Claims · Updated 2026-09-08 · 4 min read

What does CO-29 mean on a dental claim?

CARC 29 means the filing deadline expired. Whether the office writes it off or bills the patient turns on the contract — one carrier prints it both ways.

CARC 29 means the time limit for filing this claim has expired. The benefit was never judged — the payer refused to look. Who absorbs the loss is the whole question, and the reason code does not answer it: the group letters do, and the same carrier prints them both ways on the same sentence. Where the code arrives as PI, a contracted dentist writes it off and the patient owes nothing. Where it arrives as PR, the plan says it is the patient's. Some public programmes settle it outright and forbid billing the member at all. As of September 2026, across 37 dental practices, timely filing was one of the rarest denials in dentistry — 99 denied lines from 12 payers, 0.2% of all denied lines.

What we measured

Denied lines are lines paid at $0 with a stored reason: what we saw across 37 dental practices and 170+ payers, all dates, measured September 2026.

Timely filing is famous and rare. It is the twenty-third of twenty-six denial reasons by volume, below the missing tooth clause in notoriety and barely above it in count. That is not evidence it is harmless — a timely-filing denial is unrecoverable in a way that a frequency denial is not — but it does mean an office losing real money to denials is almost certainly losing it somewhere in the top four rows, not here.

What the carriers' own documents say

Delta Dental's crosswalk contains the sharpest illustration of the group code deciding the answer. Two policy codes carry CARC 29 and the identical description:

"The deadline for submitting this procedure/claim has expired." (policy codes 2DL and 2DX)

Code 2DL is printed PR to a non-participating dentist and PI to a participating one — the contracted dentist writes it off. Code 2DX is printed PR both ways. One sentence, two codes, opposite outcomes for the patient. (Delta Dental — Policy ID Mapping for CARC/RARC Health Care Policy Codes, pinned at Delta Dental of California network scope.)

Some carriers state that the deadline is absolute. The Keystone First Provider Manual (2025), for Pennsylvania HealthChoices:

"Keystone First will not grant exceptions to the Claim filing timeframes outlined in this section. Failure to comply with these timeframes will result in the denial of all Claims filed after the filing deadline."

And at least one public programme forbids passing the loss to the patient. From the Renaissance TennCare provider manual for adults (version 8, November 2025):

"If Renaissance denies a service(s) on a claim due to late submission, participating dentists are prohibited from billing members for the amount that Renaissance would have paid."

Why it depends on the contract

Two different contract terms govern a timely-filing denial and they pull in opposite directions. The first is the deadline itself, which is set per carrier, per product line and sometimes per state, and which ranges across published provider manuals from a few months to two years for the same act of sending a claim. The second is the hold-harmless term: whether the participation agreement lets the dentist bill a patient for an amount the plan would have paid but for the office's own delay. Delta answers that differently on two codes; Renaissance's TennCare book answers it once, for everybody.

Both terms live in the dentist's agreement rather than in the patient's benefit booklet, which is why a patient cannot look this up and an office can. Note also that a missed deadline is not always an appeal: Keystone First routes timely-filing denials into its provider dispute track rather than its appeals track, and a dispute filed in the wrong lane dies there.

What to do

• Look up your own filing deadline for that carrier and product before assuming the denial is right. The spread across published manuals is large enough that offices routinely write off claims that were still inside the window.
• If the claim was submitted on time, appeal with the proof of first submission — the date of the original transmission is the evidence, not the resubmission.
• Read the group letters before telling the patient anything. PI means the office absorbs it. On a public programme, check whether the manual forbids billing the member outright.
• File it in the lane the carrier names. Some carriers handle timely filing as a dispute rather than an appeal.
• On a secondary claim, check when the clock actually started. Several carriers run it from the primary plan's payment rather than the date of service, which means a claim that looks late may not be.
• Track claim age by carrier deadline rather than by a single house rule, and chase anything unpaid before its own deadline rather than at a fixed number of days.

Numbers last refreshed September 2026.

All articles · Kaylie