CARC (Claim Adjustment Reason Code)
Claim Adjustment Reason Code
X12-maintained codes communicating why a claim or service line was paid differently than billed.
1 min read · Last reviewed May 23, 2026
At a glance
- Category
- Denials & Appeals
- Acronym for
- Claim Adjustment Reason Code
- Primary sources
- 2
- Workspace handoff
- denial workbench →
Where this comes up
This is denial-workbench territory. A remit posts with a CARC/RARC, the biller decides whether to rebill, appeal, or write off, and the appeal packet has to cite the chart, the order, and the payer's own policy language. Recurring patterns trace back to an upstream workflow gap.
Full definition
What it is in practice
CARCs appear on the 835 electronic remittance advice (ERA) and on paper EOBs. Each adjustment line carries a CARC, an adjustment group code (CO, OA, PI, PR), and a dollar amount. CMS uses CARCs to standardize denial reasons across payers.
How it shows up in your practice
Build a denial dashboard keyed on CARC. The top 10 CARCs typically explain 80% of revenue leakage. Pair every CARC with its RARC for context.
Sources
- CMS — Claim Adjustment Reason Codeshttps://x12.org/codes/claim-adjustment-reason-codes
- CMS — 835 Electronic Remittance Advicehttps://www.cms.gov/medicare/billing/electronic-billing-edi-transactions/electronic-billing-edi-transactions-process
Map your top CARCs in the Denial Workbench
Open denial workbench →Related terms
- Denials & AppealsRARC (Remittance Advice Remark Code)X12-maintained codes that supplement the CARC with additional information about a claim adjustment.
- Denials & AppealsDenial ManagementThe end-to-end workflow of identifying, categorizing, appealing, and preventing claim denials.
- Denials & Appeals835 Electronic Remittance Advice (ERA)The HIPAA-mandated electronic transaction by which payers communicate payment and adjustment information to providers.
- Denials & AppealsCO (Contractual Obligation)An X12 adjustment group code indicating the patient is not responsible because the amount is a contractual write-off.
- Denials & AppealsPR (Patient Responsibility)An X12 adjustment group code indicating the patient owes the amount (deductible, coinsurance, copay, or non-covered service).
D3rx is a healthcare-billing and compliance research aid maintained by D3rx Inc. Articles are drafted by an LLM (Anthropic Claude) against primary HHS, OCR, CMS, eCFR, NIST, and state-regulator publications, and reviewed for restraint and source fidelity by the D3rx team.
Reviewer status: a named credentialed reviewer (CHC, CHPC, or healthcare attorney) is being engaged. Until that engagement is finalized, this page does not claim credentialed review.
Related across the archive
- Glossary835 Electronic Remittance Advice (ERA)The HIPAA-mandated electronic transaction by which payers communicate payment and adjustment information to providers.
- GlossaryCO (Contractual Obligation)An X12 adjustment group code indicating the patient is not responsible because the amount is a contractual write-off.
- GlossaryDenial ManagementThe end-to-end workflow of identifying, categorizing, appealing, and preventing claim denials.
- GlossaryPR (Patient Responsibility)An X12 adjustment group code indicating the patient owes the amount (deductible, coinsurance, copay, or non-covered service).
- GlossaryRARC (Remittance Advice Remark Code)X12-maintained codes that supplement the CARC with additional information about a claim adjustment.
- GlossaryAppeal LetterThe written request to a payer to reconsider a denied or partially-paid claim.
- GlossaryCO-109 (Claim Not Covered by Payer)Contractual Obligation 109 — the claim is not covered by this payer/contractor.
- BillingHow to Appeal an Insurance Denial: Step-by-Step GuideClaim denied? Step-by-step appeal process with payer deadlines, denial code fixes, appeal letter template, and escalation options.
This glossary entry is a research aid for billing and compliance staff. It does not provide legal, medical, or financial advice and does not replace counsel. References cited link to primary sources at HHS, OCR, CMS, eCFR, NIST, and the relevant payer or industry body.