Denied claims slow down revenue, increase administrative workload, and impact cash flow. One of the most common denial codes practices encounter is CO 16, and while it may look simple, it often hides multiple underlying issues.

At Billing Care Solutions, we help healthcare practices identify the cause of CO 16 denials, correct the errors, and prevent them from recurring—ensuring fast, accurate reimbursement.

What Is CO 16 Denial Code?

CO 16 – Claim/service lacks information or has invalid information.

This means the payer could not process the claim because required information was missing, incomplete, or incorrect.

CO 16 denials often include an additional Remark Code (Nxxx or Mxxx) explaining exactly what is wrong.

Common Reasons for CO 16 Denials

CO 16 can occur for many reasons. The most frequent include:

✔ Missing or invalid patient information

  • Incorrect date of birth

  • Wrong patient name

  • Missing subscriber ID

  • Incorrect policy number

✔ Missing or invalid provider information

  • NPI mismatch

  • Missing taxonomy

  • Incorrect place of service

  • Wrong billing address

✔ Coding errors

  • Wrong CPT or ICD-10 code

  • Invalid code pair

  • Missing modifiers

  • Expired or non-billable code

✔ Authorization or referral missing

  • Prior authorization not obtained

  • Referral number not included

✔ Data entry mistakes

  • Typing errors

  • Missing required claim fields

How to Fix a CO 16 Denial

The solution depends on the attached remark code, but here is a general approach:

1. Review the Explanation of Benefits (EOB) or ERA

Look for the remark code associated with CO 16; this tells you what is missing or invalid.

2. Correct the incomplete or incorrect information

Depending on the cause:

  • Update patient demographics

  • Correct subscriber ID or insurance details

  • Fix coding or modifier errors

  • Add missing authorization/referral

  • Update NPI, taxonomy, or POS

3. Resubmit the corrected claim

After correcting the issue, resubmit the claim as a corrected claim if the payer requires it.

4. Verify eligibility before resubmitting

Sometimes CO 16 is triggered because the payer information is outdated.

Common CO 16 Remark Codes and What They Mean

Here are some examples:

N264 – Missing required information

→ Add missing clinical or administrative details.

N290 – Missing provider consent or signature

→ Ensure required signatures are attached.

M51 – Missing/incomplete/invalid procedure code(s)

→ Correct CPT/HCPCS codes.

MA63 – Missing or invalid patient identifier

→ Update patient/member ID.

Understanding these remark codes is critical to correcting the claim quickly.

How to Prevent CO 16 Denials

Prevention is key to maintaining clean claims and minimizing billing delays. At Billing Care Solutions, we recommend:

✔ Eligibility verification before every visit

Confirm coverage, subscriber ID, PCP requirements, and benefits.

✔ Accurate patient demographic entry

Train staff to double-check spelling, DOB, gender, and policy numbers.

✔ Authorization tracking

Use a system to monitor prior auth requirements and expiration dates.

✔ Regular coding audits

Ensure accurate codes, modifiers, and documentation.

✔ Provider credentialing checks

Verify NPI, taxonomy, and network contracts are current.

✔ Use of claim scrubbers

Catch errors before claims are submitted.

These small steps dramatically reduce CO 16 denials.

Examples of CO 16 Denials in Real Practice

Example 1: Invalid Member ID

A claim is denied because the subscriber ID was missing a digit.
→ Correct ID, resubmit as a corrected claim.

Example 2: Missing Modifier

A bilateral procedure was billed without modifier 50.
→ Add correct modifier and resubmit.

Example 3: Missing Prior Authorization

MRI billed without required authorization.
→ Appeal with authorization or obtain retro auth (if allowed).

Example 4: Incorrect Place of Service

A telehealth visit billed with office POS.
→ Correct to POS 02 or 10 (depending on payer).

How Billing Care Solutions Helps Resolve CO 16 Denials

Our experts help practices:

  • Identify the root cause of CO 16 denials

  • Interpret remark codes accurately

  • Correct and resubmit claims quickly

  • Track payer-specific rules

  • Implement prevention workflows

  • Reduce denials through proactive auditing

Our goal is simple: clean claims, faster payments, and fewer headaches.

Final Thoughts

CO 16 denial code is one of the most common and broad denial reasons in medical billing, but it’s also one of the most fixable. With the right processes in place—accurate data entry, eligibility checks, and coding audits—your practice can significantly reduce CO 16 denials and maintain a healthy revenue cycle.

If you need help reducing denials or improving billing accuracy, Billing Care Solutions is here to support your practice every step of the way.