Why Dental Claims Get Denied: 6 Common Reasons and the Fixes That Prevent Them

Every denied dental claim comes with a reason. On your electronic remittance advice (ERA), that reason appears as a Claim Adjustment Reason Code, or CARC. Most practices look at the dollar amount and move on. The practices that collect the most read the code, fix the claim, and then fix the habit that caused it.

Here are six common reasons dental claims are denied, the reason codes you may see, and how to prevent each one. Reason codes can vary by payer and situation, so always confirm the codes on your own ERAs.

1. The plan was not active on the date of service

Codes you may see: CARC 27 (expenses incurred after coverage terminated) or CARC 26 (expenses incurred prior to coverage)

The patient's plan terminated before the visit, or had not started yet. This often happens when a patient changes jobs and the office relies on insurance information from a prior visit.

Prevention: Verify eligibility before every appointment, and confirm the policy is active on the actual date of service.

2. A frequency limitation or maximum was reached

Code you may see: CARC 119 (benefit maximum for this time period or occurrence has been reached)

The plan only covers a procedure a certain number of times in a period, or the patient has used their annual maximum.

Prevention: A basic eligibility check that shows only category percentages is not enough. Verify frequency limitations and remaining benefits before treatment, and build them into the patient's estimate.

3. An age limitation applies

Code you may see: CARC 6 (procedure inconsistent with the patient's age)

Some procedures are covered only for patients within certain age ranges.

Prevention: Include age limitations in your verification process, especially for procedures commonly limited by age.

4. The secondary claim was sent without the primary EOB

Code you may see: CARC 22 (this care may be covered by another payer per coordination of benefits)

When a patient has two plans, the secondary payer needs to see how the primary payer processed the claim.

Prevention: Hold secondary claims until the primary explanation of benefits (EOB) arrives, then submit the secondary claim with the primary EOB attached.

5. Images or clinical documentation were missing

Codes you may see: CARC 252 (an attachment or other documentation is required) or CARC 16 (claim lacks information or has submission or billing errors)

Many procedures require radiographs, periodontal charting, photos, or clinical notes to support medical necessity.

Prevention: Know which procedures each major payer requires attachments for, and send images and narratives with the first submission instead of waiting for a request.

6. The payment looks routine but is actually an underpayment

Code you may see: CARC 45 (charge exceeds fee schedule or maximum allowable), with group code CO (contractual obligation)

This one is not technically a denial, which is why it is so easy to miss. A CO-45 adjustment is normal when a payer applies your contracted fee. It becomes a problem when the payment does not match your contract, for example when a claim is paid under a leased network the practice did not expect, or when the wrong fee schedule is attached to a plan in your practice management system.

Prevention: Compare payments against your contracted fees, confirm each plan is linked to the correct fee schedule, and question adjustments that look larger than expected.

Turn denials into prevention

Denials are expensive twice: once in the delayed or lost payment, and again in the staff time it takes to rework the claim. The goal is not just to appeal faster. It is to see fewer denials each month.

Track your denials by reason code every month. When the same code keeps appearing, trace it back to its source, whether that is verification, documentation, coordination of benefits, or fee schedule setup, and fix the process there.

Learn how Revv Systems handles dental insurance verification and denial management, or book a revenue review to see which denials are costing your practice the most.