Validity and effectiveness of banaee condition (condition agreed upon before the contract but not mentioned in it) in Iranian jurisprudence and civil law

Before drafting the contract, following preliminary negotiations or on the basis of Islamic business practice and custom, the parties may accept some requirements and make the contract based on it, but do not specify it in the contract or do not need to repeat it in the text of the contract. A dispute has arisen in the validation and identification of the condition agreed before the contract, which is also called banaee, tabani or tavati condition, and the extent of the effect and influence of the condition included in the contract to such conditions.Since the tabani condition is not in the scope of composition and is a preliminary condition, the validity and origin of its effect and the extension of the effect and influence of the condition in the contract to this type of agreement which is neither explicit (conformity) nor implied (implicit) ) is not mentioned in the text of the contract, it is not easily possible and its acceptance faces harmful legal consequences and serious obstacles at the stage of soboot( as something is in reality) and esbat(as we think something is).