The parol-evidence rule is a contract-law principle that generally prohibits the introduction of any extrinsic evidence contradicting or varying the terms of a complete and final written agreement. Extrinsic evidence refers to any evidence outside the four corners of the written agreement.

I. Article 2’s Parol-Evidence Rule

Article 2 has its own version of the parol-evidence rule. Found in Section 2-202, the rule says that any term on which the parties’ confirmatory memoranda agree, or any term...