Introduction to Offer and Acceptance
For a legally binding contract to exist in English law, the parties must reach an agreement. Agreement is analysed through the rules of offer and acceptance — one party (the offeror) makes an offer, and the other party (the offeree) accepts it on the same terms. Together with consideration and intention to create legal relations, offer and acceptance form the bedrock of contract formation.
Offer and acceptance is a core topic on CAIE A-Level Law (9084) Paper 3 (contract law), examined consistently across the May/June and October/November series. For students in Pakistan, Bangladesh, India, Malaysia, and Sri Lanka, mastering the distinction between an offer and an invitation to treat — and the postal rule — is essential for both problem questions and essay-based evaluation questions.
These rules appear in every A-Level Law contract paper and are tested frequently through problem scenarios involving shops, advertisements, auctions, and postal communications. Mastering the distinctions — particularly between offers and invitations to treat — is essential for top marks.
What Is an Offer?
An offer is a definite and unequivocal expression of willingness to be bound on specific terms, communicated to the offeree. The offeror must intend to be bound immediately upon acceptance — this distinguishes a genuine offer from merely expressing interest or inviting negotiation.
Crucially, an offer must be distinguished from an invitation to treat. An invitation to treat is not an offer — it is an invitation to others to make offers, which the party can then accept or reject. Goods displayed in a shop window or on a shelf are invitations to treat, not offers (Pharmaceutical Society of GB v Boots Cash Chemists [1953]).
Offers vs Invitations to Treat: Key Cases
Carlill v Carbolic Smoke Ball Co [1893] — Advertisement promising £100 to anyone who used the product and caught flu was held to be a unilateral offer to the world, not merely an invitation to treat. The Court of Appeal found the company liable to Mrs Carlill. Landmark authority on unilateral contracts.
Fisher v Bell [1961] — A flick knife displayed in a shop window with a price tag was an invitation to treat, not an offer to sell. The shopkeeper was not guilty of ‘offering for sale’ an offensive weapon under the Restriction of Offensive Weapons Act 1959.
Pharmaceutical Society v Boots [1953] — Drugs on a self-service shelf were invitations to treat. The offer was made by the customer at the till. Acceptance occurred when the pharmacist accepted payment. Important for establishing where in the transaction a contract forms.
Harvey v Facey [1893] — A telegram stating the lowest acceptable price for property was not an offer — it was merely a statement of minimum price. No contract was formed when the buyer purported to accept it.
Rules of Acceptance
Acceptance must be unconditional and correspond exactly with the terms of the offer — the ‘mirror image’ rule. A purported acceptance that introduces new terms is a counter-offer, which destroys the original offer and cannot later be accepted (Hyde v Wrench [1840]).
Acceptance must be communicated to the offeror before it takes effect. In face-to-face or telephone negotiations, communication of acceptance is immediate. The offeror can specify the method of acceptance — if so, that method (or one equally expeditious) must be used.
The postal rule is an important exception: where it is within the reasonable contemplation of the parties that the post may be used as a means of acceptance, acceptance takes effect when the letter is posted — not when it is received (Adams v Lindsell [1818]). This rule applies even if the letter is delayed or lost.
Revocation, Lapse and Termination of Offers
An offer may be revoked (withdrawn) at any time before acceptance, even where the offeror has promised to keep it open — unless consideration has been paid for the option to keep it open. Revocation must be communicated to the offeree before they accept (Byrne v Van Tienhoven [1880]).
An offer lapses and can no longer be accepted after a reasonable period of time, or after the death of either party in most circumstances. A counter-offer also terminates the original offer (Hyde v Wrench [1840]). A mere request for information does not terminate an offer (Stevenson v McLean [1880]).
Exam Technique: Contract Formation Questions
Always begin by identifying whether a valid offer exists — distinguish from invitations to treat using the relevant authorities. Then determine whether there has been a valid acceptance: check the mirror image rule, communication, and whether any postal rule issue arises. Address any revocation issues by checking whether it was communicated before acceptance.
For problem questions, trace each communication chronologically and apply the relevant rule at each step. State a conclusion on whether a binding contract has been formed and, if so, at what point.
Contract Law Formation for CAIE Students in Asia
CAIE A-Level Law students across Asian examination centres are assessed on English contract law principles that may differ significantly from the domestic contract law of their home countries. This is an important point: the examination tests English law as it stands, not local commercial practice. Students must apply English authorities such as Carlill v Carbolic Smoke Ball Co [1893] and Adams v Lindsell [1818] directly to CAIE scenarios.
A recurring challenge for students studying offer and acceptance in Pakistan, Bangladesh, India, and Malaysia is applying the postal rule correctly in examination scenarios involving chains of written communications. Many students lose marks by applying the postal rule where it is not applicable (for example, to email communications, where acceptance takes effect on receipt). Precise understanding of when each rule applies is the difference between a Band 4 and Band 5 answer.
Access to structured, recorded teaching on contract formation — covering offers, invitations to treat, counter-offers, revocation, and the postal rule — allows students in Asia to build the depth of understanding that CAIE problem questions demand, regardless of their proximity to a specialist law school.
Frequently Asked Questions
What is the difference between an offer and an invitation to treat?
An offer is a definite expression of willingness to be bound on acceptance. An invitation to treat (such as goods on a shelf or an advertisement) invites others to make offers, which the advertiser may accept or reject. See Boots [1953] and Fisher v Bell [1961].
Is an advertisement always an invitation to treat?
Not always. Carlill v Carbolic Smoke Ball Co [1893] established that a sufficiently certain advertisement promising specific benefits can be a unilateral offer to the world, binding on those who fulfil its terms.
When does acceptance take effect under the postal rule?
Under the postal rule (Adams v Lindsell [1818]), acceptance takes effect when the letter is posted — not when it is received by the offeror. This applies where it is within the parties’ reasonable contemplation that the post may be used.
What is a counter-offer and what effect does it have?
A counter-offer is a purported acceptance that introduces different terms. It destroys the original offer (which can no longer be accepted) and itself constitutes a new offer. See Hyde v Wrench [1840].
Can an offeror revoke an offer after it has been made?
Yes — an offer can be revoked at any time before acceptance, even if the offeror promised to keep it open (unless consideration was paid for the option). Revocation must be communicated to the offeree to take effect (Byrne v Van Tienhoven [1880]).
Key Takeaways
- Offer: definite, unequivocal, communicated willingness to be bound on specific terms.
- Invitation to treat: not an offer — examples include shop displays (Boots), advertisements (usually), and auction lots.
- Carlill v Carbolic Smoke Ball Co [1893]: advertisements can be unilateral offers to the world.
- Acceptance must mirror the offer exactly — any variation is a counter-offer (Hyde v Wrench [1840]).
- Postal rule: acceptance takes effect on posting, not receipt (Adams v Lindsell [1818]).
- Revocation must be communicated before acceptance to be effective.
- Counter-offer destroys the original offer — it cannot later be accepted.
Access Recorded A-Level Law Lectures — Available Across Asia
If you are an A-Level Law student in Pakistan, Bangladesh, India, Malaysia, Sri Lanka, or elsewhere in Asia and are looking for high-quality recorded lectures taught by an experienced CAIE Law teacher, we are here to help. Our recorded lecture series covers all CAIE A-Level Law (9084) topics — including Contract Law — with examination technique, worked problem questions, and full mark scheme guidance. Message us directly on WhatsApp: https://wa.me/923458099831 — or visit our contact page: https://alevellawteacher.com/contact-us/