Official CARC description: “An attachment/other documentation is required to adjudicate this claim/service.” Here’s what it actually means, why it fires, and how to get the claim paid.
The payer won't decide without paperwork — records, invoices, or certificates. Not a denial on the merits; the claim is parked until you supply the documents.
Liability group: CO = Contractual Obligation — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.
Also written: CO-252, CO252, “denial code 252”, “252 denial code” or “reason code 252” — same CARC, different ERA formatting.
Read the RARC to identify the exact document requested
Send it through the payer's designated channel (portal upload beats fax) with the claim number on every page
Calendar the follow-up — payers routinely “lose” these after 45–60 days of silence
For repeat offenders, attach the documentation proactively at first submission
Not an appeal — a document delivery. It becomes an appeal only if the payer denies after receiving records; then appeal on the merits with a point-by-point rebuttal.
Fill in the denial facts — use placeholders, never real patient data (the letter keeps [PATIENT NAME]-style fields so you can merge real details privately). A payer-ready draft with an enclosure checklist comes back in ~20 seconds.
Your appeal letter draft will appear here.
The official CARC description for CO 252 is: “An attachment/other documentation is required to adjudicate this claim/service.” In practice: The payer won't decide without paperwork — records, invoices, or certificates. Not a denial on the merits; the claim is parked until you supply the documents.
Denial code 252 under the CO group (Contractual Obligation) means: An attachment/other documentation is required to adjudicate this claim/service. The number is the reason; the CO prefix decides who is liable — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.
Yes. CO 252, CO-252, CO252 and “denial code 252” are the same CARC — clearinghouses, payer portals and PM systems just print it differently. Only the group prefix (CO, PR, OA or PI) changes the meaning, because it changes who has to absorb the amount.
CO stands for Contractual Obligation — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.
Not an appeal — a document delivery. It becomes an appeal only if the payer denies after receiving records; then appeal on the merits with a point-by-point rebuttal.