CPT 99199: Usage, Documentation, Billing Rules & Examples

When a specific CPT code is not available for a medical service or procedure, CPT 99199—the unlisted special service, procedure, or report code—is used. Medical coders and billers rely on this code to report services that are not represented by any existing CPT code. Before billing an unlisted procedure, it is essential to first confirm that complete and appropriate documentation is obtained from the provider.

This guide explains the meaning, eligibility, correct usage, documentation needs, billing rules, comparable unlisted codes, and examples of when CPT 99199 may apply.

What Does CPT Code 99199 Represent?

CPT 99199 is a general-purpose unlisted healthcare service code used to report services, treatments, or supplies not described under any current CPT code. Providers typically use this code for uncommon, innovative, or infrequently performed services that do not fall under standard CPT categories.

Because the service is outside existing CPT descriptions, clear supporting documentation is necessary to justify the use of 99199, prevent denials, and support reimbursement.

This code ensures that providers can accurately report and be reimbursed for unique services. Although it may seem broad or unclear, it serves as an important tool for capturing services that do not have a defined CPT code.

Eligibility for Using CPT 99199

The type of service performed determines whether CPT 99199 is appropriate. The service must be:

• Medically necessary
• Not accurately described by any existing, active CPT code

Providers should also verify insurance coverage, as payers may have different policies regarding unlisted codes.

CPT 99199 may apply to the following categories:

1. Unusual or Experimental Services

Used when the service is new, rare, or experimental and lacks an established CPT code.

2. Emergency Situations

May be used in urgent cases where no time is available to identify a more suitable code. However, thorough documentation is required.

3. Investigational Services

Used for investigative or trial-based procedures that require billing but have no assigned CPT code.

4. When No HCPCS Code Exists

If a HCPCS code does not exist for a procedure typically performed by a physician, CMS may allow the use of CPT 99199 as a replacement.

Correct Usage of CPT 99199

Use CPT 99199 when a provider performs a service not addressed by a current CPT code. Before submitting a claim:

• Confirm no other CPT or Category III code accurately describes the procedure
• Ensure complete documentation is available
• Avoid using a code that only partially describes the service, per CPT guidelines

Only use CPT 99199 when no existing CPT code is appropriate.

Documentation Requirements

When reporting CPT 99199, a cover letter or detailed explanation must accompany the claim to justify why an unlisted code was used.

Documentation should include:

• A description of the service or procedure
• Comparable codes to justify the billed value
• Operative notes or relevant medical records
• Reason why no established CPT code applies

Because unlisted code claims are manually reviewed, strong documentation is key to avoiding denials.

Billing Guidelines for CPT 99199

Keep the following billing rules in mind:

• Do not select a code that only partially represents the service
• Use 99199 only when no defined CPT code exists
• If a Category III code applies, use it instead of an unlisted code
• Provide a cover letter explaining the choice of 99199
• Include at least one comparable CPT code to support pricing
• Attach operative notes or other clinical documents to reduce denial risk

Comparable Unlisted Codes

CPT 99199 has no exact equivalent, but the following codes are similar in that they represent unlisted services in specific specialties:

Examples of When CPT 99199 May Be Used

Below are 10 examples illustrating appropriate use of CPT 99199:

1. A clinician performs a rare diagnostic test that has no unique CPT code.
2. A physician provides an experimental therapy for a chronic disorder not represented by existing CPT codes.
3. A specialist removes a foreign object from the airway using a new technique not described by current CPT codes.
4. A provider performs complex wound care involving multiple advanced steps not covered under any specific CPT code.
5. A doctor delivers a one-of-a-kind neurological treatment with no defined CPT code.
6. A specialist performs a unique cardiovascular diagnostic procedure outside standard active CPT listings.
7. A clinician conducts a specialized genetic test for a rare inherited disease without an assigned CPT code.
8. A provider performs a complex procedure to correct a congenital defect not described by current CPT codes.
9. A physician administers a new therapy for a rare autoimmune condition that has not yet been assigned a CPT code.
10. A clinician performs an unconventional pain-management procedure with no existing CPT code.

Conclusion

CPT 99199 is essential for reporting unique, uncommon, or innovative medical services that lack a designated CPT code. It is used for experimental treatments, emergency or investigative services, and procedures without an existing CPT or HCPCS code.

Because this is a broad, unlisted code, it should only be used as a last resort. Thorough documentation and clear justification are vital to support the claim, prevent denials, and maintain compliance.