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Posting rule

The posting rule, also known as the mailbox rule or postal acceptance rule, is a longstanding principle in common law contract formation that deems an acceptance of an offer effective upon its dispatch—typically when posted in the mail—rather than upon its receipt by the offeror, thereby creating a binding contract at the moment of posting even if the communication is delayed, lost, or never arrives.^[1]^[2]^[3] This rule emerged in the early 19th century to address uncertainties arising from the unreliability of postal services during that era, with its foundational precedent established in the English case Adams v. Lindsell (1818), where the court held that acceptance by letter was complete upon posting to promote fairness and finality in negotiations conducted via mail.^[1]^[2] Over time, it has been adopted and refined in various common law jurisdictions, including the United Kingdom, where it applies specifically to postal acceptances unless the offer dictates otherwise, and the United States, where it serves as the default for bilateral contracts under the Restatement (Second) of Contracts § 63 (1981), though some states like California extend it cautiously to option contracts.^[3]^[1]^[2] In practice, the posting rule facilitates prompt contract formation in non-instantaneous communications, such as traditional mail or telegrams, by shifting the risk of transmission to the offeror once the acceptance is properly dispatched, but it does not apply to revocation of offers, which must be received to take effect, nor to option contracts where acceptance generally requires receipt.^[1]^[2] Parties may contractually override the rule by specifying that acceptance must be received, and it is codified in frameworks like the Uniform Commercial Code in the U.S. for sales of goods.^[2]^[1] In contemporary contexts, the rule's relevance has diminished with the rise of instantaneous electronic communications, where courts often apply a "receipt rule" instead—treating acceptance via email or fax as effective upon arrival in the recipient's system—though debates persist on its application to digital methods, with jurisdictions varying in their interpretations to balance tradition and modern efficiency.^[3]^[2]^[1]

Overview and Principles

Definition

The posting rule, also known as the postal acceptance rule, is a principle in contract law that provides an exception to the general requirement that acceptance of an offer must be communicated to the offeror to form a binding contract. Under this rule, an acceptance becomes effective and creates a contract at the precise moment it is posted—such as when placed in a mailbox or delivered to postal authorities—rather than upon receipt by the offeror.^[4]^[5] This rule applies specifically to non-instantaneous methods of communication like the postal service, but only where the offer was made by post or where post constitutes a reasonable mode of reply based on the circumstances and ordinary business usage.^[5] For instance, if an offer is sent by mail and the offeree posts their acceptance on Day 1, the contract is formed on that day, even if the acceptance letter arrives on Day 3 or is lost in transit.^[4] The rule originated in the 19th century to mitigate uncertainties arising from delays and unreliability in postal systems, which were the primary means of long-distance communication at the time.^[5]

Rationale and Scope

The posting rule, also known as the mailbox rule, serves primarily to provide certainty in the formation of contracts by establishing a fixed moment when acceptance becomes effective—namely, upon proper posting—thereby avoiding the uncertainties arising from postal delays or non-delivery.^[4] This rationale addresses the potential for an infinite regress in communication, where each party awaits confirmation of receipt, which could indefinitely postpone contract enforceability.^[6] Additionally, the rule encourages the use of postal communication as a low-cost method for distant transactions by allocating the risk of loss or delay to the offeror, who benefits from initiating the offer and can specify alternative methods if desired.^[7] It also prevents offerors from revoking their offers after the offeree has posted an acceptance but before it arrives, protecting the offeree's reliance on the transaction.^[8] The scope of the posting rule is narrowly confined to acceptances sent via post where post is a reasonable or contemplated method of communication in the circumstances, and it does not extend to offers, revocations, or rejections, which generally take effect only upon receipt by the intended recipient.^[1] For the rule to apply, the post must be a reasonable or contemplated method of communication in the circumstances, such as when the offer was made by mail or when distance makes it practical.^[6] It explicitly excludes instantaneous forms of communication, like telephone or telex, where acceptance is effective only upon actual receipt to ensure both parties are simultaneously aware of the agreement.^[7] A critical limitation is that the offeree must post the acceptance properly, including using the correct address and sufficient postage; failure to do so, such as through the offeree's negligence, means no contract is formed if the letter is lost or delayed.^[8] The rule presupposes a reliable postal system, as developed in the 19th century, but it leaves a gap in addressing modern digital equivalents like email, where courts have debated but not uniformly extended its application.^[4]

Historical Development

Origins in English Law

The posting rule, also known as the postal acceptance rule, emerged in early 19th-century English law as the use of mail for business communications became increasingly common in Britain, driven by the expansion of reliable postal services that addressed uncertainties arising from transmission delays.^[9] This development was particularly timely, as the postal system had evolved from sporadic local services into a more structured network, enabling merchants and traders to rely on post for negotiating contracts over distances without immediate personal interaction.^[10] The rule was first articulated in the landmark 1818 case of Adams v Lindsell, where the defendants mistakenly addressed a letter offering wool to the plaintiffs on September 2, 1817; the letter arrived on September 5 due to the error, prompting the plaintiffs to post their acceptance the same day, which reached the defendants on September 9.^[11] By then, the defendants had sold the wool to a third party on September 8, leading to a dispute over contract formation. The Court of King's Bench ruled in favor of the plaintiffs, holding that acceptance was complete upon posting the letter, thereby forming a binding contract at that moment to prevent offerees from being indefinitely bound to wait for replies amid postal uncertainties.^[4] This decision resolved the practical issue of mail delays by deeming the post office an agent of the offeror once the acceptance was dispatched.^[12] This judicial innovation was influenced by the broader expansion of the General Post Office (GPO) during the 1780s and 1810s, a period marked by the introduction of mail coaches in 1784 that connected major towns like London, Edinburgh, Liverpool, and Manchester, increasing route mileage from around 4,110 miles in 1797 to support growing commercial volumes.^[9] Gross postal revenue rose from £387,092 in 1780 to £2,191,562 by 1820, reflecting a surge in letter traffic that made post a standard medium for business contracts, particularly in industrializing regions where personal delivery was impractical.^[9] Infrastructure improvements, such as faster coach speeds of 8-9 miles per hour and extended Penny Post services to cities like Birmingham and Bristol by 1793, further entrenched the post's reliability for contractual negotiations.^[9] Initially, the rule's scope was limited to situations where the post was the anticipated or reasonable method of reply, as determined by the circumstances of the offer, thereby setting a precedent that would shape the evolution of common law principles on offer and acceptance without extending to instantaneous communications.^[4]

Key English Cases

The postal acceptance rule, first articulated in Adams v Lindsell (1818), was further developed through subsequent English cases that clarified its application, scope, and limitations. In Dunlop v Higgins (1848) 1 HL Cas 381, the House of Lords confirmed that the rule applies even if the acceptance letter is delayed in the post and arrives after the offeror has attempted to withdraw, thereby establishing that posting creates a binding contract regardless of timely delivery.^[13] The case involved a Scottish partnership dispute where an acceptance was posted but delayed due to misdirection, yet the court upheld the contract's formation at the point of posting, emphasizing the rule's role in providing certainty in postal communications.^[14] Household Fire and Carriage Accident Insurance Co Ltd v Grant (1879) LR 4 Ex D 216 extended the rule to situations where the acceptance is posted but the contract is never actually delivered or received, rendering the agreement irrevocable upon posting.^[15] Thesiger LJ, in the majority judgment, rejected arguments that non-delivery invalidated the contract, stating that the offeror assumes the risk of postal failure by inviting acceptance via post, and affirmed that such contracts are binding despite any subsequent loss of the notice.^[16] This decision solidified the irrevocability of acceptance once posted, even in share allotment scenarios where the offeree later sought to avoid liability.^[17] Henthorn v Fraser 2 Ch 27 clarified that the postal rule applies only where using the post is a reasonable mode of acceptance, not excluded by the offeror, with effectiveness occurring on the date of posting.^[18] The Court of Appeal held that in this case involving a loan offer for property, the post was reasonable given the parties' locations (one in Blackburn and one in Rawtenstall), and the acceptance posted before the offer's revocation was effective immediately, preventing withdrawal.^[19] Fry LJ emphasized that the offeror must specify an alternative method if post is unsuitable, thereby refining the rule's preconditions for applicability.^[20] In Stevenson, Jaques & Co v McLean (1880) 5 QBD 346, the court ruled that the postal acceptance rule pertains solely to unqualified acceptances and does not extend to mere inquiries or revocations, which require actual communication to be effective.^[21] The case arose from a telegram inquiry about payment terms on an iron sale offer, which the court treated as a request for information rather than a counter-offer, keeping the original offer open; Lush J noted that such communications by post or telegraph do not bind unless they constitute acceptance.^[22] This distinction preserved the rule's focus on acceptances while ensuring inquiries do not inadvertently trigger it.^[23] Entores Ltd v Miles Far East Corp 2 QB 327 distinguished the postal rule from instantaneous methods of communication, such as telex, applying the general rule that acceptance is effective upon receipt for instantaneous communications, while the posting rule (effective upon dispatch) applies to non-instantaneous postal scenarios.^[24] Denning LJ reasoned that telex, like telephone or personal delivery, allows immediate knowledge of acceptance or faults, so the general rule of communication upon receipt applies, not posting; this prevented the contract from forming in Amsterdam (where the telex was sent) and placed it under English jurisdiction.^[25] The decision highlighted the rule's obsolescence for modern rapid communications, influencing its non-application to faxes and emails in later contexts.^[26]

Common Law Jurisdictions

United Kingdom

In England and Wales, the posting rule remains a cornerstone of common law governing contract formation, whereby acceptance of an offer by post is effective upon posting, provided it is a reasonable method of communication and the offeror has not specified otherwise.^[3] This principle, unaltered by statute, continues to apply to postal services operated by Royal Mail, where courts uphold it for standard contractual acceptances but may scrutinize its use if posting is deemed unreasonable in modern contexts, such as when faster alternatives like email are available.^[27] No major legislative overrides have diminished the rule's validity for physical mail in the 20th and 21st centuries, though its practical invocation has become rare amid the digital shift toward instantaneous communications. The Electronic Communications Act 2000 facilitates electronic transactions but does not extend the posting rule to email, which is instead governed by the receipt principle from Entores Ltd v Miles Far East Corp , treating email as instantaneous and effective only upon receipt by the offeror.^[28] Post-2000 case law on the posting rule is sparse, reflecting its limited relevance to contemporary disputes dominated by electronic methods, yet the doctrine persists as valid for traditional postal contracts.^[29] In Scotland, the posting rule similarly operates under common law influence from English precedents, making acceptance effective upon posting for postal communications, though the jurisdiction's civil law heritage introduces nuances favoring receipt in certain non-postal scenarios.^[30] As of November 2025, the rule remains intact despite the introduction of the Contract (Formation and Remedies) (Scotland) Bill on 2 October 2025, which proposes reforming it to align more closely with a general receipt rule for non-instantaneous acceptances; the bill has not yet passed into law.^[31]

United States

In the United States, the posting rule is commonly referred to as the "mailbox rule," a principle adopted from English common law that deems an acceptance of an offer effective upon dispatch, such as when properly posted with the United States Postal Service (USPS) or an equivalent authorized medium, provided the offer does not specify otherwise.^[1]^[32] This rule applies uniformly across states in traditional mail-based communications, binding the offeror at the moment of mailing regardless of receipt or delay in transit.^[1] A key affirmation of the mailbox rule occurred in Cantu v. Central Education Agency (1994), where the Texas Court of Appeals held that a school district's acceptance of a teacher's resignation via mail was effective upon mailing, thereby terminating her employment contract, even though she later attempted to withdraw it.^[33] The court emphasized that the rule operates without requiring the offeror to explicitly authorize mail, as long as it is a reasonable medium under the circumstances, underscoring its role in providing certainty in postal acceptances.^[33] The mailbox rule includes notable variations, particularly for option contracts, where acceptance generally must be received by the offeror to be effective, rather than merely dispatched, to prevent premature binding during the option period. However, California deviates from this general exclusion in Palo Alto Town & Country Village, Inc. v. BBTC Co. (1974), where the state Supreme Court ruled that, absent contrary provisions in the option agreement, a mailed notice of exercise is timely and effective upon dispatch if sent within the option period, even if received afterward.^[34] The Restatement (Second) of Contracts § 63 codifies the mailbox rule nationally, stating that an acceptance is operative upon dispatch when using an invited medium like mail, but explicitly requires receipt for option contract acceptances unless the offer provides otherwise, allowing offerors to override the rule by specifying terms. While the mailbox rule maintains uniform application for postal communications across U.S. jurisdictions, it has become outdated in the digital era, where the Uniform Electronic Transactions Act (UETA), adopted in 49 states, supersedes traditional postal principles for electronic records and signatures by validating electronic acceptances with equivalent legal effect, often operative upon dispatch if the sender's system generates an electronic record capable of accurate retrieval.

Australia

In Australian contract law, the posting rule—also known as the postal acceptance rule—follows foundational English precedents but imposes a more stringent condition: the use of post must be explicitly authorized or impliedly contemplated by the offeror as a means of communicating acceptance for the rule to take effect upon posting.^[35] This requirement ensures that the exception to the general rule of actual communication does not apply indiscriminately, limiting its scope to situations where postal communication aligns with the parties' intentions or reasonable expectations.^[36] The High Court clarified this limitation in Tallerman & Co Pty Ltd v Nathan's Merchandise (Victoria) Pty Ltd (1957), where negotiations for the sale of goods involved contentious correspondence between parties in Sydney and Melbourne.^[35] Chief Justice Dixon and Justice Fullagar held that posting an acceptance letter on 4 June 1952 did not form a binding contract, as the circumstances indicated the offeror expected actual notification rather than reliance on the post office as a common agent.^[35] They emphasized that the postal exception arises only from the unique public trust in postal services and applies solely when post is within the parties' contemplation, distinguishing it from instantaneous methods where receipt governs.^[35] In contemporary practice, the rule remains applicable to mail sent via Australia Post, with courts evaluating reasonableness based on contextual factors such as the geographical distance between parties and established business norms.^[36] For instance, in intercity or interstate transactions where post is a customary channel, acceptance is complete upon proper posting of a prepaid, correctly addressed letter, provided no contrary intention appears in the offer.^[36] However, this assessment underscores Australia's narrower application compared to broader English interpretations, prioritizing offeror authorization over mere convenience.^[35] The Electronic Transactions Act 1999 (Cth) modifies the posting rule for digital communications, treating email as dispatched when sent but rendering acceptance effective only upon receipt, rather than mere dispatch. Under section 14(1), an electronic communication is received when it enters the recipient's designated information system or, if none is designated, when it comes to their attention. This receipt-oriented approach aligns with the Act's goal of facilitating e-commerce while diverging from the dispatch-based postal exception, as courts have not extended the traditional rule to email absent specific contemplation. Post-2000 judicial developments on the postal rule remain limited, with few reported cases addressing its nuances in light of evolving communication technologies.

Civil Law Jurisdictions

Receipt Rule Principle

In civil law systems, the receipt rule provides that an acceptance of an offer becomes effective only when it is received by the offeror or their authorized agent, rather than upon dispatch, thereby requiring actual delivery to establish mutual awareness and consent in contract formation.^[37] This principle underscores the importance of the offeror's knowledge of the acceptance, ensuring that a binding agreement arises solely from verifiable communication between the parties.^[37] The rationale for the receipt rule lies in its emphasis on clarity, fairness, and symmetry in the treatment of contract elements, as it aligns the effectiveness of acceptances with the rules governing offers and revocations, all of which require receipt to take effect.^[37] By placing the risk of non-delivery on the sender, the rule avoids granting the offeree an unbargained-for advantage and promotes deliberate use of communication methods, particularly in non-instantaneous scenarios like postal services.^[37] This contrasts with the posting rule in common law jurisdictions, where acceptance is generally effective upon dispatch.^[37] The receipt rule is codified in key civil law statutes, such as §130 of the German Bürgerliches Gesetzbuch (BGB), which states that declarations of intent made to an absent person become effective when they reach the addressee, unless a revocation arrives simultaneously or earlier.^[38] Similarly, Article 1118 of the French Civil Code defines acceptance as the offeree's manifestation of will to be bound, producing effects only from the time it reaches the offeror, with Article 1121 further confirming that the contract is concluded upon the arrival of the acceptance.^[39] Under this approach, there is no exception for postal delays or losses; if the acceptance fails to reach the offeror, no contract forms, incentivizing the sender to employ reliable transmission methods.^[37]

Specific Examples

In Germany, the Bürgerliches Gesetzbuch (BGB) establishes the receipt rule for contract formation under § 130, which provides that a declaration of intent made to an absent person takes effect upon reaching the addressee.^[40] Specifically, § 147(2) BGB stipulates that for offers not made in the presence of the offeree or via instantaneous communication, acceptance is effective as soon as the offeror receives it, placing the risk of non-delivery—such as postal loss or delays—on the offeree, as the contract does not form until the offeror receives the acceptance.^[41] This principle is reinforced by § 151 BGB, which addresses situations where a declaration is not received, rendering it ineffective if the sender cannot prove receipt, as seen in judicial interpretations emphasizing actual delivery over dispatch.^[42] In France, the reformed Civil Code of 2016 codifies the receipt principle in Article 1118, allowing revocation of acceptance until it reaches the offeror, thereby making the contract binding only upon the offeror's receipt of the manifestation of consent. Article 1121 further requires that consent be expressed and reach the offeror to form the contract, rejecting any dispatch-based rule for postal communications. The Cour de cassation has upheld this principle in rulings confirming that acceptance via post is ineffective if not received by the offeror, with the offeree bearing the risk of transmission failures like loss in transit. In Italy, the Codice Civile adopts the receipt rule under Article 1326, which states that a contract is concluded when the acceptance reaches the offeror within the specified or reasonable time frame, ensuring effectiveness only upon communication rather than dispatch.^[43] Article 1326(2) complements this by treating non-conforming acceptances as counter-offers, but the core principle remains that uncommunicated acceptance does not bind the parties, leaving postal risks—such as undelivered letters—with the sender. Italian courts consistently apply this to void contracts where acceptance fails to arrive, prioritizing the offeror's awareness of consent.

International and Model Laws

UNCITRAL Model Law

The UNCITRAL Model Law on Electronic Commerce, adopted in 1996, addresses the timing of acceptance in electronic contract formation through Article 15, which establishes rules for the dispatch and receipt of data messages, such as emails. Under Article 15(1), dispatch occurs when the data message enters an information system outside the originator's control. Receipt, per Article 15(2), happens when the message enters the addressee's designated information system, or if none is designated, when it enters any information system of the addressee. This framework ensures that electronic communications are treated equivalently to paper-based ones for legal purposes, with the place of dispatch and receipt deemed to be the parties' respective places of business to provide certainty in cross-border scenarios.^[44] Article 15 defines dispatch and receipt for data messages, which jurisdictions may use to apply receipt-based rules for electronic acceptances unless parties agree otherwise, contrasting with the dispatch-based postal rule and offering a functional equivalent tailored to e-commerce's instantaneous nature. The Guide to Enactment clarifies that these rules dispel uncertainty in contract formation by focusing on system entry as the key event, aligning with receipt principles prevalent in instantaneous communications while avoiding the risks of the postal rule, such as lost messages after dispatch. This approach promotes legal predictability without extending outdated postal analogies to digital environments.^[45] The Model Law has significantly influenced domestic legislation to foster uniformity in electronic contracting. In the United Kingdom, the Electronic Communications Act 2000 draws on its principles to validate electronic signatures and communications in contract formation, enabling digital equivalents without requiring paper. Similarly, in the United States, the Uniform Electronic Transactions Act (UETA), adopted by most states, incorporates Article 15 directly into Section 15, which mirrors the dispatch and receipt rules to govern electronic records in transactions. These adoptions enhance cross-border digital contracts by harmonizing rules on acceptance timing. Although the 1996 Model Law predates the widespread use of email and modern digital tools, UNCITRAL's Working Group IV on Electronic Commerce has, as of 2025, been addressing gaps through sessions focused on emerging technologies like AI and blockchain in digital trade, without introducing specific revisions to analogies with the postal rule.^[46]

CISG Provisions

The United Nations Convention on Contracts for the International Sale of Goods (CISG), adopted in 1980, establishes a uniform framework for international sales contracts, including rules on offer and acceptance that predominantly follow the receipt rule.^[47] Under Article 18(2), an acceptance becomes effective at the moment the indication of assent reaches the offeror, meaning it must enter the offeror's sphere of control, such as their place of business or designated communication channel.^[47] This provision ensures certainty in cross-border transactions by tying contract formation to the offeror's awareness or potential awareness of the acceptance, rather than the offeree's dispatch.^[48] Unlike some domestic systems, the CISG does not incorporate a general postal exception allowing acceptance by mere dispatch; instead, dispatch may bind the parties only if the offer explicitly provides for it or if established practices between the parties or international trade usages indicate as much.^[48] Complementing this, Article 16(1) reinforces the receipt principle by stating that an offer remains revocable until a contract is concluded, but revocation is effective only if it reaches the offeree before or at the same time as the acceptance communicates to the offeror.^[47] This aligns the irrevocability of the offer with the moment acceptance reaches the offeror, preventing premature revocations once the offeree has committed to the terms.^[49] The CISG applies automatically to contracts for the sale of goods between parties whose places of business are in different contracting states, provided the states are parties to the convention, unless the parties expressly exclude it.^[47] It excludes consumer transactions, such as sales of goods bought for personal, family, or household use, focusing instead on commercial dealings.^[47] As of 2025, 97 countries, representing a significant portion of global trade, are parties to the CISG. In addressing modern communications, the UNCITRAL Digest of Case Law on the CISG (2016 edition) clarifies that for electronic means like email, acceptance "reaches" the offeror when it enters their information system, such as upon delivery to the offeror's server, making it accessible even if not yet read.^[48] This interpretation draws from case law, including decisions where email acceptance was deemed effective upon server receipt, emphasizing accessibility over actual review.^[48] The absence of a postal exception underscores the CISG's preference for receipt in all media, avoiding uncertainties associated with delayed or lost mail.^[48] These developments highlight the CISG's adaptability to evolving trade practices while maintaining uniformity across jurisdictions.^[50]

Exceptions and Modern Applications

Revocation and Limitations

The revocation of an offer under the posting rule operates distinctly from acceptance. An offeror may revoke an offer at any time before the offeree posts their acceptance, but revocation becomes effective only upon actual receipt by the offeree, not upon posting.^[8] This principle was established in Byrne & Co v Van Tienhoven & Co (1880), where the defendants posted a revocation after the plaintiffs had already mailed their acceptance; the court held the revocation ineffective because it had not reached the plaintiffs prior to their posting, rendering the contract binding upon dispatch of the acceptance. In contrast, the landmark case of Household Fire Insurance Co v Mews (1879) affirmed that acceptance by post is complete and irrevocable upon proper posting, preventing subsequent revocation by the offeror even if the letter is lost or delayed.^[8] Several limitations circumscribe the application of the posting rule, ensuring it aligns with the parties' intentions and practical realities. The rule applies exclusively to acceptances and does not extend to counter-offers or rejections, which take effect only upon receipt by the offeror to avoid unintended contractual obligations.^[1] Similarly, if the offer expressly requires receipt of the acceptance—such as by stipulating "reply by return of post"—the posting rule is displaced, and acceptance is effective only when received.^[8] The rule is also invalidated if the postage is faulty, meaning the acceptance must be correctly addressed, stamped, and deposited with the postal service; mere placement in a mailbox without proper precautions does not suffice.^[1] Furthermore, the posting rule excludes instantaneous methods of communication, such as telephone or telex, where acceptance must be received to form the contract.^[8] In the context of option contracts within common law jurisdictions like the United States, the posting rule faces an additional restriction. Under the Restatement (Second) of Contracts § 63(b), acceptance of an option contract—where the offeror has promised to keep the offer open—is not operative until received by the offeror, overriding the general dispatch rule to protect the offeror's reliance on the option.^[1] This exception ensures that the offeree's exercise of the option does not bind the offeror prematurely if the notice is lost in transit. Notably, even if mail is lost after proper posting, the acceptance remains binding under the rule, as illustrated in the originating case of Adams v Lindsell (1818), where a misdirected acceptance letter was deemed effective upon dispatch despite never reaching the offeror.^[1]

Electronic Communications

In the digital era, the traditional posting rule faces significant challenges when applied to electronic communications, as these methods blur the lines between instantaneous and delayed transmission. Email acceptances are generally not governed by the postal rule and are instead treated as instantaneous communications under principles established in Entores Ltd v Miles Far East Corporation 2 QB 327, where acceptance becomes effective upon receipt by the offeree rather than dispatch, to ensure certainty in contract formation.^[26] This approach aligns with the near-instantaneous nature of email delivery in modern networks, distinguishing it from physical post. However, debates persist in jurisdictions like the United Kingdom, where the Electronic Communications Act 2000 facilitates the use of electronic methods for contractual notices and signatures without explicitly extending the postal rule; if transmission is deemed non-instantaneous due to delays, some interpretations allow dispatch to govern, though courts prioritize receipt to mitigate risks of lost or delayed messages.^[28]^[29] In the United States, the Uniform Electronic Transactions Act (UETA) §15 provides a framework for timing in electronic records, defining an electronic acceptance as "sent" when it leaves the sender's control and enters a system outside their domain, but "received" only upon entering the recipient's designated information processing system in a processable form, regardless of the recipient's awareness.^[51] This structure does not uniformly adopt an "email box rule" equivalent to the postal rule; instead, effectiveness defaults to receipt unless parties agree otherwise, promoting reliability in asynchronous digital exchanges. There is no federal mandate imposing dispatch for all electronic acceptances, leaving variations across adopting states and emphasizing party agreement for clarity. Recent judicial trends reinforce a preference for the receipt rule in email-based acceptances to avoid uncertainty, rendering the postal rule largely outdated for digital norms where rapid transmission is standard. Emerging digital technologies exacerbate gaps in applying the posting rule, particularly with AI chatbots and blockchain-based smart contracts, where equivalents to "posting" remain undefined under traditional contract law. AI-driven interactions, such as chatbot negotiations, raise enforceability issues since AI lacks independent legal agency, potentially requiring human oversight for valid acceptance and leaving formation timing ambiguous without explicit protocols.^[52] Blockchain smart contracts self-execute upon code deployment and condition fulfillment on distributed ledgers, bypassing dispatch-receipt dichotomies entirely, yet they encounter challenges in proving intent and modification, as immutable code may not satisfy common law requirements for offer and acceptance.^[53] To address these uncertainties, legal scholars recommend that parties explicitly specify communication methods and timing rules in offers, overriding default principles and tailoring formation to digital contexts for reduced litigation risk.^[54]

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### Summary of Mailbox Rule (Posting Rule)
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E-mail and the Postal Rule - Society for Computers & Law
Jan 1, 2002 · It states that, in cases where it is reasonable to communicate by post, a binding contract is achieved when the acceptor commits his acceptance to the post.
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You've got mail: the postal acceptance rule and Scots law
Dec 20, 2012 · The postal acceptance rule in Scots law means an acceptance is effective when the letter is posted, not when it reaches the offeror, if the ...
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Contract (Formation and Remedies) (Scotland) Bill
Oct 2, 2025 · A Bill for an Act of the Scottish Parliament to make provision in relation to formation of contract and remedies for breach of contract; ...
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Foundations of Law - The Mailbox Rule - Lawshelf
Mailbox Rule: The principle that an acceptance becomes effective, and binds the offeror, once it has been properly mailed. Repudiation of a Contract: A ...
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Maria Diosel Cantu v. Central Education Agency; Lionel R. Meno, in ...
Maria Cantu sued over her resignation, which the court ruled was accepted by mail, rescinding her contract. The court affirmed the trial court's decision.
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Palo Alto Town & Country Village, Inc. v. BBTC Company - Justia Law
The sole issue confronting us in this case is whether, absent any provisions in the option contract to the contrary, a written notice by the optionee of his ...Missing: Bay Builders mailbox
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Tallerman & Co Pty Ltd v Nathan's Merchandise (Vic) Pty Ltd [1957] HCA 10; (1957) 98 CLR 93 (18 February 1957)
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Agreement — Australian Contract Law
Communication of acceptance and the postal rule To be effective, acceptance must be communicated - a mental decision to accept is not sufficient.
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https://uknowledge.uky.edu/klj/vol79/iss3/5
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https://www.gesetze-im-internet.de/englisch_bgb/englisch_bgb.html#p0401
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French Civil Code 2016 | Trans-Lex.org
Art. 1118. – An acceptance is the manifestation of the will of the offeree to be bound on the terms of the offer. As long as the ...CODE CIVIL TITLE IIITHE... · Sub-section 2Offer and... · Sub-section 1Nullity
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https://www.gesetze-im-internet.de/englisch_bgb/englisch_bgb.html#p0191
[41]
https://www.gesetze-im-internet.de/englisch_bgb/englisch_bgb.html#p0196
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https://www.gesetze-im-internet.de/englisch_bgb/englisch_bgb.html#p0200
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Art. 1326 codice civile - Conclusione del contratto - Brocardi.it
Oct 10, 2025 · L'accettazione deve giungere al proponente nel termine da lui stabilito o in quello ordinariamente necessario secondo la natura dell'affare o ...Missing: receipt | Show results with:receipt
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UNCITRAL Model Law on Electronic Commerce (1996) with ...
The Model Law on Electronic Commerce (MLEC) aims to enable and facilitate commerce conducted using electronic means.
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None
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Working Group IV: Electronic Commerce
Working Group IV: Electronic Commerce · 69th session, 20-24 October 2025, Vienna · 68th session, 24-28 March 2025, New York · 67th session, 18-22 November 2024, ...Missing: blockchain | Show results with:blockchain
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[PDF] United Nations Convention on Contracts for the International Sale of ...
Apr 11, 1980 · The United Nations Convention on Contracts for the International Sale of Goods is a UN publication from New York, 2010.
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[PDF] UNCITRAL Digest of Case Law on the UN Convention on Contracts ...
This is the UNCITRAL Digest of Case Law on the United Nations Convention on Contracts for the International Sale of Goods, 2016 Edition.
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Art. 16 CISG | CISG-online.org
16 CISG. (1) Until a contract is concluded an offer may be revoked if the revocation reaches the offeree before he has dispatched an acceptance.
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(PDF) Acceptance sent through email; is the postal rule applicable?
Aug 6, 2025 · This paper focuses on the application of the postal rule to email, due to the controversy surrounding the application of the “instantaneous” test to emails.<|separator|>
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CISG Advisory Council Opinion No 1 (Revised)
A period of time for acceptance fixed by the offeror in simultaneous electronic communication begins to run from the moment that the offer reaches the offeree.
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[PDF] UNIFORM ELECTRONIC TRANSACTIONS ACT (1999)
Jan 20, 2000 · The Uniform Electronic Transactions Act (1999) was drafted to address legal barriers to the use of electronic records and documents, due to the ...Missing: Influence | Show results with:Influence<|separator|>
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Forming Binding Agreements Through Email - Law.com
Oct 16, 2025 · New York courts treat emails as valid for forming contracts if they show mutual agreement, clear terms, and meet formal requirements.
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Contract Law in the Age of Agentic AI: Who's Really Clicking “Accept”?
Apr 9, 2025 · A foundational legal question is whether transactions initiated and executed by an AI tool on behalf of a user are enforceable. Despite the ...Missing: equivalents | Show results with:equivalents
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Formation of Smart Contracts under Contract Law (Chapter 4)
In this chapter, the blockchain-based smart contracts and the process of contract formation are discussed and exemplified.
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From smart legal contracts to contracts on blockchain: An empirical ...
The objective is to provide an assessment of both the advantages and limitations associated with smart legal contracts.Missing: chatbots | Show results with:chatbots