CO-97 Denial Explained: Service Already Adjudicated by Payer

A CO-97 denial occurs when a payer determines that the billed service has already been processed under another claim. This denial typically arises when two claims include the same date of service, procedure code, provider information, or service details, making the payer view the new submission as a duplicate or overlapping charge. Because payers rely on strict adjudication logic to prevent duplicate payments, any service that appears to have been previously processed is automatically flagged under CO-97. Understanding why these denials occur is essential for avoiding repeat submissions, ensuring accurate claim corrections, and maintaining clean billing workflows.

What CO-97 Means

A CO-97 denial indicates that the payer has determined the billed service has already been processed under another claim. This typically happens when two submissions appear identical or when part of the service was already included in a previously adjudicated claim—either as a bundled component, duplicate entry, or overlapping service. Payers use automated claim-matching logic that compares dates of service, procedure codes, provider identifiers, modifiers, and diagnosis combinations. When the payer’s system finds a match or detects overlapping services, it flags the new submission as already adjudicated and issues a CO-97 denial.

Common Reasons for CO-97

Duplicate claim submission for the same service:

The most frequent cause is when the same service, on the same date, with the same CPT/HCPCS code, patient, and provider, is unintentionally sent more than once due to workflow overlap, system auto-resubmission, or human error. The payer views the second claim as a duplicate of one that has already been paid.

Service already included on another paid claim:

Sometimes, the service is legitimately billed once but appears as part of another claim, such as when multiple line items or visits are grouped. Any additional attempt to bill the same line is flagged as already processed.

Overlapping dates of service in facility, therapy, or home-health billing:

When date ranges, service intervals, or therapy minutes overlap across claims, especially in SNF, rehab, or home health settings, the payer may assume the services duplicate previous encounter data.

Missing or incorrect modifiers make distinct services look identical:

Suppose separate services performed on the same day aren’t differentiated using proper modifiers (e.g., 25, 59, XS, XE). In that case, the payer may assume they represent the same service and deny them as already adjudicated.

Incorrect submission of corrected or adjusted claims:

Providers sometimes submit corrected claims as brand-new claims instead of using the proper frequency codes (7, 8, etc.). The payer interprets the resubmission as a duplicate of the previously processed claim.

Bundled services billed separately:

Some services are not separately reimbursable because they are included in a comprehensive procedure code. When providers bill individual components that the payer bundles into one payment, the payer denies the additional charges as already adjudicated.

Why CO-97 Denials Occur

CO-97 denials occur when the payer’s adjudication system identifies a service as already processed, either fully or partially, under another claim. Payers use automated matching logic, comparing dates of service, procedure codes, provider identifiers, and claim history, to prevent duplicate or redundant payments. When any service appears duplicated, bundled, or previously included in another encounter, the payer issues a CO-97 denial. Understanding the root causes helps prevent unnecessary rework and ensures clean, accurate billing.

Duplicate submission of identical services

This happens when the same claim is submitted twice, often due to workflow overlap, staff duplication, clearinghouse resubmissions, or EHR automation. Even if unintentional, the payer identifies the repeat and denies it as already adjudicated.

Overlapping or bundled services processed under another claim

Payers often bundle related services, especially in surgery, therapy, evaluation/management, or facility billing. If components of a bundle are billed separately, the payer denies them as already paid within another claim.

Missing or incorrect modifiers that differentiate services

When distinct services performed on the same day lack modifiers such as 25, 59, XS, XE, or RT/LT, they appear identical to the payer. The system assumes duplication and issues a CO-97 denial.

Claim submitted for a service already processed under another date range

In therapies, skilled nursing, or home health, overlapping date ranges or visit counts cause payers to interpret subsequent claims as duplicates, even when they represent separate visits.

Improperly corrected claim or adjustment submission

Submitting corrections as new claims, rather than using frequency codes (7, 8, etc.), causes the payer to view them as repeats. This is one of the most common causes of CO-97 denials in RCM workflows.

COB issues where secondary payers flag previously processed services

If a primary payer has already reimbursed or denied specific services, the secondary payer may deny the same service as already adjudicated, especially if required EOB/ERA details are missing.

Premature resubmission before the payer finishes processing

If a claim is rebilled while the original is still pending, the second submission is flagged as a duplicate because the payer has already begun adjudication on the initial claim.

CMS & AAPC-Aligned Best Practices For CO-97

Preventing CO-97 denials requires strong internal workflows, precise coding, and accurate claim submission processes. By following standardized best practices, healthcare organizations can minimize duplicate billing, prevent overlapping claims, and ensure clean, compliant submissions.

Verify claim status before rebilling or resubmitting

Always check payer portals or clearinghouse status to confirm whether a claim is pending, has been processed, or has been rejected. Resubmitting too early often triggers duplicate adjudication flags.

Use correct frequency codes for corrected or adjusted claims

Claims needing correction should not be submitted as new claims. Applying proper frequency codes (e.g., 7, 8) ensures the payer recognizes the submission as an update, not a duplicate.

Apply appropriate modifiers to distinguish multiple services

When separate services occur on the same date, modifiers (e.g., 25, 59, XS, RT/LT) prevent payers from viewing them as identical. This is critical for E/M, therapy, and surgical billing.

Review payer bundling rules and NCCI edits

Understanding which services are bundled helps prevent the need to bill components separately. NCCI edits reveal code combinations that may trigger duplicate or already-adjudicated denials.

Maintain clear communication among billing, coding, and clinical teams

Many CO-97 denials result from multiple staff members handling the same encounter. Clear internal coordination ensures only one accurate claim version is submitted.

Audit overlapping services and encounter dates

Regular audits help detect patterns such as repeated visit ranges, duplicate therapy minutes, or overlapping facility stays. Catching these issues early prevents repeat CO-97 denials.

Confirm primary payer adjudication before billing secondary

Secondary payers require EOB/ERA documentation showing how the primary processed the claim. Missing or incomplete information causes the secondary payer to deny as “already adjudicated.”

Corrective Action Steps For Denial Code CO-97

Resolving a CO-97 denial requires determining whether the denial is the result of an actual duplicate, a coding issue, or an incorrectly processed claim. The steps below help ensure claims are corrected accurately and resubmitted properly.

Compare the denied claim with previously processed claims

Review past submissions for matching dates of service, CPT/HCPCS codes, provider information, and billed amounts. This identifies whether the payer flagged a legitimate duplicate or made an error.

Identify any overlapping or bundled services

Verify whether the denied service was already included in another claim, either as a separate line item or as a bundled procedure. If so, rebilling may not be the appropriate course of action.

Submit corrected claims using proper frequency codes

If the denial was caused by submitting a corrected claim as “new,” resubmit using the correct frequency code (7, 8, or appropriate payer-specific code) so the payer recognizes it as a replacement.

Add appropriate modifiers to distinguish separate services

If multiple services were performed on the same date, apply accurate modifiers (e.g., 25, 59, XE, XS) to show they are distinct and separately billable.

Rebill only valid for unpaid claim lines

Do not resubmit items the payer has already processed or bundled. Rebill only the lines that are legitimate, distinct, and eligible for separate reimbursement.

Provide EOB/ERA when billing secondary payers

For secondary claims, attach the primary payer’s adjudication details. Missing EOB information results in the secondary payer assuming the service was already processed.

Track claim status to avoid premature resubmissions

Monitor claims closely and avoid resubmitting while a claim is still pending. Premature rebilling is a common cause of CO-97 denials.

BillingFreedom – Duplicate Claim Prevention & Clean Adjudication Support

BillingFreedom helps healthcare organizations prevent CO-97 denials by ensuring every claim is submitted accurately, checked for duplication, and fully aligned with payer adjudication rules. Our team uses advanced claim-scrubbing tools, real-time status monitoring, and precise coding validation to detect overlapping services, incorrect modifiers, and duplicate submissions before claims reach the payer. By identifying and correcting issues early, BillingFreedom reduces denials, supports smooth adjudication, and protects reimbursement from unnecessary write-offs.

Beyond duplicate-claim prevention, BillingFreedom manages corrected claims, COB coordination, and comprehensive denial follow-up for services flagged as already adjudicated. Our experts ensure that corrected claims are filed with the proper frequency codes, secondary claims include the required EOBs, and distinct services are adequately differentiated with the correct modifiers. Partnering with BillingFreedom streamlines your billing workflow, minimizes rework, and ensures your revenue cycle remains efficient, accurate, and compliant.

For more details about our exceptional medical billing services, please don't hesitate to contact us via email at info@billingfreedom.com or call us at +1 (855) 415-3472.

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