CMS posted contract year 2025 Part D plan financial data on April 14, 2026, the first plan-level look at a full year under the Inflation Reduction Act benefit redesign.
Industry aggregate gain or loss margin came in roughly 14 percent below bid margin, with dispersion wider than any single year since Part D launched in 2006. The bids were written in June 2024, before any redesign experience existed.
Key Takeaways
- 14 percent below bid margin in aggregate, with three of the top ten sponsors closer to 20 percent unfavorable and two closer to 8 to 9 percent. The dispersion tracks vertical pharmacy benefit integration more than plan size.
- Plus 22 percent catastrophic phase utilization against a plus 6 to plus 10 percent base case, contributing 7 to 9 loss ratio points on its own. This is the largest single driver of the variance.
- 3.1 million enrollees reached the $2,000 out-of-pocket cap in CY 2025, more than double the number crossing the equivalent CY 2024 threshold under the transition rules.
- 60 percent plan share of catastrophic liability under the redesign against 15 percent before it, with Medicare reinsurance falling from 80 to 20 percent and manufacturers covering 20 percent.
- 4 to 6 points recovered through the risk corridor against a 14 point gross miss, leaving 8 to 10 points to be absorbed on plan financial statements and repriced in the 2027 bid.
What the April 14 Release Shows
The redesign that took effect January 1, 2025 collapsed the old four-phase benefit into three, capped beneficiary out-of-pocket costs at $2,000 annually, and rewrote the catastrophic liability split. Plans went from 15 percent of catastrophic cost to 60 percent, Medicare reinsurance from 80 percent to 20 percent, and manufacturers picked up a 20 percent catastrophic discount on brands and biologics under the Manufacturer Discount Program, plus 10 percent in the initial coverage phase.
That moved tail risk off Medicare reinsurance and onto plan balance sheets. The April release is the first measurement of how the transferred risk actually behaved, covering standalone prescription drug plans, Medicare Advantage prescription drug contracts, employer group waiver plans and the PACE drug component.
KFF put 3.1 million enrollees at the $2,000 cap in CY 2025, more than double the CY 2024 equivalent, and MedPAC's March report found total Part D spending rising materially faster than the prior five-year trend with per capita beneficiary out-of-pocket spending down sharply for those reaching the cap.
The variance decomposition matters more than the aggregate, because the drivers carry different 2027 implications.
| Variance driver | Loss ratio point contribution | Direction | Pricing implication for 2027 |
|---|---|---|---|
| Catastrophic phase utilization above base case | 7 to 9 points | Unfavorable | Recalibrate the $2,000 cap behavioral response assumption upward materially |
| Brand and biologic specialty drug mix in catastrophic | 3 to 4 points | Unfavorable | Formulary management levers weaker than assumed on specialty categories |
| Manufacturer Discount Program net economics | 1 to 2 points | Unfavorable | Discount program reduces plan liability less than original CBO score implied |
| Initial coverage phase utilization | flat to 1 point | Slightly unfavorable | Small behavioral response pulling forward initial phase fills |
| Premium stabilization demonstration offset | 2 to 3 points | Favorable | Partially absorbs base case deterioration, expires for 2026 and beyond |
| Administrative cost and rebate timing | flat to 1 point | Mixed | M3P operational costs adding a new unloaded expense line |
The Catastrophic Utilization Miss and What It Costs a 2027 Bid
The plus 22 percent catastrophic utilization shift is the finding that has to move a bid assumption, and the reason it was missed is specific.
Before the redesign, beneficiaries reached catastrophic at roughly $7,400 of total drug cost and then paid 5 percent coinsurance with no cap, which on a specialty therapy produces four and five figure monthly obligations. The Milliman and Wakely base cases used in CY 2025 bid construction, grounded in CMS Office of the Actuary and CBO work, projected a plus 6 to plus 10 percent utilization lift on the theory that patients in catastrophic were already on therapy.
What the models captured was the average adherence improvement. What they missed was continuity. Under the old design a patient's out-of-pocket path across the year was non-linear and unpredictable, and it produced mid-year discontinuations, counter abandonments and deferred refills that pushed utilization into the next plan year or off treatment. A flat ramp to $2,000 and then zero removes all three. The lift is larger than the per capita out-of-pocket saving alone would predict.
Three categories carried most of it: GLP-1s, where adherence gaps closed once the cap removed month-to-month friction; oral oncolytics and targeted therapies covered under Part D rather than Part B; and autoimmune biologics across the TNF inhibitor, IL-17, IL-23 and JAK classes, which also picked up some deferred new initiation.
For the June 2026 bid cycle that means the catastrophic assumption moves from plus 8 percent to something near plus 18 to plus 22, adjusted for the plan's own formulary mix. It also means the Manufacturer Discount Program has to be modeled drug by drug rather than at a blended rate: the program ran 1 to 2 loss ratio points unfavorable because the 20 percent catastrophic discount does not offset a jump from 15 to 60 percent plan share in exactly the high-spend categories where the utilization lift concentrated.
The Corridor Cushions the Miss Without Absorbing It
Part D runs a symmetric risk sharing corridor around each plan's bid target amount, and reading the gross variance without it overstates the damage.
Inside plus or minus 5 percent of target, the plan keeps the gain or bears the loss. Between 5 and 10 percent, CMS shares half. Beyond 10 percent, CMS shares 80 percent. The April preliminary reconciliation estimates put a substantial share of CY 2025 contracts beyond the 5 percent unfavorable threshold and a material share beyond 10 percent, recovering roughly 4 to 6 loss ratio points of the 14 point miss.
That leaves 8 to 10 points on plan financial statements, and the corridor's practical effect is not as symmetric as its design. A plan that gained on bid gives back margin above 5 percent favorable in full measure, while a plan that lost gets only partial relief above the same threshold. The mechanism is a cushion against a pricing miss, not a substitute for repricing one.
Two structural changes make the 2027 bid harder than a straight recalibration. Three of the top ten sponsors have filed notices withdrawing from specific prescription drug plan regions, concentrated where the CY 2025 variance was worst. Remaining plans in those regions inherit migrating enrollment whose morbidity and formulary mix will not mirror their historical book, which is a selection problem layered on top of a trend problem.
The premium stabilization demonstration is the other one. It contributed 2 to 3 favorable loss ratio points to CY 2025 and is rolling off, so the true clearing premium emerges across 2026 and 2027 without it. Medicare Advantage prescription drug plans can absorb some of this inside a larger bid structure, as the CMS 2027 MA final rule environment allows; a standalone drug plan has no cross-subsidy and prices the full variance into its premium.
Further Reading
- Milliman's 2026 Index Puts Retiree Health Savings at $418,000 – How this same catastrophic-phase liability shift shows up on the retiree side, driving Medicare Advantage's retiree savings requirement up 15.3% in a single year.
- CMS 2027 MA Final Rule: 2.48% Rate Notice and Actuarial Implications – The MA payment rate environment that interacts with MA-PD Part D bid construction for 2027 and shapes the joint optimization problem for integrated plan sponsors.
- Medicare Advantage 2026: An Actuarial Guide – The MA competitive and regulatory backdrop in which the Part D redesign variance gets absorbed for MA-PD contracts.
- Healthcare Cost Trends 2026 – The broader medical and pharmacy cost trend environment that frames the specialty pharmacy utilization pattern driving the Part D catastrophic phase lift.
- LDTI First Full Year for Non-Public Life Insurers – The long duration measurement framework that provides a structural parallel for assumption unlocking discipline when observed experience diverges materially from bid assumptions.
- ACA Marketplace 2026 – The individual market pricing environment that shares methodology discipline and risk adjustment framework lessons with Part D bid construction.
- Travelers Q1 2026: $325M Release and AY 2025 Uncertainty IBNR – The current cycle reserving framework for explicit uncertainty provisions that translates to health plan reserve discipline under post redesign Part D variance.
- CMS 2027 MA Rate Reversal: Risk Model Decision and Part D Segmentation – How the separate RxHCC model segments for MA-PD and standalone PDPs interact with Part D redesign experience to reshape integrated bid construction.
- Stop-Loss Carriers Rewrite GLP-1 Rules at 2026 Renewals – The employer-sponsored side of GLP-1 pharmacy cost pressure, where stop-loss carriers are deploying carve-outs and lasers that parallel the Part D catastrophic phase utilization surprise.
- CBO Flags a $500 Billion Part D Spending Gap and Calls for External Actuarial Research – How the year-one redesign variance documented above compounds into a $500 billion decade-long projection gap, with CBO publicly requesting actuarial research to explain the divergence between plan bids and baseline forecasts.
- CMS GLP-1 Bridge: $50 Copay Outside the Part D Benefit Structure – The Section 402 demonstration that followed the BALANCE model pause, removing GLP-1 obesity drug risk from Part D plans entirely while creating a federal single-payer carve-out with $1.74 billion per million users in annual costs.
- Medicare GLP-1 Bridge Launches July 1: Bid Strategy for Part D Plan Actuaries – Full operational analysis of the Bridge after CMS published complete guidance, covering BALANCE model transition uncertainty and a scenario framework for building 2028 bid assumptions before parameters are published.
- Creditable Coverage Threshold Jumps to 72% Under Part D Redesign – How the benefit enrichment documented above raises the actuarial value bar for employer-sponsored drug plans, threatening creditable status for HDHPs and high-cost-sharing designs starting in 2027.
- CMS 2027 Part D Preliminary Bid: The Stabilization Demo Ends and Standalone PDPs Return to the Market – CMS's July 28 preliminary bid confirmed the year-one experience read documented above, setting the 2027 national average bid at $296.05 and ending the Premium Stabilization Demonstration effective December 31, 2026.
Sources
- CMS: Part D Prescription Drug Coverage General Information and Redesign Technical Guidance
- CMS: Medicare Advantage and Part D Contract and Enrollment Data (Contract Year 2025 Financial Data Release)
- CMS: Part D Bid and Payment Policy, Risk Sharing Corridor Mechanics
- Milliman: Medicare Part D Research and Base Case Analyses
- Wakely: Part D Research and IRA Redesign Analysis
- MedPAC: March 2026 Report to the Congress on Medicare Payment Policy, Part D Chapter
- KFF: Medicare Part D 2026 Issue Brief and $2,000 Cap Analysis
- HHS OIG: Part D Program Audits and M3P Implementation Review
- Congressional Budget Office: Health Care Cost Estimates and IRA Part D Score Documentation
- CMS Office of the Actuary: Medicare Trustees Report and Part D Projection Documentation
- American Academy of Actuaries: Health Practice Council Medicare Part D Materials
- Government Accountability Office: Medicare Part D Oversight Reports
- NAIC CIPR: Health Insurance Topic Page and Medicare Coverage Reference