Claim adjustment reason code · X12
CARC 16: claim lacks information.
CARC 16 says something is missing or wrong on the claim, and the remark code beside it says what. Fix that item and submit a corrected claim. It is not a coverage decision.
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What X12 says CARC 16 means
Claim/service lacks information or has submission/billing error(s).
CARC 16 · Start 01/01/1995, last modified 03/01/2018.
X12 usage note: Do not use this code for claims attachment(s)/other documentation. 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.) Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.
Two rules in the usage note do most of the work. First, the payer must send at least one remark code with CARC 16, either a Remittance Advice Remark Code that is not an ALERT or an NCPDP reject reason code. Second, CARC 16 is not for claim attachments or other documentation. A request for records should come through a different code.
Read the remark code first
CARC 16 alone cannot be fixed, because it names no field. The paired RARC does. Find the RARC on the same line of the remittance, then look it up in the official X12 list of remark codes. This tool covers only a few remark codes; the full list is the source of truth. If a CARC 16 line arrives with no remark code, it breaks the X12 rule above and is worth a call to the payer.
A practical fix sequence
- Copy the RARC from the remittance for the line or claim.
- Look up its wording in the X12 remark code list and find the field it points to.
- Check the claim against your records: subscriber ID, dates of service, diagnosis pointers, procedure code and modifier, NPI, place of service.
- Correct the claim and submit it as a corrected or replacement claim in the format the payer requires. This is normally not an appeal, but confirm with the payer.
- Watch the filing deadline while you fix it. See CARC 29.
Worked example (hypothetical)
A remittance shows CO-16 on line 2 with a remark code. You look the remark code up and it points at a missing or invalid field. You correct the field, resubmit, and note the date. The original line is not appealed because nothing about coverage was decided.
Sources
- X12: Claim Adjustment Reason Codes — code text, start and last-modified dates (list dated 10/30/2026, retrieved 2026-11-01)
- X12: Remittance Advice Remark Codes — full remark code list (retrieved 2026-11-01)
Every code description and rule above was retrieved from these pages on November 1, 2026. Payers revise code lists, contracts and policies, so confirm anything that affects a claim or a deadline with the payer.
Frequently asked questions
Is CARC 16 a denial I can appeal?
It is a rejection for missing or wrong information. Fix the claim and resubmit it. Appeals are for coverage or payment decisions. Ask the payer if you are unsure which path it wants.
Why does CARC 16 always come with another code?
X12 requires at least one remark code with CARC 16, because 16 alone does not say what is missing.
Does CARC 16 mean I need to send medical records?
No. X12 says not to use CARC 16 for claim attachments or other documentation.
Not legal, billing or medical advice
This page explains published code lists and rules and runs a lookup in your browser. It cannot see your claim, your contract or any payer's policy. Confirm with the payer or your Medicare Administrative Contractor before you resubmit, appeal or bill a patient.