What does CO-97 mean on an EOB?

CO-97 means the payer considers the benefit for this service to be included in the payment for another service that was already adjudicated on the claim. CO is a contractual obligation (you generally can't bill the patient), and 97 is the bundling reason code.

Can you appeal a CO-97 denial?

Yes, when the two services were separately identifiable and the relevant NCCI edit allows a modifier override (modifier indicator 1). Add the correct modifier (often 25 or 59), attach documentation showing the services were distinct, and submit within the payer's appeal window.

What is the difference between CO-97 and CO-45?

CO-97 means a service was bundled into another already-paid service. CO-45 means the charge exceeded the contracted fee schedule amount. CO-97 is a bundling issue; CO-45 is a pricing/contractual write-off.

Which modifier fixes a CO-97 denial?

It depends on the clinical scenario. Modifier 25 is used for a significant, separately identifiable E/M service on the same day as a procedure; modifier 59 (or an X{EPSU} modifier) marks a distinct procedural service. Use the modifier the documentation actually supports.

CO-97 Denial Code: What It Means and How to Appeal It

If your remittance advice (the 835 / ERA you get back from a payer) shows CO-97, the payer is telling you something specific: they believe this service was already paid for as part of another service on the same claim. It is one of the most common “silent” denials in a medical practice. The claim looks adjudicated, money landed, and the $40 to $120 line that got zeroed out slips by unnoticed. This guide explains what CO-97 means, why it happens, and how to decide whether to appeal it.

What CO-97 actually means

CO-97 combines two standardized codes that every payer in the U.S. uses:

CO is the Claim Adjustment Group Code. It stands for Contractual Obligation, meaning the write-off is governed by your contract with the payer, and you generally cannot bill the patient for it.
97 is the Claim Adjustment Reason Code (CARC): “The benefit for this service is included in the payment/allowance for another service or procedure that has already been adjudicated.”

In plain terms: the payer bundledthis code into another one they already paid. They are not saying the service didn’t happen or wasn’t covered. They are saying they won’t pay for it separately.

Always read the RARC (Remittance Advice Remark Code) that rides alongside CO-97. The RARC, codes like N19, M15, or M144, tells you which rule drove the bundling, and that is the difference between a winnable appeal and a write-off.

Why CO-97 happens

Most CO-97 denials trace back to one of four causes:

NCCI bundling edits.The National Correct Coding Initiative defines pairs of codes that normally shouldn’t be billed together. If you submit both, the “column 2” code gets bundled into the “column 1” code.
A missing or incorrect modifier. When two services really were distinct, a modifier (most often 25, 59, or the X{EPSU} subset) tells the payer so. Leave it off and the second service looks like a duplicate.
Global surgical period.E/M visits and follow-ups that fall inside a procedure’s global period are bundled by design.
Genuinely inclusive services. Sometimes the payer is right and the work truly is part of the primary procedure. Not every CO-97 is worth appealing.

Should you appeal it?

The honest answer is “it depends,” and that judgment call is exactly why so many CO-97s get written off instead of worked. A quick triage:

Appeal when the two services were separately identifiable and a modifier was missing, applied incorrectly, or stripped by the payer despite being on the claim.
Appealwhen the NCCI edit has a modifier indicator of “1” (a modifier is allowed to override the bundle) and your documentation supports it.
Write it offwhen the NCCI indicator is “0” (no override permitted) or the service genuinely falls inside a global period.

How to appeal a CO-97 denial

The workflow that actually recovers the money:

1. Pull the RARC and the line. Identify the bundled CPT/HCPCS code and the code it was bundled into.
2. Check the NCCI edit.Look up the code pair and its modifier indicator (0 or 1). A “1” means an appeal with the right modifier can win.
3. Confirm the documentation. The clinical note must show the two services were distinct: separate sites, separate sessions, or a significant, separately identifiable E/M service.
4. Submit a corrected claim or appeal.Add the correct modifier and attach the note. Frame the argument around the specific NCCI rule and the RARC, not a generic “please reconsider.”
5. Track the deadline. Every payer has an appeal window. Miss it and the dollars are gone regardless of merit.

A note for Texas practices

Texas’s prompt-pay law (Insurance Code Chapter 1301) requires payers to adjudicate and pay cleanclaims within statutory deadlines, and it provides penalties when they don’t. A CO-97 that was applied incorrectly, then paid late once corrected, can carry statutory interest on top of the recovered principal. Most practices never calculate that interest, which is one more reason small-dollar denials are worth more than they look.

The bottom line

CO-97 is not a dead end. It’s a coding-rules question. The problem is volume and economics: a biller paid roughly $28/hour can’t afford to research a $50 bundled line, so it gets written off. That is precisely the gap Ivera was built to close, working every denial, including the small ones, autonomously. For the bigger picture, see how small denials add up to real revenue leakage.