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

The CO-97 denial code means the benefit for this service is already included in the payment for another procedure the payer adjudicated — it considers the two services bundled. Most CO-97 lines reflect a correct National Correct Coding Initiative edit, but a real share are separately identifiable services that needed an unbundling modifier and never got one. Telling those two situations apart is where CO-97 recovery actually lives.

What is the CO-97 denial code? CO-97 is a Claim Adjustment Reason Code (CARC) indicating the benefit for a service is included in the allowance for another already-adjudicated procedure; the bundled charge is a contractual write-off rather than a balance you can bill the patient.

Undeny's Take

Bundling is correct more often than frustrated billers assume — but the recoverable money sits in the genuinely separate services that needed an unbundling modifier and didn't get one. Before you appeal a CO-97, pull the NCCI edit for the code pair. If the column-two code is eligible for modifier 59 (or the more specific X{E,P,S,U} modifiers) and your documentation supports a distinct service, that documentation is your appeal. Blanket-appealing every CO-97 without an NCCI rationale just trains the payer to ignore you.

How Bundling Produces a CO-97

CO-97 belongs to the X12 Claim Adjustment Reason Code set: "The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated." In plain terms, the payer already paid for this work as part of another line. The CO group code marks it as a contractual obligation, so the amount cannot be balance-billed to the patient on an in-network claim.

When an Unbundling Modifier Applies

The code pair hits a National Correct Coding Initiative (NCCI) edit that bundles one service into the other.
An add-on code was billed without its required primary procedure, or two services overlap by definition.
A service fell inside another procedure's global period.
A separately identifiable service was performed but the claim lacked the modifier (59, XE/XP/XS/XU, or 25) that would unbundle it.

Working a CO-97 Bundling Denial

Look up the NCCI edit for the two codes to confirm whether the bundle is correct and whether a modifier is allowed.
If the services were genuinely separate and a modifier is permitted, verify your documentation supports the distinct service.
Submit a corrected claim with the appropriate modifier (59 or the specific X-modifier) rather than a bare appeal.
If the bundle was applied in error, file an appeal with the operative or session notes, or draft it with the appeal generator.

CO-97 and Adjacent Coding Codes

CO-97 is a payment-relationship code, distinct from rate and coding errors. CO-45 means the charge exceeds the allowed amount. CO-4 means the procedure code is inconsistent with the modifier used. Browse the full set under denial codes.

Frequently Asked Questions

What does CO-97 mean on a remittance?

CO-97 means the payer considers the service bundled — its benefit is already included in the payment for another procedure that was adjudicated. The CO group makes the amount a contractual write-off, not patient responsibility.

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

No. CO-97 carries the Contractual Obligation group code, so the bundled amount cannot be balance-billed to the patient on an in-network claim.

When can I appeal a CO-97 denial?

Appeal when the service was separately identifiable from the procedure it was bundled into and your documentation supports that distinction. The appeal usually succeeds only if an unbundling modifier was appropriate and the records back it up.

What modifier unbundles a CO-97?

Modifier 59 (distinct procedural service) or the more specific X{E,P,S,U} modifiers signal a separate service; modifier 25 applies to a significant, separately identifiable evaluation on the same day. Use them only when the documentation genuinely supports a distinct service.

Informational only — not legal, medical, or billing advice. Always verify against your current payer contract and policy.

Fix CO-97 denials automatically

Undeny checks the bundle rationale and drafts a payer-ready appeal in seconds. Generate an appeal · Browse denial codes