What is the parol evidence rule in real estate contracts?

The parol evidence rule prevents parties from introducing oral or written statements made before or during contract formation to contradict or modify the terms of a final written agreement. Once a real estate contract is signed as the complete and final expression of the parties' agreement, prior negotiations, verbal promises, and earlier drafts generally cannot be used to change its terms. This rule exists to protect the integrity of written contracts. Exceptions include evidence of fraud, mistake, ambiguity, or conditions precedent that were agreed upon but not included.