R2d § 216
Consistent Additional Terms
(1) Evidence of a consistent additional term is admissible to supplement an integrated agreement unless the court finds that the agreement was completely integrated. (2) An agreement is not completely integrated if the writing omits a consistent additional agreed term which is (a) agreed to for separate consideration, or (b) such a term as in the circumstances might naturally be omitted from the writing.
Professor's notes
Elements: (1) evidence of a consistent additional term is admissible to supplement an integrated agreement unless the court finds the agreement was completely integrated; (2) an agreement is not completely integrated if the writing omits a consistent additional term that is (a) agreed to for separate consideration; or (b) such a term as in the circumstances might naturally be omitted from the writing.
Sierra Diesel operationalizes (2)(b): natural-omission test allowed extrinsic evidence of express warranty despite a form merger clause.
Common misunderstanding: students think a "consistent additional term" defeats the PER automatically. § 216(2) makes the natural-omission test the central inquiry: and only available when the agreement is NOT completely integrated. The interaction with § 210 is where most PER analyses fail. Walk the steps: integration > complete or partial > if partial, § 216 lets consistent additional terms in.
Text
R2d § 216. Consistent Additional Terms.
(1) Evidence of a consistent additional term is admissible to supplement an integrated agreement unless the court finds that the agreement was completely integrated.
(2) An agreement is not completely integrated if the writing omits a consistent additional agreed term which is
(a) agreed to for separate consideration, or
(b) such a term as in the circumstances might naturally be omitted from the writing.