> ## Documentation Index > Fetch the complete documentation index at: https://dso.getlemma.com/llms.txt > Use this file to discover all available pages before exploring further. # Denial code playbook > A routing and response guide for dental denials, downgrades, benefit limitations, attachments, preauthorization, COB, timely filing, eligibility, and enrollment issues. This playbook is the operational companion to [CARC codes](/reference/edi/carc-codes). Each scenario explains what likely happened, whether to correct or appeal, and which process change may prevent a repeat. CARC and RARC definitions are copyrighted and licensed by X12, so this page and the [CARC](/reference/edi/carc-codes) and [RARC](/reference/edi/rarc-codes) references do not reproduce the full code sets. Look up an unlisted code in the current [X12 code lists](https://x12.org/codes/claim-adjustment-reason-codes), then analyze the claim facts rather than assuming the nearest example controls. ## First classify the adverse line Dental remittances include true denials, alternate-benefit downgrades, and benefit limitations. Route them separately so the denial queue remains focused on items that need correction or may support an appeal. | Type | What happened | The tell | Route to | | ------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **True denial** | The payer refused the service | \$0 paid on the line with a denial reason; often RARC detail | **Denial queue**; fix or appeal according to the tables below | | **Downgrade** | The plan paid an alternate benefit, such as a composite priced at the amalgam allowance or a porcelain crown priced at the all-metal allowance | The line **paid**, but at an allowed amount below the contracted fee for the code billed | Confirm the alternate-benefit provision and allocation; post or bill according to the remittance, contract, plan, and notice rules; appeal if the payer applied the provision incorrectly | | **Limitation / maximum** | A frequency limit was reached or the annual maximum was exhausted | Unpaid with a benefit-design reason; eligibility may show the limit | Confirm that the payer applied the plan correctly, then follow the permitted patient-billing or write-off treatment | For downgrades and limitations, start by asking whether the payer applied the plan's terms correctly. Review the benefit summary, participation agreement, remittance, and patient-notice record before appealing, writing off, or billing the patient. See [Denials vs downgrades](/concepts/payments/denials-vs-downgrades) and [Work your first downgrade](/start/first-90-days/work-your-first-downgrade). The sections below address **true denials**. ## Attachments and documentation requests Crowns, scaling and root planing, implants, and other services may pend or deny when required radiographs, periodontal charting, or narratives are missing. | CARC / RARC | Root cause | Fix or appeal | Prevention | | --------------------------------------------- | ----------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------- | | **CO-252**, attachment/documentation required | Claim submitted without documentation the payer's policy requires | **Submit the documentation** through the payer's required channel (attachment vendor, portal, mail) and respond within the window | Per-payer list of CDT codes requiring attachments; attach **at submission**, not on request | | **CO-16 + a RARC** | Claim lacks information; the RARC names what | **Read the RARC**, supply the element, resubmit | Same | | **CO-226**, provider information not provided | A prior request went unanswered | Respond immediately; the clock may already be running | Work information requests same-day | | **CO-227**, patient information not provided | The payer asked the patient for something | The patient must respond; tell them what and why | Warn patients when payers request student status, other-coverage, or accident details | | **CO-50**, not deemed necessary by the payer | Clinical documentation didn't support the service | **Appeal** with radiographs, charting, and a narrative addressing the payer's criteria | Documentation templates for the procedures payers challenge; SRP, crowns, implants | See [Dental attachments](/reference/edi/dental-attachments) for the current NEA-number workflow and the transition to the X12 275. ## Missing tooth clauses and per-tooth history Dental payers adjudicate against per-tooth history: when the tooth was extracted, when the last crown on it was placed, what was restored on which surface. | Scenario | Root cause | Fix or appeal | Prevention | | -------------------------------------------- | ------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------- | | **Missing tooth clause**; replacement denied | The plan excludes replacing teeth extracted before coverage began (plan documents govern; clauses vary) | Verify the extraction date and the clause's exact terms; **appeal** if the extraction happened during coverage or the clause has an exception (e.g., replacement of an existing prosthesis) | Ask about extraction history at treatment planning; run a predetermination before implants, bridges, and dentures | | **Replacement interval not met** | The plan covers a crown or prosthesis only every N years | Verify the prior placement date the payer holds; appeal with evidence if their history is wrong | Pull the interval from eligibility before seating; predetermine major work | | **Tooth/surface conflict** | Payer's history shows the surface already restored, or the tooth data on the claim is wrong or missing | Correct the tooth/surface data if it's a claim error; appeal with charting if the payer's history is wrong | Chart-to-claim consistency checks before submission | A **predetermination** may identify the clause, replacement interval, and payer tooth history before treatment. See [Get predeterminations](/guides/billing/get-predeterminations). ## Preauthorization absent Distinguish the two processes first. A **predetermination** is voluntary, so its absence alone does not cause a denial. A **preauthorization** is required before treatment by some plans, mainly Medicaid programs and DHMOs, and missing it can cause a denial. | CARC | Root cause | Fix or appeal | Prevention | | ---------------------------------------------------- | --------------------------------------------------------- | ---------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------- | | **CO-197**, preauthorization absent, **auth exists** | Obtained but never entered in the structured field | **Corrected claim** (freq. 7) with the authorization number | Scrubber edit blocking submission when a code on the payer's preauth list has no number | | **CO-197**, none obtained | Requirement missed at treatment planning | Request retro-authorization where the program allows it; else **appeal** with clinical documentation | Per-payer preauth-required list built into treatment planning; especially for Medicaid dental benefit administrators | | **CO-198**, authorization exceeded | Units or visits beyond what was authorized | Request additional units; appeal | Track authorized against delivered units; ortho continuation claims especially | | **CO-15**, auth invalid or doesn't apply | Auth doesn't match the code, dates, provider, or location | Verify and correct, or obtain a matching auth | Verify auth details against the planned treatment before the visit | CO-197 is a **contractual** denial; you generally cannot bill the patient for it. See [Group codes](/reference/edi/group-codes). ## Coordination of benefits Routine in dentistry: children covered under both parents' plans, ordered by the birthday rule. | CARC / RARC | Root cause | Fix or appeal | Prevention | | ---------------------------------------------- | ---------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------- | | **CO-22**, may be covered by another payer | Wrong payer billed first; birthday-rule order missed, or the payer's COB record is stale | Determine order (earlier birthday in the calendar year is primary for dependents; court orders supersede); bill the primary | Capture both plans and both parents' birth dates at registration | | **OA-23**, prior payer adjudication | Informational on secondary claims | Not a denial | Do not route to the denial queue | | **N4**, missing prior carrier EOB | Secondary claim submitted without the primary's adjudication | **Resubmit** with the primary's 835 detail in the COB loops | Automate primary-remittance attachment on secondary claims | | **MA04**, secondary needs primary payment info | Same | Same | Same | Often the patient must call the payer to update a stale COB record; you cannot do it for them. ## Timely filing | CARC | Root cause | Fix or appeal | Prevention | | --------------------------------------------------------- | ---------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------- | | **CO-29**, filing limit expired, **was submitted timely** | Payer lost it, or it bounced in a rejection loop | **Appeal** with the clearinghouse acceptance report | Weekly **no-acceptance report**; same-day rejection work | | **CO-29**, genuinely late | Charge entry lag, a claim held for an attachment that never went out, or a held claim aged out | Check exceptions: retro eligibility, COB delay. Else write off with a root cause. | Same-day charge entry; internal deadline inside the contractual one; don't let attachment gathering hold the claim past the limit | Dental timely-filing windows vary widely by payer and are short in some Medicaid programs. See [Timely filing limits](/reference/payers/timely-filing-limits) and [Beat timely filing](/guides/billing/beat-timely-filing). ## Eligibility | CARC | Root cause | Fix or appeal | Prevention | | -------------------------------------------- | ---------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------- | ---------------------------------------------------------------------------------------- | | **CO-26**, expenses prior to coverage | Service before the effective date | Verify; rebill correct payer, or bill the patient if permitted | Run eligibility at scheduling **and** check-in | | **CO-27**, coverage terminated | Coverage lapsed before service | Verify; find current coverage; rebill | Re-check at check-in, not just at booking | | **CO-31**, patient not identified as insured | Wrong member ID, name mismatch | **Correct and resubmit** | Scan the card; verify against the 271 | | **CO-32**, not an eligible dependent | Relationship or dependent coverage issue; age-outs matter in dental, where so many patients are dependents | Verify; rebill or bill the patient | Capture relationship and verify dependent status at registration | | **CO-177**, eligibility requirements not met | Plan-specific requirement | Verify with the payer | Read the 271 fully; remaining maximum and frequency counters included, not just "active" | ## Credentialing and enrollment | CARC | Root cause | Fix or appeal | Prevention | | -------------------------------------------------------- | ---------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------- | | **CO-8**, procedure inconsistent with provider type | **Taxonomy mismatch** with enrollment | Correct the taxonomy; verify enrollment | Verify claim taxonomy matches enrolled taxonomy at go-live; see [Taxonomy codes](/reference/edi/taxonomy-codes) | | **CO-185**, rendering provider not eligible | Dentist not credentialed or not linked to the group contract for the service date | Resolve the payer enrollment issue, then determine whether and how the claim may be rebilled | Track effective dates and start credentialing early in the acquisition process | | **CO-206**, NPI missing or invalid | EDI enrollment incomplete, or wrong NPI on the claim | Verify EDI enrollment and claim data | Test one claim per payer before volume | | **CO-B7**, not certified for this procedure on this date | **Service date before the dentist's effective date** | Pursue retro-effective date; else unbillable | Track effective dates in the credentialing grid | | **CO-109**, not covered by this payer | Wrong payer billed; common where a Medicaid dental benefit administrator, not the state, adjudicates | Rebill the correct entity | Verify payer ID mapping, especially for Medicaid administrators | ## Duplicates | CARC | Root cause | Fix | Prevention | | ----------------------------- | ------------------------------------------------------------------------ | ------------------------------------------------------------------ | ---------------------------------------------------------------- | | **CO-18**, exact duplicate | You resubmitted an adjudicated claim as a new original | Use **frequency code 7** referencing the original claim number | Train billers: adjudicated claims get corrected, not resubmitted | | **N522**, duplicate COB claim | The secondary already received the claim through a crossover/COB process | Don't submit the secondary separately when the primary forwards it | Know which payers forward claims (835 claim status 19–21) | ## Non-covered, usually not errors | CARC | Meaning | Action | | -------------------------------------- | ------------------------------------------------------------------------------------ | --------------------------------------------------------------- | | **CO/PR-96**, non-covered charge | Read the RARC. Benefit design; cosmetic exclusions, adult ortho, implant exclusions. | Patient responsibility with proper advance notice, or write off | | **PR-204**, not covered under the plan | Benefit design | Patient responsibility | Train billers to distinguish ordinary adjudication from a true denial. CO-45, PR-1/2/3, downgrades, frequency limits, and exhausted maximums generally need posting or patient-billing review rather than an automatic appeal. ## Prevention priorities Start with controls aimed at common sources of avoidable rework: 1. **Eligibility at scheduling and check-in**, with the 271 saved, including remaining maximum and frequency counters 2. **Attach at submission** for every CDT code on the payer's documentation list 3. **A scrubber edit blocking submission when a preauthorization is required and missing**; Medicaid and DHMO plans especially 4. **Same-day rejection and information-request work**, plus a weekly no-acceptance report 5. **Taxonomy and enrollment data verified** at every payer go-live and every acquisition 6. **Effective-date discipline**; no insured patients before a dentist's effective date 7. **Same-day charge entry** 8. **Predetermination on major work**; it prevents missing-tooth, replacement-interval, and documentation denials before the chair time is spent 9. **Automated primary-EOB attachment** on secondary claims The first six items address common enrollment, eligibility, attachment, and front-desk failures before they become aged claims.