CO 97 denial code

What CO-97 means

CO-97 means the payer treats this service as already paid: its value is included in the allowed amount of another service on the same claim or one adjudicated earlier. Nothing new is owed, so the line pays zero.

The CO group code means contractual obligation: the bundled amount is a provider write-off, and the patient cannot be billed for it.

Two engines produce most CO-97s. The first is the National Correct Coding Initiative (NCCI): CMS maintains pairs of codes where one (the Column 1 code) includes the work of the other (the Column 2 code). Bill both for the same patient and date, and the Column 2 line denies. Each pair carries a modifier indicator: 1 means an appropriate modifier can unbundle the pair when services were truly distinct; 0 means the bundle can never be broken. The second engine is the global surgical package: the surgery payment includes routine pre-op and post-op care for 0, 10, or 90 days, so related visits inside that window deny.

Common causes

• NCCI column 1/column 2 edits: a component procedure billed alongside the comprehensive procedure that includes it.
• Evaluation and management visits during a global period, billed without a modifier showing the visit was unrelated (24) or a staged/return procedure applied (58, 78, 79).
• Services inherently included in another code: supplies, standard approaches, or access work that the primary procedure’s value already covers.
• Distinct services billed without the supporting modifier. The second procedure really was separate (different site, different session), but the claim gave the edit no way to know.
• Missing documentation of separateness, so an appended modifier was appended without record support and the payer removed or ignored it.

How to fix and resubmit

1. Identify which service absorbed the payment. The remit shows the denied line; find the paid service on the same date (or the surgery whose global period covers the date).
2. Look up the edit. Check the NCCI procedure-to-procedure tables for the code pair and note the modifier indicator. If the date falls in a global period, confirm the surgery’s global days.
3. If the modifier indicator is 0, or the service is genuinely part of the paid procedure, write it off. There is no compliant path to separate payment, and appealing wastes the 120-day window you might need elsewhere.
4. If the services were truly distinct and the indicator is 1, resubmit a corrected claim with the appropriate modifier: 59 or the applicable X modifier for NCCI pairs, or the correct global-period modifier for post-op visits. The operative note or visit note must support the distinction; append nothing the record cannot back up.
5. If a properly modified claim still denies, appeal with the documentation attached: notes showing separate sessions, sites, or an unrelated diagnosis for global-period visits.

How to prevent it

Run NCCI edits in your claim scrubber before submission and update the tables quarterly; CMS revises them four times a year. Track global periods on every surgical patient so post-op visits either go unbilled (routine care) or go out with the right modifier (unrelated or new problems). Train coders that modifier 59 is a last resort with documentation behind it, not a denial-bypass key; payers audit its overuse. And distinguish CO-97 from its neighbors: CO-59 is a pricing reduction, and CO-4 is a modifier validity error. The full list is in the denial codes index.