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M50 Remark Code: Revenue Code Missing or Invalid

M50 means the payer found a revenue code on an institutional claim that is missing, incomplete, or invalid. Revenue codes identify the department or type of service on each line, so the line could not be processed.

Quick facts

Code
M50 (RARC M50)
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 is unpaid until the revenue code is corrected. The patient is not billed for the error.
Official description
Missing/incomplete/invalid revenue code(s).
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M50 means

Every line on a hospital or facility claim starts with a four-digit revenue code that tells the payer which cost center or type of service the charge belongs to: pharmacy, laboratory, room and board, therapy, and so on. M50 says the revenue code on a line was blank, malformed, or not valid for how it was used.

Because revenue codes drive pricing and edits, a bad one usually stops the line.

Common causes

  • A charge in the chargemaster is mapped to a retired or incorrect revenue code.
  • The revenue code is not allowed for the bill type, for example an inpatient-only code on an outpatient claim.
  • A revenue code that requires a HCPCS code was sent without one.
  • A three-digit code was sent without the leading zero.
  • The revenue code conflicts with the procedure or service billed.

How to fix it

  1. Check the line flagged and its revenue code against the NUBC list and payer rules.
  2. Correct the revenue code in form locator 42, adding any required HCPCS code.
  3. Fix the chargemaster entry so the error does not repeat.
  4. Resubmit as a new claim or adjustment, per the payer.

How to prevent it

Review the chargemaster at least annually for revenue code accuracy and pairing rules. A pre-submission Claims Validator check can flag revenue codes that do not fit the bill type. See claim rejection vs denial.

Codes that may appear with M50

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim is missing information or has a billing error.
  • CO-5 (The procedure code/type of bill is inconsistent with the place of service.): The revenue code is inconsistent with the bill type or place of service.
  • CO-199 (Revenue code and Procedure code do not match.): The revenue code and procedure code do not match.
  • M51 (Missing/incomplete/invalid procedure code(s).): The procedure code on the line is the problem instead.
  • MA30 (Missing/incomplete/invalid type of bill.): The type of bill is missing or invalid.
  • M20 (Missing/incomplete/invalid HCPCS.): The HCPCS code is missing or invalid.

M50 FAQ

Where are revenue codes on the UB-04?

In form locator 42, one per service line, with a description in form locator 43.

Why would a valid revenue code be rejected?

Because it is not allowed for the bill type, requires a HCPCS code that is missing, or does not match the service billed on the line.

Are revenue codes used on professional claims?

No. They are institutional claim elements. Professional claims use place of service and procedure codes instead.