Claim denials are one of the biggest drains on revenue cycle performance in healthcare. Every denied claim means delayed cash flow, added administrative work, and — if it isn’t corrected and resubmitted in time — lost revenue altogether. Understanding what your denial codes actually mean is the first step toward fixing the root cause and preventing the same denial from happening again.
Below, we break down five of the most common Claim Adjustment Reason Codes (CARCs) that billing teams run into, what triggers them, and how to resolve or appeal each one.
What Are CARC Denial Codes?
Claim Adjustment Reason Codes (CARCs) are standardized codes used by payers to explain why a claim was denied, reduced, or adjusted. They’re typically paired with a Group Code — like CO (Contractual Obligation), PR (Patient Responsibility), or OA (Other Adjustment) — that tells you who is financially responsible for the adjustment. A “CO” prefix generally means the provider cannot bill the patient for that amount; the adjustment has to be resolved through correction, appeal, or write-off. For the full official code set, refer to the Washington Publishing Company’s CARC list maintained under X12 standards.
Denial Code Quick Reference
| Code | What It Means | Typical Cause | How to Resolve |
| CO-22 | Care may be covered by another payer | Coordination of benefits (COB) mismatch | Verify COB, rebill correct primary payer |
| CO-50 | Non-covered service — not medically necessary | Diagnosis code doesn’t support medical necessity | Confirm coding accuracy, review CMS LCD guidelines, appeal with clinical documentation as permitted |
| CO-97 | Benefit bundled into another service’s payment | NCCI/bundling edit triggered | Check bundling rules, apply modifier if applicable |
| CO-109 | Claim not covered by this payer/contractor | Wrong payer billed or outdated eligibility | Reverify eligibility, resubmit to correct payer |
| CO-253 | Sequestration reduction | Mandated federal Medicare payment cut | No action needed — reconcile in financial reporting |
CO-22: This Care May Be Covered by Another Payer
CO-22 shows up when the payer believes another insurance plan should be billed first, usually due to a coordination of benefits (COB) issue. This is common when a patient has multiple active policies (for example, a secondary insurance, a spouse’s plan, or Medicare as a secondary payer) and the payer’s records don’t reflect the correct billing order.
How to fix it: Verify the patient’s coordination of benefits at the time of intake and before every visit if possible. If COB information is outdated with the payer, have the patient contact the insurer directly to update it, then resubmit the claim to the correct primary payer first.
CO-50: Non-Covered Services Not Deemed a Medical Necessity
CO-50 means the payer has determined the service isn’t medically necessary based on the diagnosis code(s) submitted, or that the documentation doesn’t support the level of service billed.
How to fix it: Review the service rendered along with any CMS LCD guidelines. Confirm the diagnosis code(s) accurately reflects the patient’s condition and supports the medical necessity of the procedure performed versus any located LCD guidelines. Update coding to align with the LCD requirements, as applicable. If medical necessity is not met, this is typically appealable with supporting clinical documentation.
CO-97: Benefit Included in Payment for Another Service
CO-97 is triggered when the payer considers the billed service already bundled into the reimbursement for another procedure billed on the same claim, meaning it won’t be paid separately.
How to fix it: Check for bundling and National Correct Coding Initiative (NCCI) edits before submission. If the services genuinely should be billed separately, an appropriate modifier (when applicable) may need to be appended, along with documentation showing the services were distinct and separately identifiable. If review of the NCCI edits confirms bundled billing, take appropriate corrective action to reflect accurate coding, and refile the claim as needed.
CO-109: Claim Not Covered by This Payer/Contractor
CO-109 means the payer you billed isn’t the correct entity to process the claim, often because the patient has since changed plans, has a different payer for that specific service type, or the claim was routed to the wrong contractor.
How to fix it: Reverify patient eligibility and payer information at the time of service and confirm you’re billing the correct plan or contractor for that specific service line. Resubmit to the correct payer once identified.
CO-253: Sequestration Reduction
CO-253 relates to the federal sequestration reduction, a mandated percentage cut applied to certain Medicare payments. Unlike the codes above, this isn’t the result of a billing error — it reflects a required, non-negotiable payment adjustment.
How to fix it: There’s typically nothing to correct or appeal here; this is an automatic reduction applied at the payer level. The best practice is simply accounting for it accurately in your revenue projections and reconciliation processes, so it isn’t mistaken for a billing error.
Building a Denial Management Strategy Into Your RCM
Individually resolving denials is necessary, but the bigger win comes from identifying patterns across your denial data. Effective [denial management within revenue cycle management] (internal link placeholder → /revenue-cycle-management/) typically includes tracking denials by code and payer to spot recurring issues, auditing front-end processes like eligibility verification and coding accuracy where most preventable denials originate, and building a standardized appeals workflow so time-sensitive denials don’t fall through the cracks.
Organizations that treat denial codes as a feedback loop — rather than a one-off fix — tend to see steady reductions in denial rates over time rather than just reactive firefighting.
Frequently Asked Questions
What is the fix for a CO-22 denial?
A CO-22 denial usually means another payer should have been billed first. Verify the patient’s coordination of benefits, update it with the payer if it’s outdated, and resubmit the claim to the correct primary insurer.
How do I appeal a CO-97 denial?
To appeal a CO-97 denial, confirm the service wasn’t correctly bundled under NCCI edits, gather documentation showing the procedures were distinct and separately identifiable, apply the appropriate modifier if applicable, and submit an appeal with supporting clinical notes to the payer.
Can AI actually reduce claim denial rates and by how much?
AI-driven denial management tools can meaningfully reduce preventable denials by flagging likely issues — such as coding mismatches or eligibility gaps — before a claim is submitted. Actual reduction rates vary by organization and payer mix, so results should be measured against your own baseline denial data.
Can AI help with denial appeals?
Yes. AI tools can help identify denial patterns, surface the most relevant supporting documentation, and speed up drafting of appeal letters, though human review is still essential to ensure clinical and payer-specific accuracy.
Final Thoughts
Denial codes like CO-22, CO-50, CO-97, CO-109, and CO-253 each point to a distinct root cause, and resolving them quickly protects both cash flow and staff time. But the real opportunity lies in using denial data proactively, tightening up front-end processes, and building appeals workflows that catch issues before they become write-offs.
How Ventra Can Help
At Ventra, we know that coding and billing are just the beginning of a strong revenue cycle. That’s why we manage them with the full weight of our proprietary data and our vCision™ AI & Automation platform—turning complex revenue cycle data into actionable insight that helps us catch issues before they become denials and get your claims paid faster.
With decades of specialized RCM experience and deep domain knowledge across the specialties we serve, our team pairs best-in-class processes with white-glove, data-driven support to reduce denials, improve coding accuracy, and accelerate reimbursement. The result is a true partner who understands what it takes to strengthen your financial performance.
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