The CO-291 denial code means the medical plan found no medical benefit and forwarded your claim to the patient’s dental plan. Do not refile yet. Confirm that the dental plan received the claim, answer any record requests, and watch for its own remittance. (Primary source: X12 Claim Adjustment Reason Codes)
In brief: CARC 291 is a routing notice. The twin code, CARC 270, means the medical plan did not forward the claim, so you must send it to the dental plan. With CO-291, track the forwarded claim and do not bill the patient yet.
Part of our denial codes library. Written by Manikandan J, CPC, CRCR, who has followed medical-to-dental handoffs for sleep medicine and oral surgery offices. Published 14 November 2026. Last updated: 14 November 2026. Code wording quoted word for word from X12. Read about the author and our editorial policy, or contact us to report an error.
What does denial code CO-291 mean?
Denial code CO-291 means the medical plan paid nothing on the line and passed the claim to the dental plan. Reason code 291 shows up when one carrier runs both benefits. The medical zero is not the final answer on the service.
| Field | Value |
|---|---|
| Code | 291 |
| Description | “Claim received by the medical plan, but benefits not available under this plan. Claim has been forwarded to the patient’s dental plan for further consideration.” |
| Group codes | No X12 group restriction; CO and OA both appear |
| Start | 11/01/2017 |
| X12 note | Use CARC 270 if the claim was not forwarded |
Source: X12 Claim Adjustment Reason Codes, checked 14 November 2026.
Methodology: the code wording is copied from the X12 list, and the claim form steps follow the NUCC instructions cited below.
Key terms: A forwarded claim is one the payer moved to another plan for you. The dental benefit is the coverage under the patient’s dental plan. CO is the contractual obligation group code.
CO-291 vs OA-291: what is the difference?
CO-291 treats the medical zero as a contract adjustment while the claim travels on. OA-291 reports the same handoff and names no one as liable. Both versions tell you the same thing: the dental plan now decides, and the patient owes nothing yet.
| Version | How to post the medical remittance | What to wait for |
|---|---|---|
| CO-291 | Zero pay, hold the balance in a forwarded-to-dental status | The dental plan’s own remittance |
| OA-291 | Same posting, no liability named | The dental plan’s own remittance |
Do not move a CO-291 balance to the patient while the dental plan is still reviewing.
Why did the medical plan forward the claim?
The medical plan forwards a claim when the service looks dental rather than medical. Oral appliances, jaw procedures and tooth-related treatment are common examples. The plan finds its medical benefit does not apply, but the dental plan might cover it.
Forwarding works only when the plan can see the patient’s dental coverage. That is why it is common when one carrier holds both policies. If the plan cannot forward, you get CARC 270 and must file the dental claim yourself, as the X12 note on CARC 291 says.
Example scenario (fictional names), part 1
CO-291 Denial Example: What Happened
Leah Sutton manages billing at Cedar Hollow Sleep Dental. Dr. Marcus Obi fitted a custom oral appliance for a patient with obstructive sleep apnea. Leah billed the medical plan on a CMS-1500 with E0486 and diagnosis G4733.
The fictional carrier holds both the patient’s medical and dental policies.
The 835 came back with CAS*CO*291 and a zero payment on E0486. A month later no dental payment had arrived. The patient asked whether the appliance bill was now theirs.
Should Leah send a new dental claim, or wait? Keep reading, or jump to how it was resolved. Keep reading, or jump to how the CO-291 denial was resolved.
How do I handle a CO-291 denial?
To handle a CO-291 denial, post the zero, hold the balance and track the claim at the dental plan. Call to confirm it arrived and ask for its new claim number. If the dental plan has no record after a fair wait, file a dental claim yourself and attach the medical remittance as proof.
- Post and hold. Record the medical zero and flag the account as forwarded to dental.
- Confirm receipt. Call the dental plan and note the new claim number.
- Answer requests. Send the sleep study, the prescription and the fitting notes if asked.
- File only if lost. If the dental plan has no claim, submit one on an ADA dental form.
- Work the dental decision. Treat a dental denial as a new denial with its own codes.
Example scenario (fictional names), part 2
How the CO-291 Denial Was Resolved
Leah called the dental plan. It had the forwarded claim, but the benefit was pended for the sleep study and the physician’s prescription.
Fix: she sent both documents and Dr. Obi’s fitting note, quoting the new claim number. She did not refile, which would have created a duplicate. She told the patient the claim was still in review.
Outcome: the dental plan paid part of the appliance up to the annual maximum. Leah moved only the remaining patient share to the patient, after the dental remittance arrived. She now sets a 21-day follow-up on every CO-291.
Names and details are illustrative; no real patient data.
Names and details are illustrative; no real patient data.
Will refiling after CO-291 cause a duplicate denial?
Yes, refiling too early can cause a duplicate denial. The dental plan already holds the forwarded claim, so a second claim for the same service can bounce as an exact duplicate, such as CO-18. Confirm the status first. Refile only when the dental plan says it has no record.
Can I bill the patient for CO-291?
No, not while the dental plan is deciding. CO-291 is a contractual zero on the medical side, not patient responsibility. Wait for the dental remittance. Any patient share will appear there as PR, such as a deductible or coinsurance. For example, the dental plan may apply an annual maximum, as the HealthCare.gov dental coverage page explains.
Related codes
| Code | Meaning |
|---|---|
| CO-270 | Medical plan: submit to the dental plan yourself |
| CO-290 | Dental plan: forwarded to the medical plan |
| CO-254 | Dental plan: submit to the medical plan yourself |
| CO-18 | Exact duplicate claim or service |
FAQ
What does CO-291 mean?
The medical plan found no benefit and forwarded the claim to the patient’s dental plan.
Do I need to refile a CO-291 claim?
Not at first. Confirm the dental plan received it, and refile only if it did not.
Is CO-291 the same as CO-270?
No. CO-270 means the claim was not forwarded. CO-291 means it was.
Which group code comes with CARC 291?
X12 sets no restriction. CO and OA both appear on medical remittances.
Does the patient owe a CO-291 amount?
No. Wait for the dental plan’s decision before billing anything.
Sources
How we checked: the CARC 291 quote was matched word for word with the X12 CARC list on 14 November 2026, including the X12 note pointing to CARC 270.
- X12, Claim Adjustment Reason Codes (CARC 291, 270, 18). Accessed 14 Nov 2026.
- X12, Remittance Advice Remark Codes. Accessed 14 Nov 2026.
- NUCC, 1500 claim form instructions. Accessed 14 Nov 2026.
- ADA, Code on Dental Procedures and Nomenclature (CDT). Accessed 14 Nov 2026.
- HealthCare.gov, dental coverage in the Marketplace. Accessed 14 Nov 2026.
Last updated: 14 November 2026 · Educational content; not legal advice.