Part B Drug Price Cuts May Arrive as Refunds CMS Has Yet to Size

Part B Drug Price Cuts May Reach Practices as Refunds Sized by a Metric CMS Has Not Chosen

Medicare’s first negotiated prices for drugs given in clinics are due by 30 November 2026, but CMS has not chosen how the discount reaches practices as a refund, leaving margins on Botox, Entyvio, Orencia, Xolair and Cimzia open into 2028.

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The consensus reading is that Medicare’s third negotiation round, which closed on 1 November, settles prices for 15 drugs from January 2028, including the first given in doctors’ offices (Goodsurance, 01/11/2026). The weak signal is in the plumbing. CMS’s draft lets a manufacturer deliver the price by selling to practices at or below it, or by refunding the difference after the claim is paid, sized by a standardized metric on which CMS offered four versions (CMS, 16/07/2026). On 5 November the final guidance was still due in fall 2026 (CMS, 05/11/2026). Practices may carry the gap into 2028 with no settled rule for its size.

Signal Identification

A regulatory pivot in implementation, not price: the discount is fixed by statute and negotiation, but the rule that moves it into practice accounts is not. Our reading is that the refund metric now decides provider margin on the first physician-administered drugs.

Time horizon: 1-2 years, and it binds 2027 to 2028, shown when CMS final guidance fixes the Part B refund metric and the first refunds on 2028 claims are paid. (Milestones: agreed prices due 30 November 2026; final guidance due fall 2026; manufacturer onboarding by 1 May 2027; prices effective 1 January 2028.)

Probability band: Medium (40 to 60%)

Geographic / Jurisdictional Scope: Primary: United States, Medicare Part B in original Medicare and Medicare Advantage. Spillover: commercial contracts priced off Medicare rates.

PrimaryUnited States

SpilloverCommercial payers

Sectors exposed:

Makers of physician-administered biologicsIndependent infusion and specialty practicesHospital outpatient departments and 340B hospitalsMedicare Advantage plansSpecialty distributors

What's Changing

CMS met its 30 September deadline to send final offers on all 15 drugs (Goodsurance, 01/10/2026); all 15 manufacturers had signed agreements, and CMS has until 30 November to publish agreed prices effective 1 January 2028 (Goodsurance, 01/11/2026). Milliman counts Botox, Cimzia, Entyvio, Orencia and Xolair among the drugs paid mainly under Part B and puts earlier list-price discounts at approximately 60% (Milliman, 07/10/2026).

The delivery rule is open. CMS says manufacturers and practices may face significant challenges establishing a reliable acquisition cost, so refunds, due within 14 days of the manufacturer receiving claim data, would use a standardized metric (CMS, 16/07/2026). In Milliman’s worked case, a drug with a $12,000 list price, a $10,000 ASP and a $6,000 maximum fair price gets a list-price refund that overpays a practice buying at ASP, while an ASP refund matches its gap until ASP falls as the maximum fair price enters the average; CMS has indicated it will not publish ASP for negotiated drugs (Milliman, 07/10/2026).

The refund metric sets a practice’s net cost, and the dates that fix it are still open

Source basis: Milliman, 07/10/2026 (illustrative case; purchase at ASP assumed; the refund and net-cost figures are the analyst’s arithmetic on Milliman’s three prices); CMS, 16/07/2026 and 05/11/2026; Goodsurance, 01/11/2026. Blue dots mark dated future steps; the orange ring marks a step with no date beyond the season.

Disruption Pathway

Three stages. To early 2027, the price is published and the rule argued: agreed prices are due by 30 November, final guidance in the fall (CMS, 05/11/2026), and manufacturers onboard to the CMS data module by 1 May 2027 (CMS, 16/07/2026). During 2027, each manufacturer picks acquisition pricing, which leaves no gap to refund, or a refund. From 1 January 2028, refunds due within 14 days test the chosen metric.

Stress concentrates in three places. Metric drift: an ASP-based refund could turn provider margin negative as ASP falls (Milliman, 07/10/2026). Duplicate discounts: CMS is not assuming responsibility for separating the 340B ceiling price from the maximum fair price (CMS, 16/07/2026). Cash flow: a trade body says CMS’s own draft names independent physician clinics among those likely to face material cash-flow problems (National Infusion Center Association, 16/09/2026). Two adaptations follow: CMS can publish refund amounts each quarter, as the American Action Forum asks (American Action Forum, 18/09/2026), and manufacturers can move selected drugs to acquisition pricing, which our reading suggests suits thin-margin practices.

Why This Matters Now

Practice and hospital finance chiefs, 340B directors, manufacturer pricing heads and Medicare Advantage finance teams own this decision. Providers are paid ASP plus a 6% add-on before sequestration (Milliman, 07/10/2026), so 2028 budgets that assume the add-on holds on a smaller drug price are untested against any of the four metrics. Our reading is that the 2028 plan should run all four, because margin differs by metric while the guidance is unwritten.

Decision-action posture for this signal: Prepare: model each refund metric and open acquisition-price talks now, then commit budgets on the final guidance.

Counter-Argument

The strongest objection is that the gap is bounded and fixable. The statute puts the duty on the manufacturer, which can sell at or below the price so no refund is needed (CMS, 16/07/2026). All selected 2028 Part B drugs are biologics with unique billing codes, so claims can be identified without new modifiers, and a quarterly public refund file would let practices estimate refunds (American Action Forum, 18/09/2026). A simple fall guidance could remove most of the problem.

That is partly right and leaves the signal standing. The rule is still unsettled more than a year before first claims (CMS, 05/11/2026), an ASP-based refund drifts as the price enters ASP (Milliman, 07/10/2026), and most NICA members say they need at least 3-6 months to prepare (National Infusion Center Association, 16/09/2026). On the available evidence, practices should plan on the refund route.

Implications

Taken together, the sources suggest a durable change with a transient trigger. The negotiated price lasts until a generic or biosimilar has been marketed for at least nine months (Milliman, 07/10/2026), so delivery becomes a standing feature of buy and bill. CMS plans to codify effectuation for 2029 onward in 2027 rulemaking (CMS, 05/11/2026), so 2028 choices set precedent. Our reading is that manufacturers with efficient refund systems and practices with modelled cash flow gain, and thinly capitalised independent practices lose most.

Early Indicators to Monitor

CMS final guidance issued before 31 December 2026 sizes Part B refunds on an ASP-based metric (option 2a or 2b).If this happens: Margin on selected drugs will erode as ASP falls; model negative-margin cases and open acquisition-price talks.
CMS names at least one Part B drug among agreed prices published by 30 November 2026.If this happens: The 2028 mechanics now apply to a named product; model that drug’s refund.
Final guidance requires claim modifiers or NDC-11 reporting on Part B claims, not separate billing codes.If this happens: Practices carry new billing work; budget it before manufacturers onboard on 1 May 2027.
A selected-drug manufacturer says before 31 December 2027 that it will price at or below the maximum fair price at acquisition.If this happens: The refund gap closes for that drug; focus cash-flow planning on the drugs still on the refund route.
CMS requires Medicare Advantage organisations to report selected Part B drug encounters on a shorter timeline.If this happens: Refund timing narrows for Medicare Advantage patients; otherwise practices with many such patients carry longer lags.

Disconfirming Signals

CMS finalises acquisition-price delivery as the Part B default, with refunds only as a fallback.
Final guidance sizes Part B refunds on list price (option 1a or 1b), so refunds exceed practices’ gaps.
Most manufacturers of selected Part B drugs announce acquisition-price terms before 1 May 2027.
A provider group such as the National Infusion Center Association says final guidance resolves its cash-flow concerns.
CMS publishes a quarterly Part B refund file with a stated method before the first 2028 claims.

Strategic Questions

Do we budget 2028 margin on selected Part B drugs at ASP plus 6%, or model each of the four refund metrics?
Do we open acquisition-price talks now, or wait for final guidance to settle the refund route?
Which of our current activities looks least wise if this signal lands?

Keywords

Medicare Drug Price Negotiation Program; maximum fair price; Part B drugs; buy and bill; standard default refund amount; average sales price; wholesale acquisition cost; Medicare Transaction Facilitator; 340B; Medicare Advantage encounter data; physician-administered biologics

Bibliography

Source tiers: Tier 1, governments, regulators and intergovernmental bodies. Tier 2, think-tanks, academic institutes, major consultancies and quality data providers. Tier 3, quality journalism and specialist trade press. Tier 4, vendor, company and practitioner sources, used only as directional corroboration.

Tier 1 Medicare Drug Price Negotiation Program and Medicare Prescription Drug Benefit Program Final Rule (CMS-4215-F). Centers for Medicare & Medicaid Services (05/11/2026).
Tier 1 Manufacturer Effectuation of MFP Draft Guidance for 2028 Medicare Drug Price Negotiation. Centers for Medicare & Medicaid Services (16/07/2026).
Tier 2 MFPs beyond Part D: What Maximum Fair Prices mean for Part B stakeholders. Milliman (07/10/2026).
Tier 2 Comments to CMS on Draft Guidance, Manufacturer Effectuation of the Maximum Fair Price in 2028. American Action Forum (18/09/2026).
Tier 3 Third Medicare Drug Negotiation Cycle Closes, Including Part B Doctor-Office Drugs for the First Time. Goodsurance (01/11/2026).
Tier 3 Medicare Sent Its Final Drug Price Offers by September 30. Manufacturers Now Have Until October 31 to Respond.. Goodsurance (01/10/2026).
Tier 4 NICA Comments on CMS Draft Guidance Regarding Manufacturer Effectuation of the Maximum Fair Price in 2028. National Infusion Center Association (16/09/2026).