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M23 Remark Code: Missing Invoice

M23 means the payer needed an invoice to process the line, typically to price an item without a fixed fee, and no invoice was submitted.

Quick facts

Code
M23 (RARC M23)
Status
Active In use since January 1, 1997; last modified August 1, 2005.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The line is unpaid until the invoice is received. The patient is not responsible for the missing document.
Official description
Missing invoice.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M23 means

Most services have a fee schedule amount, but some do not. When an item is billed under a miscellaneous or not otherwise classified code, or when the payer prices it at cost, the payer needs the invoice to determine the allowed amount. M23 says that invoice never arrived.

It generally comes with CARC 16 or 252. Some payers pend the claim and then deny it if the invoice does not follow within their time window.

Common causes

  • A not otherwise classified code was billed without an attachment.
  • The electronic claim did not indicate that an attachment was being sent.
  • The invoice was sent but not linked to the claim with the right control number.
  • The payer’s policy requires invoices above a certain charge, and the billing team was unaware.

How to fix it

  1. Get a clear copy of the invoice from purchasing or the vendor, showing net cost.
  2. Send it through the payer’s attachment channel, referencing the claim number or attachment control number.
  3. Resubmit if required. Some payers accept the invoice as additional documentation; others want a corrected claim with resubmission code 7 and the attachment.
  4. Add a description of the item in the claim narrative (box 19 or the electronic note field) when the code is unlisted.

How to prevent it

Flag every code that your payers price by invoice, and require an attachment before those claims leave. See the CO-16 guide for more on documentation-driven denials.

Codes that may appear with M23

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Information needed for adjudication is missing.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment or other documentation is required to adjudicate the claim.
  • N354 (Incomplete/invalid invoice.): An invoice was received but is incomplete or invalid.
  • M130 (Missing invoice or statement certifying the actual cost of the lens, less discounts, and/or the type of intraocular lens used.): Specific to the invoice or cost statement for an intraocular lens.
  • N649 (Payment based on invoice.): Shows that payment was based on the invoice once one is supplied.

M23 FAQ

Which services usually need an invoice?

Items billed with not otherwise classified codes, miscellaneous supplies, some drugs, and implants or equipment that the payer prices by cost.

What should the invoice show?

The manufacturer or vendor, item description, quantity, and the actual cost net of discounts. Payers may also want the patient name or claim number written on it.

How do I send the invoice?

Use the payer's attachment process, such as an electronic attachment with a matching control number, fax cover sheet, or portal upload.