Inside the CY 2027 Medicare Shared Savings Program Overhaul: Track Rebalancing, Benchmark Guardrails, Part B Cost Sharing, and the ACO Operating Software Nobody Has Built Yet, Part 1 of 4
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Abstract
CMS dropped the CY 2027 Physician Fee Schedule proposed rule (CMS 1848 P) on July 14, 2027, and buried inside it is the most consequential rework of Medicare Shared Savings Program economics since Pathways to Success. This part covers:
The track rebalance: BASIC Level E sharing rate up from 50 to 60 percent, ENHANCED positive regional adjustment weight cut from 50 to 35 percent
Benchmark mechanics: prior savings scaling factor from 50 to 75 percent, a risk adjusted 5 percent cap, a new growth adjustment, ACPT guardrails applied retroactively to 2024 through 2026 starters
Assignment plumbing: non ACO TIN primary care charges excluded from plurality math starting PY 2028
Part B cost sharing waivers for approved ACOs beginning April 2027, plus the death of prepaid shared savings
Advance investment payments moving to flat per bene amounts of 45 and 25 dollars quarterly with a rural criterion
QP determination moving to the TIN NPI combination, killing an estimated 2.38 billion dollars in spillover windfall
Quality reporting: APP Plus trimmed to eight measures, Medicare eCQMs as a new collection type, a three option CEHRT attestation replacing Promoting Interoperability reporting
The founder build list: benchmark simulation, network diligence, benefit wallet infrastructure, QP forecasting
Table of contents
The rule in one paragraph
Where the money actually went in performance year 2024
Level E gets a raise and ENHANCED gets a haircut
The ratchet, the prior savings fix, and the risk adjusted cap
ACPT guardrails and the retroactive rescue
The growth adjustment as a recruiting subsidy
Assignment plumbing and the end of the TIN two step
Part B cost sharing becomes a product surface
Advance investment payments go flat and rural
QP status stops traveling with the doctor
Quality reporting gets a real off ramp
The build list
The rule in one paragraph
The proposed rule reads like CMS finally sat down with a decade of Shared Savings Program data and asked why the incentives point where they point. The answer, repeatedly, is that the benchmark math rewards things that are not savings. ENHANCED track ACOs sitting below their regional average collect a fat regional adjustment plus a 75 percent sharing rate, which is a nice arbitrage if you can get it. Level E ACOs, which actually generate more savings to the trust funds on average, get a worse deal and enroll in smaller numbers. Clinicians in one qualifying practice drag QP status across every TIN they bill under, producing what CMS politely estimates as 2.38 billion dollars in ten year windfall. Beneficiary assignment can be nudged by where a doctor routes primary care claims. The 2027 proposal goes after all of it at once, and every fix creates a modeling problem, a compliance obligation, and a software gap. That last part is where the entrepreneurs come in.
