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CO-211 Denial Code: NDC Not Eligible for Rebate

CO-211 means the National Drug Code billed is not eligible for rebate and is therefore not covered. It is most often seen with Medicaid, which generally covers drugs only from manufacturers participating in the federal drug rebate program.

Quick facts

Code
CO-211 (CARC 211)
Status
Active In use since July 9, 2007.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The provider absorbs the cost. The drug is not covered because its NDC is not rebate-eligible, and the amount generally cannot be billed to the patient without a valid advance agreement allowed by the program.
  • PR (Patient Responsibility): Occasionally used where plan or program rules allow a non-covered drug to be the patient's responsibility, typically only with prior notice.
Official description
National Drug Codes (NDC) not eligible for rebate, are not covered.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-211 means

CARC 211 says National Drug Codes (NDC) not eligible for rebate are not covered. It applies to drug claims where the specific NDC, the 11-digit code identifying the manufacturer, product, and package, is not part of a rebate arrangement the payer relies on.

This comes up most with Medicaid, where coverage of physician-administered and outpatient drugs is generally tied to the manufacturer’s participation in the federal drug rebate program. Two products with the same active ingredient and the same HCPCS code (for example a J-code) can have different NDCs, and only one may be rebate-eligible. The HCPCS code describes the drug; the NDC identifies exactly which product was used, and that is what triggered the denial.

Common causes

  • Non-participating manufacturer: the product came from a labeler without a rebate agreement.
  • Terminated or inactive NDC on the date of service.
  • Repackaged or relabeled product with a different NDC from the original manufacturer’s.
  • Purchasing switch: the wholesaler substituted a different product and the claim carried the new NDC.
  • Wrong NDC entered, for example the NDC of a similar product rather than the vial actually used.

How to fix it

  1. Confirm the NDC on the claim matches the package actually administered (check the vial, invoice, and administration record).
  2. Check the payer’s drug file or the state Medicaid NDC list for the date of service.
  3. If the claim had the wrong NDC, correct it and send a corrected claim (frequency code 7). On a CMS-1500, the NDC typically goes in the shaded area of box 24 with the N4 qualifier, unit qualifier, and quantity.
  4. If the NDC was correct but not rebate-eligible, the denial is generally valid. Ask the payer whether an exception or prior authorization pathway exists for that product.
  5. Do not bill the patient under the CO group unless the program explicitly permits it with prior notice.

How to prevent it

  • Screen NDCs against the state Medicaid drug file before adding a product to inventory.
  • Tell purchasing and your wholesaler to avoid automatic substitutions for drugs you bill to Medicaid.
  • Record the NDC at administration, not from a default in the charge master.
  • Re-check high-cost drugs periodically, because NDC status can change.
  • Validate NDC format and qualifiers on drug lines before submission.

Specialty notes

Oncology, infusion, and other practices that buy and bill physician-administered drugs see this code most. For pharmacy claims billed through NCPDP, rebate-related rejections usually come back as pharmacy reject codes at the point of sale rather than on an 835.

Remark codes that may appear with CO-211

  • M119 (Missing/incomplete/invalid/ deactivated/withdrawn National Drug Code (NDC).): The NDC is also missing, invalid, deactivated, or withdrawn, which can overlap with rebate ineligibility.
  • N130 (Consult plan benefit documents/guidelines for information about restrictions for this service.): Points to program or plan documents on drug coverage.
  • PR-204 (This service/equipment/drug is not covered under the patient's current benefit plan): The drug or service is not covered by the patient's benefit plan for a reason other than rebate status.
  • CO-96 (Non-covered charge(s).): A general non-covered charge, used when no more specific reason applies.
  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Used when the NDC or related drug data is missing or invalid on the claim.

CO-211 FAQ

Why does Medicaid deny drugs with CO-211?

Medicaid programs generally cover outpatient drugs only when the manufacturer has a rebate agreement in place. If the specific NDC is not covered under that program, the drug line can be denied with CARC 211.

Can I just change the NDC on the claim?

Only to the NDC actually dispensed or administered. Billing a different NDC than the one used is inaccurate. If you used a non-rebate NDC, future purchasing should switch to a rebate-eligible product.

How do I check whether an NDC is rebate-eligible?

Check your state Medicaid program's drug file or the CMS drug rebate product data before purchasing or billing. Your pharmacy or wholesaler can often flag non-rebate products.