Medicare Shared Savings Program

Click to learn more about the NPRM Analysis!Background
The Medicare Shared Savings Program (MSSP) is the primary Medicare ACO program. The MSSP was derived from the Physician Group Demonstration Project, which started during the George W. Bush administration, and the MSSP was permanently authorized by the Patient Protection and Affordable Care Act. The MSSP began in 2012 with two participation options, Track 1 and 2. MSSP Track 3 was added in 2016 and the newest addition is Track 1+, which is detailed on this webpage. Track 1 has no downside risk and ACOs can only participate in Track 1 for a limited number of years. Tracks 1+, 2 and 3 all require certain levels of downside risk but have other benefits such as greater amounts of shared savings rewards and waivers from certain Medicare rules. 

Click the image above for NAACOS in-depth analysis of CMS’s newly proposed rule. 


  • CMS MSSP webpage and federal regulations governing the MSSP

  • NAACOS ACO Comparison Chart Updated for 2018 

  • NAACOS Overview of Research on ACO Performance resource catalogs key ACO studies Updated for 2017

  • NAACOS’s paperDifferences Between Medicare ACO Tracks that May Impact ACO Financial Results
    • NAACOS interactive table for ACOs to input their own projected values to help ACOs illustrate how they may perform under the various tracks. 

News and Advocacy


  • CMS issues guidance on the new Beneficiary Incentive Program

  • The application deadline for July 1, 2019 starts is February 19


  • CMS released guidance on apply for the new waiver from the Skilled Nursing Facility (SNF) 3-Day Rule

  • CMS releases final ACO ‘Pathways to Success’ rule on 12/21/18

  • NAACOS holds webinar providing in-depth review of final ‘Pathways to Success’ rule and participation options for 2019 and beyond 

  • Notice of Intent to Apply for July 1, 2019 start in new ‘Pathways to Success’ structure of the MSSP due January 18, 2019

  • 2019 MSSP application details provided on the CMS website

  • NAACOS statement on the final Pathways to Success rule

  • NAACOS analysis of the final 2019 Physician Fee Schedule and Quality Payment Program rule

  • NAACOS Review of ACO Pathways to Success Provisions included in the Medicare Physician Fee Schedule Rule 

  • Final NAACOS comments on the Proposed Pathways to Success Rule

  • NAACOS releases a report sharing ACO feedback on the proposed CMS Pathways to Success rule

  • Nine stakeholder groups urge CMS to ensure continued success of ACO program

  • What It Means to Patients: The MSSP Proposed Rule

  • 2017 performance data from CMS shows positive results, prompting NAACOS statement
    • NAACOS resource includes highlights of the 2017 MSSP results
  • NAACOS Analysis of the CMS Proposed “Pathways to Success” Rule

  • NAACOS submits comments on ways to improve Stark Law waivers for ACOs

  • CMS Proposes Rule with Changes to Medicare ACO Program, Table 2 from the proposed rule shows new MSPS options

  • ACO Spotlight Newsletter Notifies ACOs of Key Dates for participating ACOs to submit additions and deletions to their PY 2019 ACO Participant List and/or Skilled Nursing Facility (SNF) Affiliate List. The three deadlines to submit change requests to add or edit ACO participants and/or SNF affiliates are: July 31, 2018, August 29, 2018, and September 28, 2018 at 12:00 p.m. (noon) Eastern Time (ET).

  • NAACOS sends a letter to CMS urging the agency to release information as soon as possible on the 2019 MSSP application

  • NAACOS summary of the 2019/2020 Next Generation Model Methodology changes with comparison to the current methodology 

  • NAACOS resource provides highlights of the 2018 Medicare ACO class and shows ACO growth over time

  • NAACOS and five other provider organizations send a letter to CMS requesting that ACOs meeting cost or quality criteria be able to remain in Track 1

  • NAACOS comments on Extreme and Uncontrollable Circumstances policy for ACOs
  • NAACOS letter to CMS identifies PY2016 MSSP calculation error affecting ACOs with previous savings and rebased benchmarks in 2016
    • CMS Response about PY2016 Calculations

  • CMS announces 561 MSSP ACOs in 2018


  • CMS releases interim final rule establishing extreme and uncontrollable circumstances policies for the Shared Savings Program that will apply to ACOs subject to extreme and uncontrollable events such as Hurricanes Harvey, Irma, and Maria, and the California wildfires, effective for performance year 2017
  • New! Highlights of the 2016 Medicare ACO performance results
  • CMS releases performance year 2016 MSSP results, available in this Public Use File and CMS Presentation
  • NAACOS letter expresses concerns about delayed PY 2016 results, urges CMS action
  • NAACOS letter to CMS Administrator Seema Verma on ACO improvements
  • NAACOS policy paper with detailed recommendations for improving the Medicare ACO program
  • CMS Press Release on Announcement of 2017 ACO Class
  • NAACOS resource on key policy issues for ACOs in 2017
  • Talking Points on the Important Role of ACOs in Health Care Delivery Reform 
  • Performance Year 2015 Results