RARC

Definition

RARCs and CARCs travel together on an 835 but live in different segments: the CARC and its dollar amount sit in a CAS segment, while a remark code that applies to one service line sits in the LQ segment and one that applies to the whole claim sits in the MIA segment on an inpatient claim or the MOA segment on a non-inpatient one (CMS Medicare Claims Processing Manual, chapter 22, section 60.3, read 17 September 2026). X12 publishes the list as external code list 411 and, in its external code lists table, names CMS as the maintainer — the CARC list beside it is maintained by an X12 code maintenance group instead (checked 17 September 2026). CMS states the same from its own side: remark codes are maintained by CMS, but any health plan may use them where they apply. The list holds two kinds of code. Supplemental remark codes — the large majority, and what people mean by “RARC” without further qualification — add explanation to an adjustment a CARC has already described. Informational remark codes are prefaced “Alert:” and convey something about remittance processing; X12 states they are never related to a specific adjustment or CARC. The letter prefixes are historical rather than functional: M and MA codes carry start dates from 1997 onward and N codes from 2000 onward, and every payer draws on the same list. Code changes are not continuous either — CMS instructs its Medicare contractors to conduct code updates three times per year, at approximately March 1, July 1 and November 1, and notes that date discrepancies arise because the X12 site is itself updated three times a year (CMS Transmittal 13666, 25 March 2026). Four remark codes are worth knowing by sight: N382, a missing, incomplete or invalid patient identifier — correct the member ID or MBI and resubmit; MA130, which says the claim carried incomplete or invalid information, was not processed, and carries no appeal rights, so the route is a new corrected claim rather than an appeal; M76, a missing, incomplete or invalid diagnosis or condition; and M77, a place of service that is missing, incomplete, invalid or inappropriate for what was billed.

Common Misconceptions

RARCs alone are insufficient — they have to be read with the CARC beside them. The CARC says what the payer did (denied, adjusted, moved to patient responsibility) and, through its group code, who owes the balance; the remark code says why, or what was missing. The reverse trap is reading every remark code as a problem: informational codes prefaced “Alert:” are not tied to any adjustment at all, which is why CARC 16 and CARC A1 both call for a remark code that is not an Alert. The dependency runs hardest on A1: the claim-level denial you cannot work without its paired RARC is CO-A1, a container CARC that carries no reason of its own, so the remark code beside it holds every actionable detail.

Related Terms