How do I fix or resolve code CO-146?

Verify the effective date of the ICD-10-CM diagnosis code on the claim against the current ICD-10-CM code set and the date of service to determine whether the code was valid on that date. Review the medical record to confirm the actual diagnosis documented for the date of service and identify the correct ICD-10-CM code that was effective on that date. If the diagnosis code was not valid for the DOS, correct the code to one that was effective on the date of service and resubmit the corrected claim. If the diagnosis code was valid for the DOS but the payer's editing system incorrectly flagged it, file an appeal with the ICD-10-CM effective date documentation and the medical record supporting the diagnosis. Update the EHR code set to the current ICD-10-CM version to prevent future use of expired or not-yet-effective codes.

CO-146Denial CodeContractual Obligation

Code CO-146

Problem Description

Diagnosis was invalid for the date(s) of service reported.

Root Cause

The diagnosis code reported on the claim was invalid for the date(s) of service billed. This occurs when the ICD-10-CM diagnosis code was not effective on the date of service — for example, using a diagnosis code that was added in an ICD-10-CM update after the date of service, or using a code that was deleted or revised before the date of service. The payer's editing system validates each diagnosis code against the ICD-10-CM effective dates and denies claims where the code was not valid on the service date. This typically results from using outdated code books, not updating the EHR code set, or coding from a problem list that contains expired codes.

Resolution Steps

1Verify the effective date of the ICD-10-CM diagnosis code on the claim against the current ICD-10-CM code set and the date of service to determine whether the code was valid on that date.
2Review the medical record to confirm the actual diagnosis documented for the date of service and identify the correct ICD-10-CM code that was effective on that date.
3If the diagnosis code was not valid for the DOS, correct the code to one that was effective on the date of service and resubmit the corrected claim.
4If the diagnosis code was valid for the DOS but the payer's editing system incorrectly flagged it, file an appeal with the ICD-10-CM effective date documentation and the medical record supporting the diagnosis.
5Update the EHR code set to the current ICD-10-CM version to prevent future use of expired or not-yet-effective codes.

EHR Documentation Note

Claim denied CO-146 — diagnosis invalid for DOS; verified ICD-10-CM effective date, corrected to valid code for the service date, and resubmitted corrected claim.

Preventative Action

Update the EHR ICD-10-CM code set annually with the latest CDC updates and run a pre-submission validation check to flag diagnosis codes that are not effective on the date of service.

Related Codes in Contractual Obligation

CO-4

The procedure code is inconsistent with the modifier used. Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.

CO-5

The procedure code/type of bill is inconsistent with the place of service. Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.

CO-16

Claim/service lacks information or has submission/billing error(s). Usage: Do not use this code for claims attachment(s)/other documentation. At least one Remark Code must be provided (may be comprised of either the NCPDP Reject Reason Code, or Remittance Advice Remark Code that is not an ALERT.) Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.

CO-18

Exact duplicate claim/service (Use only with Group Code OA except where state workers' compensation regulations requires CO)

This directory provides reference information only and does not constitute official legal, medical, or financial billing advice. Always consult the payer's official remittance advice and current coding guidelines.