CARC 133 Active

CO-133: Service Line Pending Further Review

TL;DR

Contractual adjustment — review against your contract terms. The patient is not liable for this amount.

Action
Review & Decide
Who Pays
Provider
Appeal
No
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-133 Mean?

With CO (Contractual Obligation), the CARC 133 adjustment for service line pending further review is a contractual reduction. The provider absorbs this amount per the payer contract or regulatory payment methodology. The patient is not responsible for the adjusted amount. Review the remittance to confirm the adjustment is consistent with your contract terms.

CARC 133 appears on a remittance when the payer applies an adjustment for service line pending further review. Review the group code and any accompanying RARC codes to understand the full context of this adjustment.

Common scenarios that trigger this adjustment include: the payer has requested additional documentation (medical records, clinical notes, etc.) to complete the adjudication of the claim and is holding the service line pending receipt; The claim has been selected for medical review, prepayment audit, or clinical review, and the payer is holding the payment until the review is completed; The payer is investigating other potential insurance coverage for the patient and is holding the claim pending COB determination. The group code paired with CARC 133 determines who bears the financial responsibility — OA indicates a coordination of benefits or other payer adjustment, CO places it on the provider as a contractual obligation, PR shifts it to the patient.

How to Resolve

  1. Review the adjustment against contract terms Compare the CO-133 adjustment with your payer contract to confirm the reduction is consistent with agreed terms or regulatory methodology.
  2. Verify the adjustment amount Confirm the dollar amount of the adjustment is calculated correctly based on the contracted rate and the service provided.
  3. Appeal if the adjustment is incorrect If the adjustment does not align with contract terms, file an appeal with contract documentation and supporting evidence.
  4. Process the contractual adjustment If the adjustment is correct per contract terms, process it accordingly in your billing system. This amount cannot be transferred to the patient.
Do Not Appeal This Code

Service Line Pending Further Review recorded under CO is a contractual obligation — the provider absorbs this amount per the payer agreement. Without an error in how the contract was applied, appeals don't apply. Review the accompanying RARC codes for context and accept the adjustment when the contract terms were applied correctly.

How to Prevent CO-133

Also Filed As

The same CARC 133 may appear with different Group Codes:

OA-133 PR-133

Related Denial Codes

CO-3 — Co-payment Amount CO-85 — Patient Interest Adjustment CO-100 — Payment Made to Patient/Insured CO-101 — Predetermination: Anticipated Payment CO-105 — Tax Withholding Amount

Sources

  1. https://www.cms.gov/medicare/claims-appeals/organization-determinations
  2. https://www.aapc.com/resources/claim-adjustment-reason-code-carc
  3. https://www.mdclarity.com/denial-code/133
  4. Codes maintained by X12. Visit x12.org for official definitions.