How do I resolve a CO-51 denial?

Review the plan's Summary of Benefits to confirm the service is excluded Inform the patient in writing that the service is not covered under their plan See full resolution steps at tryarceum.com.

Can I appeal a CO-51 denial?

Yes. Most CO-51 denials can be appealed within 60-180 days depending on payer. This is appealable if documentation proves the condition was not pre-existing or if the Affordable Care Act or other regulations prohibit the exclusion. Use our free tool to generate an appeal letter.

CARC Code

51

🔴 Hard Denial

Pre-Existing Condition Not Covered

The insurance plan denied payment because the service was related to a medical condition that existed before the patient's coverage started. The plan does not cover treatment for conditions that were present prior to enrollment.

contractual

Resolution: 35%Hard difficulty21-45 days avg

How to resolve this denial

Which payer denied this claim?

Review pre-existing condition terms; appeal if lookback period has expired

1
Review the plan's Summary of Benefits to confirm the service is excluded
2
Inform the patient in writing that the service is not covered under their plan
3
Determine if an ABN was issued prior to service (required for Medicare)
4
Bill the patient for the non-covered service if an ABN was signed
5
Document the non-coverage determination in the patient account

Resolve this denial →

▶✓ Pre-action checklist — verify before contacting the payer

Review the full remittance advice (ERA/EOB) for additional RARC codes that explain the denial.
Verify the claim was submitted with correct patient eligibility and benefit information.
Check if this denial applies to a specific line item or the entire claim.

▶More about CO-51 — stats, related codes, appeal template

35%

Recovery Rate

21-45 days

Avg. Resolution

Hard

Difficulty

Occasional

Frequency

Payer-Specific Notes

How major payers handle CARC 51 by specialty.

Blue Cross Blue Shield

BCBS requires appeal submission within 180 days for most plans.

Appeal Letter Template

Generic appeal template for CARC 51 denials.

We are submitting a formal appeal for claim [CLAIM_NUMBER] for patient [PATIENT_NAME], date of service [DOS]. This claim was denied/adjusted with CARC 51 indicating: "Non-covered service — pre-existing condition.." We have reviewed the claim and are providing the attached documentation to support reconsideration. [SUPPORTING_DOCUMENTATION]. Please reconsider payment per the terms of our contract.

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