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CARC 146 · CO-146

CARC 146 Denial: Diagnosis was invalid for the date(s) of service reported — How to Fix and Appeal

Reviewed by QuickIntell RCM Editorial Team · Last reviewed

Updated

TL;DR

CARC 146 (X12 Diagnosis was invalid for the date(s) of service reported). CARC 146 denies because the ICD-10 code submitted was not valid on the date of service — typically because the code was retired or newly introduced in a code-set change.

Official X12 description

“Diagnosis was invalid for the date(s) of service reported.”

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 146 actually means

CARC 146 denies because the ICD-10 code submitted was not valid on the date of service — typically because the code was retired or newly introduced in a code-set change. Fix the ICD to one that was valid on the DOS and resubmit.

Common root causes

  • ICD-10 code changed in an October update (annual release) between scheduling and billing.
  • DOS predates the ICD-10 code's effective date.

Prevention checklist

  • ICD-10 version control in the EHR and scrubber, aligned to DOS.
  • Annual October-release bulletin reviewed by coding leadership before the cutover.

Appeal strategy — step by step

Most CARC 146 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. 1Recode to an ICD-10 valid on the DOS and submit a corrected claim.
Sample appeal-letter language for CARC 146
[Provider letterhead] Re: Appeal of CARC 146 — Claim #{claim_number} Member: {member_name} · Member ID: {member_id} Date(s) of Service: {dos} On {remittance_date} this claim was adjusted with CARC 146: "Diagnosis was invalid for the date(s) of service reported." We respectfully request reconsideration. The X12 External Code List definition of CARC 146 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 146 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 146?

Search demand rank
#70

Out of 306 seeded CARCs, ranked by combined US monthly search volume for "CARC 146", "CO-146 denial", and "denial code 146".

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 146

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 146

What does CARC 146 mean?

CARC 146 is an X12 Claim Adjustment Reason Code. The official definition is: "Diagnosis was invalid for the date(s) of service reported." In plain English, the payer is telling you cARC 146 denies because the ICD-10 code submitted was not valid on the date of service — typically because the code was retired or newly introduced in a code-set change. Fix the ICD to one that was valid on the DOS and resubmit.

How do I resolve a CARC 146 (CO-146) denial?

Start with the most common root cause: ICD-10 code changed in an October update (annual release) between scheduling and billing. First step: Recode to an ICD-10 valid on the DOS and submit a corrected claim. See the full remediation and appeal checklist on this page before filing a formal appeal.

Is CARC 146 patient responsibility?

No — CARC 146 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 146 look like on an EOB or 835 remittance?

On the 835 ERA, CARC 146 appears in Loop 2110 CAS segment as "CAS*CO*146*{amount}". On a paper EOB the same code prints in the Adjustment/Denial Reason column with the X12 description: "Diagnosis was invalid for the date(s) of service reported." — usually paired with one or more RARC remark codes in the same remittance line for additional context.

Which RARC is paired with CARC 146?

CARC 146 is commonly observed with RARC M76. 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.