Acceptance & Mailbox Rule
Contracts & Sales · Lesson 02
Acceptance & Mailbox Rule
這一課問的是：「接受」何時生效？合約在哪一刻成立？答案是 mailbox rule —— 「寄出」那一刻。
Actor
Act
Object
Standard
Consequence
Visual Scene · the picture in your head
Issue. When is acceptance effective — and at what moment is the contract formed?
這一課問的是：「接受」何時生效？合約在哪一刻成立？答案是 mailbox rule —— 「寄出」那一刻。
Core Terminology · 7 must-know
Tap a card to flip and reveal the meaning.
acceptance
Tap to see meaning
Unequivocal assent to the terms of the offer, communicated in an authorized manner.
承諾／接受：以授權之方式對要約條款作明確同意。
the mailbox rule
Tap to see meaning
Acceptance is effective on dispatch — not on receipt — for most offers.
投遞箱規則：承諾於「寄出」那一刻生效。
dispatch
Tap to see meaning
Putting the acceptance out of the offeree's control — mailing, sending, or transmitting.
寄出：將承諾交付出 offeree 之支配。
mirror image rule
Tap to see meaning
CL: an acceptance must exactly mirror the offer; any change is a counteroffer.
鏡像規則（CL）：承諾須與要約完全相符。
UCC §2-206
Tap to see meaning
Allows acceptance by any reasonable medium and by promise or beginning performance.
UCC §2-206：以任何合理方式或開始履行作出承諾。
UCC §2-207
Tap to see meaning
Modifies the mirror image for sale of goods ("battle of the forms").
UCC §2-207：修改貨物買賣中之鏡像規則。
counteroffer
Tap to see meaning
A reply that changes or adds material terms; rejects the offer and creates a new one.
還價：變更或新增重要條款的回覆。
Issue · what this lesson is really about
When is acceptance effective — and at what moment is the contract formed?
這一課問的是：「接受」何時生效？合約在哪一刻成立？答案是 mailbox rule —— 「寄出」那一刻。
Trigger words & phrases that should flag this issue:
I acceptagreedOKlet's do itI'll take itmailed the acceptance
Expression Bank · how lawyers actually say it
Six function → sentence patterns. Use these in essay applications.
| Function | English sentence | 中文 |
|---|---|---|
| State the rule | Acceptance must be unequivocal assent to the terms of the offer. | 承諾須為對要約條款之明確同意。 |
| Apply mailbox rule | Under the mailbox rule, the acceptance was effective on dispatch. | 依投遞箱規則，承諾於寄出時生效。 |
| Pin formation | The contract was formed at the moment the offeree placed the acceptance in the mail. | 合約於受要約人將承諾投入郵筒那一刻成立。 |
| Note CL mirror | Any change to a material term operates as a counteroffer, not an acceptance. | 重要條款之變更構成還價而非承諾。 |
| Note UCC §2-207 | Between merchants, additional terms enter the contract unless they materially alter it. | 商人之間，新增條款若不重大變更即進入合約。 |
| State result | A binding contract was therefore formed when the acceptance was dispatched. | 因此合約於承諾寄出時成立。 |
Rule Sentence · the workhorse
Acceptance is unequivocal assent to the offer's terms, communicated in an authorized or reasonable manner, and under the mailbox rule it is effective on dispatch.
Sentence Anatomy · 5 roles, 5 colors
Every rule sentence breaks into five visual roles.
Actor 行為人the offeree受要約人
Act 行為unequivocal assent明確同意
Object 對象the offer's terms要約條款
Standard 法律標準the mailbox rule (effective on dispatch)投遞箱規則 - 寄出即生效
Consequence 後果a contract is formed合約成立
Casebook Snapshot · a real American case
Adams v. Lindsell
Holding. Where parties contract by post, an acceptance becomes binding from the moment the letter of acceptance is placed in the mail; otherwise no contract could ever be formed by post, since each party could always be one letter behind. The mailbox rule allocates the risk of postal delay to the offeror.
Why it matters. The mailbox rule fixes the moment of formation at dispatch, not receipt. The party who chose the channel bears the risk of delays in that channel.
Mailbox rule 把合約成立時點定在「寄出」而非「收到」。
Common Mistakes · what trips students
✗ 合約在 offeror「收到」承諾那一刻成立。
✓ Mailbox rule: effective on dispatch, not receipt.
Mailbox rule 是「寄出即生效」。
✗ mailbox rule 對 rejection 與 revocation 也適用。
✓ Rejection / revocation are effective on receipt.
拒絕與撤銷是「收到」才生效。
✗ CL 與 UCC 的承諾規則相同。
✓ CL: mirror image. UCC §2-207: relaxed.
CL 鏡像；UCC §2-207 放寬。
✗ 沉默就是承諾。
✓ Silence generally is not acceptance.
沉默原則上不構成承諾。
Mini IRAC · build the Application
Issue. Was a contract formed on Monday when P mailed an acceptance of D's offer, even though D did not receive it until Wednesday?
Rule. Under the mailbox rule, an acceptance is effective on dispatch, so a contract is formed at the moment of dispatch.
Application (model). P put a signed acceptance of D's offer into the mail on Monday; D received it on Wednesday. Because the mailbox rule makes an acceptance effective on dispatch, the fact that P placed the acceptance in the mail on Monday means the offer was accepted at that moment — and the offeror's later receipt does not change the formation date.
Pick the right element for each blank:
g1.
g2.
g3.
Conclusion. Therefore, a contract was formed on Monday.
MBE Check · multiple choice
D mails P an offer to sell a piano for $3,000. P first mails a letter rejecting the offer, then changes her mind and mails an acceptance. The acceptance arrives first; the rejection arrives second. Is there a contract?
Mini Essay · write the Application paragraph
Facts. D mailed P an offer to sell a tractor for $20,000. P signed an acceptance on Tuesday morning and put it in the outgoing mail at noon. D mailed a revocation on Tuesday afternoon. The acceptance arrived Thursday; the revocation arrived Wednesday.
Call. Was a contract formed?
Practice Drill · tap to build the rule
Drop the chips here in correct order:
Tap chips to add → tap chips in the target to remove: