Denial code playbook

This playbook is the operational companion to CARC codes. Each scenario explains what likely happened, whether to correct or appeal, and which process change may prevent a repeat. This is not the full code set. CARC and RARC codes and their definitions are copyrighted and licensed by X12; reproducing the complete lists requires a license from X12, so this page (and CARC codes and RARC codes) cover only the highest-volume scenarios a dental biller actually needs. For a code that isn’t here, look it up at the authoritative source, x12.org/codes, and apply the same fix-or-appeal logic as the nearest scenario.

Step zero: which kind of adverse line is this?

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 per the tables below
Downgrade	The plan paid the alternate benefit; composite priced at the amalgam allowable, porcelain crown at the all-metal allowable	The line paid, but at an allowed amount below the contracted fee for the code billed	Patient billing; the difference follows the group code and the plan’s alternate-benefit clause; nothing to appeal if the plan is working as written
Limitation / maximum	Frequency limit hit (third prophy in a two-per-year plan) or annual maximum exhausted	Unpaid with a benefit-design reason; eligibility showed the limit	Patient billing with an explanation; benefit design, not a claim defect

Downgrades and limitations are benefit design: the appealable question is almost never “should the plan pay?” but occasionally “did the plan apply its own clause correctly?”; pull the plan’s benefit summary before writing either off. Full treatment: Denials vs downgrades and the worked example in Work your first downgrade. Everything below is for true denials.

Attachments and documentation requests

The highest-volume dental-specific family: crowns, SRP, and implants pend or deny without radiographs, perio charting, or a narrative.

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 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

These are the denials where predetermination earns its keep: it surfaces the clause, the interval, and the payer’s tooth history before the chair time is spent. See Get predeterminations.

Preauthorization absent

Distinguish the two instruments first: a predetermination is voluntary; skipping one never denies a claim. A preauthorization is required before treatment by some plans, mainly Medicaid programs and DHMOs, and skipping it does.

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.

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 and 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
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.

The prevention priority list

Start with the controls that prevent the greatest volume of avoidable rework:

Eligibility at scheduling and check-in, with the 271 saved, including remaining maximum and frequency counters
Attach at submission for every CDT code on the payer’s documentation list
A scrubber edit blocking submission when a preauthorization is required and missing; Medicaid and DHMO plans especially
Same-day rejection and information-request work, plus a weekly no-acceptance report
Taxonomy and enrollment data verified at every payer go-live and every acquisition
Effective-date discipline; no insured patients before a dentist’s effective date
Same-day charge entry
Predetermination on major work; it prevents missing-tooth, replacement-interval, and documentation denials before the chair time is spent
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.

CPOD & Legal

Payers

Clearinghouses & Vendors

EDI & Code Sets

Banking & Payments

Glossary & Appendices

Step zero: which kind of adverse line is this?

Attachments and documentation requests

Missing tooth clauses and per-tooth history

Preauthorization absent

Coordination of benefits

Timely filing

Eligibility

Credentialing and enrollment

Duplicates

Non-covered, usually not errors

The prevention priority list

​Step zero: which kind of adverse line is this?

​Attachments and documentation requests

​Missing tooth clauses and per-tooth history

​Preauthorization absent

​Coordination of benefits

​Timely filing

​Eligibility

​Credentialing and enrollment

​Duplicates

​Non-covered, usually not errors

​The prevention priority list

Step zero: which kind of adverse line is this?

Attachments and documentation requests

Missing tooth clauses and per-tooth history

Preauthorization absent

Coordination of benefits

Timely filing

Eligibility

Credentialing and enrollment

Duplicates

Non-covered, usually not errors

The prevention priority list