CO-226 Denial Code: Requested Info Not Sent by the Provider

The CO-226 denial code means the payer asked the billing or rendering provider for information and it was never sent, arrived late, or came back incomplete. The Contractual Obligation group makes the unpaid amount your write-off, not the patient's bill. The request might have been for records or, as at Louisiana Medicaid, provider enrollment data, so the remark code beside it is your map to what the payer is still waiting on.

What is the CO-226 denial code? CO-226 is a Claim Adjustment Reason Code (CARC) meaning "Information requested from the Billing/Rendering Provider was not provided or not provided timely or was insufficient/incomplete," reported with the Contractual Obligation (CO) group, and X12 requires at least one non-Alert remark code to say what was missing.

Undeny's Take

Treat CO-226 as an inbox problem before you treat it as a clinical one. Check whether the request went to an old address, a shared fax line or a portal nobody watches, and when its deadline passed. Two things follow. First, once you find the original request, answering it is often quicker than writing an appeal, so start there. Second, know which payers send it. For traditional Medicare medical review, CMS tells its contractors to deny unanswered documentation requests as CO-50 with remark M127, not CO-226. So when CO-226 appears, look to the plan's own request process, whether commercial, Medicaid or Medicare Advantage, and check that plan's portal and mail for the request.

What CO-226 Means and How Payers Use It

X12's full description of reason 226 is "Information requested from the Billing/Rendering Provider was not provided or not provided timely or was insufficient/incomplete. At least one Remark Code must be provided (may be comprised of either the NCPDP Reject Reason Code, or Remittance Advice Remark Code that is not an ALERT.)" The Medicare Claims Processing Manual (Pub. 100-04, Chapter 22) says a CO adjustment is generally "a write off for the provider" and is "not billed to the patient."

The request is not always clinical. Louisiana Medicaid's published FAQ on its provider enrollment edits lists CARC 226 with remark N831 ("You have responded to requests to revalidate your provider/supplier enrollment information") and says "CARC 226 is utilized for both educational and denial edits." Its edits deny when a billing or rendering provider's re-enrollment is not complete for dates of service on or after January 1, 2023.

Why the Payer Did Not Get What It Asked For

The request went unanswered. The letter, portal task or fax was missed, or reached the wrong location.
The answer arrived after the deadline. The 226 description specifically covers information "not provided timely."
The answer was incomplete. Missing pages, unsigned notes or the wrong date of service can all leave the payer's request open.
Enrollment or revalidation data was outstanding. As the Louisiana example shows, a Medicaid program can use 226 when provider enrollment information is incomplete.

How to Respond to a CO-226

Read the remark code on the line, then find the payer's original request. Aetna, for example, tells providers that the remarks on a pended claim's EOB say "what we need, how to send it and the submission deadline."
If you never received the request, ask the payer for a copy, the date it was sent and the address or portal it went to, and fix that contact information.
Send a complete response that references the claim number, and keep proof of what you sent and when.
If the request was about enrollment or revalidation, finish that process first, then ask the payer to reprocess or resubmit the claim as its rules require.
If you had already responded on time with everything requested, appeal and attach your proof of submission. The appeal generator can draft it.
Do not bill the patient. The CO group makes this a provider adjustment.

CO-226 Compared With M127, CO-50, CO-252 and PR-227

On traditional Medicare, the Program Integrity Manual (Pub. 100-08, Chapter 3, section 3.2.3.8) tells contractors that when requested documentation is not received in time they "shall deny the claim" using group CO, CO-50 and remark M127, missing patient medical record. CO-252 means an attachment or other documentation is required to adjudicate the claim. CO-16 means the claim itself lacks information. CARC 227 is the patient-side twin: the request went to the patient or insured instead of you. For a structured appeal, see the insurance appeal letter template.

Frequently Asked Questions

Can I bill the patient for a CO-226 denial?

No. The CO group marks the amount as a contractual adjustment, which CMS describes as a provider write-off that is not billed to the patient. The way to recover it is to answer the payer's request and have the claim reprocessed or appealed.

Does Medicare use CO-226 when I miss an additional documentation request?

Not under the Program Integrity Manual. When a Medicare contractor gets no response to a documentation request, it denies the claim as not reasonable and necessary using CO-50 with remark M127. The same manual gives providers 45 calendar days to answer a MAC, RAC or SMRC request and 30 calendar days for a UPIC request.

What is the difference between CO-226 and CO-252?

CO-226 means the payer already asked you for information and did not receive a complete, timely answer. CO-252 means the payer needs an attachment or other documentation to adjudicate the claim. With either code, the remark code on the line tells you which documents the payer wants.

Can CO-226 be about my enrollment instead of medical records?

Yes. Louisiana Medicaid, for example, uses CARC 226 with remark N831 for provider enrollment edits and sets them to deny when a billing or rendering provider's re-enrollment is incomplete. Check your enrollment status with the payer if the remark mentions revalidation.

Does CO-226 from a primary payer affect a Medicare secondary claim?

It can. CMS Transmittal 13932 (Change Request 14553) tells Part A contractors that, for dates of service from January 1, 2027, Medicare Secondary Payer claims showing CARC 226 with a primary payment amount will be rejected. Clear the primary payer's request before billing Medicare as secondary.

Informational only, not legal, medical, or billing advice. Always verify against your current payer contract and policy.

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