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.
- 1Resubmit the attachment with a corrected claim reference and the required PWK control number.
Sample appeal-letter language for CARC 163
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?
Out of 306 seeded CARCs, ranked by combined US monthly search volume for "CARC 163", "CO-163 denial", and "denial code 163".
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.
CAQH CORE code combinations for CARC 163
Under the CAQH CORE Payment and Remittance Uniform Use rule, health plans may pair CARC 163 only with the remark codes and group codes below for the defined business scenario 1 (Additional information required: missing, invalid or incomplete documentation). A combination outside this list on an 835 is itself a payer compliance issue worth raising.
| RARC | Remark description | Group code | Scenario |
|---|---|---|---|
| (no RARC) | CARC used without a remark code | CO or PI | 1 |
| M19 | Missing oxygen certification/re-certification. | CO or PI | 1 |
| M23 | Missing invoice. | CO or PI | 1 |
| M29 | Missing operative note/report. | CO or PI | 1 |
| M30 | Missing pathology report. | CO or PI | 1 |
| M31 | Missing radiology report. | CO or PI | 1 |
| M60 | Missing Certificate of Medical Necessity. | CO or PI | 1 |
| M127 | Missing patient medical record for this service. | CO or PI | 1 |
| M130 | Missing invoice or statement certifying the actual cost of the lens, less discounts, and/or the type of intraocular lens used. | CO or PI | 1 |
| M135 | Missing/incomplete/invalid plan of treatment. | CO or PI | 1 |
| M141 | Missing physician certified plan of care. | CO or PI | 1 |
| N3 | Missing consent form. | CO or PI | 1 |
| N4 | Missing/Incomplete/Invalid prior Insurance Carrier(s) EOB. | CO or PI | 1 |
| N26 | Missing itemized bill/statement. | CO or PI | 1 |
| N40 | Missing radiology film(s)/image(s). | CO or PI | 1 |
| N42 | Missing mental health assessment. | CO or PI | 1 |
| N146 | Missing screening document. | CO or PI | 1 |
| N178 | Missing pre-operative images/visual field results. | CO or PI | 1 |
| N186 | Non-Availability Statement (NAS) required for this service. Contact the nearest Military Treatment Facility (MTF) for assistance. | CO or PI | 1 |
| N214 | Missing/incomplete/invalid history of the related initial surgical procedure(s). | CO or PI | 1 |
| N221 | Missing Admitting History and Physical report. | CO or PI | 1 |
| N223 | Missing documentation of benefit to the patient during initial treatment period. | CO or PI | 1 |
| N375 | Missing/incomplete/invalid questionnaire/information required to determine dependent eligibility. | CO or PI | 1 |
| N391 | Missing emergency department records. | CO or PI | 1 |
| N393 | Missing progress notes/report. | CO or PI | 1 |
| N395 | Missing laboratory report. | CO or PI | 1 |
| N398 | Missing elective consent form. | CO or PI | 1 |
| N403 | Missing facility certification. | CO or PI | 1 |
| N439 | Missing anesthesia physical status report/indicators. | CO or PI | 1 |
| N445 | Missing document for actual cost or paid amount. | CO or PI | 1 |
| N451 | Missing Admission Summary Report. | CO or PI | 1 |
| N453 | Missing Consultation Report. | CO or PI | 1 |
| N455 | Missing Physician Order. | CO or PI | 1 |
| N457 | Missing Diagnostic Report. | CO or PI | 1 |
| N459 | Missing Discharge Summary. | CO or PI | 1 |
| N461 | Missing Nursing Notes. | CO or PI | 1 |
| N465 | Missing Physical Therapy Notes/Report. | CO or PI | 1 |
| N467 | Missing Tests and Analysis Report. | CO or PI | 1 |
| N473 | Missing certification. | CO or PI | 1 |
| N475 | Missing completed referral form. | CO or PI | 1 |
| N477 | Missing Dental Models. | CO or PI | 1 |
| N479 | Missing Explanation of Benefits (Coordination of Benefits or Medicare Secondary Payer). | CO or PI | 1 |
| N481 | Missing Models. | CO or PI | 1 |
| N485 | Missing Physical Therapy Certification. | CO or PI | 1 |
| N487 | Missing Prosthetics or Orthotics Certification. | CO or PI | 1 |
| N489 | Missing referral form. | CO or PI | 1 |
| N493 | Missing Doctor First Report of Injury. | CO or PI | 1 |
| N495 | Missing Supplemental Medical Report. | CO or PI | 1 |
| N497 | Missing Medical Permanent Impairment or Disability Report. | CO or PI | 1 |
| N499 | Missing Medical Legal Report. | CO or PI | 1 |
| N501 | Missing Vocational Report. | CO or PI | 1 |
| N503 | Missing Work Status Report. | CO or PI | 1 |
| N555 | Missing medication list. | CO or PI | 1 |
| N678 | Missing post-operative images/visual field results. | CO or PI | 1 |
| N680 | Missing/Incomplete/Invalid date of previous dental extractions. | CO or PI | 1 |
| N681 | Missing/Incomplete/Invalid full arch series. | CO or PI | 1 |
| N682 | Missing/Incomplete/Invalid history of prior periodontal therapy/maintenance. | CO or PI | 1 |
| N683 | Missing/Incomplete/Invalid prior treatment documentation. | CO or PI | 1 |
| N685 | Missing/Incomplete/Invalid Prosthesis, Crown or Inlay Code. | CO or PI | 1 |
| N686 | Missing/incomplete/Invalid questionnaire needed to complete payment determination. | CO or PI | 1 |
| N706 | Missing documentation. | CO or PI | 1 |
| N708 | Missing orders. | CO or PI | 1 |
| N710 | Missing notes. | CO or PI | 1 |
| N712 | Missing summary. | CO or PI | 1 |
| N714 | Missing report. | CO or PI | 1 |
| N716 | Missing chart. | CO or PI | 1 |
| N718 | Missing documentation of face-to-face examination. | CO or PI | 1 |
| N729 | Missing patient medical/dental record for this service. | CO or PI | 1 |
| N737 | Missing Sleep Study Report. | CO or PI | 1 |
| N739 | Missing Vein Study Report. | CO or PI | 1 |
| N745 | Missing Ambulance Report. | CO or PI | 1 |
| N749 | Missing Blood Gas Report. | CO or PI | 1 |
| N764 | Missing/incomplete/invalid Hematocrit (HCT) value. | CO or PI | 1 |
| N785 | Missing current radiology film/images. | CO or PI | 1 |
| N791 | Missing history & physical report. | CO or PI | 1 |
| N796 | Missing/incomplete/invalid Hemoglobin (Hb or Hgb) value. | CO or PI | 1 |
| N850 | Missing/incomplete/invalid narrative explaining/describing this service/treatment. | CO or PI | 1 |
| N893 | Missing/incomplete/invalid child medical evaluation form/checklist. | CO or PI | 1 |
| N896 | Missing/incomplete/invalid trauma activation sheet. | CO or PI | 1 |
| N897 | Missing/incomplete/invalid proof of member payment. | CO or PI | 1 |
| N899 | Missing Initial Evaluation Report. | CO or PI | 1 |
| N900 | Missing Therapy Notes/Report. | CO or PI | 1 |
| N902 | Missing Health Risk Assessment (HRA). | CO or PI | 1 |
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.