Claims · Updated 2026-09-08 · 5 min read

What is a RARC vs a CARC on a dental EOB?

A CARC is the money code and always carries a group code. A RARC is the explanation and moves nothing. On dental claims the RARC is where the real rule appears.

Two code vocabularies sit on every dental EOB and they do different jobs. A CARC — Claim Adjustment Reason Code — is the money code. It explains one adjustment, why the paid amount is less than the billed amount, and it always arrives with a group code (CO, PR, OA or PI) saying whose money the difference is. CARCs are numeric: 1, 45, 96, 119, 204. A RARC — Remittance Advice Remark Code — is the explanation code. It carries the detail the reason code cannot, and it moves no money by itself. RARCs are alphanumeric: N640, N130, M86, MA04. On dental claims the split matters because the reason code is frequently too coarse to act on and the remark is where the actual rule appears. Both lists are maintained publicly by X12. As of September 2026, across 37 dental practices, only about a dozen of the forty most-printed codes on dental EOB lines were unambiguously from either list.

What we measured

Single code tokens on dental remittance lines, all dates: what we saw across 37 dental practices, measured September 2026. payers counts distinct insurance companies printing that token.

The payer count is the test, and it works without knowing what any code means. A national list is drawn on by every payer, so a genuine reason or remark code shows up on EOBs from dozens of unrelated insurance companies — 51 for 45, 38 for 96, 31 for 119. A bare 1 is the counter-example: 68 payers print it, and some of them mean their own library's 1 rather than the X12 deductible code. A code printed by one or two companies while appearing at twenty-odd practices is that company's private library, and no published X12 lookup will decode it: only that carrier's own legend will. There is no third option.

What the carriers' own documents say

Delta Dental publishes the crosswalk that shows the two vocabularies working together. Each of its 938 internal policy codes maps to one reason code, one remark code and two group codes — one for a participating dentist and one for a non-participating one. Three worked rows:

"This service is not a covered benefit of the enrollee's program because there is a less expensive, professionally acceptable alternative treatment available. We have applied an alternate procedure number and allowance to ensure accurate processing." (policy code 515 — reason code 97, remark N130, patient responsibility either way)

"According to our guidelines, the fee for this procedure is considered to be part of, and included in the fee for a completed service." (policy code 718 — reason code 97, remark M15, patient responsibility for a non-participating dentist and a write-off for a participating one)

"The deadline for submitting this procedure/claim has expired." (policy code 2DL — reason code 29, remark N30, patient responsibility for a non-participating dentist and a write-off for a participating one)

All from Delta Dental — Policy ID Mapping for CARC/RARC Health Care Policy Codes, pinned at Delta Dental of California network scope.

Sometimes the remark is the entire answer. Delta prints remark code N111 on its duplicate family, and it reads:

"No appeal right except duplicate claim/service issue."

The reason code beside it says only that a maximum or a duplicate applied. The remark is what tells the office to stop.

Note also that the X12 standard requires at least one remark code alongside reason code 96, non-covered charge — the standard itself acknowledges that the reason code does not carry the cause. Delta maps 433 of its 938 policy codes onto that one reason code, and 343 onto the single remark N130, which says only to consult the plan benefit documents for restrictions on this service.

Why it depends on the contract

The reason code and the remark code describe the plan's rule. The group code describes the dentist's agreement. That is why the same policy code in Delta's table can produce identical reason and remark codes and still mean "bill the patient" at one office and "write it off" at another — the two group columns are the only difference between them.

So a dental EOB line is read in a fixed order and the order is not the order it is printed in: group code first, because it decides whose money it is; remark code second, because it names the rule; reason code last, because on a dental claim it is usually the least specific of the three.

What to do

• Read the group code, then the remark, then the reason. That order answers "who pays" and "what rule" before "what bucket".
• Count the payers before searching a code list. If only one or two insurance companies print a code, it is theirs and the legend is on their remittance.
• Treat a reason code 96 with no remark beside it as a denial with no stated cause, and ask the carrier which provision was applied.
• Keep each carrier's own legend filed with the remittance, because the private codes are the ones nobody can look up later.
• Do not act on a remark code alone. Remarks move no money — a remark on a paid line is information, not a refusal.
• Record the reason, the remark and the group letters together on the claim. Any one of the three on its own is not enough to reproduce the decision.

Numbers last refreshed September 2026.

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