Resolving CO-97 Denials: The Ultimate Guide to Unbundling Distinct Services

:::info Quick answer A CO-97 denial indicates a service was bundled into the payment for another procedure. To resolve it, check the 2026 NCCI edit tables to see if the codes can be unbundled. If documentation supports a distinct service, append the correct modifier (like 25 or 59) and submit a corrected claim. :::

You billed a major joint injection (20610) and a level 4 office visit (99214) on the exact same day. Medicare paid for the injection, but your remittance advice shows a zero payment for the office visit, accompanied by a CO-97 denial code.

Why? Because the payer's adjudication system decided the evaluation and management (E/M) service was baked into the payment for the procedure.

The official description for CO-97 reads: "The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated."

The "CO" stands for Contractual Obligation. You cannot bill the patient for the balance. You either accept the write-off, or you prove to the payer that the denied service was distinct, necessary, and separately payable.

In August 2026, payers rely on highly aggressive auto-adjudication scrubbers to bundle claims. Commercial giants like Aetna and UnitedHealthcare have tightened their logic algorithms to match—and frequently exceed—Medicare’s National Correct Coding Initiative (NCCI) edits. If you drop a claim with multiple overlapping services and fail to explicitly tell the payer why they are distinct, you will hit a CO-97 wall.

Here is how to decode the bundling logic, apply the exact modifiers required to bypass it, and overturn invalid CO-97 denials.

The Anatomy of a CO-97 Denial Code

To beat this denial, you have to understand the automated logic driving it. Claims examiners do not sit at desks manually reviewing your claims to see if the provider performed extra work. Instead, their software runs your billed CPT codes through Procedure-to-Procedure (PTP) edit tables.

When you bill two codes that the NCCI manual dictates should not happen at the same time on the same patient by the same provider, the system picks the most comprehensive code (the Column 1 code), pays it, and slaps CO-97 on the component code (the Column 2 code).

This automatic bundling happens in three primary arenas:

1. E/M services with minor surgeries: Performing a check-up on the same day as a minor procedure (with a 0- or 10-day global period).
2. Component surgeries billed alongside comprehensive surgeries: Billing a surgical approach or a closure separately from the actual primary surgery.
3. Overlapping lab panels: Billing a comprehensive panel alongside a single test that is already a component of that panel.

If the work genuinely overlaps, the CO-97 denial code is valid and you must write off the charge. But if the provider performed two entirely separate services that happened to occur on the same day, you are leaving earned money on the table by accepting the denial.

Top Triggers: Why Your Claims Hit the CO-97 Wall

Claims trigger CO-97 for highly predictable reasons. If you are seeing a spike in these denials, audit your workflow for the following common errors.

1. Missing or Unsupported Modifier 25

Medical billers often forget to append Modifier 25 to the E/M code when a significant, separately identifiable service is performed on the same day as a procedure.

However, even if you append the modifier, payers in 2026 will frequently deny the claim anyway, holding it pending medical record review. UnitedHealthcare, for example, heavily scrutinizes Modifier 25 claims. If your provider’s note for the E/M looks identical to the pre-op assessment for the injection, the CO-97 denial code will stand. The documentation must clearly show a separate History of Present Illness (HPI), a distinct exam, and an independent medical decision-making process.

2. Improper Use of Modifier 59 or X-Modifiers

Modifier 59 is the traditional "distinct procedural service" modifier, but it is heavily audited due to historic abuse. CMS created the X-modifiers to force coders to provide more specificity, and many Medicare Administrative Contractors (MACs) like Novitas and First Coast will now auto-deny a 59 modifier if an X-modifier was more appropriate.

The X-modifiers are:

• XE (Separate Encounter): A service that is distinct because it occurred during a separate encounter on the same day.
• XS (Separate Structure): A service that is distinct because it was performed on a separate organ or anatomical structure (e.g., excising a lesion on the left arm and a completely different one on the right leg).
• XP (Separate Practitioner): A service that is distinct because it was performed by a different practitioner.
• XU (Unusual Non-Overlapping Service): A service that is distinct because it does not overlap usual components of the main procedure.

If you bill two distinct lesion removals on different arms without an XS modifier, the payer assumes you unbundled a single surgical session and denies the secondary code with CO-97.

3. Global Surgical Period Overlaps

If a patient is in the 90-day global post-operative period for a major hip replacement and comes into the office complaining of a new, unrelated shoulder issue, billing a standard E/M code will trigger a CO-97. The payer's system assumes the visit is routine post-op care for the hip. You must append Modifier 24 (Unrelated E/M service by the same physician during a postoperative period) to bypass the edit.

4. Mutually Exclusive Lab Tests

Billing a Comprehensive Metabolic Panel (80053) and an individual Albumin test (82040) on the same day guarantees a CO-97 denial on the Albumin. Albumin is mathematically factored into the comprehensive panel. Unless the physician drew a separate sample at a completely different time of day for a distinct clinical reason (which would require a modifier 91 or 59), the denial is valid.

Quick Reference: CO-97 Causes and Fixes

Step-by-Step Resolution and Appeal Workflow

Do not just slap a modifier on a denied claim and resubmit it blindly. You need a structured approach to overturning CO-97 denials that aligns with the Q3 2026 NCCI edits.

Step 1: Verify the PTP Edit Logic

Find the two codes the payer pitted against each other. Go to the CMS website and pull up the current Quarter's NCCI Procedure-to-Procedure (PTP) edit tables. Locate your comprehensive code in Column 1 and your denied code in Column 2.

Look at the "Modifier Indicator" column next to that code pair:

• Indicator 0: You cannot bypass this edit. No modifier is allowed under any circumstances. Stop working the denial and write off the balance.
• Indicator 1: A modifier is allowed. You can bypass the edit and get paid if the clinical documentation supports a distinct service.
• Indicator 9: The edit was deleted, meaning the payer used outdated logic.

Step 2: Audit the Clinical Documentation

If the indicator is 1, open the patient's medical record. You need hard proof that the service was distinct. Did the provider document a separate chief complaint? Is there an assessment and plan that addresses the bundled code entirely separate from the paid code? If the provider's note is a single, continuous paragraph that casually mentions both services, your appeal will fail.

Step 3: Submit a Corrected Claim or Appeal

If you simply left the modifier off the original claim, submit a corrected claim with the appropriate modifier (25, 59, XE, XS, XP, or XU).

If you originally submitted the claim with the correct modifier and the payer ignored it and denied it anyway (a very common tactic in 2026 for payers attempting to curb costs), you must drop to paper. Submit a formal Level 1 appeal. Attach the medical records, explicitly referencing the NCCI edit tables, and physically highlight the distinct portions of the medical note that justify the unbundling.

Standard CO-97 Appeal Timeline

Prevention: Beating CO-97 Before the Claim Drops

The most profitable way to handle a CO-97 denial code is to prevent it from generating in the first place. Fixing claims on the back end costs time, delays cash flow, and increases your administrative overhead. Implement these three safeguards to clean up your front-end process.

1. Hard-Code Claim Scrubbers to Current NCCI Edits

Ensure your clearinghouse or practice management system is running the most current NCCI edit tables. The tables update quarterly. As of August 30, 2026, you should be utilizing the Q3 2026 dataset. Configure your scrubber to flag any Column 1/Column 2 code pairs before the claim transmits. The scrubber should force the biller to either add a valid modifier or intentionally drop the component code.

2. Prioritize Anatomical Modifiers

Before jumping to Modifier 59, use specific anatomical modifiers whenever possible. Appending RT (Right Side) and LT (Left Side), or specific digit modifiers like F1-F9 (for specific fingers) and T1-T9 (for specific toes), gives the payer's automated system exactly what it needs to process the unbundling without human intervention. Payers process specific anatomical modifiers much cleaner than a blanket 59.

3. Redesign EHR Templates for Distinct Documentation

Train your providers to separate their notes physically within the Electronic Health Record (EHR). If a physician performs an E/M and a minor surgery, the E/M documentation should sit in a completely different text block than the procedure note.

When a payer requests notes for a CO-97 denial, sending a neatly divided chart where the distinct evaluation is visually separated from the surgical intervention drastically improves your overturn rate. It removes the ambiguity, proves the separate work occurred, and forces the payer to reimburse you for the complete scope of care provided.

Frequently asked questions

Can I bill the patient for a CO-97 denial?

No. The 'CO' stands for Contractual Obligation. Because you have a contract with the payer, you are legally bound to accept their bundling logic unless you successfully appeal it. Billing the patient for a CO-97 balance is considered balance billing and violates your provider contract.

What is the difference between CO-97 and CO-236?

CO-97 indicates a service is bundled into another procedure that was approved or paid on the same claim. CO-236 indicates that the procedure or service is not compatible with another procedure provided on the same day, often pointing to mutually exclusive procedures rather than purely inclusive ones.

Does Modifier 59 always fix a CO-97 denial code?

No. Modifier 59 only bypasses the denial if the NCCI edit tables assign a Modifier Indicator of '1' to the code pair, and your medical documentation explicitly proves the service was distinct, separate, or performed on a different anatomical site. If the indicator is '0', no modifier will bypass the edit.

Why did Medicare deny my claim with CO-97 even though I used Modifier 25?

Medicare and commercial payers frequently run automated audits on Modifier 25. Even if the modifier is present, the payer may deny the claim pending a manual review of your clinical notes to ensure a significantly, separately identifiable E/M service was actually performed and documented.

Are NCCI edits the same for Medicare and commercial payers?

Mostly, but not entirely. While most commercial payers base their bundling logic on CMS's NCCI edits, many large payers (like Aetna and UHC) use proprietary algorithms that bundle code pairs Medicare might allow. You must check the specific commercial payer's bundling matrix when fighting a commercial CO-97 denial.