CO-266: Pharmaceutical Compound Preparation Cost Adjustment

What Does CO-266 Mean?

CO-266 classifies the compound preparation cost as a contractual write-off. The payer determined that the compounding charge either exceeds the allowed amount, is not separately billable under your contract, or was not supported by sufficient medical necessity documentation. The provider absorbs the cost and cannot transfer it to the patient.

When CARC 266 appears on a remittance, the payer has adjusted the compound preparation cost on a pharmaceutical claim. This code applies exclusively to the costs of compounding a medication — the labor, specialized equipment, and preparation fees required to create a customized pharmaceutical product that is not commercially available. It sits alongside CARC 262 (delivery), 263 (shipping), 264 (postage), and 265 (administrative) in the pharmaceutical cost adjustment family.

Compounding pharmacies are the primary recipients of this code. The payer may deny or reduce the compounding charge because the contract does not separately reimburse preparation costs, because the medical necessity for a compounded formulation was not documented, or because a commercially available alternative exists that the payer considers equivalent. Some payers have specific formularies for compounded medications and require prior authorization before compounding is covered.

This code most commonly appears with Group Code CO, making the preparation cost a contractual write-off. The provider cannot bill the patient for the adjusted amount. However, compound medication denials have higher appeal success rates when you can demonstrate that no commercially available product meets the patient's clinical needs — for example, allergy to a commercial formulation's inactive ingredient, a pediatric dosage requirement, or a combination therapy not available in manufactured form. The key is thorough documentation of medical necessity before the medication is dispensed.

Common Causes

How to Resolve

Verify compounding cost coverage under your payer contract, confirm medical necessity documentation is complete, and appeal with clinical evidence or accept the adjustment.

1. Review contract compounding coverage Check whether compound pharmaceutical preparation is a covered benefit under your contract. Note any prior authorization requirements, formulary restrictions, or cost caps.
2. Build a medical necessity case Obtain documentation from the prescribing physician explaining why the compounded formulation was clinically necessary — including why commercially available alternatives were not suitable.
3. Appeal or post the write-off If compounding is covered and medical necessity is documented, submit a formal appeal. If the contract excludes compounding charges, accept the contractual adjustment.

How to Prevent CO-266

• Verify payer compounding coverage and prior authorization requirements before dispensing compounded medications
• Obtain and document medical necessity justification from the prescribing provider before compounding
• Use correct compounding-specific billing codes and ensure charges are within allowed limits
• Maintain detailed compounding logs with ingredient lists, preparation steps, and cost breakdowns

General Prevention

• Verify payer coverage for compounded medications and associated preparation costs before dispensing
• Document medical necessity clearly, including why a commercially available alternative was not appropriate for the patient
• Use correct billing codes specific to compound pharmaceutical preparations
• Obtain prior authorization when required for compounded medications
• Conduct regular audits of compound pharmaceutical billing and coding practices

Also Filed As

The same CARC 266 may appear with different Group Codes:

Related Denial Codes