By John Fisher, JD, CHC, CCEP

Client Alert – MSSP ACO Participant Exclusivity Remains Narrow and Assignment-Based

Updated July 10, 2026

Overview

Health care organizations participating in, contracting with, or evaluating Accountable Care Organizations (ACOs) under the Medicare Shared Savings Program (MSSP) should avoid overreading the program’s exclusivity rule. The current MSSP rule remains targeted: exclusivity generally applies only to ACO participants whose claims are used to assign Medicare beneficiaries to an ACO.

The rule is not a broad prohibition on individual clinicians participating in multiple arrangements, nor does it require commercial ACOs or private payer value-based contracts to adopt the same exclusivity framework. Instead, it is principally a beneficiary-assignment safeguard designed to prevent the same assignment-related claims from being used by more than one Shared Savings Program ACO.

Key Takeaways

• ACO participants generally are not required to be exclusive to one Shared Savings Program ACO.
• The exclusivity requirement applies when an ACO participant submits claims for services used to determine the ACO’s assigned beneficiary population.
• The rule operates at the ACO participant level, typically through the Medicare-enrolled billing TIN, rather than as a blanket restriction on every individual clinician.
• Commercial ACOs and private payer arrangements are not required by the MSSP rule to impose the same exclusivity structure.

Current Rule

Under current MSSP regulations, each ACO participant must commit to the term of the ACO’s participation agreement and sign an ACO participant agreement that satisfies program requirements. As a general matter, however, ACO participants are not required to be exclusive to one Shared Savings Program ACO.

The principal exception applies to ACO participants that submit claims for services used to determine the ACO’s assigned population. Those assignment-based ACO participants must be exclusive to one Shared Savings Program ACO. If an ACO participant participates in more than one ACO and submits assignment-related claims during a benchmark or performance year, CMS may disregard the services billed through that participant’s TIN for assignment purposes.

CMS also may take pre-termination actions, terminate the ACO’s participation agreement, or both. For that reason, ACOs and participating provider organizations should treat exclusivity as a compliance and assignment issue, not merely a contracting preference.

Why It Matters

Misunderstanding the MSSP exclusivity rule can create unnecessary contracting restrictions, operational confusion, and potential antitrust sensitivity. The rule is designed to protect CMS’s beneficiary assignment methodology by ensuring that assignment-related claims point to one ACO, not to restrict all professional activity by individual practitioners.

Recommended Actions

• Review ACO participant lists and confirm which TINs submit claims used in beneficiary assignment.
• Ensure participant agreements clearly address MSSP compliance obligations, including assignment-based exclusivity where applicable.
• Distinguish MSSP exclusivity requirements from commercial ACO and private payer contracting strategies.
• Monitor changes in provider enrollment, billing arrangements, and practice affiliations during benchmark and performance years.
• Avoid imposing broader exclusivity restrictions than necessary without separate legal and business justification.

Practical Compliance Checklist

• Map participant TINs: Maintain a current inventory of all ACO participant TINs and identify which TINs submit claims for services used in beneficiary assignment.
• Confirm exclusivity status: Determine whether any assignment-based ACO participant TIN is participating in, or being proposed for, more than one Shared Savings Program ACO.
• Review participant agreements: Confirm that agreements require participants to comply with MSSP obligations, including assignment-based exclusivity where applicable.
• Monitor billing changes: Track changes in billing arrangements, provider enrollment, practice acquisitions, affiliations, and clinician moves that could affect assignment-related claims.
• Coordinate before adding participants: Evaluate exclusivity implications before adding a new participant TIN, changing a participant list, or entering into a new ACO arrangement.
• Separate MSSP and commercial strategy: Avoid importing MSSP exclusivity language into commercial ACO or private payer contracts unless there is an independent legal and business rationale.
• Document compliance review: Keep records showing how the organization evaluated assignment-based exclusivity and resolved any potential overlap.
• Escalate conflicts promptly: If a participant TIN may be submitting assignment-related claims through more than one ACO, involve legal, compliance, and operations teams before the issue affects benchmark or performance-year assignment.

Bottom line: MSSP exclusivity remains narrow and assignment-based. Organizations should focus compliance efforts on the TINs and claims that drive Medicare beneficiary assignment, while avoiding unnecessary restrictions on individual practitioners or unrelated commercial arrangements.