A tacit and tacit contract, also known as the “party contract,” which can be either a tacit contract or an unspoken contract, can also be legally binding. In the case of unspoken contracts, these are real contracts for which the parties enjoy the “benefit of the good deal”.  However, legally underlying contracts are also called quasi-contracts and the remedy is quantum, the fair value of the goods or services provided. Trade agreements assume that the parties intend to be legally bound, unless the parties explicitly state otherwise, as in a contractual document. For example, in the Rose- Frank Co/JR Crompton-Bros Ltd case, an agreement between two commercial parties was not reached because the document stipulated an “honour clause”: “This is not a commercial or legal agreement, but only a declaration of intent by the parties.” An exception arises when advertising makes a unilateral promise, such as offering a reward, as decided in the famous case of Carlill v Carbolic Smoke Ball Co, in 19th century England. The company, a pharmaceutical manufacturer, proposed a smokeball that, if it sniffed “three times a day for two weeks,” would prevent users from catching the “flu.” If the smokeball does not prevent “the flu, the company promised that it would pay $100 to the user, adding that they deposited “$1000 in the Alliance bank to show our sincerity in the file.” When Ms. Carlill complained about the money, the company argued that the complaint should not be considered a serious and legally binding offer; instead, it was a “simple mess”; However, the Court of Appeal found that Carbolic had made a serious offer to a reasonable man and found that the reward was a contractual undertaking. To be a legal contract, an agreement must have five characteristics: a meeting between minds and understanding and acceptance of reciprocal legal rights and obligations regarding certain acts or obligations that the parties plan to exchange; mutual consent to do or refrain from doing anything; a contract. A Tang Dynasty treaty recording the purchase of a 15-year-old slave for six single silk bolts and five Chinese coins All agreements are not necessarily contractual, as the parties generally must be considered the intention to be legally related.
A “gentlemen`s agreement” should not be legally applicable and “compulsory only in honour.”    Courts differ in their principles of contractual freedom.