Medicare ACOs Must Count Nurse Practitioners in Patient Assignment Starting 2026

The ACO Assignment Improvement Act of 2025 is short, but it packs a punch for how Medicare manages primary care. Starting in 2026, this bill changes the rules for the Medicare Shared Savings Program (MSSP), which is the program that runs Accountable Care Organizations (ACOs).

What’s Changing and Why It Matters

Right now, when Medicare decides which patients are officially "assigned" to an ACO for performance tracking and shared savings purposes, they primarily look at who provided the patient's primary care services. This bill, specifically in Section 2, mandates that primary care services provided by certain advanced practice providers—Nurse Practitioners (NPs), Physician Assistants (PAs), and Clinical Nurse Specialists (CNSs)—must be included in that assignment calculation. This change kicks in for performance years beginning on or after January 1, 2026.

Think of it this way: ACOs are groups of doctors and hospitals that agree to take responsibility for the overall cost and quality of care for a specific group of Medicare beneficiaries. If they keep costs down and quality up, they share in the savings. The key to this model is accurately knowing whose care they are responsible for. Before this bill, if a Medicare patient relied heavily on an NP or PA for their routine primary care, that care might not have fully counted toward assigning them to the ACO that employs those providers, potentially excluding the ACO from getting credit for managing that patient.

The Real-World Impact: Access and Recognition

This is a big deal for two main reasons: provider recognition and patient access. First, it formally recognizes the critical role NPs, PAs, and CNSs play in delivering primary care, especially in rural or underserved areas where they often serve as the main point of contact for patients. For the providers themselves, this means their work is now fully weighted in the financial and performance metrics of the ACO, integrating them more deeply into the value-based care model.

Second, for Medicare beneficiaries, this change could improve access. If an ACO knows that the patients seen by their NPs and PAs will count toward their performance metrics, they have a stronger incentive to hire, utilize, and integrate these providers. For a 65-year-old living in a town with a provider shortage, this could mean the difference between waiting months for a doctor's appointment and getting timely care from a qualified advanced practice provider who is now fully recognized by the system.

Who Bears the Cost?

While the bill is fundamentally about expanding recognition, it does shift the competitive landscape slightly. ACOs that have historically relied solely on physicians for primary care services might find that organizations heavily utilizing NPs and PAs now have a broader pool of assigned patients, potentially giving them an advantage in the Shared Savings Program. However, since the goal is better patient management, this change seems designed to reward organizations that embrace team-based care models, which often include these advanced practice providers.