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Denial code lookup. Know what it means, and how to fix it.
What the most common insurance denial codes mean, why they happen, and how to fix them. Search a code like CO-197, or a word like “authorization”.
30 codes
CO-4Modifier missing or doesn’t match the procedure
What it means. The code needs a modifier it didn’t get, or the modifier used doesn’t fit that procedure. Common with modifier 25 on same-day visits, GP on therapy claims and 95 on telehealth.
How to fix it. Check the payer’s modifier rules for that code, add or correct the modifier, and submit a corrected claim.
Most common in: All specialties
CO-5Procedure doesn’t match the place of service
What it means. The place of service on the claim isn’t valid for the code billed, for example a telehealth visit billed with an office place of service the payer doesn’t accept.
How to fix it. Confirm the correct place of service (11, 02, 10 and so on) for that payer and resubmit.
Most common in: Mental health, primary care
CO-8Procedure doesn’t match the provider type
What it means. The payer doesn’t allow that code for the provider’s specialty or taxonomy on file.
How to fix it. Check the taxonomy code on the claim and on the provider’s enrollment. If the enrollment is wrong, it needs to be updated with the payer.
Most common in: All specialties
CO-11Diagnosis doesn’t support the procedure
What it means. The diagnosis code on the claim doesn’t justify the service billed under the payer’s policy.
How to fix it. Review the documentation, use the most specific diagnosis that supports the service, and submit a corrected claim.
Most common in: All specialties
CO-15Authorization number missing or invalid
What it means. An authorization exists but its number is missing, wrong, or doesn’t cover this provider or service.
How to fix it. Get the correct authorization number from the payer portal, add it to the claim and resubmit.
Most common in: Mental health, physical therapy
CO-16Missing or incorrect information
What it means. The claim is missing something or has a billing error. The remark code (an N or M code) on the EOB tells you exactly what.
How to fix it. Read the remark code, fix the specific field (often NPI, date of birth, referring provider or subscriber ID) and resubmit.
Most common in: All specialties
CO-18Duplicate claim
What it means. The payer thinks this exact service was already billed.
How to fix it. Check whether the original claim paid. If it’s a genuine separate service, resubmit with the right modifier (for example 76 or 77) or as a corrected claim.
Most common in: All specialties
CO-22Another payer may be primary
What it means. Coordination of benefits says another insurance should pay first.
How to fix it. Confirm the patient’s primary and secondary coverage, bill the primary payer, then send the secondary claim with the primary EOB.
Most common in: All specialties
CO-26Service date before coverage started
What it means. The visit happened before the patient’s coverage began.
How to fix it. Verify the effective date. If the patient had other coverage, bill that payer; otherwise the balance may be the patient’s.
Most common in: All specialties
CO-27Service date after coverage ended
What it means. The patient’s coverage had ended by the date of service.
How to fix it. Run a new eligibility check, get the patient’s current insurance and rebill the right payer.
Most common in: All specialties
CO-29Timely filing limit passed
What it means. The claim reached the payer after its filing deadline, which can be as short as 90 days.
How to fix it. If you have proof of an earlier on-time submission, such as a clearinghouse acceptance report, appeal with it. Otherwise it’s usually a write-off.
Most common in: All specialties
CO-31Patient not identified as a member
What it means. The payer can’t match the patient to its records, usually because of a wrong member ID, name spelling or date of birth.
How to fix it. Check the insurance card and eligibility response, correct the demographics and resubmit.
Most common in: All specialties
CO-45Charge above the fee schedule
What it means. Not a true denial. The payer paid its contracted rate and adjusted off the difference.
How to fix it. No action, unless the allowed amount is below your contract. Then it’s an underpayment to dispute.
Most common in: All specialties
CO-50Not medically necessary
What it means. The payer decided the service wasn’t medically necessary based on the claim and diagnosis.
How to fix it. Appeal with clinical notes, the treatment or care plan and relevant payer policy. A strong appeal often overturns these.
Most common in: All specialties
CO-96Non-covered charge
What it means. The service isn’t covered under the patient’s plan. A remark code usually gives more detail.
How to fix it. Check the plan’s coverage. If it’s truly excluded and the patient signed a waiver or ABN where required, bill the patient.
Most common in: All specialties
CO-97Bundled into another service
What it means. The payer considers this service part of another one it already paid, often because of an NCCI edit.
How to fix it. If the services were truly separate, add a supported modifier such as 59 or XU, and submit a corrected claim or appeal with notes.
Most common in: Physical therapy, primary care
CO-109Wrong payer
What it means. This payer isn’t responsible for the claim. Common with Medicare Advantage, Medicaid plans and behavioral health carve-outs.
How to fix it. Find the right payer (for mental health, often Optum, Carelon or Magellan) and bill them.
Most common in: Mental health
CO-119Benefit maximum reached
What it means. The patient has used up the plan’s limit for this service, such as a yearly cap on therapy visits.
How to fix it. Check remaining benefits before visits. If medically necessary, request an exception or extension; otherwise the visit may be the patient’s responsibility.
Most common in: Physical therapy, mental health
CO-151Too many services or too frequent
What it means. The payer thinks the number or frequency of services isn’t supported, for example weekly long sessions or many units.
How to fix it. Appeal with documentation showing the medical need for that frequency, and check the payer’s frequency rules going forward.
Most common in: Mental health, physical therapy
CO-167Diagnosis not covered
What it means. The payer doesn’t cover the service for the diagnosis billed.
How to fix it. Confirm the diagnosis is correct and as specific as possible. If correct and excluded, follow the plan’s rules for patient billing.
Most common in: All specialties
CO-170Not payable for this provider type
What it means. The payer won’t pay this service when it’s billed by this type of provider.
How to fix it. Check whether the service must be billed under a supervising provider and whether the payer credentials this provider type.
Most common in: Mental health
CO-185Rendering provider not eligible
What it means. The provider listed as rendering isn’t eligible for the service, often because they aren’t credentialed with the payer.
How to fix it. Check the provider’s credentialing status and effective date with that payer. Fix enrollment first, then rebill.
Most common in: All specialties
CO-197Authorization missing
What it means. The payer required precertification or authorization and none was on file for the service.
How to fix it. Check whether an auth existed. If the payer allows it, request a retro authorization, then resubmit or appeal.
Most common in: Mental health, physical therapy
CO-198Authorization exceeded
What it means. Services went past the authorized number of visits or units, or past the auth dates.
How to fix it. Request an extension or new authorization, ideally before the limit is reached, and appeal where the payer allows.
Most common in: Mental health, physical therapy
CO-204Service not covered by the plan
What it means. The service, equipment or drug isn’t a benefit under the patient’s current plan.
How to fix it. Verify benefits before the visit. If excluded, inform the patient in advance and follow the payer’s rules for billing them.
Most common in: All specialties
CO-236Code combination not allowed on the same day
What it means. The payer’s NCCI or policy rules don’t allow these two procedures together on the same date.
How to fix it. If the services were distinct, use the appropriate modifier with documentation. If not, bill only the comprehensive code.
Most common in: Physical therapy, primary care
CO-242Not provided by a network provider
What it means. The service wasn’t provided by an in-network or assigned primary care provider, as the plan requires.
How to fix it. Check network status and PCP assignment. Update the PCP on file or get a referral, then resubmit or appeal.
Most common in: Primary care
PR-1Deductible
What it means. Not a denial. The patient owes this amount toward their deductible.
How to fix it. Bill the patient.
Most common in: All specialties
PR-2Coinsurance
What it means. Not a denial. The patient owes their coinsurance share.
How to fix it. Bill the patient, or the secondary insurance first if they have one.
Most common in: All specialties
PR-3Copay
What it means. Not a denial. The patient owes their copay.
How to fix it. Collect it at the visit next time, to avoid sending statements.
Most common in: All specialties
No match. Try a different code or word, or ask us about it.
What the letters in front of the code mean
The group code tells you who is responsible for the amount.
Contractual obligation
The provider absorbs it and can’t bill the patient.
Patient responsibility
The patient owes it: deductible, copay or coinsurance.
Other adjustment
Doesn’t fit the other groups, often coordination of benefits.
Payer initiated
An adjustment the payer made that isn’t the patient’s responsibility.
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