CO-97 bundling denials explained

CO-97 means the payer considers one service included in the payment for another service. It often appears when two procedure codes are billed for the same patient on the same date. The denial may be correct, or the claim may need a supported modifier. The code alone does not answer which.

Start with the National Correct Coding Initiative (NCCI). Its procedure-to-procedure edits identify code pairs that generally should not be paid together. The edit also shows whether a modifier can override the pairing in appropriate circumstances. Check the version effective on the date of service, because edits change over time.

Modifier 59 means a service was distinct from another service billed that day. XU is a more specific modifier meaning an unusual, non-overlapping service. Neither modifier is a payment shortcut. The clinical record must support separate work, timing, encounter, site, or another distinction recognized by the payer. Payer policy may prefer an X modifier over 59.

Some CO-97 denials cannot be corrected with a modifier. If the NCCI edit has a zero modifier indicator, the pair cannot be unbundled under NCCI. A denial may also be correct when the second code describes work already included in the primary service, or when the documentation does not establish a distinct service. Adding a modifier without support can create compliance risk.

Review the original claim, remittance, code pair, NCCI edit, payer policy, and clinical documentation before deciding. Then classify the outcome as correct bundling, corrected claim, or supported appeal. Experian Health's State of Claims 2025 found that 41% of providers report that more than 10% of their claims are denied, making consistent classification more useful than isolated rebilling.

First Pass Paid is building claim checks and a denial worklist for this. Join the early access list.

Sources

• Experian Health, State of Claims 2025