How does Counterclaim generate an insurance appeal letter?

Counterclaim uses a 5-agent AI pipeline. The Reader extracts claim data from your document. The Researcher identifies applicable state insurance law. The Writer drafts a formal appeal letter. The Adversary identifies weaknesses. The Editor rewrites the letter to eliminate all weaknesses. The final letter is ready to print and mail in minutes.

Is Counterclaim free to use?

Yes - Counterclaim is free during the launch period. Upload your denial letter and receive a complete adversary-tested appeal letter at no cost. No account required.

What types of insurance denials can Counterclaim handle?

Counterclaim handles all major denial types: medical necessity (CO-50), prior authorization (CO-11), experimental treatment (PR-1), fee schedule (CO-45), timely filing (PR-27), not covered (CO-4), step therapy (PR-50), and missing information (CO-16).

What file formats does Counterclaim accept?

Counterclaim accepts PDF files, JPG and PNG photos, and scanned documents of your denial letter or Explanation of Benefits (EOB).

Does Counterclaim provide legal advice?

No. Counterclaim generates appeal letters based on publicly available legal and clinical information but does not constitute legal advice. For complex cases, consult a licensed healthcare attorney or certified patient advocate.

34 codes indexed

Master list of insurance denial codes

The complete lookup of common X12 / CARC denial codes used on US health insurance Explanations of Benefits and remittance advices. Two-letter prefixes identify who is responsible for the unpaid amount: CO (Contractual Obligation, the provider must write off), PR (Patient Responsibility), OA (Other Adjustment), and PI (Payer Initiated). The numeric portion identifies the specific reason.

Codes shown in the directory below link to a full appeal guide when one is published. The 15 most-searched codes have detailed writeups, browse the deep guides here.

Showing 34 of 34 codes

Code	Description	Category	Guide
CO-4	Procedure code is inconsistent with the modifier used, or a required modifier is missing. Often a coding error the provider can correct and resubmit.	Administrative	Read guide
CO-11	Diagnosis is inconsistent with the procedure, in practice, prior authorization was missing or did not match what was billed.	Prior authorization	Read guide
CO-15	Authorization or pre-certification number was missing, invalid, or did not match the service. Verify and resubmit with the correct auth.	Prior authorization	Read guide
CO-16	Claim or service lacks information or has a submission/billing error. Read the accompanying RARC for the specific missing field.	Administrative	Read guide
CO-18	Exact duplicate claim. Verify the original was paid before resubmitting, and use a corrected-claim indicator if appropriate.	Bundling / duplicates	Read guide
CO-22	Care may be covered by another payer per coordination of benefits. Submit to the primary insurer first, then re-bill secondary.	Coordination of benefits	Read guide
CO-27	Expenses incurred after coverage terminated. Verify enrollment dates, COBRA election, and grace period rules.	Coverage	Read guide
CO-29	Time limit for filing has expired. Provide proof of timely original submission and request a good-cause exception.	Timely filing	Read guide
CO-31	Patient cannot be identified as our insured. Verify the member ID and date of birth on the claim against the insurance card.	Administrative	Read guide
CO-45	Charges exceed the contracted or legislated fee arrangement. In-network providers must write off the difference.	Fee schedule	Read guide
CO-50	Non-covered services because the payer does not deem the service medically necessary. Most common medical-necessity denial.	Medical necessity	Read guide
CO-242	Services not provided by network or primary care providers. Common when an HMO referral or PCP coordination requirement was not met.	Network	Read guide
CO-96	Non-covered charge. Read the accompanying RARC for the specific exclusion the plan is asserting.	Coverage	Read guide
CO-97	Benefit is included in the payment for another service already paid. Often used to deny out-of-network or bundled charges.	Network	Read guide
CO-109	Claim or service not covered by this payer or contractor, you must send it to the correct payer or jurisdiction.	Administrative	Read guide
CO-119	Benefit maximum for the time period or occurrence has been reached. Verify the accumulator math against your EOBs.	Coverage	Read guide
CO-167	Diagnosis is not covered. Often a state-mandated or ACA-required benefit the plan is improperly excluding.	Coverage	Read guide
CO-197	Pre-certification, authorization, notification, or pre-treatment requirement absent. Same family as CO-11 and CO-15.	Prior authorization	Read guide
CO-204	Service, equipment, or drug is not covered under the patient's current benefit plan.	Coverage	Read guide
PR-1	Deductible amount the patient owes before the plan begins paying. Verify the year-to-date accumulation if the amount looks wrong.	Patient cost-sharing	Read guide
CO-55	Procedure, treatment, or drug is deemed experimental or investigational by the payer. Frequently appealable when the treatment is FDA-approved for the diagnosis.	Medical necessity	Read guide
PR-2	Coinsurance amount the patient owes after the deductible is met.	Patient cost-sharing	No deep guide yet
PR-3	Co-payment amount the patient owes at the time of service.	Patient cost-sharing	No deep guide yet
PR-27	Expenses incurred after coverage terminated, billed to the patient. Often appealable through COBRA or grace period rules.	Timely filing	Read guide
PR-31	Patient cannot be identified as our insured. The plan is putting the eligibility burden on the patient.	Administrative	No deep guide yet
PR-49	Non-covered routine or preventive service, often a coding error since ACA preventive services must be covered at 100%.	Coverage	Read guide
PR-50	Non-covered services not deemed medically necessary, billed to the patient. Often used for step-therapy enforcement.	Medical necessity	Read guide
PR-96	Non-covered charge billed to the patient. Verify against your benefits booklet for the alleged exclusion.	Coverage	No deep guide yet
PR-119	Benefit maximum for the time period or occurrence has been reached, with the balance billed to the patient.	Coverage	No deep guide yet
PR-204	Service, equipment, or drug is not covered under the patient's plan, with the balance billed to the patient.	Coverage	No deep guide yet
OA-23	Impact of prior payer adjudication, including payments and adjustments. Common when a primary insurer has already paid.	Coordination of benefits	No deep guide yet
OA-18	Exact duplicate claim flagged by the payer's automated edits. Confirm status of the original before resubmitting.	Bundling / duplicates	Read guide
MHPAEA	Mental health or substance use parity violation, the plan applies stricter limits than to comparable medical care.	Coverage	Read guide
NSA	Surprise out-of-network bill from an emergency or in-network facility. Likely capped at in-network cost-sharing under the No Surprises Act.	Network	Read guide

Code descriptions paraphrase the official Washington Publishing Company (WPC) Claim Adjustment Reason Code (CARC) list maintained for HIPAA-mandated 835 transactions. Always read the accompanying Remittance Advice Remark Codes (RARCs) on your EOB for the full context of any denial.

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