CARC 66 Active

CO-66: Blood Deductible

TL;DR

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

Action
Review & Decide
Who Pays
Provider
Appeal
Yes
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-66 Mean?

With CO (Contractual Obligation), the CARC 66 adjustment for blood deductible 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 66 appears on a remittance when the payer adjusts payment for the blood deductible. This is a standard plan-defined cost-sharing amount that the patient is obligated to pay per their insurance benefits. The code confirms the payer processed the claim correctly and applied the plan's benefit structure as designed.

Common scenarios that trigger this adjustment include: medicare requires the patient to pay for the first 3 pints of blood per calendar year (blood deductible); Patient or blood bank did not replace the blood units, triggering the deductible; Patient has not met the annual 3-pint blood deductible. The group code paired with CARC 66 determines who bears the financial responsibility — PR shifts it to the patient, CO places it on the provider as a contractual obligation, OA indicates a coordination of benefits or other payer adjustment.

Common Causes

Cause Frequency
Contractual blood deductible adjustment Payer applies blood deductible per plan terms Most Common

How to Resolve

  1. Review the adjustment against contract terms Compare the CO-66 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 blood was replaced or the deductible was already satisfied, appeal with documentation of blood replacement or prior deductible payments.
  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.
Appeal Guide

If the blood was replaced or the deductible was already satisfied, appeal with documentation of blood replacement or prior deductible payments.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-66:

RARC Description
N381 Consult contract/fee schedule Review blood deductible contract terms →

How to Prevent CO-66

Also Filed As

The same CARC 66 may appear with different Group Codes:

PR-66 OA-66

Related Denial Codes

CO-281 — Deductible Waived Per Contractual Agreement CO-303 — Prior Payer Patient Responsibility Not Covered for QMB CO-23 — Prior Payer Adjudication Impact CO-24 — Charges Covered Under Capitation/Managed Care CO-35 — Lifetime Benefit Maximum Reached

Sources

  1. https://x12.org/codes/claim-adjustment-reason-codes
  2. https://revenuecyclemgmt.com/claim-adjustment-reason-codes/
  3. https://www.cms.gov/regulations-and-guidance/guidance/manuals/downloads/clm104c22pdf.pdf
  4. Codes maintained by X12. Visit x12.org for official definitions.