CO-16 Denial Code: Missing or Incomplete Information on Your Claim

CO-16 means the claim was adjusted because information was missing or incomplete. The group code CO (Contractual Obligation) means the provider writes off the amount for in-network care. This is an administrative denial, not a clinical one — and it is usually fixable by the provider providing the missing information.

If you see CO-16 on your EOB, call the provider's billing office. In most cases, they can provide the missing documentation and the claim will be reprocessed.

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What Information Triggers a CO-16 Denial?

Insurers require specific information to process a claim. Common missing items include:

| Missing Item | Why It Matters | |---|---| | Medical records | The insurer needs clinical documentation to support the service billed | | Referring provider information | Many plans require the name and NPI of the referring provider | | Prior authorization number | If the service required pre-approval, the authorization number must be on the claim | | Diagnosis code supporting medical necessity | The ICD-10 code must justify the procedure performed | | Patient demographic information | Incorrect name, date of birth, or member ID | | Treatment date or place of service | Missing or inconsistent service date or location |

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CO-16 vs. Other Missing-Information Codes

| Code | Meaning | Key Difference | |---|---|---| | CO-16 | Missing/incomplete information | Missing documentation or data | | CO-4 | Missing/incorrect modifier | Specifically about procedure modifiers — see CO-4 denial guide | | CO-50 | Not medically necessary | Clinical decision, not administrative — see CO-50 denial guide | | MA130 | Missing information (remark code) | Can pair with multiple CARCs |

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What to Do About a CO-16 Denial

Step 1: Identify what's missing

Read the RARC code paired with CO-16 on your EOB. The remark code specifies what information is needed. Common RARCs paired with CO-16 include:

• MA130 — Missing documentation (submit medical records)
• N657 — Additional documentation required from provider
• N129 — Missing referring provider information

Step 2: Contact the provider's billing office

The provider has access to the missing information. Ask them:

• "What specific information does the insurer need?"
• "Can you provide the missing documentation and resubmit the claim?"

Step 3: Follow up with your insurer

After the provider resubmits, confirm the claim is being reprocessed. Insurers typically have 30-60 days to process corrected claims.

Step 4: If the provider can't fix it

If the provider is unable or unwilling to resubmit, contact your insurer directly to ask what documentation you can provide yourself.

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How Hedical Can Help

Upload your EOB or denial letter to the Medical Bill & Denial Navigator. Our AI will decode your denial code and identify the specific missing information required to fix it.

Try the Bill & Denial Navigator — free for basic analysis.

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Sources

• ANSI X12 Claim Adjustment Reason Codes, Washington Publishing Company
• 29 CFR §2560.503-1 — ERISA claims procedure
• CMS Medicare Claims Processing Manual, Chapter 1