Scanning sources…acquiring signal · establishing uplink
~375
Claim Adjustment Reason Codes (X12)
~1,200
Remittance Advice Remark Codes (CMS)
5
CO · PR · OA · PI · CR
4
ACA §1104 mandated
3×/yr
Mar 1 · Jul 1 · Nov 1
16
Missing info / submission error
835 Segment Anatomy
Where CARCs and RARCs live inside the v5010X221A1 Health Care Claim Payment/AdviceCAS
Service LineCARC + Group Code (CAGC) + adjustment amount
LQ
Service LineRARC (supplemental explanation or Alert)
MIA
Claim · InpatientRARC at claim level (institutional inpatient)
MOA
Claim · Outpatient / ProfessionalRARC at claim level (institutional outpatient & professional)
Per HIPAA, all payers must use X12-maintained CARCs + CMS-maintained RARCs — no proprietary codes on the 835. A RARC is mandatory with CARCs 16, 17, 96, 125, and A1.
Claim Adjustment Group Codes (CAGC)
The 2-letter prefix on every CARC — determines who is financially responsibleCO
Contractual Obligation
Provider write-off. Never billable to the patient under contract or participation.
PR
Patient Responsibility
Deductible, copay, coinsurance, or non-covered amount the patient owes.
OA
Other Adjustment
Neither provider nor patient — typically coordination-of-benefits rebalancing.
PI
NON-MCRPayer Initiated
Payer-initiated reduction (commercial only — NOT used by Medicare per IOM Pub 100-04 Ch. 22).
CR
Correction / Reversal
Used when the payer reverses or corrects a previously posted payment.
Denial Taxonomy
Every CARC maps into one of ten operational categoriesEligibility & Coverage
CARCs
Typical RARCs
Member not eligible on DOS, coverage terminated, non-covered benefit category.
Prior Authorization & Referral
CARCs
Typical RARCs
Auth required and missing, expired, or mismatched to code/provider/DOS.
Medical Necessity
CARCs
Typical RARCs
NCD/LCD/InterQual/MCG criteria not met. Appeal ladder branches on paired RARC (e.g., N386 = NCD-driven).
Coding & Modifier
CARCs
Typical RARCs
CPT/HCPCS vs. POS / diagnosis / modifier mismatch; NCCI PTP and MUE edit failures.
Missing Info / Submission Error
CARCs
Typical RARCs
RARC is MANDATORY with CARCs 16, 17, 96, 125, A1 — read the RARC to find the specific data element.
Duplicate & Frequency
CARCs
Typical RARCs
Exact duplicate on claim-line match; frequency limits exceeded per payer policy.
Coordination of Benefits
CARCs
Typical RARCs
Another payer is primary, or this payer is not the correct payer for the claim.
Timely Filing & Deadline
CARCs
Typical RARCs
Filing limit varies 90d–1yr. Exceptions: retro eligibility, delayed primary payer, state prompt-pay laws.
Bundling / NCCI / MUE
CARCs
Typical RARCs
Service included in another payment; units exceed NCCI MUE; NCCI-associated modifier may override.
Contractual / Fee Schedule
CARCs
Typical RARCs
Write-off to allowed amount; benefit limits exhausted; multi-procedure / bilateral / assistant surgeon reductions.
Top-30 CARC Payer Cross-Walk
Usage intensity across Medicare FFS / MA / Medicaid / top commercial payers. ● heavy · ● occasional · ○ rare / not used| CARC | Grp | Description | Typical RARC | MCR FFS | MCR MA | Medicaid | UHC | Anthem | Aetna | Cigna | Humana | Centene | Molina |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | PR | Deductible amount | — | ||||||||||
| 2 | PR | Coinsurance amount | — | ||||||||||
| 3 | PR | Copayment amount | — | ||||||||||
| 4 | CO | Procedure inconsistent with modifier | M77 | ||||||||||
| 5 | CO | Procedure inconsistent with place of service | M77 | ||||||||||
| 11 | CO | Diagnosis inconsistent with procedure | M51 | ||||||||||
| 15 | CO | Authorization number missing / invalid | N54 | ||||||||||
| 16 | CO | Missing information / submission error | N56 · N130 · N522 | ||||||||||
| 18 | CO | Exact duplicate claim / service | N111 | ||||||||||
| 22 | OA | Another payer is primary (COB) | MA04 · N4 | ||||||||||
| 27 | CO | Expenses after coverage terminated | N30 | ||||||||||
| 29 | CO | Timely filing limit expired | N211 | ||||||||||
| 45 | CO | Charge exceeds fee schedule / allowed | N381 | ||||||||||
| 50 | CO | Non-covered — not medically necessary | N386 · M25 | ||||||||||
| 55 | CO | Experimental / investigational | M86 | ||||||||||
| 59 | CO | Processed per multiple surgical reduction rules | — | ||||||||||
| 96 | CO | Non-covered charge — RARC required | (any N/M) | ||||||||||
| 97 | CO | Service bundled into separately paid procedure | M15 · M80 | ||||||||||
| 109 | CO/OA | Not covered by this payer / contractor | N418 | ||||||||||
| 119 | CO | Benefit maximum met for this period | N362 | ||||||||||
| 125 | CO | Submission/billing error(s) — RARC required | (any N/M) | ||||||||||
| 150 | CO | Documentation does not support level of service | N657 | ||||||||||
| 151 | CO | Documentation does not support frequency | N435 | ||||||||||
| 167 | CO | Diagnosis not covered | M51 | ||||||||||
| 177 | PR | Patient has not met required eligibility | N30 | ||||||||||
| 197 | CO | Precertification / authorization absent | N704 | ||||||||||
| 198 | CO | Precertification exceeded | N704 | ||||||||||
| 204 | PR | Service not covered under current benefit plan | N216 | ||||||||||
| 234 | CO | Procedure is not paid separately | M15 | ||||||||||
| 236 | CO | Procedure/modifier NCCI-incompatible | M20 |
Usage intensity is informed by public MAC and payer companion guides, state Medicaid EOB crosswalks, and CAQH CORE 360 Code Combinations. Individual payer adjudication may deviate per contract or state mandate.
CAQH CORE 360 Business Scenarios
ACA §1104 mandates all health plans use CORE-approved CARC/RARC/CAGC combinations for these four scenariosAdditional Information Required — Missing/Invalid/Incomplete Documentation
Billing provider or a prior payer must submit supporting documentation.
Additional Information Required — Missing/Invalid/Incomplete Data on Claim
Claim (837) or D.0 is missing or has invalid data elements.
Billed Service Not Covered by Health Plan
The service or benefit is excluded from the member's plan.
Benefit for Billed Service Not Separately Payable
Service is bundled, included, or otherwise not paid separately.
The Code Combination List is refreshed by CAQH CORE after each WPC/X12 publication and after its biennial market-based review. Medicare MACs implement the combinations via recurring CMS Change Requests (see most recent: CR 13303 → R12191CP).
Payer-Specific Behavior Notes
HIPAA mandates the same code set, but each payer's 835 companion guide documents its own usage patternsCO · PR · OA only (PI not used per IOM Pub 100-04 Ch. 22)
CMS issues recurring CRs after each WPC/X12 cycle. CGS, First Coast (Novitas), Palmetto, NGS, WPS each publish a public 835 Companion Guide v7.x. MREP and PC Print software refresh quarterly.
All 5 group codes
CMS-4201-F parity means MA cannot deny below FFS; CARCs 197/198 (precert) are heavy on MA where they are rare on FFS. 2026 UHC Admin Guide removed PA for select cardiology/radiology — expect a drop in CARC 197.
All 5 group codes; state-specific EOB crosswalks
TMHP (Texas): 5-char EOB codes with public 835 EOB Crosswalk Table. eMedNY (NY): CAR/Remark crosswalk via eMedNY HIPAA Support → Crosswalks. Maryland MMIS: companion guide notes standard CARC/RARC replace legacy EOB codes.
All 5 group codes
835 Companion Guide v4.0 (Apr 2025) covers UHC Community Plan + Commercial. Most denials flow through Optum clearinghouse. Optum PA integration via Availity Payer Space.
All 5 group codes
InterQual-driven UM; eviCore specialty PA routing. FHIR Patient Access + Provider Directory APIs live. Monthly TiC MRF publication.
All 5 group codes
Clinical Policy Bulletins (CPBs) drive CARC 50/167 denials. Electronic PA expansion mandated via Availity in multiple states.
All 5 group codes
29th Edition MCG Care Guidelines (2025–2026). Multi-procedure reductions (CARC 59) standard: major at 100%, subsequent at 50%. TiC MRF files up to 1 TB.
All 5 group codes
Humana Data Exchange API hub. Transition Period Billing policy mitigates CARC 27 during plan switches for active treatment.
All 5 group codes
Largest Medicaid MCO. State-specific PA and billing manuals drive heavy CARC 197/109 traffic.
Maintenance Cadence
WPC/X12 publishes 3× per year; CMS issues recurring CRs; CAQH CORE refreshes on the same rhythmCARC/RARC list updated; CMS CR issues ~Nov with Jan implementation.
MACs complete MREP / PC Print refresh; deactivations take effect.
CARC/RARC list updated; CAQH CORE 360 Code Combination List refresh.
CARC/RARC list updated; synchronized RARC/CARC release cycle.
Biennial market-based review adds new code combinations per ACA §1104.
Connections
How CARC/RARC ties back to the four anchor healthcare analysesMedicare Intelligence
Medicare contractors use only CO/PR/OA. MAC recurring-update CR cadence drives MREP/PC Print refreshes.
Availity (Payer Connectivity)
Availity normalizes the 835 across 2,000+ payers; the denial-management module triages by CARC/RARC and enforces CAQH CORE 360 compliance.
Medical Necessity Denials
CARC 50 & 167 are the canonical medical-necessity denials. Appeal ladder branches on paired RARC (e.g. N386 = NCD-driven denial).
TandemStride Care Management
Group Code determines patient-facing balance. Care-management coordinators script follow-ups differently for CO (provider) vs. PR (patient).
References
Canonical sources for CARC, RARC, and 835 payer guidance