The parol evidence rule is a crucial aspect of contract law that governs the use of external evidence in contract disputes. It aims to uphold the integrity of written agreements by limiting the introduction of prior or contemporaneous agreements that contradict the final contract.

This rule has exceptions, including ambiguity, fraud, mistake, and collateral agreements. Understanding these exceptions is key to determining when external evidence can be used to interpret or supplement a written contract. Knowing how to apply this rule is essential for maintaining contract reliability.

The Parol Evidence Rule

Parol evidence rule definition

• Substantive rule of contract law governs admissibility of extrinsic evidence in contract disputes
• Promotes integrity and certainty of written contracts by prohibiting introduction of prior or contemporaneous oral or written agreements that contradict or vary terms of final written contract
• Binds parties to terms of final written document
• Allows for reliability and predictability of written contracts

Excluded evidence types

• Prior negotiations and agreements
  • Oral or written communications between parties before final written contract executed (draft agreements, letters of intent, preliminary documents)
• Contemporaneous oral agreements
  • Oral agreements or understandings made at same time as written contract execution not included in final written contract
• Contradictory or supplementary terms
  • Evidence contradicting or varying written contract terms
  • Attempts to add terms or conditions not found in written contract

Exceptions to parol evidence rule

• Ambiguity
  • Unclear or multiple interpretations of written contract language
  • Extrinsic evidence admitted to clarify intended meaning of ambiguous terms
• Fraud
  • One party induces other to enter contract through fraudulent misrepresentation or concealment of material facts
  • Extrinsic evidence admitted to prove fraud existence and invalidate contract
• Mistake
  • Both parties enter contract under shared mistaken belief about material fact
  • Extrinsic evidence admitted to reform contract to reflect parties' true intentions
• Collateral agreements
  • Separate oral or written agreements not contradicting or varying main contract terms
  • Admitted if independent and not integrated into final written contract

Admissibility of extrinsic evidence

1. Determine if written contract is complete integration

   • Integrated agreement is final expression of parties' intent, supersedes prior or contemporaneous agreements
   • Extrinsic evidence generally not admissible to vary or contradict fully integrated contract terms

2. Identify type of extrinsic evidence offered (prior negotiations, contemporaneous oral agreements, contradictory terms)

   • Determine if evidence falls within recognized exceptions to parol evidence rule

3. Apply relevant exception, if applicable

   • If contract ambiguous, consider extrinsic evidence to clarify term meanings
   • If fraud or mistake alleged, evaluate evidence to determine if it supports claim
   • For collateral agreements, assess if truly independent of main contract

4. Make determination on admissibility of extrinsic evidence

   • If no exception applies, parol evidence rule likely bars admission of evidence
   • If exception applies, extrinsic evidence may be admissible to supplement or interpret written contract