RARC N291: Missing, Incomplete, or Invalid Rendering Provider Secondary Identifier
RARC N291 means the rendering provider's secondary identifier — usually the taxonomy code or a payer-assigned number — is missing, incomplete, or invalid on the claim. It rides with CO-16 as unprocessable. The fix is adding the correct rendering taxonomy or secondary ID and resubmitting a corrected claim.
- Type
- Informational (supplemental)
- Usually paired with
- CO-16, RARC N290
- Fixable?
- Yes — always
- Typical fix
- Add correct rendering taxonomy/secondary ID; resubmit corrected claim
What does remark code N291 mean?
Official X12 text: "Missing/incomplete/invalid rendering provider secondary identifier." The payer has the rendering NPI but needs a supporting identifier — most often the taxonomy code — to finish identifying the provider. It is blank, invalid, or does not match what the payer has linked to that NPI, so the line will not process.
ERA mini-example: 90837 (psychotherapy, 60 minutes) billed $175.00 denies with CO-16 and N291 from a Medicaid plan because the rendering taxonomy was omitted. Resubmitted with the behavioral-health taxonomy in the 2310B loop matched to the provider's NPI, the session pays.
Which denial code does N291 come with?
Almost always CO-16, and very often alongside N290 when both the primary NPI and the secondary taxonomy are missing at once. N290 is the NPI; N291 is the taxonomy or secondary ID. Use the denial code lookup to separate the two so you correct the right field.
How do you fix an N291 denial?
- Confirm the exact taxonomy code the payer expects for that rendering provider and specialty.
- Match it to the taxonomy on file in the payer's provider record — a mismatch denies just like a blank.
- Populate the rendering taxonomy in the 2310B secondary identifier loop, not the billing loop.
- Submit a corrected claim and verify acceptance before it reaches the payer again.
How do you prevent N291?
Store each rendering provider's correct taxonomy in your system and confirm it matches what every payer has on file during credentialing. For payers known to require rendering taxonomy — many Medicaid and behavioral-health plans — set your claim template to auto-populate the 2310B taxonomy. Reconcile provider taxonomy against payer records whenever a clinician adds a specialty, so the claim and the payer file never drift apart.
Frequently asked questions
It is a supporting identifier beyond the NPI — most often the provider's taxonomy code, sometimes a payer-assigned legacy or specialty number. Payers use it to route the claim to the right benefit or fee schedule when the NPI alone is ambiguous. N291 fires when that secondary value is missing, mismatched, or not the one the payer has on file.
Because N291 is not about the NPI — that is N290. N291 is the taxonomy or secondary ID. If the taxonomy on the claim does not match what the payer has linked to that NPI in their provider file, it denies regardless of a valid NPI. Confirm the exact taxonomy the payer expects for that provider and specialty.
No. Many pay on the NPI alone. But some — particularly Medicaid plans and certain commercial payers — require the rendering taxonomy in the 2310B loop to distinguish specialty or fee schedule. When you see N291 from a specific payer, treat rendering taxonomy as mandatory for that payer going forward, not optional.
Sources & further reading
Reviewed by the ImmediCare Solutions RCM team
Certified billers and coders handling claims across 50+ specialties nationwide. This entry is reviewed against current payer policy and CMS rules. Last review: Jul 5, 2026.
Stop losing revenue to problems like this.
A free billing audit shows exactly where your practice is leaking money — no cost, no commitment.
