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. 

CMS created a new program structure for MSSP in a December 2018 final rule that the agency calls Pathways to Success. More information on that new structure can be found on our page dedicated to the Pathways rule. Click the image above for NAACOS in-depth analysis of CMS’s final Pathways rule. 


NAACOS-Member Resources 

  • NAACOS chart comparing Direct Contracting and other high-risk ACOS

  • Timeline Reviewing Key Dates for ACOs in 2019

  • NAACOS chart of CMS Innovation Center models and their overlap with ACOs

  • New in 2019- Annual ACO CEHRT Attestation Requirement

  • NAACOS review assesses the impact of high-low revenue designations

  • NAACOS ACO Comparison Chart updated for 2019 to reflect the new Pathways structure and old MSSP structure

  • NAACOS holds webinar providing in-depth review of final ‘Pathways to Success’ rule and participation options for 2019 and beyond 
  • NAACOS Review of ACO Pathways to Success Provisions included in the Medicare Physician Fee Schedule Rule 

  • NAACOS Analysis of the CMS Proposed “Pathways to Success” Rule

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

  • NAACOS resource on key policy issues for ACOs in 2017

  • Talking Points on the Important Role of ACOs in Health Care Delivery Reform  

CMS Resources 

News and Advocacy


  • The application deadline for July 1, 2019 starts was February 19
    • NAACOS released a statement calling for CMS to extend the deadline into March


  • CMS releases final ACO ‘Pathways to Success’ rule in December 2018
  • Study Shows ACOs Saved Medicare $1.84 Billion from 2013 to 2015

    • 2017 performance data from CMS shows positive results, prompting NAACOS statement
      • NAACOS resource includes highlights of the 2017 MSSP results 
  • CMS Proposes Rule with Changes to Medicare ACO Program, Table 2 from the proposed rule shows new MSSP options

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

  • 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

2017 and earlier

  • CMS releases interim final rule establishing extreme and uncontrollable circumstances policies in MSSP for ACOs subject events such as Hurricanes Harvey, Irma, and Maria, and the California wildfires, effective for performance year 2017 
    • 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 March 2017 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
  • Performance Year 2015 Results
  • CMS Releases June 2015 MSSP ACO Final Rule  affecting numerous MSSP policies.
    • CMS summary of the June 2015 Final Rule Provisions for ACOs under the MSSP

    • NAACOS Statement Regarding CMS June 2015 MSSP ACO Final Rule  
  • Performance Year 2013 Results
  • CMS Announces 123 New Accountable Care Organizations