An offer is a definite statement of the offeror's willingness to be bound should certain conditions be met.
If a purported acceptance does vary the terms of an offer, it is not an acceptance but a counteroffer and, therefore, simultaneously a rejection of the original offer.
Auctions are governed by the Sale of Goods Act 1979 (as amended), where section 57(2) provides: “A sale by auction is complete when the auctioneer announces its completion by the fall of the hammer, or in other customary manner.
Until the announcement is made any bidder may retract his bid”. Many jurisdictions have passed e-signature laws that have made the electronic contract and signature as legally valid as a paper contract.
In contrast, domestic and social agreements such as those between children and parents are typically unenforceable on the basis of public policy. Balfour a husband agreed to give his wife £30 a month while he was away from home, but the court refused to enforce the agreement when the husband stopped paying.
In contrast, in Merritt v Merritt the court enforced an agreement between an estranged couple because the circumstances suggested their agreement was intended to have legal consequences.In order for a contract to be formed, the parties must reach mutual assent (also called a meeting of the minds).This is typically reached through offer and an acceptance which does not vary the offer's terms, which is known as the "mirror image rule".declared consideration to be a “Right, Interest, Profit, Benefit, or Forbearance, Detriment, Loss, Responsibility”.Thus, consideration is a promise of something of value given by a promissor in exchange for something of value given by a promisee; and typically the thing of value is goods, money, or an act.For example, John Smith, a former lawyer may implicitly enter a contract by visiting a doctor and being examined; if the patient refuses to pay after being examined, the patient has breached a contract implied in fact.A contract which is implied in law is also called a quasi-contract, because it is not in fact a contract; rather, it is a means for the courts to remedy situations in which one party would be unjustly enriched were he or she not required to compensate the other. Where something is advertised in a newspaper or on a poster, the advertisement will not normally constitute an offer but will instead be an invitation to treat, an indication that one or both parties are prepared to negotiate a deal. The company, a pharmaceutical manufacturer, advertised a smoke ball that would, if sniffed "three times daily for two weeks", prevent users from catching the 'flu.In a reward contract, for example, a person who has lost a dog could promise a reward if the dog is found, through publication or orally.The payment could be additionally conditioned on the dog being returned alive.Those who learn of the reward are not required to search for the dog, but if someone finds the dog and delivers it, the promisor is required to pay.In the similar case of advertisements of deals or bargains, a general rule is that these are not contractual offers but merely an "invitation to treat" (or bargain), but the applicability of this rule is disputed and contains various exceptions.