Reviewed Sep 20, 2026 · maintained by Erin Rose · general reference, not legal advice
What the remit says
CO-16 — “Claim/service lacks information or has submission/billing error(s).”
Usually with: M119 “Missing/incomplete/invalid/ deactivated/withdrawn National Drug Code (NDC)”; M123 “Missing/incomplete/invalid name, strength, or dosage of the drug furnished”.
Verbatim, X12 code lists 11/1/2025.
Why it lands on drug claims
The NDC goes on the drug line in the 837P loop 2410 LIN segment with the N4 qualifier, as 11 digits in 5-4-2 format with no hyphens, followed by the quantity and unit of measure (UN, ML, GR, F2, ME). A 10-digit NDC from the box has to be padded with a leading zero in the right segment — the packaging shows 4-4-2, 5-3-2 or 5-4-1 and the zero goes in the short segment. Pad the wrong segment and the NDC is "valid" but points at nothing: M119.
M119 also returns for a real NDC that is deactivated or withdrawn — a discontinued vial size, or a biosimilar's pre-launch NDC. The CMS quarterly NDC-HCPCS crosswalk is the reference for which NDCs a J-code accepts in the current quarter.
Medicaid and Medicaid managed-care plans require the NDC on every physician-administered drug line for rebate reporting (the Deficit Reduction Act of 2005 made it a federal requirement), and most commercial payers now require it on specialty drugs. Medicare Part B does not require the NDC on most J-code lines, so the same claim format can pass Medicare and fail everyone else.
The fix
- Compare the NDC on the line to the vial actually used (the 10-digit package NDC) and rebuild it as 11 digits with the zero in the correct segment.
- Confirm the NDC is on the current quarter's CMS NDC-HCPCS crosswalk for that J-code; if the vial is discontinued, the crosswalk names the replacement.
- Check the quantity and unit of measure on the NDC segment: it is the amount in the package unit (mL for a solution), not the HCPCS billing units.
- Resubmit as a corrected claim. This is never an appeal.
What to attach
- Nothing on the first pass — this is a corrected claim
- If the payer rejects a correct NDC: the vial label and the crosswalk page listing the NDC under the J-code
Corrected claim or appeal?
Corrected claim, always. Rebuild the 11-digit NDC with the zero in the short segment, confirm it is on the current quarter's crosswalk for the J-code, fix the quantity and unit of measure, resubmit as frequency 7.
Medicare windows (redetermination 120 days, reconsideration 180 days, ALJ 60 days) and the commercial path are on the denials hub, cited to 42 CFR Part 405 Subpart I; the edits are CMS's NCCI tables.
Frequently asked
- The NDC is right off the box. Why M119?
- Because the box shows 10 digits and the claim needs 11. The missing zero belongs in whichever segment is short (4-4-2 → 0xxxx-xxxx-xx; 5-3-2 → xxxxx-0xxx-xx; 5-4-1 → xxxxx-xxxx-0x). Padding the wrong segment makes a different, nonexistent NDC.
- Does Medicare need the NDC on J-code lines?
- Not on most Part B claims, which is why a practice that bills Medicare cleanly gets CO-16/M119 from Medicaid and commercial payers on the same claim format. The NDC segment should be on every drug line regardless.
- What unit goes in the NDC quantity field?
- The package unit: milliliters of solution (ML), units for a vial of powder (UN), grams (GR). Not the J-code billing units. A 100 mg/10 mL vial given in full is 10 ML on the NDC segment and, for a per-1-mg code, 100 billing units on the line.
Related references
The NDC, quantity and unit on every drug line
Claim Check carries the 11-digit NDC and package quantity for the vial you used on the drug line, in the format Medicaid and commercial payers reject when it is missing.
Open Claim CheckSources & how this is maintained
- Computed on this page
- Nothing — this denial has no table fact; the code text is verbatim X12. Edits vintage Q3 2026.
- Authored
- The 10-to-11-digit padding trap, deactivated NDCs, and why the same claim passes Medicare and fails Medicaid.
- Corrections
- Send one with the remit line.