CMS proposed on July 14, 2026 to raise the BASIC track Level E shared savings rate from 50% to 60% for Medicare Shared Savings Program agreements that start January 1, 2027. The ENHANCED track rate stays at 75%, so the gap between the two tracks would shrink from 25 percentage points to 15.
The change sits in the CY 2027 Medicare Physician Fee Schedule proposed rule (CMS-1848-P). Practices that belong to an accountable care organization (ACO), or weigh joining one, will see it in their benchmark math and their reporting duties.
What CMS proposed for sharing rates and benchmarks
CMS published a separate Shared Savings Program fact sheet on July 14, 2026. The comment period ran 60 days and closed September 14, 2026. Forvis Mazars, in an August 3, 2026 analysis, reports the same Level E change.
Two benchmark proposals move in opposite directions. CMS would cut the maximum weight of the positive regional adjustment for ENHANCED ACOs from 50% to 35%. It would raise the prior savings adjustment scaling factor from 50% to 75%, which gives more credit to ACOs that already cut spending.
The current 5% cap on upward benchmark adjustments would become a risk-adjusted cap built on national per capita fee-for-service spending for the assignable population. The CMS fact sheet gives no new cap figure.
A new guardrail applies to the accountable care prospective trend (ACPT). For agreement periods that begin January 1, 2027 or later, the ACPT could be no more than 1 percentage point below national growth and no more than 1.5 percentage points above it. For ACOs that started in 2024, 2025 or 2026, the lower limit would apply retroactively from performance year 2025. CMS delays performance year 2025 financial reconciliation to November 2026 to apply it.
| Item | Current | Proposed |
|---|---|---|
| BASIC Level E sharing rate | 50% | 60% |
| ENHANCED positive regional adjustment, maximum weight | 50% | 35% |
| Prior savings adjustment scaling factor | 50% | 75% |
| Cap on upward benchmark adjustments | 5% | Risk-adjusted, no figure given |
| ACPT limits versus national growth | None | 1.0 point below, 1.5 points above |
Source: CMS fact sheet on the CY 2027 Physician Fee Schedule proposed rule, Medicare Shared Savings Program provisions, July 14, 2026.
How large the program is today
CMS reported on February 4, 2026 that 14.3 million Medicare beneficiaries were in ACO-coordinated care as of January 2026. That is up 4.4% from 13.7 million in 2025.
The Shared Savings Program had 511 ACOs for performance year 2026, up from 476 in 2025. CMS approved 134 applications, of which 72 came from new ACOs and 62 from ACOs that renewed or re-entered. The program served 12.6 million beneficiaries, a 12.3% increase from 2025, and included more than 700,000 providers and organizations.
Results for performance year 2024, the latest reconciled year, were $4.1 billion in shared savings earned by ACOs and $2.5 billion in savings to Medicare.
CMS also stated that 82.8% of Shared Savings Program ACOs sit in Level E of the BASIC track or in the ENHANCED track for 2026. That figure combines the two tracks, so it does not show how many ACOs sit in Level E alone. The 10-point sharing-rate change reaches only that Level E group.
Advance investment payments and dates
For performance year 2028 and later, CMS proposes advance investment payments of $45 per beneficiary who is enrolled in the Part D low-income subsidy, is dually eligible for Medicare and Medicaid, or lives in a micropolitan or noncore county. The payment is $25 per beneficiary who meets none of those criteria, and CMS caps it at 10,000 beneficiaries. Forvis Mazars lists the same $45 and $25 amounts on a quarterly basis.
Several dates matter for planning. Approved plans could begin a Part B cost-sharing reduction on April 1, 2027, with applications expected in early 2027. Prepaid shared savings payments continue through December 31, 2027. ACOs would have to give beneficiary notices by May 30 of the performance year unless CMS sets a later date.
Assignment rules change later. The new methodology applies from the performance year that begins January 1, 2028. It requires at least one month of concurrent Part A and Part B enrollment within a 12-month assignment window, with no Medicare group health plan enrollment, including Medicare Advantage, in that month. Experience with risk uses a five-year lookback.
Reporting thresholds for ACO practices
Quality reporting rules also change. ACOs must report on participant TINs that represent at least 95% of assigned beneficiaries. The MIPS data completeness requirement stays at 75% of applicable beneficiaries.
The APP Plus quality set would hold eight measures starting in performance year 2027: five eCQM-type measures, two administrative claims measures and CAHPS for MIPS. Five of the measures are ACO-reported, with Quality IDs 001, 112, 113, 134 and 236. CMS would remove Quality ID 305 (substance use disorder treatment) and Quality ID 493 (adult immunization status).
A TIN could be excluded from an electronic prescribing metric if it had fewer than 100 permissible prescriptions. CMS also proposes flat-benchmark scoring for Medicare eCQMs, starting with the CY 2027 performance period, which feeds the 2029 MIPS payment year.
CMS has not published a final rule. The proposed figures above can change before it does, and the agency gave no savings estimate or ACO count by track in the fact sheet.
Sources
- CMS, Calendar Year 2027 Medicare Physician Fee Schedule Proposed Rule (CMS-1848-P): Medicare Shared Savings Program, July 14, 2026
- CMS, 2026 Medicare Accountable Care Organization Initiatives Participation Highlights, February 4, 2026
- Forvis Mazars, 2027 Medicare Physician Fee Schedule Rule: Key Updates, August 3, 2026
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