Reference
Denial codes, with the fix beside each.
Claim adjustment reason codes (CARC) grouped by what went wrong: the claim, the coverage, or the bundling. The remark codes (RARC) on the remittance say which field; this page says what to do.
The claim itself
Claim adjustment reason codes (CARC) that mean the claim, not the care, was wrong. Group CO puts the cost on the practice; PR on the patient.
| Code | Meaning | Usual cause | What to do |
|---|---|---|---|
CO-16 | Claim lacks information or has a submission or billing error | A required field is missing or wrong; the remark code (RARC) says which, for example M76 (diagnosis) or N29 (documentation). | Read the RARC, correct the field, resubmit as a corrected claim. |
CO-4 | Procedure code is inconsistent with the modifier used, or a required modifier is missing | Laterality, 25, 26/TC or an X modifier is missing or wrong. | Add or correct the modifier and resubmit. |
CO-11 | Diagnosis is inconsistent with the procedure | The diagnosis does not support the procedure, or an unspecified code was used where a specific one exists. | Check the payer's coverage policy for the procedure; recode from the note. |
CO-18 | Exact duplicate claim or service | The claim was sent twice, or the same code twice without a modifier. | Do not resubmit; if the second line was a distinct service, append 76, 77 or 59 and send a corrected claim. |
CO-29 | The time limit for filing has expired | The claim reached the payer after its filing deadline (often 90 to 365 days). | Appeal with proof of timely filing if you have it; otherwise write off. Fix the queue that let it age. |
CO-22 | This care may be covered by another payer per coordination of benefits | The payer believes it is secondary. | Bill the primary first, then send with the primary's EOB. |
CO-27 | Expenses incurred after coverage terminated | The policy ended before the date of service. | Verify eligibility; bill the patient's current plan or the patient. |
PR-31 | Patient cannot be identified as our insured | Wrong ID, name spelling or date of birth. | Confirm the card and resubmit. |
CO-109 | Claim not covered by this payer or contractor | Wrong payer, wrong plan, or a carve-out (for example behavioral health) | Send to the right payer named on the card or in the EOB. |
CO-252 | An attachment or other documentation is required to adjudicate | The payer wants records, an invoice or an operative note. | Send what the RARC names, through the payer's portal, within its window. |
Coverage and necessity
The payer accepted the claim and decided not to pay for the care.
| Code | Meaning | Usual cause | What to do |
|---|---|---|---|
CO-50 | Not deemed a medical necessity by the payer | The diagnosis or frequency does not meet the coverage policy (LCD or plan policy). | Appeal with the note and the policy criteria met; if an ABN was signed, bill the patient with GA. |
CO-96 | Non-covered charge | The service is excluded by the plan. | Check the RARC; bill the patient where the contract allows, or write off. |
CO-197 | Precertification, authorization or notification absent | No prior authorization on file for a service that needs one. | Request retro-authorization where the payer allows it; otherwise appeal with the clinical urgency. Fix the scheduling step that skipped it. |
CO-15 | Authorization number missing, invalid or does not apply | The number is wrong, expired, or for a different code or date. | Match the authorization to the claim and resubmit. |
CO-198 | Precertification exceeded | More units or visits than the authorization allowed. | Request an extension; bill the covered units. |
CO-167 | Diagnosis not covered | The plan excludes this diagnosis for this service. | Recode only if the note supports it; otherwise appeal or bill the patient per contract. |
CO-204 | Service not covered under the patient's current benefit plan | A benefit the plan does not include (for example refraction). | Bill the patient; collect at the visit next time. |
CO-119 | Benefit maximum for this period has been reached | Visit or dollar cap (therapy, chiropractic, dental). | Bill the patient after confirming the cap; track caps at scheduling. |
CO-151 | Payer deems the information does not support this many or this frequency of services | Units exceed the medically unlikely edit or a frequency limit. | Check the MUE; appeal with documentation if the units were correct. |
Bundling and provider status
Paid, but folded into something else, or not payable by this provider here.
| Code | Meaning | Usual cause | What to do |
|---|---|---|---|
CO-97 | The benefit for this service is included in the payment for another service already adjudicated | NCCI bundling, or a visit inside a global period. | If the services were distinct, corrected claim with 59, an X modifier, 24 or 25 as the case fits; otherwise accept. |
CO-236 | This procedure or procedure/modifier combination is not compatible with another procedure on the same day | An NCCI edit with no modifier allowed, or a modifier that the edit does not accept. | Read the edit's modifier indicator; if it is 0, the pair is never payable together. |
CO-234 | This procedure is not paid separately | A status-B code, bundled by policy. | Accept; do not bill the patient. |
CO-B15 | This service requires a qualifying service to be received and covered | An add-on code without its primary on the claim, or the primary was denied. | Resubmit with the primary code; appeal the primary first if it was denied. |
CO-170 | Payment denied when performed by this type of provider | The provider's specialty or credential is not eligible for the code. | Bill under the eligible provider if one was involved; otherwise write off. |
CO-171 | Payment denied when performed by this type of provider in this type of facility | Place of service and provider type conflict. | Correct the place of service if wrong; otherwise write off. |
CO-B7 | This provider was not certified or eligible to be paid for this procedure on this date | Credentialing lapsed or was not complete on the date of service. | Hold claims until credentialing is effective; appeal with the effective date. |
CO-45 | Charge exceeds the fee schedule or maximum allowable | The contractual write-off, not a denial. | Post the adjustment; nothing to appeal. |
CO-253 | Sequestration reduction | The 2% Medicare reduction in force. | Post the adjustment. |
PR-1 / PR-2 / PR-3 | Deductible / coinsurance / copayment | Patient responsibility per the plan. | Bill the patient; collect copays at the visit. |
Fewer denials start at the phone.
Eligibility and authorization questions reach your team as tasks before the visit, not as denials after it.