2.3 Acceptance & the Mailbox Rule

Acceptance & the Mailbox Rule

Acceptance is the final exercise of power granted by an offer, resulting in the creation of a binding contract. This section examines how acceptance is manifested, the timing rules governing dispatch and receipt under the Mailbox Rule, the strict requirements of the common law Mirror Image Rule, and the commercial realities codified in the UCC § 2-207 Battle of the Forms.

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I. Nature and Mechanics of Acceptance

Definition of Acceptance

Under Restatement (Second) of Contracts § 50, acceptance is a manifestation of assent to the terms thereof made by the offeree in a manner invited or required by the offer.

Who Holds the Power of Acceptance?

An offer can be accepted only by the person or entity to whom it was directed. The power of acceptance is strictly personal and non-assignable. An offeree cannot transfer the power of acceptance to a third party. (Contrast: Once a binding option contract or final contract is formed, the resulting contractual rights are freely assignable unless restricted by contract or statute).

Modes of Acceptance: Bilateral vs. Unilateral Contracts

• Bilateral Contracts: An offer seeking a return promise. Under modern law (Restatement (Second) § 32), unless an offer unambiguously dictates otherwise, an offer is presumed to invite acceptance either by promising to perform or by actual performance.
• Unilateral Contracts: An offer expressly requiring acceptance solely through full completion of the requested act. Notice of acceptance is generally not required unless the offeree has reason to know the offeror has no adequate means of learning of the performance with reasonable promptness.

Acceptance under UCC § 2-206 (Sales of Goods)

Under UCC § 2-206(1)(b), an order or offer to buy goods for prompt or current shipment invites acceptance either by a prompt promise to ship or by the prompt or current shipment of conforming or non-conforming goods:

• Conforming Goods Shipped: Operates as acceptance, forming a contract.
• Non-Conforming Goods Shipped: Operates simultaneously as an acceptance and a breach.
• The Accommodation Exception: If the seller ships non-conforming goods and seasonably notifies the buyer that the shipment is offered only as an accommodation to the buyer, the shipment does not operate as an acceptance. Instead, it constitutes a counteroffer, which the buyer is free to accept or reject without breach.

Silence as Acceptance

As a general principle, an offeror cannot unilaterally mandate that the offeree's silence will constitute acceptance ("If I do not hear from you by Friday, we have a contract"). Under Restatement (Second) § 69, silence operates as acceptance in only three narrow circumstances:

1. The offeree takes the benefit of offered services with reasonable opportunity to reject them and reason to know they were offered with the expectation of compensation;
2. The offeror has stated or given the offeree reason to understand that assent may be manifested by silence, and the offeree in remaining silent intends to accept;
3. Because of previous dealings, it is reasonable that the offeree should notify the offeror if they do not intend to accept.

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II. The Mailbox Rule (Adams v. Lindsell)

Contractual communications do not occur instantaneously across distances. The Mailbox Rule establishes default timing rules allocating the risk of transmission delays or lost mail.

The Core Rule: Dispatch vs. Receipt

• Acceptance by Mail / Dispatch: An acceptance dispatched by an authorized or reasonable medium is legally effective upon proper dispatch (the moment it is placed in the custody of the US Postal Service or private courier with proper postage and address), regardless of whether it ever reaches the offeror.
• All Other Communications Effective on Receipt: Revocations, rejections, counteroffers, and initial offers are legally operative only upon actual receipt by the intended recipient (or delivery to their place of business/residence).

┌─────────────────────────────┬────────────────────────────────────────────────────────┐
│ Communication Type          │ Effective Timing                                       │
├─────────────────────────────┼────────────────────────────────────────────────────────┤
│ Offer                       │ Effective on RECEIPT                                   │
│ Revocation by Offeror       │ Effective on RECEIPT                                   │
│ Rejection by Offeree        │ Effective on RECEIPT                                   │
│ Counteroffer by Offeree     │ Effective on RECEIPT                                   │
│ Acceptance by Offeree       │ Effective on DISPATCH (Mailbox Rule)                   │
└─────────────────────────────┴────────────────────────────────────────────────────────┘

Four Critical Exceptions to the Mailbox Rule

1. Offeror Stipulates Receipt ("Master of the Offer")

The offeror may alter the default rule by explicitly stating in the offer: "Acceptance is effective only upon receipt at my office by 5:00 PM on Friday." In this scenario, the mailbox rule is bypassed; dispatch does not conclude the contract.

2. Option Contracts (Restatement § 63(b))

The Mailbox Rule does not apply to the exercise of an option contract. Acceptance under an existing option contract is effective only upon receipt by the offeror before the option expiration date.

3. Rejection Dispatched First, Followed by Acceptance ("The Race")

If an offeree mails a rejection first and subsequently changes their mind and mails an acceptance, the Mailbox Rule is suspended.

• Whichever communication the offeror receives first controls.
• If the rejection is received first: The offer is terminated immediately, and the later-arriving acceptance is treated as a counteroffer.
• If the acceptance is received first: A binding contract is formed at the moment of receipt.

4. Acceptance Dispatched First, Followed by Rejection

If an offeree mails an acceptance first and later sends a rejection (e.g., via telegram, overnight courier, or phone):

• A binding contract was formed at the moment the acceptance was dispatched under the Mailbox Rule.
• The subsequent rejection is legally a nullity or an offer to repudiate/rescind.
• Detrimental Reliance Estoppel: If the offeror receives the rejection first and materially and detrimentally relies on it (e.g., selling the goods to a third party) before receiving the acceptance, the offeree is equitable estopped from enforcing the contract.

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