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M123 Remark Code: Missing Drug Name, Strength, or Dose

M123 means the claim was missing, incomplete, or had invalid information about the name, strength, or dosage of the drug furnished. Payers need this detail to identify and price the drug, especially under not otherwise classified codes.

Quick facts

Code
M123 (RARC M123)
Status
Active In use since January 1, 1997; last modified February 28, 2003.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The drug line was not paid due to missing drug detail. The provider corrects and resubmits; the patient is not billed.
Official description
Missing/incomplete/invalid name, strength, or dosage of the drug furnished.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M123 means

A HCPCS code for a drug often describes a specific product and a unit, but not always. When you bill a drug under a not otherwise classified code, or when the payer needs to verify dosing, it relies on a description with the drug’s name, strength, and dosage administered. M123 tells you that description was absent, incomplete, or did not make sense.

The drug may be fully payable once the payer can identify it and calculate the amount.

Common causes

  • A not otherwise classified drug code billed without a narrative.
  • A narrative that lists the drug name but not the strength or amount given.
  • Description text truncated by the field length on the claim.
  • Units on the line that do not match the dose described.
  • A new drug without its own code yet, billed without enough detail.

How to fix it

  1. Get the details from the administration record: product name, strength per unit, total dose, and route.
  2. Add the description in the payer’s required field, along with the NDC if applicable.
  3. Check units so the billed units match the dose and the code’s unit definition.
  4. Resubmit, using frequency code 7 with the original claim number if it was adjudicated.
  5. Attach an invoice if the payer prices unlisted drugs from cost.

How to prevent it

  • Create drug master entries that automatically include name and strength in the claim narrative for unlisted codes.
  • Train staff to record total dose administered, not just vials used.
  • Validate unlisted-code lines with a Claims Validator before submission.

Codes that may appear with M123

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim lacks information, identified by M123 as the drug description.
  • M119 (Missing/incomplete/invalid/ deactivated/withdrawn National Drug Code (NDC).): The NDC itself was missing, invalid, or inactive.
  • N350 (Missing/incomplete/invalid description of service for a Not Otherwise Classified (NOC) code or for an Unlisted/By Report procedure.): The description for a not otherwise classified or unlisted code was missing.
  • M70 (Alert: The NDC code submitted for this service was translated to a HCPCS code for processing, but please continue to submit the NDC on future claims…): An alert that the NDC was translated to a HCPCS code for processing.

M123 FAQ

When do payers ask for drug name and dosage?

Most often when a drug is billed with a not otherwise classified HCPCS code, because the code alone does not identify the product.

Where does this information go?

In the claim note or line description fields of the electronic claim, or box 19 or the shaded area of box 24 on paper, following the payer's instructions.

Is the NDC enough?

Sometimes. Some payers want both the NDC and a text description with name, strength, and dose. Check the payer's requirements.