CO-97 means the payer considers this service part of another one it already paid, so there is no separate payment. If the two were really separate, a modifier such as 59, XS or 25 with supporting documentation may be appropriate. If not, it is a correct write-off.
Billing therapy codes? See which mental health code pairs CMS bundles in 2026, with a free pair checker. Physical therapy? See PT code pairs and modifier 59.
The official wording
The X12 Claim Adjustment Reason Code list defines 97 as: "The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated."
The letters in front are the group code. CO means contractual obligation (the provider absorbs it), PR means patient responsibility, and OA is other adjustment. The same reason code can come with different group codes, so always read both.
What CO-97 is telling you
Many procedures include smaller services: a surgical package includes routine follow-up, and some codes include supplies or simple tests. NCCI edits list pairs that should not be paid together. CO-97 is the payer applying one of those rules.
Send us the list: payer, date of service, denial code and amount. No patient names needed. We will tell you which claims can still be fixed, which need an appeal, and which deadlines are close. Free, usually within 2 business days. Want the full picture? Get a free 90-day denial audit from your ERA files.
Run a billing company? Add a trained biller from $8/hour, first 25 claims free.
Common causes
- An NCCI procedure-to-procedure pair billed without a modifier.
- A visit during a global surgical period without modifier 24, 25 or 57 where one applies.
- Supplies billed separately that are included in the procedure.
How to fix it
- Check the NCCI edit for the code pair and whether a modifier is allowed.
- Read the note. Was it a different site, a different session or a separate problem?
- If yes, send a corrected claim with the right modifier.
- If no, post it as a contractual adjustment.
How to prevent it
- Run NCCI edits in the claim scrubber.
- Teach providers what documentation supports modifiers 25 and 59.
Remark codes that come with CO-97
| Remark code | Official wording | What to do |
|---|---|---|
| M15 | "Separately billed services/tests have been bundled as they are considered components of the same procedure. Separate payment is not allowed." | The service is part of another code billed that day. Check the NCCI edit before adding any modifier. |
| N20 | "Service not payable with other service rendered on the same date." | The two services cannot be paid on the same date unless a modifier applies and the notes support it. |
| M80 | "Not covered when performed during the same session/date as a previously processed service for the patient." | The payer already processed a service from the same session. Check the first claim. |
A CO-97 example
| Line on the remittance | Amount | What it means |
|---|---|---|
| 20610 joint injection | $150.00 | Paid |
| 99213 office visit, same day, no modifier | $110.00 | CO-97 with M15: included in the injection |
| Paid on the visit | $0.00 | Bundled |
The payer treats the visit as part of the injection. If the notes show a separate problem was treated, add modifier 25 to the visit and send a corrected claim. If not, the bundling is right.
CO-97 versus CO-4 and CO-236
| Code | What the payer is saying |
|---|---|
| CO-97 | This service is paid as part of another service |
| CO-4 | The modifier is missing or wrong |
| CO-236 | This pair of codes is not allowed together under NCCI or the payer's rules |
CO-97 checklist
- ☐ You checked the NCCI edit for the code pair.
- ☐ The notes support a separate service if you add a modifier.
- ☐ You did not add modifier 59 just to get paid.
- ☐ The fix goes as a corrected claim.
Questions people ask about CO-97
Can I use modifier 59 to fix every CO-97?
No. Modifier 59 is only for services that were truly distinct, such as a different site or session, and the note has to show it. Overusing it is an audit risk.
Can I bill the patient for CO-97?
No. The service is considered paid within the other procedure.
Can I bill the patient for a CO-97?
No. The payer considers the service already paid inside another service, and the CO group means you cannot bill the patient.
Seeing CO-97 on your remittances?
Send us 25 claims and we will group your denials by reason and remark code and show you which fix removes the most of them. Free, no setup fee.
Start the free 25-claim trialFiling limits, appeal windows and claim addresses change quietly. Get one short email a month with what changed and the free tools we add.
One email a month. No spam. Unsubscribe any time.Other denial code guides
All denial code guides
PR-1 · PR-2 · PR-3 · CO-4 · CO-5 · CO-11 · CO-15 · CO-16 · OA-18 · CO-22 · OA-23 · CO-24 · CO-26 · CO-27 · CO-29 · CO-31 · CO-45 · CO-49 · CO-50 · CO-59 · PR-96 · CO-97 · CO-109 · CO-119 · CO-129 · CO-140 · CO-146 · CO-151 · CO-167 · CO-170 · CO-181 · CO-185 · CO-197 · CO-198 · PR-204 · CO-234 · CO-236 · CO-242 · CO-252 · CO-253 · CO-288 · CO-A1 · CO-B7 · MA130 · N130 · N23 · N290
Timely filing limits by payer: Cigna timely filing limit · HealthSpring timely filing limit · Aetna timely filing limit · UnitedHealthcare timely filing limit · Humana timely filing limit · corrected claim timely filing limits
Sources: X12 Claim Adjustment Reason Code list (97), read October 12, 2026; CMS Medicare guidance where Medicare rules are mentioned. Last reviewed October 26, 2026. General information, not coding or legal advice. Payer rules differ, so check the remark code and the payer's own policy. Remark code wording from the X12 RARC list as published by claim.md, read October 26, 2026.