CO-211 is a drug denial you will almost always see from a Medicaid plan. It means the National Drug Code on the claim belongs to a product that does not qualify for the Medicaid drug rebate, so the plan will not cover it. The drug may be fine clinically. The problem is who made or packaged it, or which NDC your system sent. (Primary source: X12 Claim Adjustment Reason Codes)
In brief: CARC 211 reads “National Drug Codes (NDC) not eligible for rebate, are not covered.” Check the NDC on the claim against the vial you actually gave. If the claim used the wrong NDC, send a corrected claim with the right one. If the vial itself is from a non-rebate labeler, the charge is a contract write-off, and purchasing needs to change.
Part of our denial codes library. Written by Manikandan J, CPC, CRCR, who has worked Medicaid physician-administered drug denials for clinics and infusion centers. Published 23 October 2026. Last updated: 23 October 2026. Code wording quoted word for word from X12.
Why Medicaid ties coverage to rebates
The Medicaid Drug Rebate Program is a federal program in which drug makers sign a rebate agreement with CMS so that states can cover their outpatient drugs. A labeler without an agreement, or a product left off the program, is not covered. MACPAC, the advisory body that reports to Congress on Medicaid, explains the program on its prescription drug policy page.
The labeler is the company named in the first segment of the NDC. It can be the maker or a repackager. That is why two vials of the same drug can get different answers.
| CARC 211 at a glance | Detail |
|---|---|
| Official text | “National Drug Codes (NDC) not eligible for rebate, are not covered.” |
| Start date | 07/09/2007 |
| Usual payer | State Medicaid and Medicaid managed care |
| Patient billing | No, under group code CO |
Four ways a clinic ends up with CO-211
- A default NDC in the charge master. The system sends the same NDC for every J-code, even after the supplier changed.
- A repackaged vial. Some repackagers are not in the program, so their NDC is not covered.
- A product dropped from the program. A labeler can end its agreement, and old stock can still be on the shelf.
- A typo or format slip. An 11-digit NDC built from a 10-digit label can point to a different product, such as a different package size.
Example scenario (fictional names), part 1
CO-211 Denial Example: What Happened
Rosa Delgado handles billing for Pinecrest Family Health, a rural clinic with two doctors. A Medicaid patient received a medroxyprogesterone injection, J1050, during a routine visit.
The state Medicaid plan returned CAS*CO*211 on the drug line. The office visit on the same claim paid.
Rosa looked up the NDC on the claim. It belonged to a repackager the clinic had stopped buying from last spring.
Was the vial wrong, or was the claim wrong? Keep reading, or jump to how the CO-211 denial was resolved.
How to fix a CO-211 denial
- Match the vial. Pull the lot log or the medication administration record and read the NDC from the actual package used.
- Look up the labeler. Check your state Medicaid NDC list or the CMS rebate product data to see if that NDC is covered.
- If the claim NDC was wrong, send a corrected claim. On the CMS-1500 the NDC goes in the shaded part of Box 24A with the N4 qualifier and the unit. On the UB-04 it goes in FL 43 next to the drug line.
- If the vial was not rebate eligible, the line is a write-off under CO. Tell purchasing so the next order comes from a covered labeler.
Other drug remarks may come with it, such as M119, “Missing/incomplete/invalid/ deactivated/withdrawn National Drug Code (NDC).” That one points to a bad or retired NDC rather than a rebate issue.
Example scenario (fictional names), part 2
How the CO-211 Denial Was Resolved
The clinic’s lot log showed the injection came from a current, rebate-eligible labeler. The charge master still held the old repackager’s NDC for J1050.
Fix: Rosa sent a corrected claim with frequency code 7 and the right NDC in the shaded part of Box 24A, using the N4 qualifier and UN1. She also asked the office manager to update the J1050 entry in the charge master.
Outcome: Medicaid paid the drug line on the corrected claim. A monthly check of drug NDCs against invoices was added to the clinic’s routine.
Names and details are illustrative; no real patient data.
- Box 24A shaded / FL 43: old repackager NDC replaced with the NDC on the vial used, as N4 + 11 digits + UN1 (placeholder NDCs).
- Box 22 / FL 4 + FL 64: frequency code 7 with the original claim number (type of bill 0137).
- Box 24D / FL 44: J1050 with Z30.013 (entered as Z30013) is unchanged.
CO-211 vs other drug and NDC codes
| Code | What it points to | Typical fix |
|---|---|---|
| CO-211 | NDC not rebate eligible | Right NDC or write-off |
| CO-16 + M119 | NDC missing or invalid | Add a valid NDC |
| CO-4 | Modifier issue | Correct the modifier |
| CO-96 | Non-covered charge | Check the benefit |
| CO-B7 | Provider not certified for the service | Check enrollment |
For a refresher on code sets, see what CPT codes are. The NUCC 1500 claim form manual explains the shaded Box 24 NDC format.
Keeping NDCs clean
- Update the charge master the day a new supplier’s stock arrives.
- Scan or key the NDC from the vial at the point of care when your system allows it.
- Run a quarterly report of CO-211 lines by labeler. A pattern points straight at purchasing.
FAQ
What does CO-211 mean?
The payer says the NDC billed is not eligible for the Medicaid drug rebate, so the drug is not covered.
Can I bill the patient for CO-211?
No. Group code CO makes it the provider’s responsibility.
Where does the NDC go on the CMS-1500?
In the shaded area of Box 24A, starting with the N4 qualifier, then the 11-digit NDC and the unit.
Where does the NDC go on the UB-04?
In FL 43, the description field, on the same line as the drug’s revenue code.
Is CO-211 the same as an invalid NDC?
No. An invalid or missing NDC usually comes with remark M119. CO-211 means the NDC is valid but not covered under the rebate rules.
Sources
How we checked: each code quote on this page was matched word for word with the X12 CARC and RARC lists on 23 October 2026.
- X12, Claim Adjustment Reason Codes (CARC 211). Accessed 23 Oct 2026.
- X12, Remittance Advice Remark Codes (M119). Accessed 23 Oct 2026.
- MACPAC, Prescription drugs in Medicaid. Accessed 23 Oct 2026.
- NUCC, 1500 Claim Form Reference Instruction Manual. Accessed 23 Oct 2026.
Last updated: 23 October 2026 · Educational content; not legal advice.