For an acceptance to form a contract, four things have to be true at the same time: the response must unconditionally agree to the offer’s terms, it must come from the person the offer was directed to, it must be communicated to the offeror in an appropriate way, and it must happen before the offer expires. Miss any one of these requirements of acceptance in contract law and no contract exists, however clearly you thought you had a deal.
Each requirement does real work, and each has exceptions that matter.
Unconditional Agreement to the Offer’s Terms
An acceptance must reflect complete, unqualified agreement to the terms the offeror proposed. Courts apply an objective test: would a reasonable person looking at the offeree’s words or conduct conclude they intended to be bound on the offeror’s terms? That shared understanding is sometimes called a meeting of the minds.
The Mirror Image Rule
Under the common law mirror image rule, acceptance has to match the offer exactly. Change a price, add a condition, or move a deadline and you haven’t accepted. Your response becomes a counteroffer, which kills the original offer and swaps the roles. The original offeror can then take or leave your counteroffer, but the original deal is gone.
Negotiations fall apart here all the time. Someone thinks they’ve accepted, but a single added phrase (“I accept, provided you deliver by Friday”) turns the response into a counteroffer and leaves both sides without a contract.
The UCC Softening for Sales of Goods
The mirror image rule can be harsh in commercial transactions where buyers and sellers trade forms with slightly different boilerplate. The Uniform Commercial Code, which governs sales of goods, relaxes the rule. A response that clearly expresses acceptance still operates as acceptance even if it includes additional or different terms, unless the offeree expressly conditions acceptance on the offeror’s agreement to those new terms.1Legal Information Institute. Uniform Commercial Code 2-207 – Additional Terms in Acceptance or Confirmation
Between merchants, the additional terms automatically become part of the contract unless they materially alter the deal, the original offer expressly limited acceptance to its own terms, or the offeror objects within a reasonable time. For non-merchants, the extra terms are treated as proposals the offeror can take or leave. Outside the UCC — service agreements, employment contracts, real estate deals — the full mirror image rule still applies.
The Right Person Has to Accept
Only the person or group the offer was directed to has the power to accept. An offer is personal to its intended recipient and cannot be transferred. If a third party tries to accept, no contract forms; at most, their response might count as a new offer the original offeror can consider.
Offers can target a specific individual, a defined group, or the general public. A reward posted on a bulletin board is open to anyone who performs the requested act. A job offer letter is directed at one named person. Either way, the acceptance has to come from within the intended class of offerees.
Legal Capacity
Being the right person is not enough. The offeree must also have legal capacity to contract. Contracts accepted by minors (people under 18 in most states) are generally voidable at the minor’s option: the minor can walk away, but the adult on the other side cannot. People who lack mental capacity to understand the agreement, or who are so impaired by substances that they cannot understand it, are treated similarly.
Authority When a Business Is Accepting
When an organization is the offeree, the question is whether the individual who accepted had authority to bind it. Someone with actual authority — explicit or implicit permission from the organization — can form a binding contract. Even without actual authority, someone with apparent authority can bind the organization if the company’s own conduct led the offeror to reasonably believe that person could accept for it. The risk falls on the company, not on a third party who relied in good faith on appearances.
Communicating the Acceptance
Acceptance generally has to be communicated to the offeror before a contract exists. An uncommunicated intention to accept, however sincere, creates nothing.
Express acceptance is the most straightforward form: a spoken or written statement that clearly indicates agreement. Signing a contract, saying “I accept,” or sending a confirmation email all qualify. Implied acceptance arises from conduct. If someone delivers goods and you use them without objection, your behavior can show acceptance even though you never said anything.
Acceptance by performance applies to unilateral contracts, where the offeror asks for an action rather than a promise. If someone offers $500 for the return of a lost dog, you accept by returning the dog, not by promising to look. Completing the requested act is both the acceptance and the performance, and no separate notice is needed.
When the Offer Dictates the Method
The offeror controls the terms of the offer, including how it can be accepted. If the offer says “reply by certified mail only” or “acceptance must be received in writing by March 1,” that is the only route to a valid acceptance. A different method, or a missed deadline, means no contract unless the offeror voluntarily honors the non-conforming response.
When the offer doesn’t specify a method, the offeree can accept by any reasonable means. Under the UCC, an offer to buy or sell goods invites acceptance either through a promise to perform or through actual performance, such as shipping the goods, unless the offer clearly says otherwise.2Legal Information Institute. Uniform Commercial Code 2-206 – Offer and Acceptance in Formation of Contract
When Silence Can Count
As a default, silence is not acceptance. You can’t bind someone by mailing them a product and declaring that failure to respond means they bought it. Narrow exceptions exist:
- The offeree benefits from services they had a chance to refuse, knowing the other party expected to be paid.
- The offeror has indicated silence is an acceptable form of acceptance, and the offeree stays silent intending to accept.
- A prior course of dealing between the parties has established that silence means agreement.
- The offeree exercises control over unsolicited goods, for example by using them rather than returning them.
Outside these situations, an offeror cannot impose a duty to respond on anyone.
Electronic Acceptance
Clicking “I agree,” typing your name in a signature field, or signing on a tablet screen can all constitute valid acceptance. Federal law prohibits courts from refusing to enforce a contract solely because an electronic signature or record was used.3Office of the Law Revision Counsel. 15 USC 7001 – General Rule of Validity
Two overlapping laws cover this. The federal Electronic Signatures in Global and National Commerce Act (E-SIGN) applies to transactions in interstate or foreign commerce. The Uniform Electronic Transactions Act (UETA), adopted by the vast majority of states, covers electronic transactions more broadly. Both establish the same core principle: electronic signatures and records carry the same legal weight as paper. For the signature to hold up, both parties must intend to sign, both must consent to doing business electronically, the signature must be tied to the record, and the signed document must stay accessible to both sides.4National Credit Union Administration. Electronic Signatures in Global and National Commerce Act (E-Sign Act)
Accepting Before the Offer Ends
An acceptance is only valid while the offer is still open. Once the offer terminates, any attempt to accept is legally meaningless, or at best counts as a fresh offer the other side can take or leave.
Offers end in several ways. The offeror can revoke the offer any time before acceptance, as long as the revocation is communicated to the offeree; a private change of heart doesn’t count. The offeree can reject the offer outright or respond with a counteroffer, either of which ends it. You cannot reject an offer on Monday and try to accept the same offer on Wednesday. An offer with a stated deadline expires at that deadline; one without a stated deadline expires after a reasonable time, and what counts as reasonable depends on circumstances (an offer to sell perishable goods has a shorter life than an offer to sell real estate). The death or legal incapacity of either party before acceptance generally terminates the offer automatically, and so does destruction of the subject matter.
The Mailbox Rule
When the parties communicate by mail or similar non-instantaneous methods, timing matters. The mailbox rule, also called the dispatch rule, says acceptance takes effect the moment the offeree sends it, not when the offeror receives it. Drop your acceptance letter in a mailbox on Tuesday and the contract forms Tuesday, even if the offeror doesn’t open it until Friday.5Legal Information Institute. Mailbox Rule
The practical effect is real. If the offeror mails a revocation on Wednesday and the offeree mailed an acceptance on Tuesday, the acceptance wins, because it took effect on dispatch while the revocation only takes effect on receipt. If you mail your acceptance on the last day and it arrives after the deadline, the contract still formed on the day you sent it, assuming you used an authorized method.
The rule has limits. It applies only when the offeree uses a method the offer invited or that’s reasonable in the circumstances. It doesn’t apply if the offer specifically says acceptance is effective only on receipt. And some courts have questioned how it applies to email and other near-instantaneous electronic communications, since the rationale was built around postal delay.
Offers That Cannot Be Revoked
Most offers can be pulled back any time before acceptance, which creates risk for offerees who need time to evaluate. Two mechanisms keep an offer open.
An option contract is a side agreement where the offeree pays consideration in exchange for the offeror’s promise to hold the offer open for a set period. Even a small payment can make the option enforceable. During that window, the offeror cannot revoke. Option contracts are common in real estate transactions and executive compensation. A related doctrine protects offerees who have already begun performance under a unilateral contract: once performance has started in good faith, most courts require the offeror to keep the offer open long enough for the offeree to finish.
Under the UCC, a merchant who makes a signed written offer to buy or sell goods and promises in that writing to hold the offer open cannot revoke it during the stated period. No consideration from the offeree is required. If no time is stated, the offer stays open for a reasonable period, and the maximum irrevocable period under this rule is three months. If the firm offer language sits on a form the offeree supplied, the offeror has to separately sign that specific term, which prevents someone from burying an irrevocability clause in their own paperwork.6Legal Information Institute. Uniform Commercial Code 2-205 – Firm Offers
When Acceptance Has to Be in Writing
For some contracts, a valid acceptance isn’t enough on its own: the agreement also has to be in a signed writing to be enforceable. The statute of frauds, adopted in some form by every state, applies to sales of real estate or interests in land, contracts that cannot be performed within one year, promises to pay someone else’s debt, contracts made in consideration of marriage (such as prenuptial agreements), and sales of goods at or above a dollar threshold (typically $500 under the UCC).
The writing doesn’t have to be a formal contract. A signed letter, email, or series of texts can satisfy the requirement, as long as the essential terms are there and the party being held to the deal signed it. If your acceptance falls into one of these categories and nothing is in writing, a court may refuse to enforce the contract even when both sides clearly intended to be bound.
Canceling After You’ve Accepted
A valid acceptance usually locks you in, but in limited situations the law lets you unwind the deal anyway. The FTC’s Cooling-Off Rule gives consumers three business days to cancel certain sales made at their home, workplace, or a seller’s temporary location such as a hotel room or convention center. The rule also covers sales where you invited a salesperson to present at your home.7Federal Trade Commission. Buyer’s Remorse: The FTC’s Cooling-Off Rule May Help The rule carries exclusions by dollar amount and setting, and it doesn’t apply to real estate, insurance, or sales conducted entirely online, by mail, or by phone.8eCFR. 16 CFR Part 429 – Rule Concerning Cooling-Off Period for Sales Made at Homes or at Certain Other Locations Many states add their own cancellation rights for industries like health clubs, timeshares, and home improvement contracts; the federal three-day rule is a floor, not a ceiling.