Where both parties to an agreement make a material error of fact for the agreement [Article 20]; For an agreement to be considered a contract, the law requires the presentation of certain ingredients. These requirements or criteria are commonly referred to as elements of a valid contract. For a contract to be concluded, an offer made must support acceptance, for which consideration is payable. Both parties must intend to establish a legal relationship in a legal matter, which must be freely registered and should be possible. The elements of a valid contract are offer and acceptance, intention to create legal relationships, capacity of the parties, legal purpose, security and legal consideration. “A contract is an actionable promise or a promise. Each of these promises consists of two parts, a promiser and a promise, an expression of a common intention and expectation in The Promised Action or Tolerance. According to Salmond, “the contract is an agreement that creates and defines obligations between the parties.” Free consent: The free consent of all contracting parties is another essential element. There are two aspects to this concept.

The following cases illustrate how all contracts are agreements; In the case of an invitation to treatment, where an invitation to treatment is simply an invitation to receive an offer. An invitation to treatment is an indicator of a party`s willingness to negotiate adherence to a contract. It is a technique used by a party that wants another party to make an offer and cannot be interpreted or the terms are accepted as if it were a valid legal offer in itself. (Carlill v Carbolic Smoke Ball Company). The exhibition of goods in a store is an invitation to process. (Pharmaceutical Society of Great Britain v Boots Cash Chemists (Southern) Ltd). An advertisement that gives information about the goods for sale and their price is usually more of an invitation to treatment than an offer. (Partridge vs. Crittenden).

According to the above definitions, there must be two elements in each definition of a tender. First, the supplier must indicate, either orally, in writing or by conduct, that he is prepared to negotiate with the tenderer. 1- There should be an agreement between two parties. An agreement is reached when one party makes or receives a proposal and the other party accepts the offer. 2- The parties to the agreement should be able to conclude contracts. 3- There should be legal advice and purpose in relation to the agreement. 4- There should be free consent of the parties when they conclude an agreement. .