What is CARC?
Also called: claim adjustment reason code · CO-45 · CO-16
The group code is the operational fork. CO means the provider absorbs it and may not bill the patient. PR means the balance moves to patient responsibility. Posting a CO adjustment as PR is a compliance problem, not a clerical one.
CARCs are frequently qualified by a RARC that carries the specific detail. CO-16 in particular is nearly meaningless on its own — it says information is missing, and only the accompanying RARC says what.
Where Vizora handles this
Primary sources
Where "CARC" is defined by the bodies that set the rules, rather than by us.
- Claim Adjustment Reason Codes (CARC) (opens in a new tab)
X12 — The authoritative, maintained CARC list. Our denial code lookup explains these in plain English; X12 is where the canonical definitions live.
- Remittance Advice Remark Codes (RARC) (opens in a new tab)
X12 — The remark codes that qualify a CARC on an ERA. Reading the RARC is usually what tells you whether a denial is appealable.
Last reviewed August 20, 2026
Related terms
RARC
A remittance advice remark code supplements a CARC with the specific reason behind an adjustment. Where a CARC says information is missing, the RARC says which information. Reading the RARC is usually what determines whether a denial is correctable, appealable, or genuinely final.
ERA
An electronic remittance advice, transmitted as an X12 835 file, is the payer's electronic explanation of how a claim was adjudicated. It reports what was allowed, what was paid, what was adjusted and why — using CARC and RARC codes — and it drives automated payment posting.
Denial
A denial is a claim the payer adjudicated and refused to pay. It differs from a rejection, which never entered adjudication. That distinction determines your remedy: a rejected claim is corrected and resubmitted, while a denied claim must be appealed within the payer's deadline.
Contractual Adjustment
A contractual adjustment is the difference between a provider's billed charge and the contracted allowed amount with that payer. It is not a loss and not collectible from the patient — it is the discount agreed to in the contract, and it must be recorded separately from write-offs.
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