Reference

CARC Denial Codes

Claim Adjustment Reason Codes explain why a claim was denied. Use this guide to understand each code, the best appeal strategy, and expected success rates for behavioral health.

9 soft denials

8 hard denials

54% avg overturn

CO-4SoftCoding

overturn85%

Procedure code inconsistent with modifier used or required modifier missing

Strategy

Correct & resubmit

Notes

Check modifier requirements. Common: missing -25 on E/M with procedure, wrong laterality modifier.

CO-11SoftCoding

overturn80%

Diagnosis inconsistent with the procedure

Strategy

Correct & resubmit

Notes

ICD-10 does not support the CPT billed. Review medical necessity linkage. May need more specific diagnosis.

CO-16SoftCoding

overturn90%

Claim lacks information or has submission/billing error(s)

Strategy

Correct & resubmit

Notes

Most common soft denial. Check RARC for the specific missing field or formatting issue.

CO-18SoftDuplicate

overturn70%

Exact duplicate claim/service

Strategy

Verify & resubmit

Notes

Verify not a true duplicate. If distinct service, resubmit with corrected frequency code (7 or 8).

CO-22SoftCOB

overturn65%

Care may be covered by another payer per coordination of benefits

Strategy

Verify & resubmit

Notes

COB issue. Verify primary/secondary insurance order. Include EOB from primary when billing secondary.

CO-27HardEligibility

overturn15%

Expenses incurred after coverage terminated

Strategy

Write off

Notes

Check for retroactive coverage or COBRA. Low overturn unless DOS was near coverage end date.

CO-29HardFiling

overturn10%

Time limit for filing has expired

Strategy

Write off

Notes

Only appeal with proof of timely original submission — clearinghouse receipt or tracking number.

CO-50HardNecessity

overturn55%

Not deemed medically necessary by the payer

Strategy

Formal appeal

Notes

Requires clinical documentation. Reference payer policy, AMA guidelines, peer-reviewed literature.

CO-96HardNon-covered

overturn20%

Non-covered charge(s)

Strategy

Write off

Notes

Service excluded from plan. Check RARC for specifics. Low success unless plan interpretation is wrong.

CO-97SoftCoding

overturn60%

Benefit included in payment for another service

Strategy

Correct & resubmit

Notes

Bundling issue. Check CCI edits. May need modifier -59 or X modifiers to unbundle.

CO-109SoftEligibility

overturn70%

Claim not covered by this payer/contractor

Strategy

Verify & resubmit

Notes

Wrong payer. Verify correct insurance and resubmit to appropriate payer.

CO-119HardLimit

overturn30%

Benefit maximum for this time period has been reached

Strategy

Formal appeal

Notes

Visit/dollar limit exceeded. Appeal if medically necessary — Mental Health Parity Act may apply.

CO-151HardNecessity

overturn50%

Information submitted does not support this many services

Strategy

Formal appeal

Notes

Frequency dispute. Appeal with clinical justification for the number of units or visits.

CO-197HardAuth

overturn40%

Precertification/authorization absent

Strategy

Retroactive auth

Notes

Attempt retroactive authorization. Otherwise appeal with proof of existing auth or that service type doesn't require it.

CO-204HardNon-covered

overturn15%

Service not covered under patient's current benefit plan

Strategy

Write off

Notes

Benefit exclusion. Review plan documents. Low overturn unless parity laws apply.

CO-236SoftCoding

overturn75%

Procedure/modifier combination not compatible with another already adjudicated

Strategy

Correct & resubmit

Notes

Modifier conflict. Review NCCI edits and ensure proper modifier application.

CO-252SoftCoding

overturn85%

Attachment/documentation required to adjudicate this claim

Strategy

Correct & resubmit

Notes

Missing documentation. Submit requested records. High overturn when docs are provided.

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