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CARC 45 · CO-45

CARC 45 Denial: Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arra… — How to Fix and Appeal

Reviewed by QuickIntell RCM Editorial Team · Last reviewed

Updated

TL;DR

CARC 45 (X12 Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement). CARC 45 is the contractual write-off — the difference between what you billed and what the payer's contracted / Medicare-allowed rate permits.

Official X12 description

“Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.”

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 45 actually means

CARC 45 is the contractual write-off — the difference between what you billed and what the payer's contracted / Medicare-allowed rate permits. This is expected on every in-network claim and is the single largest recurring adjustment in most medical practices' accounting. It is not a denial and not appealable. The action is to post the adjustment correctly and reconcile it against your contracted fee schedule so you can catch payer underpayments against the contract.

Common root causes

  • Standard contractual discount between billed charges and the payer's allowed amount.
  • Out-of-network reduction against the payer's usual-and-customary or Medicare-based benchmark (when applicable).

Prevention checklist

  • Post CARC 45 adjustments to a contractual-adjustment account, not a bad-debt or denial account, so denial analytics stay clean.
  • Reconcile allowed amounts against your loaded fee schedule at the claim-line level to catch payer underpayments disguised as normal CARC 45 adjustments.

Appeal strategy — step by step

Most CARC 45 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. 1Not appealable as a denial — this is a contractual adjustment.
  2. 2If the allowed amount is less than your contracted rate, appeal as an underpayment: cite the contracted fee schedule and line-level variance.
  3. 3For out-of-network balance-billing situations, check state surprise-billing laws (No Surprises Act / state equivalents) before pursuing the patient for the CARC 45 difference.
Sample appeal-letter language for CARC 45
[Provider letterhead] Re: Appeal of CARC 45 — Claim #{claim_number} Member: {member_name} · Member ID: {member_id} Date(s) of Service: {dos} On {remittance_date} this claim was adjusted with CARC 45: "Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement." We respectfully request reconsideration. The X12 External Code List definition of CARC 45 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 45 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 45?

Search demand rank
#2

Out of 306 seeded CARCs, ranked by combined US monthly search volume for "CARC 45", "CO-45 denial", and "denial code 45".

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 45

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 45

What does CARC 45 mean?

CARC 45 is an X12 Claim Adjustment Reason Code. The official definition is: "Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement." In plain English, the payer is telling you cARC 45 is the contractual write-off — the difference between what you billed and what the payer's contracted / Medicare-allowed rate permits. This is expected on every in-network claim and is the single largest recurring adjustment in most medical practices' accounting. It is not a denial and not appealable. The action is to post the adjustment correctly and reconcile it against your contracted fee schedule so you can catch payer underpayments against the contract.

How do I resolve a CARC 45 (CO-45) denial?

Start with the most common root cause: Standard contractual discount between billed charges and the payer's allowed amount. First step: Not appealable as a denial — this is a contractual adjustment. See the full remediation and appeal checklist on this page before filing a formal appeal.

Is CARC 45 patient responsibility?

No — CARC 45 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 45 look like on an EOB or 835 remittance?

On the 835 ERA, CARC 45 appears in Loop 2110 CAS segment as "CAS*CO*45*{amount}". On a paper EOB the same code prints in the Adjustment/Denial Reason column with the X12 description: "Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement." — usually paired with one or more RARC remark codes in the same remittance line for additional context.

Can CARC 45 be appealed successfully?

Yes — when the root cause does not apply to the specific claim. Overturn rates are strongest when the appeal cites the X12 definition, the payer's own published policy, and documentation that rebuts the payer's rationale. The sample appeal language block above is a starting point; always adapt it to the payer's reconsideration form.

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.