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APPEAL

CO-4 Modifier Appeal Letter

Appeal template for CARC CO-4 (modifier mismatch). Walks through correct modifier documentation and supporting clinical rationale.

CO-4 Modifier Appeal Letter

[PRACTICE_NAME] [PRACTICE_ADDRESS] [PRACTICE_CITY_STATE_ZIP] [PRACTICE_PHONE] [PRACTICE_FAX] NPI: [RENDERING_PROVIDER_NPI] Tax ID: [PRACTICE_TAX_ID] [DATE] [PAYER_NAME] [PAYER_APPEALS_DEPARTMENT] [PAYER_ADDRESS] [PAYER_CITY_STATE_ZIP] Re: Appeal of Claim Denial -- CARC CO-4 (Procedure Code Inconsistent with Modifier Used) Patient Name: [PATIENT_FIRST_NAME] [PATIENT_LAST_NAME] Member ID: [MEMBER_ID] Date of Service: [DATE_OF_SERVICE] Claim Number: [CLAIM_NUMBER] Procedure Code: [CPT_CODE] Modifier(s) Reported: [MODIFIERS_REPORTED] Dear Appeals Review Committee: I am writing to appeal the denial of the above-referenced claim under CARC CO-4. The denial indicates that the procedure code is inconsistent with the modifier(s) used. We respectfully submit that the modifier(s) reported on this claim were correctly applied based on the documented clinical circumstances and the applicable NCCI policy. CLINICAL RATIONALE FOR MODIFIER: Modifier [MODIFIER_CODE] was appended to procedure [CPT_CODE] to indicate [MODIFIER_CLINICAL_REASON]. Specifically, on [DATE_OF_SERVICE], [PATIENT_FIRST_NAME] [PATIENT_LAST_NAME] underwent [PROCEDURE_DESCRIPTION] in conjunction with [SECOND_PROCEDURE_OR_CIRCUMSTANCE]. The treating provider documented [SPECIFIC_DOCUMENTATION_QUOTE] supporting that the services were [DISTINCT_SEPARATE_OR_BILATERAL_AS_APPLICABLE]. NCCI POLICY SUPPORT: Per the CMS NCCI Policy Manual, Chapter [CHAPTER_NUMBER], Section [SECTION_NUMBER], modifier [MODIFIER_CODE] is appropriate when [CITED_NCCI_GUIDANCE]. The code pair [PRIMARY_CPT] / [SECONDARY_CPT] permits modifier override when documentation supports the clinical distinction described above. We have enclosed the relevant excerpt from the NCCI Policy Manual along with the operative or procedure note that demonstrates the supporting documentation. CORRECTED CLAIM (IF APPLICABLE): [USE THIS PARAGRAPH ONLY IF SUBMITTING A CORRECTED CLAIM] Upon review, we have determined that modifier [ORIGINAL_MODIFIER] was reported in error. The clinically appropriate modifier is [CORRECTED_MODIFIER], which we have applied to the enclosed corrected claim. We respectfully request that the payer process the corrected claim under frequency code 7 and re-adjudicate accordingly. ENCLOSED DOCUMENTATION: 1. Operative or procedure note from [DATE_OF_SERVICE] 2. NCCI Policy Manual excerpt: Chapter [CHAPTER_NUMBER], Section [SECTION_NUMBER] 3. Clinical documentation supporting modifier application 4. Corrected claim form (if applicable) 5. Original Explanation of Benefits dated [EOB_DATE] This appeal is submitted within the [APPEAL_DEADLINE_DAYS]-day filing window from the EOB date. We respectfully request re-adjudication of the original claim or, if a corrected claim was enclosed, processing of the corrected submission. If the Appeals Review Committee determines that clinical review is warranted, we are available for peer-to-peer discussion at [PRACTICE_PHONE]. Respectfully, [PROVIDER_NAME], [PROVIDER_CREDENTIALS] [PROVIDER_TITLE] NPI: [RENDERING_PROVIDER_NPI] Enclosures: [NUMBER_OF_ENCLOSURES] cc: Patient file

Clinical Rationale for Modifier

CO-4 reviewers look for documentation that the modifier reflects what actually happened clinically, not just billing convenience. Quoting the operative note directly is more persuasive than paraphrasing it.

NCCI Policy Manual Citation

The NCCI Policy Manual is the authoritative source for modifier-pair logic. Citing the specific chapter and section signals that the appeal is grounded in published policy, not provider preference, and reduces the chance of a secondary denial.

Common Modifier-Pair Mistakes

CO-4 most often results from modifier 59 used without a Column 1/Column 2 distinction, modifier 25 attached to non-E/M codes, or bilateral modifier 50 reported on inherently bilateral procedures. Naming the correct modifier and the reason it applies short-circuits the most common reviewer objections.

Peer-to-Peer Offer

Offering a peer-to-peer review at the close of the letter signals confidence and gives the medical director a fast path to overturn without writing a second appeal. Escalate to peer-to-peer when the modifier is clinically nuanced rather than purely procedural.

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