⚡ 10-Second Rule
A yes only makes a deal if it matches the offer and arrives the way the rules allow.
🧒 ELI-10 Scene
Mia writes her pen pal Leo: "Trade my sticker album for your comic collection? Reply by Friday." Leo drops his "yes!" letter in the mailbox Thursday night. It won't arrive until Saturday, but the trade locked in the moment the letter left his hand. That's the magic of mailing a yes. Now imagine Leo instead wrote, "Yes — but only if you throw in your unicorn page." That letter isn't a yes at all. It's a brand-new trade idea, and it erases Mia's original one. And if Leo simply never answers? Silence usually means nothing. Mia can't trap him by writing, "no reply means we have a deal."
⚖️ Actual Rule
Acceptance is a manifestation of assent to the offer's terms, made in a manner the offer invites (Restatement (Second) of Contracts § 50, paraphrasing). At common law, the mirror image rule applies: a reply that adds or changes terms is not an acceptance but a counteroffer, which also rejects the original offer (Restatement § 59, paraphrasing). Under the mailbox rule, an acceptance is effective on dispatch if properly sent, while rejections and revocations are effective on receipt (Restatement § 63, paraphrasing, following Adams v. Lindsell, 1 B. & Ald. 681 (K.B. 1818)); the dispatch rule does not apply to option contracts, where acceptance is effective on receipt, and if a rejection is dispatched first, a later-dispatched acceptance is effective only if it arrives before the rejection. An offer may invite acceptance by promise, by performance, or by either; under UCC § 2-206(1)(a), unless unambiguously indicated otherwise, "an offer to make a contract shall be construed as inviting acceptance in any manner and by any medium reasonable in the circumstances." A unilateral offer — one accepted only by complete performance — becomes irrevocable once the offeree begins performing, creating an option (Restatement § 45, paraphrasing). Silence is not acceptance except in narrow cases: the offeree takes offered benefits knowing payment is expected, prior dealings make silence reasonable assent, or the offeree intends silence as acceptance where the offer so allows (Restatement § 69, paraphrasing).
ELI-10 translation: a clean yes, sent an allowed way, seals the deal — usually the instant it's sent — but a changed yes is a new offer, and saying nothing is normally not a yes.
🔍 Ask These Questions
- Is there a live offer, and is this the person it was made to? (Only the invited person can say yes, while the offer still breathes.)
- What kind of yes did the offer invite — a promise, an act, or either? (Did the offeror want words, work, or whichever?)
- Does the reply mirror the offer exactly? (Any "yes, but..." is a new offer that kills the old one.)
- When was the yes effective — on sending, under the mailbox rule? (A mailed yes usually counts the moment it's dropped in.)
- Does a mailbox exception apply — an option contract, or a rejection sent first? (Options need the yes to arrive; after a mailed no, whichever letter lands first wins.)
- Is someone claiming silence was a yes? (Staying quiet almost never makes a deal, unless past habits or taken benefits say otherwise.)
⚠️ Bar Trap
Exam language: Examiners test the mailbox rule's exceptions more than the rule itself: an acceptance under an option contract is effective on receipt, not dispatch, and an offeree who mails a rejection first cannot resurrect dispatch-effectiveness — the acceptance controls only if it outraces the rejection to the offeror.
ELI-10: The mailed-yes magic has off switches. If the offer was locked open by an option, the yes must actually arrive. And once you mail a no, it's a footrace — whichever letter lands first decides.
🧪 Question
On March 1, Priya mailed Marcus a signed offer to sell her catering van for $9,000, stating that the offer would remain open until March 10. On March 5, Marcus mailed Priya a letter stating, "I can't do $9,000 — I decline." On March 6, having secured a loan, Marcus mailed a second letter stating, "I accept your offer of the van for $9,000." The March 6 acceptance arrived on March 8. The March 5 rejection arrived on March 9. Priya, who had not sold the van to anyone else, now refuses to perform, asserting that no contract was formed.
Was a contract formed?
(A) Yes, because Marcus's acceptance became effective when he mailed it on March 6. (B) Yes, because Marcus's acceptance reached Priya before his rejection did. (C) No, because Marcus's rejection terminated the offer when he mailed it on March 5. (D) No, because an offeree who dispatches a rejection loses the power to accept the offer.
Answer: (B). When a rejection is dispatched before an acceptance, the mailbox rule's dispatch-effectiveness does not apply; the acceptance is effective only if it arrives before the rejection. Marcus's acceptance arrived March 8, ahead of the March 9 rejection, so a contract was formed on receipt of the acceptance.
💡 Why the Wrong Answers Are Wrong
- (A) applies dispatch-effectiveness after a rejection was already mailed; the rejection-first exception displaces the mailbox rule.
- (C) makes the rejection effective on dispatch; rejections, unlike acceptances, are effective only on receipt.
- (D) invents a forfeiture rule; the power to accept survives so long as the acceptance beats the rejection to the offeror.
- ELI-10: The misconception is thinking mailing always freezes the moment. Once a no is in the mail, timing flips to a race, and only the first letter to arrive speaks.
