What are the exceptions to the parol evidence rule?

The parol evidence rule generally states that extrinsic evidence cannot be used to contradict, vary, or add to the terms of a fully integrated written contract. However, there are exceptions to this rule where extrinsic evidence may be admissible:

Ambiguous terms:

Extrinsic evidence can be used to clarify ambiguous terms in a contract if the terms are unclear or subject to multiple interpretations.

Oral agreements:

If there are oral agreements made prior to the written contract that are not in conflict with it, they may be admissible to supplement the written contract.

Collateral agreements:

Extrinsic evidence of collateral agreements that do not contradict the written contract may be admissible.

Subsequent modifications:

If there are subsequent modifications to the written contract, extrinsic evidence of these changes may be admissible.

Mistake, fraud, illegality:

Extrinsic evidence may be admissible to show mistake, fraud, or illegality that could render the contract void or voidable.

Integration clause:

If a contract contains an integration clause (a clause stating the contract is the complete and final agreement), extrinsic evidence may still be admissible to show exceptions to this clause.

Course of dealing/performance:

Extrinsic evidence of the parties' course of dealing or performance may be used to interpret or supplement the written contract.