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- X12 defines CARC 16 as claim/service lacks information or has submission/billing error(s).
- Usually resubmit. CO-16 points to a data problem.
- 2.
What CO-16 means
X12 defines CARC 16 as "Claim/service lacks information or has submission/billing error(s)." Its usage note says at least one Remark Code must be provided, either an NCPDP reject reason or a Remittance Advice Remark Code that is not an alert. So a CO-16 is never the whole story. The RARC next to it tells you which field failed.
The good news: CO-16 is usually a fixable data problem, not a coverage decision. Correct the field and resubmit under the payer's corrected-claim rules. Some payers pair it with RARC MA130, which X12 says means the claim contains incomplete or invalid information and "no appeal rights are afforded because the claim is unprocessable," asking for a new claim with complete and correct information. In that case you resubmit instead of appealing.
Watch out. Do not resend the same claim. If anything was wrong, submit a corrected claim so the payer does not deny it as a duplicate.
Remark codes that commonly ride with CO-16 on ABA claims
| RARC | X12 definition | Where to look |
|---|---|---|
| N290 | Missing/incomplete/invalid rendering provider primary identifier. | Rendering NPI (CMS-1500 item 24J) for the RBT, BCaBA or BCBA, per the payer's rendering rules. |
| N286 | Missing/incomplete/invalid referring provider primary identifier. | Referring physician NPI. ABA often requires a physician referral or order. |
| M77 | Missing/incomplete/invalid/inappropriate place of service. | Place of service code for home, clinic, school or telehealth. |
| M51 | Missing/incomplete/invalid procedure code(s). | CPT code on the line, for example 97153 versus 97155. |
| N822 / N823 | Missing procedure modifier(s). / Incomplete/Invalid procedure modifier(s). | Credential modifiers (HM, HN, HO), group-size modifiers, telehealth modifiers. |
| N575 | Mismatch between the submitted ordering/referring provider name and the ordering/referring provider name stored in our records. | Referring provider name spelled differently from the payer file. |
Why ABA claims hit CO-16 so often
An ABA claim carries more people than most professional claims: a billing provider, often a different rendering provider on each line, a supervising analyst, and a referring physician. Each has an identifier the payer checks. ABA also leans on modifiers. Florida Medicaid's fee schedule, for example, uses HN to mark a BCaBA on 97155 and 97156, TS for a behavior reassessment on 97151, GT for family training by telemedicine, and UN through US to show group size on 97154 and 97158. A missing or wrong modifier is a submission error.
Time and units are the other big source. Florida Medicaid's coverage policy (section 8.2) bills behavior analysis in 15-minute units: divide total minutes by 15, and a remainder of 8 minutes or more counts as one more unit while a remainder under 8 does not. When the units on the claim do not follow from the start and end times in the session note, the claim and the record disagree. A payer may not deny that as CO-16, but an auditor will notice.
How to fix a CO-16
- Read every RARC on the line. If there is none, call the payer: X12's usage note says one is required.
- Find the field in your claim data (837P loop or CMS-1500 item) and compare it with the source: the NPI registry, the referral on file, the authorization, the session note.
- Correct the data at the source, not just on the claim, so the next claim does not repeat the error.
- Resubmit as a corrected or new claim, as the payer instructs. Watch the timely filing limit; X12 CARC 29 means "The time limit for filing has expired."
Prevent it upstream
Most CO-16 causes start in the session record: the wrong rendering provider attached to the session, a place of service that does not match where the note says the session happened, a missing modifier for the practitioner's credential, or units that do not match the documented minutes. Checking each note against those rules before the claim is built removes the bulk of them.
Whatever software you use, the pattern is the same: the claim is built from the session note, so most of these problems can be caught before the claim is submitted.
Tip. Read the RARC on the same remittance line. It often names the exact field or document the payer wants.
FAQ
What does denial code CO-16 mean?
X12 defines CARC 16 as claim/service lacks information or has submission/billing error(s). The payer must send at least one remark code that explains what is missing or wrong.
Should I appeal a CO-16 or resubmit?
Usually resubmit. CO-16 points to a data problem. If the payer also sends RARC MA130, X12 says the claim is unprocessable with no appeal rights, and a new claim with complete information is expected.
How are ABA units calculated in Florida Medicaid?
In 15-minute units: total minutes divided by 15, with a remaining 8 or more minutes counting as one unit and fewer than 8 not counting, per the Florida Medicaid Behavior Analysis Services Coverage Policy section 8.2.
Stop denials where they start.
Most of what payers reject was visible in the note. Let us show you on your own claims.
Related guides
Sources
- X12, Claim Adjustment Reason Codes
- X12, Remittance Advice Remark Codes
- X12, Claim Adjustment Group Codes
- NUCC, 1500 Claim Form Reference Instruction Manual (v13, July 2025)
- AHCA, Behavior Analysis Fee Schedule, January 1, 2025 (incorporated in Rule 59G-4.002, F.A.C.)
- AHCA, Florida Medicaid Behavior Analysis Services Coverage Policy (Dec 2024), incorporated in Rule 59G-4.125, F.A.C.
Last reviewed October 2026. This page summarizes public rules and vendor pages for education; it is not legal or billing advice. Payer contracts and plan manuals can add requirements, so confirm with the payer.