How to Fix CO-97 Denials in OB/GYN Billing

CO-97 — "The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated" — is one of the most common denial codes in OB/GYN billing. It's frustrating because it can indicate either a legitimate bundling rule or a payer error, and distinguishing between the two requires knowing your CPT code bundles cold.

What CO-97 Means

When a payer returns CO-97, they're telling you they already paid for the service you're billing as part of a different payment they made on the same claim or a prior claim. They're not saying the service wasn't provided — they're saying they consider it bundled into something else.

In OB/GYN billing, CO-97 most commonly appears in these scenarios:

Global package bundling: You billed a separate E/M visit (99213–99215) alongside a global maternity delivery code (59400, 59510). The payer considers the E/M included in the global package.

Surgical procedure bundling: You billed two surgical procedures where one is considered a "component" of the other under National Correct Coding Initiative (NCCI) edits. For example, billing 58661 (laparoscopic oophorectomy) alongside 58662 (laparoscopic excision of lesion) without modifier 59 to indicate a separate, distinct service.

Add-on code issues: A code intended as an add-on to a primary procedure was billed without the primary, or the primary was denied, causing the add-on to be bundled with nothing.

Why CO-97 Happens in OB/GYN

OB/GYN has a uniquely high density of NCCI bundling rules because so many procedures share anatomical sites and are commonly performed together. The surgical suite for an OB/GYN is often the same for pelvic floor repair, hysterectomy components, and adnexal surgery — and the bundling edits don't always reflect clinical reality.

Common CO-97 situations in OB/GYN:

• ›Postpartum care visit billed within the global package period
• ›Office colposcopy and LEEP billed without modifier 59 on same service date
• ›Hysteroscopy with biopsy where the biopsy (58100) is bundled into the hysteroscopy (58558)
• ›Anesthesia services billed in addition to global surgical package

Step-by-Step Appeal Process

Step 1: Identify the pair

Determine which two codes triggered the CO-97. This is usually visible in the 835 ERA transaction or the paper EOB under the line-item detail.

Step 2: Check NCCI edits

Use CMS's NCCI edit lookup tool to determine whether the two codes have a Column 1/Column 2 relationship. If they do, check whether the edit allows a modifier to override the bundle.

Step 3: Apply the correct modifier

If the services were genuinely distinct (different anatomical sites, different operative sessions, separate encounters), apply modifier 59 (Distinct Procedural Service) or the appropriate X modifier (XE, XS, XP, XU) based on payer preference.

Step 4: Draft the appeal letter

Your appeal should include:

• ›Claim number and date of service
• ›The specific CO-97 denial and the two codes involved
• ›Clinical documentation showing the services were distinct
• ›Reference to the NCCI edit and the applicable modifier justification
• ›The operative report, if applicable

Step 5: Track timely filing deadlines

CO-97 appeals have payer-specific timely filing deadlines — typically 90–180 days from the original denial date. Track these carefully.

Prevention Tips

Pre-submission claim scrubbing: Configure your PM system to flag code pairs with known NCCI bundling relationships before claims go out. Most modern EHR/PM systems have this capability.

Modifier mapping: Build a reference sheet for your most common procedure pairs and the modifiers that correctly unbundle them. Share it with all clinical staff who enter charges.

Global period tracking: For maternity-related CO-97 denials, the solution is accurate global period documentation. Every antepartum, delivery, and postpartum service needs to be coded with reference to whether the patient is inside or outside a global maternity package.

Audit your top denial codes monthly: If CO-97 appears in your top 5 denial codes month after month, there's a systemic coding error that needs to be identified and corrected at the source.

CO-97 denials are among the most recoverable in OB/GYN billing — the key is moving quickly, knowing your NCCI edits, and building prevention into your claim submission workflow.