Medicare Accountable Care Organizations

The Center for Medicare & Medicaid Services (CMS) announced that there will be 561 Accountable Care Organizations (ACO) in the Medicare Shared Savings program in 2018, an increase from 480 in 2017. The number of beneficiaries in these ACOs in 2018 is 10.5 million.


  • Shared Savings ACOs receive a portion of any financial savings if they meet quality and cost benchmarks. Providers can also choose to share in losses in exchange for receiving a higher percentage of savings. For 2018, 101 ACOs have chosen these higher risk/reward payment tracks.


CMS also announced that 58 ACOs will participate in the Next Generation ACO model which gives participants the opportunity to take on even higher levels of financial risk, up to 100 percent. In exchange, Next Generation ACOs receive a greater share of potential savings.


The chart below outlines several ACO models, their main features, and the number of ACOs in each for 2018. For a list of all Shared Savings ACOs by state, go to the CMS page, "ACOs in Your State." It explains how to obtain detail on each organization.




Type of ACO


More Details

Number of ACOs

Shared Savings
Providers share in financial savings if they meet quality and cost benchmarks. Providers can also choose to share in losses in exchange for a higher percentage of shared savings.

ACOs can select from three payment tracks:


  • Track 1: ACOs share in savings, but not losses. Called “one-sided” financial risk.
  • Track 2: ACOs share in savings, but also financial losses. Called “two-sided” risk.
  • Track 3: ACOs can receive a greater share of savings (beyond Track 2) if they also agree to a greater share of losses. Also called two-sided financial risk.



Providers share in a greater percentage of financial savings than Shared Savings ACOs, but also a greater percentage of financial losses. 


The Pioneer ACO program concluded in 2016.
9 Pioneer ACOs in 2016
Next Generation
Providers can take on even greater financial risk than Pioneer ACOs, including total financial risk for providing care for a specific population.
The program is structured to set more predictable financial targets for ACOs, and to allow greater flexibility in care management and patient engagement. Such ACOs have greater availability of telehealth and post-discharge home visit services
Comprehensive End-Stage Renal Disease Care Model (CEC)
Dialysis facilities, nephrologists, and other kidney care professionals provide coordinated care for ESRD patients.

Large dialysis organizations (those with 200+ facilities) are eligible for shared savings payments, but also are liable for shared losses. They also share in greater levels of risk than their smaller counterparts. 


Small dialysis organizations (those with fewer than 200 facilities) are eligible to receive shared savings payments, but are not liable for shared losses. Beginning in 2017, they have the option to assume downside financial risk, accompanied by the opportunity for greater shared savings.