Also known as: parol evidence rule · parole evidence · extrinsic evidence
Written by attorneys · grounded in primary & secondary sources — see below
A substantive rule of law that renders inoperative prior or contemporaneous agreements, whether oral or written, to the extent they contradict or add to the terms of a completely integrated written agreement.
Pierce Patterson sold land to Prosperity Investments under a contract containing a merger clause declaring the writing the complete agreement. After closing, Prosperity sought to enforce an earlier oral promise by Patterson to fund utility upgrades omitted from the deed. The court applied the parol evidence rule and merger doctrine to exclude the oral promise, leaving Prosperity without a remedy on that claim.
Buyer and Seller signed a fully integrated supply contract containing a merger clause. Buyer later attempted to enforce an earlier oral side agreement that added volume discounts omitted from the writing. The court applied the parol evidence rule and excluded the prior oral term.
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Pilar Pena and Peak Performance signed a detailed supply contract with an integration clause. Pena later sought to introduce earlier memos setting a minimum purchase volume omitted from the writing. The court first ruled the writing completely integrated, then barred the memos under the parol evidence rule.
Acme Corp and Beta LLC executed a fully integrated services agreement. Beta sought to add an earlier written schedule of fees omitted from the final document. The court held the writing completely integrated and excluded the prior schedule under the parol evidence rule.
Vendor and Purchaser signed a detailed asset purchase agreement with an integration clause. Purchaser later offered a prior letter of intent that added an earn-out term absent from the writing. The court applied the parol evidence rule and refused to consider the earlier letter.
Patrick Phan bought equipment from Precision Tools under a writing that described an express warranty. A separate oral statement purported to disclaim the warranty. The court construed the statements consistently where possible and excluded the disclaimer to the extent it contradicted the writing.
The court makes this determination as a preliminary question by examining the writing's completeness and specificity, including any merger clause, before applying the parol evidence rule.
Evidence of fraud, mutual mistake, or collateral agreements not intended to merge into the writing may still be admitted in many jurisdictions.
Extrinsic evidence is admissible to resolve latent ambiguities or to show lack of testamentary intent, as in cases of sham wills.
Words creating an express warranty and words negating it are construed consistently when reasonable. Otherwise the negation is inoperative to the extent it contradicts the writing.
…do not have the consequences that a decision to terminate a person's life does. At common law and by statute in most States, the parol evidence rule prevents the variations of the terms of a written contract by oral testimony. The statute of frauds makes unenforceable oral contracts to leave property by will, and statutes regulating the…