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M79 Remark Code: Missing or Invalid Line Charge

M79 means the charge amount for a service was missing, incomplete, or invalid. The payer cannot price a line without a valid billed charge, so it is usually rejected under CO-16 until you correct box 24F and resubmit.

Quick facts

Code
M79 (RARC M79)
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 line was not paid because of a billing data error. The provider corrects it; the patient owes nothing for the rejected line.
Official description
Missing/incomplete/invalid charge.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M79 means

Payers need a billed charge on every line to calculate the allowed amount, apply “lesser of” pricing rules, and report adjustments. M79 says the charge was not usable. It might be absent, zero on a billable service, negative, malformed (extra decimals or characters), or inconsistent with the units on the line.

This is a line-level data problem and not a coverage judgement, so the service has not really been evaluated yet.

Common causes

  • A procedure missing from the charge master or fee schedule, so the system dropped in a blank or $0.00 charge.
  • Manual claim entry errors in box 24F.
  • A charge that did not scale when units were changed, or a split line where one half lost its charge.
  • Clearinghouse or file format issues that strip or misplace amounts.
  • Line charges that do not add up to the claim total, triggering validation on both.

How to fix it

  1. Find the rejected line and look at the charge exactly as sent in the 837 or on the claim form.
  2. Enter the correct charge from your fee schedule, multiplied appropriately for the units billed.
  3. Recalculate the claim total in box 28 so it matches the sum of lines.
  4. Resubmit. Send a new claim if it was rejected before processing, or a corrected claim with frequency code 7 if it was adjudicated.

How to prevent it

  • Audit your charge master when adding new services or annual code updates, so no billable code lacks a price.
  • Block claims with zero or blank charges on billable lines before submission.
  • Use a Claims Validator to confirm line charges and totals reconcile.

M79 is one of many information rejections covered in the CO-16 guide. If the claim never reached adjudication, rejection versus denial explains the resubmission difference.

Codes that may appear with M79

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim is missing information needed to adjudicate the line, specifically its charge.
  • M54 (Missing/incomplete/invalid total charges.): Refers to the total charges for the claim rather than an individual line charge.
  • M53 (Missing/incomplete/invalid days or units of service.): Points to missing or invalid units, which often breaks alongside charges when lines are built wrong.
  • MA130 (Your claim contains incomplete and/or invalid information, and no appeal rights are afforded because the claim is unprocessable.): Tells you the whole claim is unprocessable and must be submitted as a new claim.

M79 FAQ

Can I bill a service at zero dollars?

Some payers accept zero-charge lines for reporting-only codes, but most require a positive charge for billable services. A zero or blank charge on a billable line is a common M79 trigger.

Where is the line charge on the CMS-1500?

Box 24F. The total of all lines goes in box 28, and the two must agree.

Is M79 appealable?

It is a data error, so correct the charge and resubmit rather than appealing.