CO-211 denial code
National Drug Codes not eligible for rebate are not covered
How to fix it
Verify the NDC matches the product administered and check the plan's formulary.
How to prevent it
Validate NDCs against the plan formulary before administering high-cost drugs.
In practice
A practice administers a drug and bills using the NDC from a package it did not actually use. The number does not match the plan's rebate arrangements, and the claim returns CO-211.
Plans negotiate rebates with manufacturers at the level of the specific product package, so the identifier on the claim determines both coverage and price. A different manufacturer's equivalent product may not be covered at all.
Verify the identifier matches the package administered and check it against the plan's formulary. Where the covered product differs from the one stocked, the answer is a purchasing decision rather than a billing one.
What sits behind it
The identifier is package-specific rather than drug-specific, which surprises practices used to thinking in terms of the molecule. The same drug from two manufacturers, or in two package sizes, carries different numbers and can carry different coverage.
Formulary positions change on their own schedule, and a product covered last quarter can move. For high-cost drugs the check belongs before administration, since the exposure on a single claim can be substantial and there is no recovery once the drug is given.
Documenting the exact product administered, including the identifier from the package, is what makes accurate billing possible. Practices recording only the drug name reconstruct the identifier at billing time, which is where the mismatch enters.
Related codes
Terms used here — HCPCS · Medical Necessity · Prior Authorization
How we handle it — Medical Coding · Prior Authorization · Denial Management
Primary sources
The rules behind CO-211, at the bodies that publish them.
- Medicare Coverage Database (LCD/NCD) (opens in a new tab)
Centers for Medicare & Medicaid Services — Searchable national and local coverage determinations. The direct answer to whether a diagnosis supports medical necessity for a given procedure.
- Medicare Benefit Policy Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — What Medicare covers and under what conditions, as distinct from how a claim is processed. The starting point for any coverage or medical necessity question.
- Advance Beneficiary Notice of Noncoverage (ABN) (opens in a new tab)
Centers for Medicare & Medicaid Services — The form and the rules for issuing it. Whether a non-covered service can be billed to the patient usually turns on whether a valid ABN was obtained beforehand.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-211
Because it identifies the package rather than the drug, and plans negotiate rebates at that level. The same molecule from a different manufacturer or in a different package size carries a different identifier and can carry entirely different coverage.
By checking the identifier against the plan's formulary before administration rather than at billing. Once the drug is given there is no recovery, and a single denied biologic claim can outweigh a month of routine denial volume.
The identifier from the package actually used, not just the drug name. Practices recording only the name reconstruct the identifier at billing time, and that reconstruction is where mismatches enter.
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