The postal rule is a favourite exam point because it fixes the exact moment (and place) a contract forms, and because it behaves differently from the ordinary receipt rule. It sits within the wider law of offer and acceptance.
The general rule: acceptance on receipt
Ordinarily, acceptance is effective only when it is communicated to and received by the offeror (Entores Ltd v Miles Far East Corporation [1955] 2 QB 327 England & Wales, applied by the Supreme Court in Kelly v Cruise Catering Ltd [1994] IESC 3 Ireland; Brinkibon v Stahag Stahl [1983] 2 AC 34 England & Wales). The postal rule is the exception to this, not the starting point.
The postal exception
Where the post is a contemplated method of acceptance, acceptance is complete on posting. The rule originates in Adams v Lindsell (1818) 1 B & Ald 681 Court of King's Bench (E&W) — without it, no postal contract could ever be concluded (an infinite regress of confirmations). It applies even where the letter is lost and never delivered (Household Fire Insurance v Grant (1879) 4 Ex D 216 England & Wales).
Irish law adopts the rule. In Sanderson v Cunningham [1919] 2 IR 234 Court of Appeal (IE) an insurance contract was formed where the acceptance was posted, not where it was received. The Supreme Court applied the rule in Kelly v Cruise Catering Ltd [1994] IESC 3 Ireland: the plaintiff signed his contract of employment in Dublin and posted it to Oslo, so acceptance was complete on posting and the contract was made in Dublin. Blayney J accepted that an acceptance may be lost in the post but held that this was "not a relevant consideration in the present case where the signed contract was received", and that there were "no circumstances here calling for any divergence from the well-established rule". In Phoenix Rock Enterprises v Hughes [2025] IEHC 126 Ireland, the High Court stressed that the rule is a limited exception that applies only where the parties intended agreement to be concluded that way.
When the postal rule does not apply
- Contrary wording. The rule is ousted where the offer requires actual communication — e.g. an option exercisable by notice in writing to the offeror needs receipt (Holwell Securities Ltd v Hughes [1974] 1 WLR 155 England & Wales, adopted in Ireland by Haughton J in Knockacummer Wind Farm Ltd v Cremins [2016] IEHC 95 Ireland).
- Mis-addressed or improperly posted letters. The rule does not protect a letter wrongly addressed through the acceptor's own carelessness.
- Where it was not reasonable to use the post — for example, known postal disruption.
Instantaneous and electronic communications
The postal rule does not generally apply to electronic communications. Electronic acceptance operates on a receipt basis, in line with the treatment of instantaneous communications such as telephone and telex (Entores [1955] 2 QB 327; Brinkibon [1983] 2 AC 34 England & Wales). In Ireland, s.21 of the Electronic Commerce Act 2000 — headed "Time and place of dispatch and receipt of electronic communications" — sets out the statutory default rules for when and where an electronic communication is taken to be sent and received. Whether a given message is an offer or an acceptance still turns on how the process is structured.
The full, exam-ready version
Formation I: offer, termination, acceptance (including the postal rule), certainty and formalities — with the full case table, worked cross-border examples and a model-answer skeleton.
see the full Contract course →Still unclear?
Does the postal rule apply if the acceptance letter is lost?
Yes — where the post was a contemplated method, acceptance is complete on posting even if the letter is delayed or never arrives (Household Fire & Carriage Accident Insurance Co Ltd v Grant). Kelly v Cruise Catering is not authority for the never-arrives case: there the posted contract was in fact received, and Blayney J said so expressly.
When does the postal rule not apply?
Where the offer requires actual receipt (Holwell Securities v Hughes), where the letter is mis-addressed through the acceptor's fault, or where it was unreasonable to use the post.
Does the postal rule apply to email?
No — the postal rule does not generally apply to electronic communications. Electronic acceptance operates on a receipt basis (in line with instantaneous communications: Entores; Brinkibon), and in Ireland s.21 of the Electronic Commerce Act 2000 governs the time and place of receipt.
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