Dental claim denials: the common reasons and how to appeal

PearlFlow guides · November 14, 2026

A $0 line on an EOB isn’t always the final word. Some denials are mistakes you can fix and resend, some are the plan working as designed, and the rest are worth fighting. Here’s how to tell them apart and how to appeal in writing.

First, read the denial on the EOB

Every denied line comes with codes: a group code (who owes the money), a reason code (why it wasn’t paid) and often a remark code with more detail. Our guide to reading the codes on a dental EOB explains them. Read them together, then sort the denial into one of three piles:

Either way, post the $0 line and the reason before you do anything else. Our payment posting checklist covers how.

The most common dental claim denial reasons

Reason codes below are from the official X12 list. Always read the whole line, remark codes included.

1. Frequency limits

Many plans cover some services only at set intervals. The ADA gives the example of cleanings and exams covered twice a plan year or every six months: if the rule is every six months, a visit even a day early is denied. Many plans also pay for only one full-mouth series of X-rays in five years (ADA). On the EOB this usually shows as CARC 119 (benefit maximum reached) or 151 (frequency). Check the payer’s history against yours. A visit at another office counts, but a miscounted date is worth appealing.

2. Missing X-rays, narratives or attachments

CARC 16 (“lacks information”) or 252 (“an attachment/other documentation is required”) usually means the reviewer didn’t have enough to decide. The ADA notes that the payer’s dental consultant may only be looking at the claim form. A good narrative describes the clinical condition, the procedure, and why extra time or materials were needed. Send what was missing, the way the payer asks for it.

3. Eligibility or coverage terminated

CARC 27 means the service was after coverage ended; 26 means it was before coverage began. The ADA has warned that offices are often asked to refund payments months later because the employer never told the payer the patient’s coverage had changed (ADA). Ask the patient about new coverage and bill the right plan.

4. Missing tooth clause

Some plans won’t pay to replace a tooth that was missing before the patient’s coverage started. The ADA points out this doesn’t mean the treatment wasn’t needed. If the tooth was lost after coverage began, appeal with the records that show when it was extracted.

5. Downgrades and alternate benefits

A least expensive alternative treatment clause pays for the cheapest option the plan accepts, even when the dentist recommends something else. The ADA’s example: the dentist recommends a fixed bridge, but the plan pays only for a removable partial denture. Look for CARC 169 (“Alternate benefit has been provided”). Downcoding is when the payer pays using a different code from the one you reported. If the EOB gives no explanation, the ADA advises appealing in writing (ADA News). Whether the patient owes the difference depends on your contract and state law.

6. Coordination of benefits order

CARC 22 means another plan may need to pay first. Generally, the plan where the patient is the employee is primary. For children covered by both parents, the parent whose birthday comes earlier in the year is usually primary. The secondary plan will usually wait for the primary’s EOB (ADA). Confirm the order with the patient, bill the primary, then send the secondary with the primary’s EOB.

7. Timely filing

CARC 29 means the filing deadline passed. Limits are set by the payer and program. One large dental carrier says claims received more than 12 months after treatment generally may not be paid, and some programs allow much less, such as 90 days for Texas CHIP. If a claim is denied for late filing, that carrier says you may bill the patient only their coinsurance or copay, not the amount the plan would have paid (Delta Dental). Appeal only if you can prove you filed on time, such as with a clearinghouse acceptance report.

8. Duplicate claim

CARC 18 (“exact duplicate claim/service”) usually means the claim was sent again while the first was still in process. Find the original before you do anything else. If something needs to change, send a corrected claim the way the payer asks, not a brand-new one.

How to appeal a dental insurance denial

The ADA is clear: a proper appeal is a written request to reconsider the claim, and a phone call is not acceptable (ADA). Follow these steps:

  1. Follow the plan’s instructions. Use its deadline, its form and the department it names. Put the word “appeal” in the title, in the text and on any cover letter.
  2. Identify the claim. Include the patient and subscriber, the claim number, dates of service, procedure codes and tooth numbers. Some payers ask for a copy of the EOB and the original claim (Aetna Dental).
  3. Make the clinical case. The ADA suggests radiographs, photographs, charting and a narrative “even if this appears obvious to you.” Include anything you didn’t send with the original claim.
  4. Offer a call. The ADA suggests asking the payer’s dental consultant to call before denying again, and giving times when the dentist is free.
  5. Track it and keep going. Log the date sent and set a follow-up date. Some plans allow up to three appeals with different consultants, so use every level.

Timely filing and appeal deadlines

There is no single national deadline. Check the payer’s provider manual and your contract.

If appeals run out, the ADA suggests a complaint to the state insurance commissioner when the plan is state-regulated. If the plan is self-funded, it suggests the patient contact their employer’s benefits manager. The NAIC lists every state insurance department.

How to prevent denials

Keep a simple denial log by payer and reason. The patterns show which fix to make first.

Sources

This guide is general information, not legal or billing advice. Check your payer contracts and your state’s rules for your own practice.