On October 1, 2026, the Centers for Medicare & Medicaid Services (CMS) will officially open the Medicare Part D Claims Data 340B Repository for data submissions by 340B covered entities and their third-party administrators (TPAs). In August 2026, CMS published a comprehensive guidance suite—including a four-page Frequently Asked Questions (FAQ) document, an operational Fact Sheet, and the Companion Guide Version 1.0 (OMB Control No. 0938-1485, expiration date 11/30/2028)—establishing the technical architecture and regulatory parameters of the new portal.
For hospital health system pharmacy leadership, 340B compliance officers, contract pharmacy administrators, and pharmaceutical manufacturer gross-to-net teams, this launch intersects with statutory mandates under the Inflation Reduction Act (IRA):
If a covered entity opts not to submit claims data during the 2026 voluntary testing window, does that decision affect its 340B drug reimbursement, and will CMS use October 1 repository files to adjust manufacturer Part D inflation rebate invoices this year?
The direct operational answers clarify critical boundaries between testing-period data collection and formal rebate adjudication:
- 2026 reporting is voluntary: For dates of service (DOS) throughout calendar year 2026, repository participation is strictly voluntary. Covered entities are encouraged to enroll and submit files to test systems and workflows, but non-participation carries no statutory or administrative penalty in 2026.
- Repository data will not alter 2026 inflation rebate invoices: CMS explicitly states in the August 2026 FAQ and Fact Sheet that repository data will not be used in Part D inflation rebate calculations unless and until CMS proposes and finalizes a policy in future notice-and-comment rulemaking to do so.
- Prescriber-Pharmacy Methodology remains the 2026 statutory mechanism: Under Section 1860D-14B of the Social Security Act, CMS is required to remove 340B units from Part D inflation rebate calculations beginning January 1, 2026. For 2026 invoices, CMS relies exclusively on its claims-based Prescriber-Pharmacy Methodology, matching Prescription Drug Event (PDE) prescriber NPIs affiliated with registered covered entities against designated 340B contract pharmacies.
- Testing-period data cannot be used for MFP effectuation: CMS confirmed that repository data collected during the testing period will neither be used to deduct units from manufacturer inflation rebate invoices nor used for other IRA programs, including Maximum Fair Price (MFP) effectuation under the Medicare Drug Price Negotiation Program.
- No impact on covered entity 340B drug payment: Submissions do not alter reimbursement, acquisition discounts, or dispensing fees received by covered entities, clinics, or pharmacies. Part D inflation rebates are financial transactions between manufacturers and the Medicare Trust Fund, not provider payment mechanisms.
- Strict account separation from the Medicare Transaction Facilitator (MTF): An existing MTF role does not open the 340B repository. Users must complete a separate 340B repository account-creation process. Existing CMS Identity Management (IDM) username and password may be reused.
- Proposed 2027 mandate is not yet final: In the Calendar Year (CY) 2027 Physician Fee Schedule (PFS) proposed rule (CMS-1848-P; comments close September 14, 2026), CMS proposed making repository reporting a mandatory condition of Medicare enrollment beginning January 1, 2027. That mandate remains a proposal subject to public comment, not an active 2026 rule.
┌──────────────────────────────────────────────────────────────────────────────────────────────────┐
│ CMS PART D 340B CLAIMS REPOSITORY OPERATIONAL SCORECARD │
├──────────────────────────┬───────────────────────────────────────────────────────────────────────┤
│ Regulatory Element │ Documented Status / Operational Specification │
├──────────────────────────┼───────────────────────────────────────────────────────────────────────┤
│ Portal Go-Live Date │ October 1, 2026; Access Portal at 340bimpl.cms.gov/sec340b/ │
│ Operative Guidance │ CMS FAQ (Aug 2026); Fact Sheet (Aug 2026); Companion Guide V1.0 │
│ Information Collection │ OMB Control No. 0938-1485 (Expires 11/30/2028); CY 2026 PFS 90 FR 49266│
│ 2026 Participation Mode │ Voluntary testing period for dates of service on/after Jan 1, 2026 │
│ 2026 Rebate Calculation │ Repository data NOT USED in rebate math; Prescriber-Pharmacy applies │
│ Scope of Requested Data │ All Part D-paid 340B dispenses (in-house & contract, all Part D NDCs) │
│ Initial Submission Due │ Q1–Q3 2026 (DOS Jan 1 – Sep 30, 2026) due December 31, 2026 │
│ File Upload Standards │ .xlsx or .csv; 2 GB limit; Table 1 seven core fields in first 30 cols │
│ Data Privacy & Sharing │ Data NOT shared with manufacturers or Part D plan sponsors │
│ MTF / Pilot Separation │ Separate IDM role; distinct from MTF and HRSA 340B Rebate Pilot │
│ Proposed Future Mandate │ CY 2027 PFS (CMS-1848-P) proposed mandatory reporting; comments 9/14/26│
└──────────────────────────┴───────────────────────────────────────────────────────────────────────┘
What Opens on October 1, 2026, and Is 2026 Reporting Mandatory?
The launch of the Medicare Part D Claims Data 340B Repository represents the technical culmination of rulemaking established in the CY 2026 Physician Fee Schedule final rule (90 FR 49266 at 49750).
Voluntary Testing Framework for CY 2026
Under the operational guidelines released in August 2026:
- Go-Live Date: The repository web interface opens for registration and batch file uploads on October 1, 2026.
- Voluntary Scope: Covered entities, child sites, and authorized TPAs are invited to enroll and submit historical and concurrent claims data for dates of service on or after January 1, 2026.
- No Penalties for 2026 Inaction: Participation is entirely optional throughout calendar year 2026. A hospital or clinic that chooses not to register or upload files in 2026 incurs no Medicare billing sanctions, no enrollment revocations, and no loss of 340B eligibility.
┌──────────────────────────────────────────────────────────────────────────────────────────────────┐
│ CMS 340B REPOSITORY SUBMISSION TIMELINE & DUE DATES │
├───────────────────────┬───────────────────────────────┬───────────────────┬──────────────────────┤
│ Reporting Quarter │ Dates of Service (DOS) Window │ Submission Window │ Regulatory Status │
├───────────────────────┼───────────────────────────────┼───────────────────┼──────────────────────┤
│ Q1, Q2, Q3 2026 │ Jan 1, 2026 – Sep 30, 2026 │ Due Dec 31, 2026 │ Voluntary Testing │
│ Q4 2026 │ Oct 1, 2026 – Dec 31, 2026 │ Due Mar 31, 2027 │ Voluntary Testing │
│ Q1 2027 │ Jan 1, 2027 – Mar 31, 2027 │ Due Jun 30, 2027 │ Proposed Mandatory │
│ Q2 2027 │ Apr 1, 2027 – Jun 30, 2027 │ Due Sep 30, 2027 │ Proposed Mandatory │
│ Q3 2027 │ Jul 1, 2027 – Sep 30, 2027 │ Due Dec 31, 2027 │ Proposed Mandatory │
│ Q4 2027 │ Oct 1, 2027 – Dec 31, 2027 │ Due Mar 31, 2028 │ Proposed Mandatory │
└───────────────────────┴───────────────────────────────┴───────────────────┴──────────────────────┘
The submission timeline establishes a standard quarter-plus-one-quarter cadence: entities submit claims within one calendar quarter following the close of the reporting quarter. The initial submission window consolidates the first nine months of 2026 into a single filing due December 31, 2026.
How Is CMS Removing 340B Units from 2026 Part D Inflation Rebates?
The Inflation Reduction Act requires CMS to calculate and invoice manufacturers for Part D inflation rebates when the price of a Part D rebatable drug increases faster than the rate of general inflation. Section 1860D-14B(b)(1)(B) of the Social Security Act mandates that CMS exclude units dispensed under the 340B Drug Pricing Program from these rebate calculations, preventing double-counting of manufacturer discounts.
The Prescriber-Pharmacy Methodology
Because repository data collection is in a voluntary testing phase, CMS is not using those files to compute 2026 statutory rebate invoices. The August 2026 FAQ states CMS will not use repository data in Part D inflation rebate calculations unless and until it proposes and finalizes a policy to do so. For all 2026 dates of service, CMS is applying its established Prescriber-Pharmacy Methodology:
┌──────────────────────────────────────────────────────────────────────────────────────────────────┐
│ PRESCRIBER-PHARMACY METHODOLOGY VS. REPOSITORY CLAIMS SCOPE │
├───────────────────────┬───────────────────────────────────┬──────────────────────────────────────┤
│ System Dimension │ Prescriber-Pharmacy Method (2026) │ 340B Claims Data Repository │
├───────────────────────┼───────────────────────────────────┼──────────────────────────────────────┤
│ Authority / Basis │ IRA Statute / CMS 2026 Invoicing │ CY 2026 PFS Final Rule (90 FR 49266) │
│ Data Source │ Prescription Drug Event (PDE) + │ Direct Covered Entity / TPA batch │
│ │ HRSA 340B OPAIS Database Match │ file uploads via web portal │
│ Matching Logic │ Prescriber NPI affiliated with │ Exact 11-digit NDC, Rx Number, Fill, │
│ │ covered entity AND dispensing │ Pharmacy NPI, and 340B CE ID │
│ │ pharmacy is 340B contract pharmacy│ │
│ In-House Dispenses │ MAY MISS (in-house pharmacy │ CAPTURED: Explicitly requests all │
│ │ PDEs not paired as contract │ in-house entity dispenses │
│ Contract Pharmacy │ CAPTURED via contract registration│ CAPTURED via pharmacy NPI & Rx match │
│ Rebate Effectuation │ ACTIVE: Directly removes units │ TESTING ONLY: Zero rebate effect in │
│ │ from 2026 manufacturer invoices │ 2026; future rulemaking required │
│ Drug Product Scope │ Part D rebatable drugs only │ All Part D-paid 340B dispenses │
└───────────────────────┴───────────────────────────────────┴──────────────────────────────────────┘
The In-House Pharmacy Gap
The structural limitation of the Prescriber-Pharmacy Methodology is that it relies on identifying contract pharmacy relationships in HRSA's Office of Pharmacy Affairs Information System (OPAIS). When a 340B hospital or clinic dispenses a Part D drug through its own in-house pharmacy, standard PDE records frequently lack a contract-pharmacy flag. Consequently, the Prescriber-Pharmacy algorithm may fail to identify some in-house 340B dispenses, leaving those units in the manufacturer's rebate base.
The 340B repository is engineered specifically to eliminate this gap by capturing both in-house and contract-pharmacy dispenses directly from covered entity records. However, until CMS completes formal rulemaking to transition from the Prescriber-Pharmacy algorithm to repository claims matching, the Prescriber-Pharmacy Methodology remains the sole operative mechanism.
Companion Guide Table 1: Technical File Specifications and Data Elements
To participate in the testing window, covered entities and TPAs must format data in accordance with the Medicare Part D Claims Data 340B Repository Companion Guide Version 1.0 (released June 18, 2026).
┌──────────────────────────────────────────────────────────────────────────────────────────────────┐
│ COMPANION GUIDE VERSION 1.0 (TABLE 1) DATA DICTIONARY │
├────┬─────────────────────────────┬───────────┬──────────────┬────────────────────────────────────┤
│ # │ Field Name │ Data Type │ Format / Len │ Description & Validation Rules │
├────┼─────────────────────────────┼───────────┼──────────────┼────────────────────────────────────┤
│ 1 │ Covered Entity 340B ID │ CHAR │ CHAR(13) │ Unique 340B ID assigned by HRSA. │
│ │ │ │ │ Alphanumeric OPAIS ID. │
├────┼─────────────────────────────┼───────────┼──────────────┼────────────────────────────────────┤
│ 2 │ Date of Service (DOS) │ DATE │ Standard │ Accepted formats: CCYYMMDD, │
│ │ │ │ formats │ CCYY-MM-DD, MM/DD/YYYY, M/D/YYYY, │
│ │ │ │ │ DD-MMM-YYYY, DDMONYYYY (DOS ≥2026) │
├────┼─────────────────────────────┼───────────┼──────────────┼────────────────────────────────────┤
│ 3 │ Prescription/Reference Num │ CHAR │ CHAR(12) │ Prescription or service reference │
│ │ │ │ │ number from dispensing system. │
├────┼─────────────────────────────┼───────────┼──────────────┼────────────────────────────────────┤
│ 4 │ Fill Number │ CHAR │ CHAR(2) │ Two-digit fill number (00 to 99). │
│ │ │ │ │ Original fill or refill number. │
├────┼─────────────────────────────┼───────────┼──────────────┼────────────────────────────────────┤
│ 5 │ National Drug Code (NDC-11) │ CHAR │ CHAR(11) │ 11-digit NDC, zero-padded, │
│ │ │ │ │ STRICTLY NO HYPHENS OR SPACES. │
├────┼─────────────────────────────┼───────────┼──────────────┼────────────────────────────────────┤
│ 6 │ Dispensing Pharmacy NPI │ CHAR │ CHAR(10) │ 10-digit National Provider Ident. │
│ │ │ │ │ of dispensing in-house or contract.│
├────┼─────────────────────────────┼───────────┼──────────────┼────────────────────────────────────┤
│ 7 │ Claim Record Indicator │ CHAR │ CHAR(1) │ Blank = Original/Active claim │
│ │ │ │ │ R = Replacement / Reversal record │
│ │ │ │ │ ('A' accepted and treated as Blank)│
└────┴─────────────────────────────┴───────────┴──────────────┴────────────────────────────────────┘
Technical Upload Rules and Correction Protocols
- File Format and Capacity: Submissions must be delivered as
.xlsx(Excel) or.csv(comma-separated values) files uploaded directly through the repository web interface. Maximum file size is 2 GB per upload. - Column Mapping Constraint: All seven mandatory fields must reside within the first 30 columns of the uploaded spreadsheet or delimited file. Columns beyond position 30 are ignored by the intake parser.
- No In-Place Edits (The R-Then-Blank Protocol): The repository does not allow users to modify previously submitted records in place. To correct an erroneous record:
- Step 1: Submit a record identical to the original claim, with the Claim Record Indicator set to
R(Reversal/Replacement). - Step 2: Submit a new record containing the corrected data elements, with the Claim Record Indicator left Blank (Original/Active).
- Step 1: Submit a record identical to the original claim, with the Claim Record Indicator set to
- NDC Formatting: NDCs must be submitted in 11-digit format (
5-4-2configuration converted to 11 digits with leading zeros). The Companion Guide requires CHAR(11) with no dashes. Hyphenated values such as12345-6789-01do not match that format.
System Boundaries: Repository vs. MTF vs. HRSA 340B Rebate Pilot
Health systems must distinguish between multiple concurrent federal drug pricing and dispute mechanisms to avoid credentialing confusion:
┌──────────────────────────────────────────────────────────────────────────────────────────────────┐
│ FEDERAL DRUG PRICING & DISPUTE SYSTEMS COMPARISON │
├───────────────────────┬───────────────────────────────┬──────────────────────────────────────────┤
│ System / Platform │ Operating Agency / Authority │ Core Function & Scope │
├───────────────────────┼───────────────────────────────┼──────────────────────────────────────────┤
│ Part D 340B Claims │ CMS / IRA Section 1860D-14B │ Covered entity reporting of Part D 340B │
│ Repository (340bimpl) │ CY 2026 PFS Final Rule │ dispenses to exclude units from inflation│
│ │ │ rebate invoices; voluntary in 2026. │
├───────────────────────┼───────────────────────────────┼──────────────────────────────────────────┤
│ Medicare Transaction │ CMS / IRA Section 1191–1198 │ Manufacturer-to-pharmacy data module for │
│ Facilitator (MTF) │ Drug Price Negotiation Prog. │ Maximum Fair Price (MFP) effectuation; │
│ │ │ separate repository account; existing │
│ │ │ CMS IDM credentials may be reused. │
├───────────────────────┼───────────────────────────────┼──────────────────────────────────────────┤
│ HRSA 340B Rebate │ HRSA / Section 340B PHSA │ Manufacturer-sponsored rebate pilots and │
│ Models & Litigation │ D.C. Circuit Court Review │ upfront discount challenges; distinct │
│ │ │ from CMS Part D inflation rebate rules. │
├───────────────────────┼───────────────────────────────┼──────────────────────────────────────────┤
│ Hospital 340B OPPS │ CMS / Section 1833(t) SSA │ Hospital Part B outpatient payment rates │
│ Payment Rules │ CY 2027 OPPS Proposed Rule │ (e.g. ASP-minus-33.4% comment clock); │
│ │ │ separate Part B reimbursement mechanism. │
└───────────────────────┴───────────────────────────────┴──────────────────────────────────────────┘
Account Separation and Privacy Firewalls
- Distinct CMS IDM Profiles: A user registered in the CMS Identity Management system for the Medicare Transaction Facilitator cannot open the 340B repository on MTF role permissions alone. The FAQ requires a separate 340B repository account-creation process. Existing CMS IDM username and password may be reused; a second IDM login is not required.
- Firewall Against Manufacturers and Plans: The August 2026 FAQ affirms that CMS will not share repository claims files with pharmaceutical manufacturers or Medicare Part D plan sponsors. Data submitted to the repository is held strictly confidential by CMS and its designated contractor for inflation rebate administration.
- Independence from HRSA Litigation: The repository is an internal CMS Part D inflation rebate tracking tool, entirely independent of the 340B rebate-model court ruling regarding manufacturer upfront pricing restrictions.
Proposed CY 2027 Physician Fee Schedule Mandate: What Remains Proposed
While 2026 reporting is voluntary, covered entities must monitor notice-and-comment rulemaking for future compliance obligations.
The CY 2027 PFS Enrollment Condition Proposal
In the CY 2027 Physician Fee Schedule proposed rule (CMS-1848-P, published in the Federal Register on July 16, 2026), CMS proposed the following policy:
- Mandatory Reporting: Beginning with dates of service on or after January 1, 2027, all 340B covered entities dispensing Part D drugs would be required to submit claims data to the repository.
- Condition of Medicare Enrollment: CMS proposed making repository reporting an enforceable condition of Medicare provider enrollment under 42 C.F.R. Part 424. Under the proposal, persistent failure to report could subject a provider to Medicare enrollment revocation.
- Public Comment Clock: Public comments on the proposed rule close on September 14, 2026.
Critical Status Check: As of August 31, 2026, the 2027 mandate is a proposed rule only. It has not been finalized and cannot be enforced against covered entities. CMS will issue its final determination in the CY 2027 PFS final rule, typically published in early November.
Intersecting Clocks: 340B OPPS, MFP Non-Duplication, and Portfolio Context
The opening of the Part D 340B repository operates alongside several critical policy timelines across our healthcare coverage:
- Today's OPPS Comment Deadline: On August 31, 2026, public comments close on CMS's proposed Part B hospital outpatient 340B payment cuts. For detailed analysis of the Part B hospital rate methodology, see our review of the 340B OPPS ASP-minus-33.4 comment deadline.
- MFP Non-Duplication Coordination: Manufacturer access teams managing 340B discount identification under Medicare Drug Price Negotiation should consult our guide on 340B/MFP non-duplication workflow.
- Litigation Background: For legal analysis of manufacturer attempts to convert 340B statutory discounts into retrospective rebates, review our report on the 340B rebate-model court ruling.
Frequently Asked Questions
Do covered entities have to enroll in the 340B repository in 2026?
No. Registration and submission for dates of service in calendar year 2026 are entirely voluntary. Covered entities are encouraged to participate to test data pipelines and column-mapping workflows, but no penalties apply for non-participation in 2026.
Will CMS use October 1 submissions to calculate 2026 Part D inflation rebates?
No. CMS confirmed in its August 2026 FAQ and Fact Sheet that data submitted during the testing period will not be used in Part D inflation rebate calculations unless and until CMS proposes and finalizes a policy in future rulemaking. For 2026, CMS uses the Prescriber-Pharmacy Methodology to remove 340B units from rebate invoices.
Is the 340B repository the same system as the Medicare Transaction Facilitator?
No. The 340B repository (hosted at 340bimpl.cms.gov) is a CMS data collection portal for Part D inflation rebate unit identification. The Medicare Transaction Facilitator (MTF) is a separate system facilitating Maximum Fair Price (MFP) effectuation between manufacturers and dispensers. Both use CMS IDM for authentication, but users must complete a separate 340B repository account-creation process. Existing CMS IDM credentials may be reused; a second IDM account is not required.
Does the repository replace the HRSA 340B Rebate Pilot?
No. The CMS Part D Claims Data 340B Repository is an IRA statutory tracking mechanism administered by CMS. It is completely distinct from HRSA's 340B Drug Pricing Program oversight, manufacturer rebate pilots, and ongoing federal litigation.
Sources
- Centers for Medicare & Medicaid Services (CMS): Medicare Part D Claims Data 340B Repository FAQs. Published August 2026. 4 pages. https://www.cms.gov/files/document/cms-medicare-part-d-340b-repository-faqs.pdf
- Centers for Medicare & Medicaid Services (CMS): Fact Sheet: Medicare Part D Claims Data 340B Repository. Published August 2026. OMB Control No. 0938-1485. https://www.cms.gov/files/document/cms-medicare-part-d-340b-repository-fact-sheet.pdf
- Centers for Medicare & Medicaid Services (CMS): Medicare Part D Claims Data 340B Repository Companion Guide Version 1.0. Released June 18, 2026. OMB Control No. 0938-1485 (expires 11/30/2028). https://www.cms.gov/files/document/cms-medicare-part-d-340b-repository-companion-guide.pdf
- Centers for Medicare & Medicaid Services (CMS): Medicare Inflation Rebate Program Overview. Repository landing documentation, file templates, and submission schedule. Retrieved August 31, 2026. https://www.cms.gov/initiatives/medicare-prescription-drug-affordability/overview/medicare-inflation-rebate-program
- Federal Register / CMS: Medicare and Medicaid Programs; Calendar Year 2026 Payment Policies Under the Physician Fee Schedule. Final Rule (90 FR 49266 at 49750). https://www.federalregister.gov/public-inspection/2025-19787/medicare-and-medicaid-programs-calendar-year-2026-payment-policies-under-the-physician-fee-schedule
- Federal Register / CMS: Medicare and Medicaid Programs; CY 2027 Payment Policies Under the Physician Fee Schedule and Other Changes to Part B. Proposed Rule (CMS-1848-P, 91 FR). Published July 16, 2026; comments close September 14, 2026. https://www.federalregister.gov/documents/2026/07/16/2026-14327/medicare-and-medicaid-programs-cy-2027-payment-policies-under-the-physician-fee-schedule-and-other
- Social Security Administration: Social Security Act Section 1860D-14B – Part D Inflation Rebates. 42 U.S.C. § 1395w-114b. https://www.ssa.gov/OP_Home/ssact/title18/1860D-14B.htm
- American Hospital Association (AHA): CMS releases fact sheet, FAQs on 340B claims data repository. AHA News Headline. Published August 27, 2026. https://www.aha.org/news/headline/2026-08-27-cms-releases-fact-sheet-faqs-340b-claims-data-repository
