RARC M123: Missing, Incomplete, or Invalid Name, Strength, or Dosage of the Drug
RARC M123 means the drug's name, strength, or dosage is missing, incomplete, or invalid on the claim — the payer cannot confirm what drug and how much was given. It rides with CO-16. The fix is supplying the full drug name, strength, and dosage (often in the line note or NDC detail) and resubmitting.
- Type
- Informational (supplemental)
- Usually paired with
- CO-16
- Fixable?
- Yes — always
- Typical fix
- Supply full drug name, strength, dosage; resubmit corrected claim
What does remark code M123 mean?
Official X12 text: "Missing/incomplete/invalid name, strength, or dosage of the drug furnished." The payer cannot confirm which drug was given or how much, because the descriptive detail — the drug name, its strength, or the dosage administered — is absent or incomplete. This is most common on unclassified and not-otherwise-classified drug codes that carry no identity on their own.
ERA mini-example: J3490 (unclassified drug) billed $210.00 denies with CO-16 and M123 because the line note did not state the drug name, strength, or amount given. Resubmitted with "drug name 40 mg, 2 units administered" in the 2400 note plus the NDC, the payer can price it and the line pays.
Which denial code does M123 come with?
Almost always CO-16, since the claim is missing information needed to adjudicate and is unprocessable. It very often rides with M119 when the NDC is also missing or invalid on the same drug line. Separate the two — NDC versus drug description — in the denial code lookup so you fill the right field.
How do you fix an M123 denial?
- Confirm the exact drug administered, its strength, and the dosage from the medication or infusion record.
- Enter the full drug name, strength, and dosage in the line-level note (box 19 or the 2400 NTE segment).
- Pair it with a valid NDC and quantity so the payer has both the identity and the amount.
- Submit a corrected claim and verify the descriptive detail actually transmitted, since some clearinghouses truncate long notes.
How do you prevent M123?
Build a required-note rule for every unclassified and NOC drug code so a claim cannot go out without the drug name, strength, and dosage populated. Pull the drug detail straight from the eMAR or infusion documentation at charge entry rather than reconstructing it later. Confirm your clearinghouse passes the full line note without truncation, and pair every drug line with both a valid NDC and quantity so M119 and M123 are prevented together.
Frequently asked questions
For unclassified or not-otherwise-classified drug codes (like J3490 or J9999), the payer cannot tell what was given from the HCPCS alone, so the drug name, strength, and dosage must be supplied in the line-level note (box 19 or the 2400 NTE segment) along with the NDC. M123 fires when that descriptive detail is blank or incomplete on a code that requires it.
M119 is about the NDC — the numeric drug identifier being missing or invalid. M123 is about the human-readable drug information — name, strength, and dosage. They travel together on drug claims because payers want both the code and the description, but they fail for different reasons, so fix each one on its own field.
Because unclassified and NOC drug codes carry no drug identity by design — they are placeholders. The payer relies entirely on the narrative you supply to price them. Bill one without the name, strength, and dosage in the note and there is nothing for the payer to adjudicate, so M123 is almost automatic. Always attach the full drug detail to these codes.
Sources & further reading
Reviewed by the ImmediCare Solutions RCM team
Certified billers and coders handling claims across 50+ specialties nationwide. This entry is reviewed against current payer policy and CMS rules. Last review: Jul 5, 2026.
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