The third and final rule of admissibility is that under UCC 2-202, parol evidence cannot be contradicted by a writing conceived as a “definitive expression” of the integrated agreement, but by (a) a commercial/commercial/performance history and (b) evidence of consistent complementary conditions, unless the letter is a full and exclusive statement of contractual terms. (a) An insurance policy is carried out on goods “on board ships from Calcutta to London”. The goods are shipped aboard a particular ship that is lost. The fact that this particular vessel was exempted orally from the policy cannot be proven. In addition, Section 48 of the Registration Act, 1908, provides that all non-will documents duly registered under this Act, relating to personal or real property, take effect against any order, arrangement or declaration concerning that property, unless the agreement or declaration was accompanied or shipped with the property. This was done by Delhi High Court, in the case of Nanak Builders and Investors Pvt. Ltd. vs. Vinod Kumar Alag AIR 1991 Delhi 315, the court having decided that even an oral agreement can be a valid and enforceable contract. Therefore, it is not strictly necessary, in the strict sense, for a contract to be entered into in writing, unless the parties themselves are considering reducing the terms of the contract. The concept of an oral contract is sometimes used as a synonym for an oral contract. Since the term verbal can also mean that words are used only in addition to the use of spoken words, the term oral contract should be preferred if the clarity is maximum.  For the rule to take effect, the contract in question must first be a definitive integrated handwriting; it must be, according to the Tribunal`s judgment, the final agreement between the parties (unlike a simple project, z.B.).
A final agreement is a partial or complete integration, provided it has an agreement indicating its purpose.  If it contains certain, but not all, conditions on which the parties have agreed, it is a partial integration. This means that the letter was a final agreement between the parties (not just preliminary negotiations) on some conditions, but not in relation to others. On the other hand, if the letter contained all the conditions on which the parties agreed, it would be a complete integration. One way to ensure that the contract can be considered a definitive and complete integration is by the inclusion of a merger clause stipulating that the contract is in fact the overall agreement between the parties. However, many recent cases have found that merger clauses are only a rebuttable presumption. An oral contract is a kind of business contract that is described and agreed upon by oral communication, but not written.