Collateral Contracts Unpacked: Your Guide to Crucial Side Agreements

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Yes, but it’s more complex. An “entire agreement” clause in the main contract may weaken the enforceability of collateral contracts, especially if the side promise conflicts with or adds to the written terms. That said, if the collateral agreement is truly separate and consistent, courts may still consider it valid.

They can be enforceable, but proving them is difficult. The lack of written documentation makes it harder to establish the specific promise, the intent to create legal relations, and the exact terms. This is why written records, even of preliminary discussions, are recommended.

Courts look at whether the statement was promissory in nature—i.e., a clear commitment rather than a general opinion or exaggeration. Timing, context, and the reliance placed on the promise all factor into this assessment.

They appear in both contexts. While more common in B2B deals, collateral contracts can also apply in consumer settings—for example, when a consumer is assured of a product feature not explicitly listed in the warranty or main purchase agreement.

In most cases, the collateral contract will be overridden. Courts prioritize the express terms of the main agreement, especially when they are clearly worded. A contradictory side promise is unlikely to be upheld.

Either party can initiate it, depending on who makes the promise that influences contract formation. It often stems from the party providing assurances to secure the deal.