Top 10 CARC Denial Codes Explained (And How to Fix Them)
If you work in medical billing or revenue cycle management, you’ve seen these codes more times than you can count. Claim Adjustment Reason Codes (CARCs) tell you why a payer denied, reduced, or adjusted a claim — but the two- or three-digit code alone rarely tells you what to actually do about it.
This guide breaks down the 10 CARC denial codes that show up most often in day-to-day billing, what each one really means, and the specific action to take so the claim doesn’t sit in your AR bucket for another 30 days.
What Is a CARC Code?
A CARC (Claim Adjustment Reason Code) is a standardized code used on the ERA/EOB to explain why a payer adjusted a claim’s payment. They’re maintained by the X12 standards committee and used across nearly every US payer — Medicare, Medicaid, and commercial insurers alike. The code set is updated several times a year, so codes you see today may shift slightly in future releases.
CARCs are often paired with a RARC (Remittance Advice Remark Code), which adds more specific detail. Together, they tell the full story of why a claim wasn’t paid as billed.
Why This Matters More Than Ever
Claim denial rates in the U.S. have climbed significantly in recent years — from roughly 30% in 2022 to over 40% at many practices today. Industry estimates put the average cost of reworking a single denied claim at around $30, regardless of whether it’s ultimately paid. Perhaps most striking: an estimated 65% of denied claims are never appealed at all, even though the majority of claims that are appealed end up getting paid.
That gap — between what’s recoverable and what actually gets recovered — is almost entirely a function of how quickly and confidently a billing team can read a denial code and act on it.
The 10 Most Common CARC Denial Codes
1. CO-45 — Charge Exceeds Fee Schedule
Category: Contractual Adjustment · Appealable: No (write-off) What it means: The billed amount is higher than the payer’s contracted or allowable rate. What to do: This is almost always a contractual write-off, not something to bill the patient for. Adjust the difference and move on — but if this code appears frequently for a specific payer, it’s worth reviewing your fee schedule to make sure charges are set correctly.
2. CO-16 — Claim Lacks Information
Category: Missing Information · Appealable: Usually correctable What it means: Something required for processing is missing — often paired with a RARC that specifies exactly what. What to do: Check the paired RARC first. Common culprits include a missing referring provider NPI, an incomplete modifier, or absent authorization number. Correct and resubmit.
3. CO-197 — Precertification/Authorization Absent
Category: Authorization · Appealable: With documentation What it means: The payer required prior authorization and doesn’t have one on file for this service. What to do: Verify whether authorization was actually obtained before the visit. If it was, submit an appeal with proof. If it wasn’t, some payers allow a retro-authorization request — check payer-specific policy before writing this off as a loss.
4. CO-97 — Benefit Included in Payment for Another Service
Category: Bundling / NCCI · Appealable: With documentation What it means: This service is bundled into a related procedure that was already paid. What to do: Review the claim against NCCI (National Correct Coding Initiative) edits. If the bundling is inappropriate for this specific case, an appeal with modifier correction (like -59) may recover the payment.
5. CO-29 — Timely Filing Limit Expired
Category: Timely Filing · Appealable: Often hard to overturn What it means: The claim was submitted after the payer’s filing deadline. What to do: This one is largely preventable. If you have documented proof of an earlier timely submission (a clearinghouse report, for example), appeal immediately — most payers have a short window for these appeals too.
6. CO-11 — Diagnosis Inconsistent with Procedure
Category: Coding / Linkage · Appealable: With documentation What it means: The ICD-10 code billed doesn’t support medical necessity for the CPT/HCPCS code billed. What to do: Review the coding pairing against payer-specific LCD/NCD policies. This often requires provider documentation review before resubmitting with a corrected or better-supported diagnosis code.
7. CO-18 — Duplicate Claim/Service
Category: Duplicate Claim · Appealable: With documentation What it means: The payer’s system shows this exact claim was already submitted. What to do: First confirm it isn’t actually a duplicate in your own system. If the original claim was denied incorrectly and this is a legitimate resubmission, appeal rather than resubmitting again — resubmitting a “duplicate” repeatedly can flag the account for audit.
8. CO-50 — Non-Covered, Not Medically Necessary
Category: Medical Necessity · Appealable: With documentation What it means: The payer has determined this service doesn’t meet their medical necessity criteria. What to do: Pull the clinical documentation and compare it against the payer’s specific medical policy for that CPT code. If the documentation supports necessity, this is appealable — but success depends heavily on documentation quality.
9. CO-109 — Claim Not Covered by This Payer/Contractor
Category: Wrong Payer · Appealable: Usually correctable What it means: The patient may have different or additional coverage, or the claim was sent to the wrong payer. What to do: Re-verify eligibility for the date of service. This is often a simple fix — the patient may have switched plans and the front desk didn’t catch it at check-in.
10. CO-119 — Benefit Maximum Reached
Category: Benefit Maximum · Appealable: No (plan limit) What it means: The patient has hit a visit limit or dollar cap under their plan for this service type. What to do: Confirm the plan’s actual limit (some are per calendar year, some per benefit year). If the limit truly has been reached, this becomes patient responsibility — but always verify before billing the patient.
Why Tracking These Codes Matters
Individually, each denial looks like a small administrative fix. At scale, they add up fast. A practice submitting 1,000 claims a month with a 12% denial rate is dealing with 120 denied claims every single month — each one requiring staff time to research, correct, and resubmit.
Tracking which CARC codes show up most often for your practice — and for which payers — turns denial management from reactive firefighting into a targeted process improvement effort. If CO-197 is your top denial, the fix is tightening front-end authorization checks. If CO-16 dominates, the fix is a claim-scrubbing process before submission.
Quick Reference Table
| Code | Category | Typically Fixable? |
|---|---|---|
| CO-45 | Contractual adjustment | No (write-off) |
| CO-16 | Missing information | Yes |
| CO-197 | Authorization | Sometimes |
| CO-97 | Bundling | Sometimes |
| CO-29 | Timely filing | Rarely |
| CO-11 | Coding mismatch | Sometimes |
| CO-18 | Duplicate | Investigate first |
| CO-50 | Medical necessity | Sometimes |
| CO-109 | Wrong payer | Yes |
| CO-119 | Benefit maximum | No |
Next Steps
Understanding what a denial code means is only step one. The real value comes from knowing how often each one is hitting your claims — and what it’s costing you in lost revenue and rework labor.
Try the Denial Cost Calculator to see what your current denial rate is actually costing your practice each month, or use the CARC/RARC Lookup Tool to search any code you’re seeing on your remittances right now.