdown before you sign is one of the fastest ways to protect yourself.
When to Consult a Lawyer
For high-stakes contracts — employment agreements, business partnerships, real estate purchases, or anything involving large sums of money — it’s worth paying for legal advice. A lawyer can spot issues you might miss and negotiate better terms on your behalf.
The Bottom Line
Most contracts you encounter are technically legal and enforceable. But “legal” doesn’t mean “fair,” and a valid contract can still contain terms that are heavily stacked against you. The key is knowing what to look for: Are all six elements present? Are there any signs of unconscionability, duress, or misrepresentation? Are specific clauses — like non-competes or arbitration waivers — enforceable in your state?
Understanding these fundamentals puts you in a stronger position every time you’re handed a document and a pen. Don’t sign until you know exactly what you’re agreeing to.