CO-9 and CO-10 Denial Code Description

In medical billing, the CO-9 denial code indicates that the diagnosis code submitted on a claim is not consistent with the patient’s age. This means that the medical condition or diagnosis reported does not align with the expected conditions for someone of that particular age.

For example, if a claim is submitted for a 5-year-old patient with a diagnosis code typically associated with conditions found in adults, such as hypertension or certain types of arthritis, the insurance payer may issue a CO 9 denial code. In this case, the diagnosis code is considered inconsistent with the patient’s age because the reported condition is not commonly seen in young children.

To avoid this type of denial, medical billers need to ensure that the diagnosis codes selected accurately reflect the patient’s age and medical history. Using age-appropriate codes is essential for proper reimbursement and compliance with coding guidelines. If there is a legitimate reason for an unusual diagnosis in a particular age group, additional documentation or justification may be required to support the claim and prevent a CO 9 denial.

CO 10 Denial Code- The diagnosis is inconsistent with the patient’s gender

The denial code “Co 10” in medical billing indicates that the claim has been denied because the diagnosis listed on the claim is inconsistent with the patient’s gender. This means that the diagnosis code used does not align with the gender of the patient for whom the claim was submitted.

Let’s consider a case example:

Suppose a male patient visits a healthcare provider for a routine check-up, and the provider submits a claim with a diagnosis code typically associated with female-specific conditions, such as pregnancy-related codes. In this case, the insurance company may deny the claim with the “Co 10” denial code because the diagnosis does not match the gender of the patient.

To address this issue, the healthcare provider needs to ensure that the diagnosis codes used accurately reflect the patient’s condition and gender. It’s crucial for medical coders and billing staff to double-check the diagnosis codes and ensure they align with the patient’s demographic information to avoid such denials.

In summary, the “Co 10” denial code related to inconsistency with the patient’s gender emphasizes the importance of accurate coding and billing practices to prevent errors in the submission of claims.

Step by Step Handle CO-9 and CO-10 Denial in AR-Follow up

Call to insurance company and give them proper information about denial with denial date and claim number as well.

  1. Denial Reason: The claim has been denied due to an inconsistency between the diagnosis code and the patient’s age or gender.
  2. Denial Date Inquiry: You’re requesting information on the date of the denial.
  3. Invalid Diagnosis Code Inquiry: You want to know which specific diagnosis code is considered invalid. If there are multiple codes, you’re seeking clarification on all of them.
  4. Payment History Check: Depending on the response to the previous question, you’re checking if the same diagnosis code has been paid with the same Current Procedural Terminology (CPT) code before.
    • Yes: Proceed to question 5.
    • No: Move to question 6.
  5. Reprocess Claim Inquiry: You’re asking if it’s possible to reprocess the claim since payment has been received for the same CPT code.
    • Yes: Move to question 7.
    • No: Proceed to question 8.
  6. Time Limit for Corrected Claim: In case the claim cannot be reprocessed, you’re inquiring about the time limit for submitting a corrected claim.
  7. Turnaround Time (TAT) for Reprocessing: You’re asking about the expected turnaround time for the claim to be reprocessed.
  8. Appeal Process: Since the claim cannot be reprocessed, you’re inquiring about the appeal process.
    • Fax or Mailing Address: Asking for the fax number or mailing address where the appeal should be sent.
  9. Time Limit for Appeal Submission: You’re asking about the time limit for submitting the appeal.
  10. Claim and Call Reference Numbers: Requesting the claim number (if not available) and call reference number for documentation purposes.
  11. Complete Scenario Request: Asking for a complete overview of the scenario with all the details provided, including denial reason, denial date, specific invalid diagnosis code(s), payment history, decision on reprocessing, time limits, and appeal process information.

CO 8 Denial Code| Procedure code inconsistent with provider

CO 4 Denial Code – Procedure code is inconsistent with the Modifier

CO 5 Denial Code – Procedure Code is Inconsistent with Place of Service


  • NSingh (MBA, RCM Expert)

    The author and contributor of this blog "NSingh" is working in Medical Billing and Coding since 2010. He is MBA in marketing and Having vaste experience in different scopes of Medical Billing and Coding as AR-Follow-up, Payment Posting, Charge posting, Coding, etc.