Introduction

In this unpublished but instructive decision, the Sixth Circuit affirmed the dismissal of an unjust enrichment claim brought by a long‑time independent sales consultant against his agency partners. The court held that an express, integrated commission agreement that expressly limits a consultant’s compensation to a defined revenue stream bars equitable recovery for other, related revenue arising from the same clients. The court also reaffirmed two key procedural and interpretive principles: (1) at the Rule 12(b)(6) stage, courts may consider contracts attached to a motion to dismiss when they are central to the plaintiff’s claims; and (2) where an agreement is unambiguous and fully integrated, the four‑corners rule forecloses reliance on extrinsic communications—such as a CFO email—to expand compensation rights not granted by the contract.

The dispute arose when Plaintiff‑Appellant Matthew Mosser, a Kentucky‑based independent sales consultant, sought a commission on Cramer‑Krasselt’s “Ready for the Workday” media campaign for Cintas, a client Mosser helped cultivate. Defendants‑Appellees Cramer‑Krasselt Company and CKYP, LLC (together, “Cramer”) denied the commission, contending that Mosser’s agreement entitled him only to a percentage of “Local Search” (search‑engine marketing) management fees—expressly excluding “other business” with the same clients unless separately negotiated. Mosser sued in the Eastern District of Kentucky for unjust enrichment; he did not plead breach of contract, nor did he amend to add that claim. The district court dismissed the case under Rule 12(b)(6) and denied post‑judgment relief, and the Sixth Circuit affirmed.

Summary of the Opinion

The Sixth Circuit (Judge Cole, joined by Judges Kethledge and Nalbandian) affirmed dismissal of Mosser’s unjust enrichment claim. Applying both Kentucky and Illinois law—because there was no material difference for the issues presented—the court held:

• An unjust enrichment claim cannot proceed where an express contract governs the subject matter of the dispute. Here, the 2019 Independent Sales Consultant Agreement and its 2019–2022 extensions comprehensively addressed Mosser’s compensation and expressly limited it to Local Search management fees, disclaiming entitlement to other revenue from the same clients unless separately negotiated.
• The agreement was unambiguous and contained an integration clause, so the court would not consider extrinsic evidence—including a CFO email—in interpreting or expanding compensation rights.
• Even if the CFO email were considered, it confirmed that no separate agreement existed to compensate Mosser for the Cintas media campaign.
• At Rule 12(b)(6), the district court properly considered the written agreement and its extensions (attached to the motion to dismiss) because they were central to the claim; that consideration did not convert the motion to one for summary judgment.

Because these conclusions resolved the case, the court did not reach the alternative request to transfer the case to Illinois under the forum non conveniens doctrine or to enforce any forum selection clause.

Analysis

1) Precedents Cited and Their Influence

The opinion draws on a line of Kentucky, Illinois, and Sixth/Seventh Circuit authorities reinforcing three interlocking propositions:

• Unjust enrichment is unavailable when an express contract governs the subject matter:
  • McCarthy v. Ameritech Publishing, Inc., 763 F.3d 469, 487 (6th Cir. 2014): Unjust enrichment is a quasi‑contract theory that cannot override an express contract covering the dispute’s subject.
  • Nash‑Finch Co. v. Casey’s Foods, Inc., 762 F. App’x 218, 225 (6th Cir. 2018) (quoting Codell Constr. Co. v. Commonwealth, 566 S.W.2d 161, 165 (Ky. Ct. App. 1977)): Under Kentucky law, where there is an explicit (and performed) contract, unjust enrichment has no application.
  • Mashallah, Inc. v. W. Bend Mut. Ins. Co., 20 F.4th 311, 324–25 (7th Cir. 2021) (quoting Blythe Holdings, Inc. v. DeAngelis, 750 F.3d 653, 658 (7th Cir. 2014)): Under Illinois law, an unjust enrichment claim cannot stand where a specific contract governs the parties’ relationship.
• The four‑corners rule bars extrinsic evidence when a contract is unambiguous and integrated:
  • Harper v. The Oversight Comm. (In re Conco, Inc.), 855 F.3d 703, 711 (6th Cir. 2017), citing Hoheimer v. Hoheimer, 30 S.W.3d 176, 178 (Ky. 2000): Absent ambiguity, a court discerns intent from the four corners of the instrument under Kentucky law.
  • Davis v. G.N. Mortgage Corp., 396 F.3d 869, 878 (7th Cir. 2005): Illinois follows a four‑corners rule that presumes a writing expresses the parties’ intentions and is not altered by extrinsic evidence.
• At Rule 12(b)(6), courts may consider documents “central to” the claim without converting to summary judgment:
  • Bassett v. Nat’l Collegiate Athletic Ass’n, 528 F.3d 426, 430 (6th Cir. 2008); Rondigo, L.L.C. v. Township of Richmond, 641 F.3d 673, 680–81 (6th Cir. 2011): Courts may consider documents attached to the motion to dismiss if referenced by the complaint and central to the claim.
  • Bates v. Green Farms Condo. Ass’n, 958 F.3d 470, 483–84 (6th Cir. 2020): Clarifies the boundary between Rule 12(b)(6) consideration and conversion to Rule 56.
• Pleading standards:
  • Bell Atl. Corp. v. Twombly, 550 U.S. 544, 570 (2007); VCST Int’l B.V. v. BorgWarner Noblesville, LLC, 142 F.4th 393, 399 (6th Cir. 2025): Claims must be plausible on their face; courts accept well‑pleaded facts and draw reasonable inferences in the plaintiff’s favor.
• Substantive tests for unjust enrichment:
  • Kentucky: KSA Enters., Inc. v. Branch Banking & Tr. Co., 761 F. App’x 456, 467 (6th Cir. 2019) (quoting Jones v. Sparks, 297 S.W.3d 73, 78 (Ky. Ct. App. 2009)).
  • Illinois: Cleary v. Philip Morris Inc., 656 F.3d 511, 516 (7th Cir. 2011) (quoting HPI Health Care Servs., Inc. v. Mt. Vernon Hosp., Inc., 545 N.E.2d 672, 679 (Ill. 1989)).

Together, these authorities firmly anchor the court’s conclusion that Mosser’s sole avenue was a contract claim (if any), not unjust enrichment, and that the written agreement’s unambiguous terms control without recourse to extrinsic emails.

2) The Court’s Legal Reasoning

The court’s reasoning proceeds in three steps:

1. The governing contract is central and dispositive.

   The 2019 Independent Sales Consultant Agreement (effective January 1, 2019), along with 2019–2022 extensions, defines Mosser’s compensation as 20% of net revenue from “Clients’ Local Search Business” during the term. The agreement also states:

   • “[Mosser] shall not be entitled to revenue with respect to other business from Clients, whether directly through [Cramer] or [its] affiliates.”
   • “The compensation set out above shall be [Mosser’s] sole compensation under this Agreement.”
   • It is an integrated agreement: “constitutes the entire understanding” and “supersedes all prior discussions [and] agreements.”

   The 2021 and 2022 extensions go further, clarifying that “any incremental project work or revenue outside the [Cintas search engine account] are not part of the commission and will be negotiated separately,” and they repeat the “no entitlement to other business” clause. “Clients” includes Cintas. In short, the agreements expressly channel Mosser’s commission to Local Search management fees and disclaim automatic compensation for other revenue streams from the same clients—such as a Cintas media campaign—unless separately negotiated.

2. Unjust enrichment is barred where a contract covers the subject.

   Under both Kentucky and Illinois law, unjust enrichment is a quasi‑contract remedy that does not apply when a valid, enforceable agreement governs the subject matter. Because the agreements expressly define Mosser’s compensation, foreclosing entitlement to revenue from “other business” with Clients absent a separate negotiation, equity cannot be used to rewrite the bargain. The proper vehicle—if any—is a breach‑of‑contract claim. Mosser, however, did not plead breach of contract and did not seek to amend to add that claim.

3. Extrinsic evidence cannot expand unambiguous, integrated terms.

   Mosser sought to rely on a May 31, 2023 CFO email. But the court held that the four‑corners rule (under both Kentucky and Illinois law) prohibits using extrinsic evidence to vary or supplement an unambiguous, integrated contract. The email, in any event, stated that the “current agreement … clearly states that you would be compensated for work related only to Cintas Local Search” and that there was “no agreement … where both parties mutually agree” to commissions on the “Ready for the Workday” campaign—an admission that actually undercut Mosser’s position.

3) Impact and Practical Implications

This decision has several practical consequences for litigants and contracting parties, especially in commission‑based relationships:

• Pleading strategy matters. Where a written agreement governs compensation, plaintiffs should plead breach of contract (and, where permissible, plead unjust enrichment in the alternative only if arguing the contract is invalid, unenforceable, or does not cover the subject matter). Failing to plead contract theories can be outcome‑determinative at the Rule 12(b)(6) stage.
• Integration and exclusivity clauses are potent. Provisions stating that listed compensation is “sole compensation” and disclaiming entitlement to “other business” from the same clients are enforceable as written. Expect courts to apply them strictly to preclude quasi‑contract claims for adjacent revenue streams (e.g., upsells, cross‑channel campaigns).
• “Negotiate separately” means: no pay absent a separate deal. Where an extension says incremental project work is “not part of the commission” and “will be negotiated separately,” entitlement depends on proof of an actual separate agreement. Absent such proof, courts will not imply payment through unjust enrichment.
• Limited scope for extrinsic emails. Unilateral emails from executives do not create entitlement contrary to an unambiguous, integrated contract. Even ambiguous snippets are unlikely to overcome four‑corners interpretation at the pleading stage unless the contract itself is ambiguous.
• 12(b)(6) record. Contracts and amendments attached to a motion to dismiss can be considered if central to the claim; this can be outcome‑determinative without discovery. Plaintiffs should anticipate that their agreements will be before the court at the pleading stage.
• Choice‑of‑law pragmatism. Where Kentucky and Illinois doctrines are aligned, courts may bypass a conflict analysis and apply both; litigants should be prepared to brief both bodies of law when differences are non‑material.
• Non‑precedential but persuasive. Although “not recommended for publication,” the opinion synthesizes widely accepted Kentucky/Illinois and Sixth/Seventh Circuit principles and is likely to be persuasive in similar commission and vendor‑agency disputes.

4) What the Court Did Not Decide

• Forum selection and forum non conveniens. The court did not reach Cramer’s alternative request to transfer to Illinois; thus, no new guidance was given on the forum clause or the FNC analysis in this context.
• Ambiguity scenarios. The case involved an unambiguous, integrated contract. The court did not address how different the analysis might be if the contract were ambiguous or silent on specific revenue streams.
• Substantive entitlement under contract law. Because Mosser did not plead breach of contract, the panel did not analyze whether he could have prevailed on any contract theory (e.g., course of dealing, modification, or separate agreement formation).

Complex Concepts Simplified

• Unjust Enrichment (Quasi‑Contract): An equitable remedy designed to prevent one party from unfairly benefiting at another’s expense when no enforceable contract governs the transaction. It cannot be used to circumvent an express contract covering the same subject.
• Subject‑Matter Bar: If a valid contract addresses the “subject matter” of the dispute (here, how and when a consultant is paid), equitable claims like unjust enrichment are barred as a matter of law.
• Integration Clause: A contract provision stating that the written agreement is the complete and exclusive statement of the parties’ agreement, superseding prior negotiations or side communications. It triggers the four‑corners rule.
• Four‑Corners Rule: When a contract is unambiguous, a court interprets it solely based on its text, without resorting to external evidence (emails, conversations, prior drafts).
• Rule 12(b)(6) and “Central to the Claim” Documents: On a motion to dismiss, courts can consider documents referenced in the complaint and central to the claim (like the governing contract) without converting the motion to summary judgment.
• Pleading in the Alternative: Plaintiffs may plead both contract and unjust enrichment in the alternative—but only if they plausibly allege facts suggesting the contract is invalid, unenforceable, or does not cover the subject. When the contract governs, unjust enrichment must be dismissed.

Key Takeaways

• Where a commission agreement states that defined commission is the consultant’s “sole compensation” and expressly excludes “other business” from the same clients absent a separate deal, unjust enrichment claims seeking commissions on those other revenue streams will be dismissed at the pleading stage.
• Courts will rely on the agreement’s plain text and integration clause; extrinsic emails cannot create new compensation rights or inject ambiguity that is not in the contract.
• Plaintiffs should plead breach of contract—and, if appropriate, alternative equitable claims premised on the contract’s invalidity or silence—rather than relying solely on unjust enrichment where a written agreement governs compensation.
• Defendants should attach the operative contract and extensions to a Rule 12(b)(6) motion; if the contract is central to the plaintiff’s claim, the court can consider it without converting to summary judgment.

Conclusion

Mosser v. Cramer‑Krasselt reinforces a straightforward but powerful rule: an integrated, unambiguous commission agreement that delineates compensation and excludes other revenue streams forecloses unjust enrichment claims aimed at capturing additional commissions from the same client relationships. The case also underscores procedural and interpretive guardrails—courts may consider central contract documents at Rule 12(b)(6), and the four‑corners rule bars extrinsic evidence when the contract is clear. While unpublished, the decision crisply harmonizes Kentucky and Illinois law and offers a practical roadmap for drafting, litigating, and enforcing commission agreements in agency and consulting relationships.