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CO-226 Denial Code: Provider Didn't Send Requested Info

CO-226 means the payer requested information from the billing or rendering provider, and it was not provided, not provided on time, or was insufficient or incomplete. The remark code tells you what the payer asked for.

Quick facts

Code
CO-226 (CARC 226)
Status
Active In use since September 21, 2008; last modified July 1, 2013.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The provider is responsible because the provider did not supply the requested information. The amount generally cannot be billed to the patient.
Official description
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.)
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-226 means

CARC 226 says information requested from the billing or rendering provider was not provided, was not provided timely, or was insufficient or incomplete. It is the end of a sequence: the payer received the claim, sent a request for more information (an additional documentation request, a records request, or a development letter), and then closed the claim when the response didn’t satisfy the request.

X12 requires at least one remark code with CARC 226, and that remark is what tells you what was missing. Medical records, an itemized bill, operative notes, and invoices are common examples.

Think of CO-226 as a documentation-workflow denial. The service may be perfectly payable; the payer just never got what it needed to decide.

Common causes

  • Records request not answered within the payer’s deadline.
  • Request sent to the wrong place, such as an old mailing address or an unmonitored portal inbox.
  • Partial response, such as progress notes without the signed order or the plan of care.
  • Response not linked to the claim, for example missing the claim number or a cover sheet, so the payer could not match it.
  • Illegible or unsigned documents treated as insufficient.

How to fix it

  1. Read the remark code and any request letter to see exactly what was asked for.
  2. Assemble a complete response: every requested document, signed and dated, with the payer’s cover sheet or claim number on each page.
  3. Send it through the channel the payer specifies (portal upload, fax, or electronic attachment) and keep proof of submission.
  4. Ask whether the payer reopens the claim on receipt or needs a reconsideration or appeal. Follow that path within its deadline.
  5. If you never received the request, document that and ask the payer to accept the information now. Then correct the address or contact on file.
  6. Do not send a duplicate claim, which can trigger a duplicate denial. See CO-18 duplicate claims.

How to prevent it

  • Assign one owner to watch every payer channel for documentation requests, including portals, mail, and fax.
  • Log each request with its due date and track it to completion.
  • Keep your correspondence address current with every payer.
  • Build standard record packets for services that often draw requests, so responses are complete the first time.
  • Watch for patterns; an ERA Analyzer can show which payers and services generate CO-226 most often.

For more on attachment and documentation denials, see CO-16 missing or invalid information and the related CO-252 page.

Remark codes that may appear with CO-226

  • M127 (Missing patient medical record for this service.): The medical record for the service was the missing item.
  • N706 (Missing documentation.): Documentation was missing entirely.
  • N705 (Incomplete/invalid documentation.): Documentation was received but was incomplete or invalid.
  • N26 (Missing itemized bill/statement.): An itemized bill or statement was requested and not received.
  • CO-227 (Information requested from the patient/insured/responsible party was not provided or was insufficient/incomplete.): The information was requested from the patient or insured rather than from the provider.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment is required before the claim can be adjudicated; it usually appears before a request goes unanswered.
  • CO-251 (The attachment/other documentation that was received was incomplete or deficient.): Documentation was received but was deficient, and the information is still needed.
  • CO-163 / CO-164 (Attachment referenced on the claim not received, or not received timely.): The claim said documentation was coming, and it never arrived or arrived late.

CO-226 FAQ

Can a CO-226 denial be reversed?

Often, yes. Many payers will reopen or reconsider the claim once they receive the requested information, although some require a formal appeal. Check the payer's instructions and deadlines.

Why did I get CO-226 when I never saw a request?

Requests can go to an old address, a portal inbox nobody monitors, or a different department. Ask the payer when and where the request was sent, and fix the routing.

Can I bill the patient for CO-226?

No. The provider did not supply the information, so the CO group keeps the liability with the provider.

How is CO-226 different from CO-16?

CO-16 means the claim itself was missing data or had billing errors. CO-226 means the payer asked for more information after receiving the claim, and that request went unanswered or was answered incompletely.