What is the denial code for a bundled service?

CO-97 is the main bundling code: the service is considered part of another procedure already paid for the same patient and date. Code-pair conflicts post as CO-236, mutually exclusive procedures as CO-231, and procedures that are never paid separately as CO-234.

Can modifier 59 fix a bundling denial?

Only when the NCCI edit for that code pair has a modifier indicator of 1 and the record documents a distinct service, such as a separate site, session, or incision. An indicator of 0 means no modifier can bypass the edit. Appending 59 without that documentation is a common audit target.

Bundling and NCCI denial codes

Bundling denials all say a version of the same thing - this line is not paid on its own - but the reason differs, and so does whether a modifier can help. CO-97 means the service is part of another service already adjudicated for the same patient and date. CO-236 and CO-231 come from code-pair edits: the combination is incompatible, or the procedures are mutually exclusive in one encounter. CO-234 means the procedure is never paid as a separate line. CO-59 is not a denial at all but a multiple procedure reduction, and CO-107 means an add-on or dependent service arrived without the primary service it depends on.

Also described as: included in another service; NCCI edit; procedure-to-procedure edit; mutually exclusive procedures; multiple procedure reduction; add-on code without its primary.

The 6 codes and what separates them

CO-97 - Service is bundled into another service already adjudicated
The service is considered a component of another procedure paid for the same patient and date, so it is not separately payable.
Who pays: Provider
CO-236 - Procedure combination is not compatible with another procedure
The two codes conflict under the payer's code-pair edits - for Medicare and Medicaid, the NCCI procedure-to-procedure edits - and cannot both be paid as submitted.
Who pays: Provider
CO-231 - Mutually exclusive procedures were billed for the same encounter
The two procedures cannot reasonably be performed or reported together in the same encounter.
Who pays: Provider
CO-234 - This procedure is not paid separately
The payer does not pay this procedure as its own line, whatever else is on the claim.
Who pays: Provider
CO-59 - Payment reduced under multiple or concurrent procedure rules
Payment on the secondary procedures was reduced under multiple or concurrent procedure rules - a reduction, not a denial.
Who pays: Provider
CO-107 - The related or qualifying service was not identified on the claim
The service only pays alongside a primary or qualifying service, and the payer could not find that service.
Who pays: Provider

How to tell which one you have

For CO-97, CO-236, and CO-231, look up the edit for the exact code pair. The NCCI modifier indicator decides everything: an indicator of 0 means no modifier can bypass the edit, and an indicator of 1 means a modifier such as 59 or XS can bypass it when the documentation shows a genuinely separate service - a different site, a different session, or a separate incision. CO-234 is not about a pair at all, so modifiers do not help. CO-59 is usually correct; check only that the payer ranked the highest-valued procedure first and did not reduce an exempt code. CO-107 is fixed by billing the primary service, or by resubmitting once the primary claim has adjudicated.

Frequently asked questions

What is the denial code for a bundled service?: CO-97 is the main bundling code: the service is considered part of another procedure already paid for the same patient and date. Code-pair conflicts post as CO-236, mutually exclusive procedures as CO-231, and procedures that are never paid separately as CO-234.
Can modifier 59 fix a bundling denial?: Only when the NCCI edit for that code pair has a modifier indicator of 1 and the record documents a distinct service, such as a separate site, session, or incision. An indicator of 0 means no modifier can bypass the edit. Appending 59 without that documentation is a common audit target.

Other denial reasons

Out of network No prior authorization Not medically necessary Service not covered Coding mismatch or invalid code Patient not eligible or coverage ended Another payer is responsible Missing information, duplicate, or late filing Provider not eligible or not credentialed Benefit or unit limit reached Deductible, coinsurance, or copay Paid less than billed

Every denial code in one table

Last reviewed October 3, 2026.

These are original plain-English summaries written for reference, not the official X12 code descriptions. Payer handling of any code varies by contract - always verify against the remittance advice and your payer agreement before adjusting a claim.