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

No. The CO group code assigns the amount to the provider as a contractual obligation. Balances that are the patient's responsibility carry the PR group code instead. Billing a patient for a CO amount is a contract problem, not a collections opportunity.

Should I add modifier 59 to fix a CO-97 denial?

Only when the services really were distinct and the medical record says so. Modifier 59 and the more specific X modifiers exist to identify genuinely separate services, not to override a correct bundling edit. Appending a modifier to force payment on a service that truly was included is exactly the pattern payer audits look for.

What does denial code CO-97 mean?

Q: What does denial code CO-97 mean?

CARC 97 means the benefit for the service is included in the payment or allowance for another service or procedure that has already been adjudicated. In plain terms, the payer considers it bundled. The CO group code means contractual obligation, so the amount is a provider write-off under your participation agreement.

The payer is telling you the service was bundled: payment for it is considered part of the payment for something else on the claim that has already been adjudicated. The CO half tells you who eats the money.

Read the code in two halves

CO is the claim adjustment group code and means contractual obligation. It assigns the adjustment to you under your participation agreement. It is a write-off, and you cannot bill the patient for it. Amounts that belong to the patient carry PR instead, and the difference between those two letters is the difference between an adjustment and a receivable.

97 is the claim adjustment reason code, and its published description is that the benefit for this service is included in the payment or allowance for another service or procedure that has already been adjudicated. Bundled, in other words.

Why it usually fires

The service fell inside a global surgical package — routine pre- or post-operative care billed separately from the surgery.
A procedure-to-procedure edit treated one code as a component of the other.
The service is considered incidental to the primary procedure.
An add-on code was billed without, or with the wrong, primary procedure.
An evaluation and management service was billed the same day as a procedure without a documented, separately identifiable reason.
Panel components were billed individually instead of as the panel.

The remark code carries the real detail

CARC 97 tells you a bundling decision happened. The remittance advice remark code on the same line usually tells you which one. Codes in the bundled and incidental family are the common companions, and they often name the relationship — components of the same procedure, incidental to a primary procedure, or included in the surgical allowance. Read the whole remittance line rather than the CARC alone, because the remark is what tells you whether there is anything to argue about.

What to do with it

Decide whether the bundling was right. Was the date inside a global period? Is there a published edit pairing these codes? If the edit was correct, the correct response is to adjust it off. Reworking a valid bundling denial is unpaid labor.
If the services genuinely were separate, say so with the right modifier. Modifier 59 and the more specific X modifiers exist to identify distinct services; modifier 25 identifies a separately identifiable E/M on the day of a procedure; the global-period modifiers cover unrelated care during a global. Use them only where the medical record supports it. A pattern of modifiers appended to force payment on genuinely bundled services is precisely what audits look for.
Choose the right route. A coding error on your side is usually a corrected claim. A disagreement with the payer's edit is usually an appeal. They have different deadlines — see how long you have to appeal.

What to ask if you call the payer

Which claim line or procedure it was bundled into. Which edit or policy was applied. Whether a corrected claim or an appeal is the right route in their system. The deadline for that route. And the call reference number before you hang up.

Reason and remark code descriptions are maintained externally and revised periodically, and payers differ in how they apply the same code. Check the current published wording and the payer's own policy before you build a workflow on any one interpretation. This is general information, not coding advice for a specific claim.

The follow-up call is the expensive part

HoldForYou places the payer call, sits through the hold and asks these questions for you, then returns the denial reason, the CARC code, the next action and the call reference number as structured fields. See how it works for billing teams.