Denial Code CO-97: Service Already Adjudicated

CO-97 is a denial code that confuses both patients and providers because the insurer is not saying the service was unnecessary — it is saying the service was already paid for as part of something else. CARC CO-97 translates to: "The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated."

In plain terms: the insurer believes it already paid for this service when it paid a different, larger claim.

The Most Common Cause: Global Surgical Periods

The most frequent trigger for CO-97 is the global surgical period. When a surgeon performs a procedure, Medicare and most commercial insurers apply a global package concept:

• 0-day global: The day of surgery only
• 10-day global: Surgery day plus 10 postoperative days
• 90-day global: Surgery day plus 90 postoperative days

During the global period, certain follow-up visits and services are considered "included" in the surgical fee. If a provider bills separately for a service that falls within the global period — even if it was a distinct visit for a different reason — the insurer may deny it as CO-97.

Services that often trigger CO-97 within a global period:

• Post-op office visits for wound checks
• Suture removal
• Routine follow-up imaging
• Care management calls

The Component Billing Problem (Unbundling)

CO-97 also appears in non-surgical contexts when a provider bills component codes separately when a comprehensive code already covers the bundle. For example:

• Billing separately for a urinalysis and a urinalysis with microscopy when only the comprehensive code should be billed
• Billing an E&M (office visit) on the same day as a procedure when the E&M is considered part of the procedure's pre-service work

The National Correct Coding Initiative (NCCI) edits — maintained by CMS — define which code pairs cannot be billed together without a modifier. These are called "bundling edits."

When CO-97 Is Wrong: Your Appeal Rights

CO-97 is sometimes applied incorrectly. You have grounds to appeal when:

1. The service was for a new or unrelated condition during the global period. If a patient breaks their arm during a 90-day global period for a knee replacement, the arm treatment is not part of the knee surgery's global package. The key is documentation — the medical record must clearly show the separate, unrelated condition. Modifier -79 (Unrelated Procedure During the Postoperative Period) is the correct modifier to use.

2. The service required a return to the operating room. Modifier -78 applies when a related procedure requires the patient to return to the OR during the global period (e.g., treating a post-op complication). This should be billed separately.

3. The bundling edit applies but a modifier exception exists. NCCI edits have column 1/column 2 pairs, and some allow modifier -59 (Distinct Procedural Service) or one of its subset modifiers (XE, XS, XP, XU) to unbundle them when the services were truly separate and distinct.

4. The "previously adjudicated" service was for a different patient, date, or claim. Sometimes CO-97 is a system error where claims are cross-referenced incorrectly.

Step-by-Step Appeal Process

Step 1: Identify what the insurer says was "already paid." Call the insurer and ask which specific claim or service the CO-97 is referencing. Get the claim number and date of the previously adjudicated service.

Step 2: Compare the two services. Are they actually the same service? Were they performed on the same date? Is one truly a component of the other?

Step 3: Determine the applicable NCCI edit. Look up the code pair at the CMS NCCI Policy Manual or the NCCI web-based tool. Determine if a modifier can overcome the edit.

Step 4: Work with your provider on the corrected claim. If modifier -59, -78, or -79 should have been applied, the provider must submit a corrected claim with the appropriate modifier and documentation of the distinct service.

Step 5: File a formal appeal if the corrected claim is denied. Include:

• A clear explanation of why the services are distinct
• Supporting clinical documentation (operative notes, progress notes)
• Reference to the applicable NCCI modifier exception
• A letter from the surgeon or treating physician if the global period argument applies

Sample Appeal Language

"We are appealing the CO-97 denial for [CPT code] on [date of service]. This service was not included in the global package for [prior procedure/code] billed on [prior date] because [it was performed for an unrelated diagnosis / it required a separate return to the operating room / it falls outside the global period]. Modifier [-79/-78/-59] was applied to indicate a distinct procedural service. We have attached supporting clinical documentation and respectfully request reprocessing."

CO-97 denials require specificity and documentation. The insurer's bundling logic is automated — your appeal is your chance to provide the human context that the system cannot see.

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Related Reading:

• How to Write an Insurance Appeal Letter
• What Is Medical Necessity?
• Internal vs External Insurance Appeal