How do I resolve a CO-55 denial?

Verify the rendering provider's specialty as credentialed with the payer Confirm the CPT code is within the provider's licensed scope of practice See full resolution steps at tryarceum.com.

Can I appeal a CO-55 denial?

Yes. Most CO-55 denials can be appealed within 60-180 days depending on payer. This determination is appealable if clinical evidence, peer-reviewed studies, or medical necessity documentation demonstrates the treatment is medically appropriate and not experimental. Use our free tool to generate an appeal letter.

CARC Code

55

🔴 Hard Denial

Experimental or Investigational Treatment

The insurance company has denied this claim because they consider the procedure, treatment, or drug to be experimental or investigational and not yet proven effective for standard care. The payer does not cover services that are still in the research or testing phase.

medical necessity

Resolution: 58%Medium difficulty14-30 days avg

How to resolve this denial

Which payer denied this claim?

Verify provider credential for service and appeal or refer to specialist

1
Verify the rendering provider's specialty as credentialed with the payer
2
Confirm the CPT code is within the provider's licensed scope of practice
3
Review if the payer requires a specific specialty for this procedure
4
If provider is qualified, submit appeal with provider's credentials and state license
5
If procedure was referred to or performed with a specialist, update the claim accordingly
6
Update credentialing records to ensure all provider specialties are on file with each payer

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-55 — stats, related codes, appeal template

58%

Recovery Rate

14-30 days

Avg. Resolution

Medium

Difficulty

Occasional

Frequency

Payer-Specific Notes

How major payers handle CARC 55 by specialty.

Medicare

Certain procedures restricted to specific specialty taxonomy codes; verify with Medicare PECOS

UnitedHealthcare

Hospitalist billing for surgical procedures triggers specialty mismatch; ensure correct provider role

Common 835 Combinations

CARC 55 most often appears with these Group Code + RARC combinations on 835 remittances.

COCO-55The payer has determined the service, treatment, or drug is experimental orAppealable

Look up any combination →

Appeal Letter Template

Generic appeal template for CARC 55 denials.

We are appealing denial of claim [CLAIM_NUMBER] under CARC 55. Dr. [PROVIDER_NAME] holds [CREDENTIALS] and is licensed in [STATE] to perform [PROCEDURE]. Enclosed are the provider's state license, board certification, and credentialing agreement confirming this service is within scope.

Generate a personalized appeal letter →

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