An entire agreement clause, sometimes called a merger clause or integration clause, is a contractual provision stating that the written contract constitutes the complete and final agreement between the parties, superseding all prior negotiations, representations, and understandings. The purpose of such a clause is to create certainty by ensuring that the parties' rights and obligations are determined solely by reference to the written document they have signed. In theory, this prevents either party from later claiming that additional promises were made during negotiations that should form part of the contract. The underlying principle is that once parties have reduced their agreement to writing and included an entire agreement clause, the written document represents the totality of their bargain, and neither party should be able to introduce evidence of prior oral statements or written communications to add to, vary, or contradict the terms of that document.
The legal basis for entire agreement clauses rests on the parol evidence rule, a common law doctrine that restricts the use of extrinsic evidence to interpret or supplement a written contract that the parties intended to be complete. When parties include an entire agreement clause, they are signalling their intention that the written document be treated as the complete expression of their agreement. Courts across the common law provinces, including British Columbia, Alberta, Saskatchewan, and Ontario, generally give effect to this intention, though the extent to which an entire agreement clause actually achieves its purpose depends on factors that many business owners do not fully appreciate. In Quebec, the Civil Code of Quebec, as of the date of authorship, governs contractual interpretation, and while the civil law approach differs in its analytical framework, similar principles regarding the primacy of written agreements and the parties' common intention operate to give effect to clauses that purport to establish the complete agreement between parties.