CO-A1 denial code
A generic denial. X12 requires a remark code alongside it, and that remark code carries the actual reason.
“Claim/Service denied. At least one Remark Code must be provided … Usage: Use this code only when a more specific Claim Adjustment Reason Code is not available.”
Start 01/01/1995 · Last modified 11/16/2022 · X12 adjustment reason code list
What it usually means in behavioral health
A1 is only supposed to be used when no more specific adjustment reason code fits, so the work starts with the remark codes on the same line.
The group code still matters. CO generally means a contractual write-off the provider can't bill to the patient. OA means no other group applies, so the remark code and the contract decide who is liable. PR can be billed to the patient, after checking the verification record.
Common causes
- A1 with M62 or N54: authorization number or authorization match problems
- A1 with N95: the provider type can't bill the service
- A1 with N20: a service not payable with another service the same day
- A1 with N30: patient ineligible for the service
- A1 with N130: a plan benefit restriction applies
Correct and resubmit, or appeal?
Decide from the remark code. Claim-data problems get corrected and resubmitted; MA130 means no appeal rights and a new claim. Coverage or clinical determinations get appealed.
What to do
Read every remark code on the line, and skip any marked Alert; those are informational.
Decide correct-and-resubmit or appeal based on what the remark code says.
Check the corrected-claim and timely-filing deadlines.
Report A1 volume by paired remark code; an A1 count on its own hides the real pattern.
Often seen with
Got a CO-A1 on your desk?
Send us the facts on that one denial — codes, payer, level of care, and dollar amount, no patient information — and within 2 business days we’ll tell you whether to correct or appeal, the deadline to watch, and what evidence would answer it. Free.