Denials feel random until you sort them by reason. Then a pattern shows up: almost all of them start before the claim is submitted — at verification, in plan setup, or in the chart. Fix them there and the appeals pile shrinks on its own.
Codes below are the standard claim adjustment reason codes (CARCs) you'll see on an electronic remittance (ERA/835). Paper EOBs often use the payer's own wording for the same thing.
The ten at a glance.
| Denial | CARC | Starts at | Upstream fix |
|---|---|---|---|
| 1. Not covered on date of service | 27 | Verification | Re-check eligibility 48 hrs out |
| 2. Wrong payer order (COB) | 22 | Verification | Ask about other coverage every visit |
| 3. Waiting period or missing tooth clause | — | Verification | Capture exclusions on the breakdown |
| 4. Frequency limit exceeded | 119 | Plan setup | Record last service dates |
| 5. Annual maximum reached | 119 | Plan setup | Track remaining max in the PMS |
| 6. Downgrade / alternate benefit | — | Plan setup | Flag downgrade rules before quoting |
| 7. Pre-authorization missing | 197 | Treatment planning | Pre-auth before you produce |
| 8. Attachment missing or weak | 252 | Chart | No high-value claim goes out bare |
| 9. Coding or data error | 16 | Claim entry | Scrub claims before submission |
| 10. Filed too late | 29 | Process | Submit same day, work AR daily |
95%+
A first-pass acceptance rate above 95% is achievable when eligibility, plan rules and attachments are handled before submission. Below that, the fix is upstream — not more appeal capacity.
Eligibility.
1. Patient not covered on the date of service.
- On the ERA: CARC 27, "expenses incurred after coverage terminated."
- Why: coverage was checked once — at the first visit, or weeks ago — and the patient changed jobs or plans since.
- Fix: re-verify eligibility 48 hours before every appointment, not just new patients.
2. Wrong payer billed as primary.
- On the ERA: CARC 22, "may be covered by another payer per coordination of benefits."
- Why: a spouse's plan, a new job's plan or Medicaid wasn't on file, or the birthday rule wasn't applied for a child.
- Fix: ask about other coverage at every visit and store the primary/secondary order in the PMS.
Plan rules.
3. Waiting period or missing tooth clause.
- On the EOB: usually a non-covered or exclusion remark in the payer's own wording.
- Why: major services fall inside a waiting period on a new plan, or the plan won't pay to replace a tooth lost before coverage began.
- Fix: capture waiting periods and the missing tooth clause on every full breakdown — they belong on the verification checklist.
4. Frequency limit exceeded.
- On the ERA: CARC 119, "benefit maximum for this time period or occurrence has been reached."
- Why: a second prophy, bitewing set or FMX inside the plan's window — often because the last service was done at another office.
- Fix: get history with last service dates during verification, and schedule around it.
5. Annual maximum reached.
- On the ERA: also CARC 119.
- Why: nobody tracked how much of the annual max was used, so treatment was planned against benefits that were already gone.
- Fix: record remaining max on the breakdown and update it as claims pay. Phase large treatment plans across benefit years where it makes clinical sense.
6. Downgrade or alternate benefit.
- On the EOB: paid at a lesser procedure's rate — composite paid as amalgam, for example.
- Why: the plan has an alternate benefit provision the front desk didn't know about, so the estimate was wrong.
- Fix: flag downgrade rules during verification and quote the patient's real portion up front.
7. Pre-authorization required but not obtained.
- On the ERA: CARC 197, "precertification/authorization/notification/pre-treatment absent."
- Why: the procedure needed approval under that plan — common with Medicaid and some commercial plans for major work — and the work was done first.
- Fix: check pre-auth rules at treatment planning and don't schedule production until it's approved.
Documentation and coding.
8. Attachment missing or doesn't support the code.
- On the ERA: CARC 252, "an attachment/other documentation is required."
- Why: no X-ray, perio charting or narrative — or an image that's unreadable or doesn't show what was billed.
- Fix: a simple rule: crowns, SRP, extractions, implants and other high-value codes don't submit without their attachments.
9. Coding or data error.
- On the ERA: CARC 16, "claim/service lacks information or has submission/billing error(s)."
- Why: wrong tooth number or surface, an outdated CDT code, a typo in the member ID, or a missing provider NPI.
- Fix: scrub every claim before it goes out — tooth, surface, code, IDs — and keep CDT codes current each January.
Process.
10. Timely filing limit missed.
- On the ERA: CARC 29, "the time limit for filing has expired."
- Why: a claim that never left, got rejected at the clearinghouse unnoticed, or sat waiting for an attachment. The most avoidable denial of all — a claim that would have paid, lost to the clock.
- Fix: submit same day, check clearinghouse rejections daily, and work AR follow-up every business day.
Two more worth watching: duplicate claims (CARC 18), usually from re-submitting instead of checking status, and unanswered payer requests for more information, which quietly turn into denials.
Find your top three.
- Pull the last 90 days of denials and sort them by reason code.
- Rank by dollars, not count. One crown denial outweighs ten prophy denials.
- Fix the top bucket at its source — verification, plan setup, chart or claim entry — before adding appeal capacity.
The full prevention playbook is in how to reduce dental claim denials. Denial management and appeals are built into our dental billing and RCM service. Not sure where your denials cluster? Book a call.