CARC 146 Active

CO-146: Diagnosis Invalid for Date of Service

TL;DR

Provider responsibility — correct the issue and resubmit the claim. The patient is not liable for this amount.

Action

Verify & Resubmit

Who Pays

Provider

Appeal

Patient Impact

None

Disclaimer

This content is for informational purposes only and does not constitute professional billing advice. Always verify information against your payer contracts and current coding guidelines. Consult a certified billing specialist for specific claim issues.

What Does CO-146 Mean?

With CO (Contractual Obligation), the CARC 146 adjustment is the provider's responsibility. The payer denied or reduced payment because of the diagnosis code used on the claim was valid at one point but has been retired or replaced with a newer code effective before the date of service. The patient is not liable for this amount.

CARC 146 appears on a remittance when the payer identifies an issue related to diagnosis invalid for date of service. This is a technical billing or coding problem that must be corrected before the claim can be processed for payment. The denial indicates the claim data did not meet the payer's adjudication requirements.

Common scenarios that trigger this adjustment include: the diagnosis code used on the claim was valid at one point but has been retired or replaced with a newer code effective before the date of service; The diagnosis code used on the claim has a future effective date and was not valid on the date the service was rendered; The ICD-10 code lacks required specificity digits — the code was submitted without the necessary 4th, 5th, 6th, or 7th character required for the date of service. The group code paired with CARC 146 determines who bears the financial responsibility — CO places it on the provider as a contractual obligation, OA indicates a coordination of benefits or other payer adjustment, PR shifts it to the patient.

Common Causes

Cause	Frequency
Expired ICD-10 diagnosis code The diagnosis code used on the claim was valid at one point but has been retired or replaced with a newer code effective before the date of service	Most Common
Truncated diagnosis code The ICD-10 code lacks required specificity digits — the code was submitted without the necessary 4th, 5th, 6th, or 7th character required for the date of service	Most Common
ICD-10 code not yet effective The diagnosis code used on the claim has a future effective date and was not valid on the date the service was rendered	Common
Typographical error in diagnosis code A data entry error resulted in an invalid diagnosis code being submitted on the claim	Common
Annual ICD-10 update not applied The provider's billing system was not updated with the latest annual ICD-10 code changes effective October 1, resulting in use of outdated codes	Common
Diagnosis code not valid for patient age or sex The submitted diagnosis code is clinically inconsistent with the patient's demographic information for the date of service	Occasional

How to Resolve

Review the remittance details Examine the CO-146 adjustment and any accompanying RARC codes to identify the specific reason for the denial.
Identify the root cause Determine which issue applies: expired ICD-10 diagnosis code, iCD-10 code not yet effective, truncated diagnosis code, among others.
Correct the claim Address the identified issue — update the claim data in your billing system to resolve the diagnosis invalid for date of service problem.
Resubmit the corrected claim Submit the corrected claim following the payer's resubmission guidelines. Include any supporting documentation that addresses the denial reason.

Do Not Appeal This Code

This denial indicates the diagnosis code was invalid for the date of service. Correct the diagnosis code to one that was active on the service date and resubmit the claim rather than appealing.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-146:

RARC	Description
M77	Missing/incomplete/invalid diagnosis or condition Verify the diagnosis code is valid for the date of service and resubmit with the correct ICD-10 code →
N130	You may need to review plan documents or guidelines Review payer-specific coding guidelines for diagnosis code requirements on this service →

How to Prevent CO-146

Update billing system code tables promptly when annual ICD-10 updates are released each October 1
Use claim scrubbing software that validates diagnosis codes against the date of service before submission
Train coding staff to verify diagnosis code specificity requirements and effective dates
Regularly review CMS and AMA updates for ICD-10 code additions, revisions, and deletions
Implement automated checks that flag truncated or expired diagnosis codes before claim submission
Maintain a crosswalk of recently retired codes to their replacement codes for quick reference

Also Filed As

The same CARC 146 may appear with different Group Codes:

OA-146 PR-146

Related Denial Codes

CO-167 — Diagnosis Not Covered CO-9 — Diagnosis Inconsistent with Patient Age CO-10 — Diagnosis Inconsistent with Patient Gender CO-11 — Diagnosis Inconsistent with Procedure CO-181 — Procedure Code Invalid on Date of Service

Sources

https://www.mdclarity.com/denial-code/146
https://myfcbilling.com/denial-code-146-diagnosis-invalid-for-the-date-of-service/
https://x12.org/codes/claim-adjustment-reason-codes
https://medicaid-documents.dhhs.utah.gov/Documents/pdfs/ClaimDenialCodes.pdf
Codes maintained by X12. Visit x12.org for official definitions.