CO-66: Blood Deductible

What Does CO-66 Mean?

CO-66 shifts the blood deductible away from the patient and onto the provider as a contractual write-off. This is unusual for CARC 66 and typically indicates either a specific contractual arrangement where the provider has agreed not to collect blood deductibles, or a payer processing error where PR should have been used instead.

When CARC 66 appears on a remittance, the payer is telling you that blood or blood product charges were not reimbursed because the patient's blood deductible has not been satisfied. This is distinct from a standard annual deductible (CARC 1) — the blood deductible specifically applies to whole blood and packed red blood cell transfusion services.

Under Medicare Part A, patients are responsible for the first three pints of blood per calendar year unless those pints are replaced through a blood donation program. Commercial payers may have their own blood deductible structures. CARC 66 is overwhelmingly paired with Group Code PR, making the unreplaced blood charges the patient's direct financial responsibility. When you see CO-66, it typically signals a contractual arrangement where the provider absorbs the blood deductible cost — this is uncommon and worth verifying.

The practical impact depends on your facility's blood banking operations. If your hospital runs a blood replacement program, patients or their designees can donate blood to offset the deductible. Tracking replacement pints and coordinating with the blood bank before billing can prevent unnecessary patient balances and reduce collection friction. For Medicare patients, the blood deductible resets each calendar year, so watch for a fresh round of CARC 66 adjustments in January.

Common Causes

How to Resolve

Confirm the blood deductible status is accurate, check for replacement pints, then bill the patient or write off the amount depending on the group code.

1. Review your payer contract Check your participation agreement for any clauses addressing blood deductible collection. Confirm whether CO-66 is consistent with your contract terms.
2. Verify the group code is correct CO-66 is uncommon. Contact the payer to confirm this was not a processing error where PR should have been assigned. If the payer confirms PR is correct, request a corrected remittance.
3. Post the contractual adjustment If CO-66 is validated, write off the blood deductible amount as a contractual allowance. Do not transfer this balance to the patient.
4. Document for contract review If CO-66 is recurring with this payer, document the financial impact for your next contract renegotiation cycle.

Common RARC Pairings

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

How to Prevent CO-66

• Maintain a reference of payer contracts that include blood deductible write-off provisions so billing staff know which plans generate CO-66
• Audit remittances regularly to catch CO-66 assignments that should have been PR-66, since the incorrect group code directly impacts collectible revenue
• Negotiate clearer contract language around blood deductible handling during payer contract renewals

General Prevention

• Maintain an updated summary of each payer contract's blood deductible handling rules so billing staff know which plans generate CO-66 adjustments
• Audit remittances regularly to catch CO-66 assignments that should have been PR-66
• Document recurring CO-66 write-offs for contract renegotiation discussions

Also Filed As

The same CARC 66 may appear with different Group Codes:

Related Denial Codes