Denial Code CO-9
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Diagnosis code is inconsistent with the patient's age.
The CO-9 denial code indicates that the payer identified a conflict between the diagnosis reported on the claim and the patient's age.
This may occur when an age-specific diagnosis is reported for a patient outside the appropriate age range, the wrong diagnosis code is selected, or the patient's date of birth is incorrect. The diagnosis and demographic information should both be verified before the claim is corrected or appealed.
About CO-9
Denial Code
Group Code
Category
Quick Facts
CO (Contractual Obligation)
CO-9 is a Claim Adjustment Reason Code (CARC) used when the diagnosis reported on a claim conflicts with the patient's age. Resolution typically requires reviewing the diagnosis, patient demographics, medical documentation, and applicable age-related coding requirements.
CO-9
Patient Responsibility
Common Payers
Next Step
Generally No
Medicare, Medicaid, Commercial
Review Diagnosis
Diagnosis Age Conflict
What Does CO-9 Mean?
The CO-9 denial code means the diagnosis submitted on the claim is inconsistent with the patient's age.
Certain ICD-10-CM diagnoses apply to specific stages of life, such as newborn, pediatric, maternal, or age-related conditions. Payer claim edits may compare the diagnosis with the patient's age on the date of service and flag combinations that do not meet applicable coding or coverage requirements.
CO-9 does not automatically mean the diagnosis is wrong. Incorrect demographic information can create the same conflict even when the diagnosis was reported correctly.
Common Causes
CO-9 may occur when:
The patient's date of birth is incorrect.
The payer has inaccurate demographic information.
An incorrect diagnosis code was selected.
An age-specific diagnosis was reported outside its applicable age range.
A pediatric diagnosis was reported for an adult patient.
A newborn or perinatal diagnosis does not match the patient's age.
Claim demographics do not match payer records.
The diagnosis does not accurately reflect the documented condition.
The first step is determining whether the conflict originates from the diagnosis code or patient demographics.
How To Fix CO-9
When CO-9 appears on a claim:
Review the EOB or ERA.
Verify the patient's date of birth.
Confirm the patient's age on the date of service.
Compare claim demographics with payer records.
Review the reported ICD-10-CM diagnosis.
Compare the diagnosis with the medical documentation.
Check applicable age requirements for the diagnosis.
Correct demographic or diagnosis errors when identified.
Submit a corrected claim when appropriate.
Request payer review when the original information is accurate.
Never replace a correctly documented diagnosis simply to bypass an age-related claim edit.
Documentation to Review
Before correcting or appealing CO-9, review:
Patient date of birth.
Eligibility information.
Original claim.
ICD-10-CM diagnosis codes.
Medical record.
EOB or ERA.
Registration information.
Applicable coding requirements.
The documentation should support both the patient's demographic information and the diagnosis reported for the encounter.
Billing and Claim Considerations
CO-9 differs from CO-6 because CO-9 involves the relationship between the diagnosis and patient age, while CO-6 involves the procedure or revenue code and patient age.
If the patient's date of birth was entered incorrectly, correct the demographic information and follow the payer's corrected-claim procedures. If the demographics are accurate, review the diagnosis selection and supporting documentation.
Diagnosis coding should reflect the condition documented by the provider. A diagnosis should not be changed solely because another code is more likely to pass the payer's age edit.
Additional remark codes on the remittance advice should also be reviewed because they may provide more detail about the payer's reason for rejecting the diagnosis-age combination.
ICD-10-CM Codes to Review
Unlike CPT or HCPCS codes, ICD-10-CM diagnosis codes are directly relevant to CO-9 because the denial specifically involves a diagnosis-age conflict.
Review the actual ICD-10-CM code reported on the denied claim for:
Age-specific coding requirements.
Newborn or perinatal applicability.
Pediatric applicability.
Maternal or age-dependent conditions.
Documentation supporting the diagnosis.
This keeps the review focused on the diagnosis that actually triggered CO-9 rather than implying that a small group of diagnosis codes universally causes the denial.
Common Billing Mistakes
Common mistakes involving CO-9 include:
Entering the patient's date of birth incorrectly.
Selecting an age-inappropriate diagnosis.
Using an outdated diagnosis from a previous encounter.
Failing to review age-specific coding requirements.
Assuming the diagnosis is wrong without checking demographics.
Changing a diagnosis without supporting documentation.
Resubmitting the unchanged claim.
Appealing before determining whether the claim contains an error.
Reviewing both the diagnosis and patient demographics before resubmission can prevent repeated CO-9 adjustments.
When Should CO-9 Be Appealed?
A corrected claim is generally appropriate when the wrong diagnosis or incorrect demographic information caused CO-9.
An appeal or payer review may be appropriate when:
The patient's date of birth is correct.
The diagnosis accurately reflects the documented condition.
The diagnosis is appropriate for the patient's age.
Medical documentation supports the diagnosis.
The payer applied an incorrect age edit.
A processing error caused the adjustment.
When both the diagnosis and patient information are correct, supporting documentation should accompany the appeal when required by the payer.
Frequently Asked Questions
What is the difference between CO-9 and CO-6?
CO-9 involves a diagnosis that conflicts with the patient's age. CO-6 involves a procedure or revenue code that conflicts with the patient's age.
Does CO-9 always mean the diagnosis code is wrong?
No. An incorrect date of birth or inaccurate payer demographic record can cause an otherwise valid diagnosis to fail an age edit.
Should the diagnosis be changed after receiving CO-9?
Only when the original diagnosis was incorrectly coded and the medical documentation supports the correction. A diagnosis should never be changed solely to obtain reimbursement.
Can a corrected date of birth resolve CO-9?
Yes. If incorrect demographic information caused the age conflict, correcting the information may allow the claim to process properly.
What should be checked before appealing CO-9?
Verify the patient's date of birth, age on the date of service, diagnosis code, medical documentation, payer records, and applicable diagnosis coding requirements.
Related Denial Codes
CO-6 Denial Code
Procedure or revenue code conflicts with the patient's age.
CO-10 Denial Code
Diagnosis conflicts with the patient's gender.
CO-11 Denial Code
Diagnosis conflicts with the procedure reported on the claim.
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