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CARC 163 · CO-163

CARC 163 Denial: Attachment/other documentation referenced on the claim was not received — How to Fix and Appeal

Reviewed by QuickIntell RCM Editorial Team · Last reviewed

Updated

TL;DR

CARC 163 (X12 Attachment/other documentation referenced on the claim was not received). CARC 163 indicates the claim referenced an attachment (via PWK segment or cover sheet) that the payer never received.

Official X12 description

“Attachment/other documentation referenced on the claim was not received.”

Source: X12 Claim Adjustment Reason Codes. The X12 External Code Lists are the single authoritative source for every CARC descriptor — always verify against the current release before building a claim-scrub rule.

What CARC 163 actually means

CARC 163 indicates the claim referenced an attachment (via PWK segment or cover sheet) that the payer never received. Resubmit the attachment through the payer's designated channel (fax, portal, or EDI PWK) with the claim reference number, and rebill as needed.

Common root causes

  • PWK segment indicated an attachment but none was received.
  • Fax/portal upload of the attachment failed or was mis-linked to the wrong claim.

Prevention checklist

  • Automated PWK-matching: queue a verification within 48 hours of submission to confirm the attachment was received.
  • Standard cover-sheet template that includes the PWK control number and claim ID.

Appeal strategy — step by step

Most CARC 163 denials clear faster with the right remediation than with a formal appeal. Work the steps in order and escalate only when a lower-effort path has been ruled out.

  1. 1Resubmit the attachment with a corrected claim reference and the required PWK control number.
Sample appeal-letter language for CARC 163
[Provider letterhead] Re: Appeal of CARC 163 — Claim #{claim_number} Member: {member_name} · Member ID: {member_id} Date(s) of Service: {dos} On {remittance_date} this claim was adjusted with CARC 163: "Attachment/other documentation referenced on the claim was not received." We respectfully request reconsideration. The X12 External Code List definition of CARC 163 does not apply to this claim for the following reasons: 1. [Cite the clinical / coding / policy fact that rebuts the adjustment] 2. [Cite the supporting documentation attached — op note, EOB, LCD/NCD citation, NCCI edit indicator, modifier rationale] 3. [Cite the payer's own policy where applicable] Attached: {list supporting documents} Please process payment under the member's benefits. If additional information is required, contact the billing office at {provider_phone} or {provider_email}. Sincerely, {billing_manager_name}, {credentials}

Edit the bracketed fields before sending. This template is a starting point; a payer-specific appeal form may still be required — check the provider portal first.

Payer-specific notes

Payer-specific behavior for CARC 163 publishes here as the QuickIntell anonymized denial ETL ingests sufficient volume. In the meantime, consult the payer directory for the relevant provider manual and appeal form.

How common is CARC 163?

Search demand rank
#72

Out of 306 seeded CARCs, ranked by combined US monthly search volume for "CARC 163", "CO-163 denial", and "denial code 163".

Platform frequency
Pending ETL

Platform frequency ranks publish once the anonymized denial-rate pipeline reaches the publication threshold (strategy §12 Phase 2).

How QuickRCM prevents CARC 163

QuickRCM catches the root causes above before the 837 leaves the clearinghouse:

  • Claim-scrub rules fire on every root cause listed above — the scrub references the same X12 CAS segment logic that drives the denial, so what the payer checks, QuickRCM checks first.
  • When a denial lands, QuickRCM routes it to the correct worker with the documentation bundle already attached (op note, LCD citation, modifier rationale, EOB, primary 835).
  • Appeal templates tuned to each CARC (including this one) pull the supporting facts from the claim and fill the bracketed fields automatically.
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Frequently asked questions — CARC 163

What does CARC 163 mean?

CARC 163 is an X12 Claim Adjustment Reason Code. The official definition is: "Attachment/other documentation referenced on the claim was not received." In plain English, the payer is telling you cARC 163 indicates the claim referenced an attachment (via PWK segment or cover sheet) that the payer never received. Resubmit the attachment through the payer's designated channel (fax, portal, or EDI PWK) with the claim reference number, and rebill as needed.

How do I resolve a CARC 163 (CO-163) denial?

Start with the most common root cause: PWK segment indicated an attachment but none was received. First step: Resubmit the attachment with a corrected claim reference and the required PWK control number. See the full remediation and appeal checklist on this page before filing a formal appeal.

Is CARC 163 patient responsibility?

No — CARC 163 is typically carried under CO (Contractual Obligation) or OA (Other Adjustment), which means it is the provider's responsibility, not the patient's. Do not bill the patient unless the 835 CAS group code is PR.

What does CARC 163 look like on an EOB or 835 remittance?

On the 835 ERA, CARC 163 appears in Loop 2110 CAS segment as "CAS*CO*163*{amount}". On a paper EOB the same code prints in the Adjustment/Denial Reason column with the X12 description: "Attachment/other documentation referenced on the claim was not received." — usually paired with one or more RARC remark codes in the same remittance line for additional context.

Which RARC is paired with CARC 163?

CARC 163 is commonly observed with RARC M127, N706. The RARC narrows the reason — for example, pointing at a missing modifier, an LCD citation, or a specific policy. Fix the underlying CARC first; the RARC usually clears with the corrected claim.

Disclaimer

This page is operational reference for medical-billing professionals. It is not legal, clinical, or contractual advice. X12 code descriptors are maintained by the X12 External Code Lists; always verify against the current X12 release and the payer's own published policy before submitting or appealing a claim.