## **What is HCPCS C9399?**
HCPCS code C9399 is designated for "Unclassified drugs or biologicals" as maintained by the Centers for Medicare & Medicaid Services (CMS) and the National Uniform Billing Committee. It applies to new drugs and biologicals approved by the FDA on or after January 1, 2004, which do not have an assigned, specific HCPCS code. This code falls under the category of miscellaneous drugs and biologicals and supplies.
It is used primarily for billing when a new FDA-approved drug or biological product has not yet been assigned its own unique HCPCS code under the Outpatient Prospective Payment System (OPPS) or Ambulatory Surgical Center (ASC) payment systems. Usage of C9399 enables providers to bill for these new medications until a product-specific HCPCS code and payment rate are established.
Diagnostic radiopharmaceuticals and contrast agents are generally excluded from this billing and are instead packaged with procedural payments unless granted pass-through status. Payment for drugs or biologicals billed with C9399 is manually priced by the MAC, typically at 95% of the Average Wholesale Price (AWP) under OPPS to cover acquisition and pharmacy costs.
## **HCPCS code C9399 documentation requirements**
HCPCS code C9399 documentation requirements include the following key elements:
- When billing with C9399, providers must include the National Drug Code (NDC) number for the drug or biological being administered.
- The total quantity of the drug administered should be documented and included, expressed in the applicable unit of measure.
- The date the drug was furnished to the patient must be recorded.
- Each occurrence of C9399 should be billed with a corresponding unit of one on the claim, regardless of the actual quantity administered; the quantity detail is reported separately.
- Providers should report one drug per revenue line and include the NDC, quantity, unit of measure, and date of service in the "Remarks" section of the CMS-1450 claim form or its electronic equivalent.
- For claims processed through Direct Data Entry, the NDC, quantity, and related information must be reported on the NDC page.
- For drug wastage billing with C9399, documentation must include the date, time, and quantity wasted in the patient's medical record. The wastage amount cannot be billed to another patient or reused.
All documentation must be thorough and visible for claim review and manual pricing, as C9399 claims require additional verification for medical necessity.
## **HCPCS code C9399 billing requirements**
HCPCS code C9399 billing requirements include:
- C9399 is used to report new FDA-approved drugs or biologicals that do not have a specific HCPCS code assigned yet.
- Providers must bill each occurrence of C9399 with a unit value of one, regardless of the actual quantity of the drug administered.
- The National Drug Code (NDC) number of the drug, the quantity administered, the applicable unit of measure, and the date the drug was furnished must be included on the claim.
- This detailed information is submitted in the "Remarks" section of the CMS-1450 claim form or its electronic equivalent, and also on the NDC page for Direct Data Entry (DDE) claims.
- Revenue code 0636 is used when billing C9399 in hospital outpatient claims.
- When billing for drug wastage, providers submit one line for the drug administered and one line with the JW modifier for the wasted amount, documenting wastage in the medical record.
- Payment for drugs or biologicals billed under C9399 is typically based on the Average Sales Price (ASP) plus 6%, as mandated by Medicare Part B payment policy since January 1, 2005. Manual pricing is performed using the NDC information provided on the claim to determine the correct ASP-based payment amount. Fiscal intermediaries and Medicare Administrative Contractors (MACs) process claims accordingly, with beneficiary coinsurance calculated on the allowed amount.
- C9399 acts as a placeholder code that triggers review based on NDC information provided.
## **Other relevant codes**
- **J3490** - Unclassified drugs
- **J3590** - Unclassified biologics
- **J9999** - Not otherwise classified, antineoplastic drugs
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