The formation of a contract in English law is primarily governed by the “offer and acceptance” model, a framework where courts search for a clear proposal from one party that has been met by a matching assent from another. While this model provides a degree of certainty that allows commercial parties to understand their rights and liabilities, it has faced significant criticism for being a rigid, “mechanical” tool that sometimes forces the messy reality of negotiations into artificial “slots”.
The Nature of an Offer and the Invitation to Treat
At its core, an offer is an expression of a willingness to be bound by specific terms without further negotiation. The crucial task for a court is to distinguish a genuine offer from an “invitation to treat” (or negotiate), which is merely a preliminary statement of a party’s negotiating position. This distinction is determined objectively; the law is not concerned with a party’s secret subjective intentions but with how their words and conduct would appear to a reasonable person.
To promote commercial consistency, the courts have established prima facie rules for common transactions. For instance, advertisements are generally regarded as invitations to treat rather than offers to protect vendors from being bound to an unlimited number of contracts for potentially limited stock (Partridge v Crittenden). Similarly, the display of goods in a shop or window is typically an invitation to treat; the contract is not formed until the customer presents the item at the till (the offer) and the shopkeeper accepts the payment (Boots Cash Chemists). However, these rules can be displaced if the language used is “clear, definite, and explicit,” as seen in Lefkowitz, where an advertisement for fur coats was held to be an offer because it specified “first come, first served”.
In more complex processes like tenders, the general rule is that an invitation to bid is an invitation to treat. However, courts may find a collateral offer to follow a specific procedure.
In Blackpool and Fylde Aero Club, the court held that a party who invites tenders and prescribes a clear deadline is contractually bound to at least consider all timely and conforming bids, even if they are not bound to accept any of them. Similarly, in auctions, while bids are offers and the fall of the hammer is acceptance, an auction advertised “without reserve” creates a collateral contract with the highest bona fide bidder, preventing the auctioneer from withdrawing the lot simply because the price is too low (Barry v Davies).
The Mechanics of Acceptance
An acceptance must be a final and unqualified expression of assent to the terms of the offer. Under the “mirror image” rule, any attempt to vary the terms of the offer is not an acceptance but a counter-offer, which effectively “kills” the original offer so that it can no longer be accepted (Hyde v Wrench). This often leads to a “battle of the forms” in commercial settings, where parties exchange conflicting standard terms. The traditional English approach follows the “last shot” doctrine, where the party who fires the final “shot”—meaning the last person to send their terms before the contract is performed—wins the battle.
For an acceptance to be effective, it must generally be communicated to the offeror so that they are not bound by a contract of which they are unaware (Entores). There are three major nuances to this communication requirement:
- Silence: As a general rule, silence cannot amount to acceptance. A party cannot impose a contract on another by stating that they will assume agreement unless they hear otherwise (Felthouse v Bindley).
- The Postal Rule: This is a major exception to the communication requirement. Where it is reasonable to use the post, an acceptance is effective the moment it is posted, even if it is lost and never reaches the offeror (Adams v Lindsell, Household Fire v Grant). However, this “artificial” rule can be excluded by the offeror if they require actual “notice” or communication (Holwell Securities).
- Instantaneous Communications: Modern technologies like telephone, telex, and email are treated as instantaneous. In these cases, the postal rule does not apply; acceptance is only effective when it is received by the offeror during normal business hours.
Unilateral Contracts
Unilateral contracts—where one party promises a benefit (such as a reward) in exchange for an act—present unique challenges for the offer and acceptance model. In these cases, performance of the act is the acceptance, and the requirement for communication is usually waived (Carlill v Carbolic Smoke Ball Co). A seedy world of 19th-century medical quackery helped establish that an offer to the “whole world” can ripen into a contract with any individual who fulfills the conditions.
A difficult question in unilateral contracts is when an offer can be revoked. While the general rule allows revocation at any time before acceptance, the courts have mitigated this to prevent opportunism. Once an offeree has begun to perform the requested act, there is an implied obligation on the offeror not to prevent the condition from being satisfied, effectively barring revocation while performance is ongoing (Daulia, Errington).
Termination of an Offer
Finally, an offer does not remain open indefinitely.
It can be terminated by rejection, the lapse of time (either a stipulated period or a “reasonable” time), or the failure of a condition. Most importantly, an offer can be revoked at any time before acceptance, provided the revocation is communicated to the offeree.
Notably, this communication does not need to come directly from the offeror; it is effective if the offeree receives reliable information from a third party that the offeror has changed their mind or sold the subject matter to someone else (Dickinson v Dodds). A promise to keep an offer open for a set time is generally not binding under English law unless the offeree has provided “consideration” (something of value) to keep that option open.