There are many ways to terminate a contract. They are: A term can be implied on the basis of habits or uses in a particular market or context. In the Australian case Con-Stan Industries of Australia Pty Ltd v Norwich Winterthur (Aust) Limited, the terms of a concept to be included by Customs were established. For a term to be invoked by Customs, it must be “known and accepted to the extent that any person who makes a contract in that situation can reasonably be considered to have introduced that clause in the treaty.”  :p 8-9 conditions may be implied because of the actual circumstances or the behaviour of the parties. In the case of BP Refinery (Westernport) Pty Ltd/Shire of Hastings, the Privy British Council proposed a five-step test to determine the situations in which the facts of a case may be subject to conditions. The traditional tests were the “enterprise efficiency test” and the “bystander officious test.” As part of the business test test, first proposed in The Moorcock , the minimum requirements required to give the contract the company`s effectiveness are implicit. In the context of the officious bystander test (named at Southern Foundries (1926) Ltd v Shirlaw , but in fact from Reigate v. Union Manufacturing Co (Ramsbottom) Ltd , a term can only be implied if an “abominable spectator” who is part of the contract negotiations suggests that the parties would immediately agree. The difference between these tests is questionable.
b) the contract provides for an advantage. On the other hand, budgetary and social agreements such as those between children and parents are generally unenforceable on the basis of public order. For example, in the English case Balfour v. Balfour, a man agreed to give 30 dollars a month to his wife while he was not home, but the court refused to enforce the agreement when the husband stopped paying. On the other hand, in Merritt/Merritt, the Tribunal imposed an agreement between an insane couple, because the circumstances suggested that their agreement should have legal consequences. If the promise of the contract is not kept, the victim can file an appeal. If something is advertised in a newspaper or on a poster, the ad is not normally an offer, but an invitation to process, an indication that one or both parties are ready to negotiate an agreement.    In the United States, an unusual type of non-opposable contract is a personal employment contract to work as a spy or secret agent.