Claims · Updated 2026-09-08 · 4 min read
What does CO-204 or PR-204 mean on a dental EOB?
204 means the service is not covered under the patient's plan. PR-204 is the patient's bill; CO-204 and PI-204 are the write-off. Same code opposite answers.
204 is the plainest of the non-coverage codes: this service is not covered under the patient's current benefit plan. There is nothing to appeal about the benefit itself — the plan does not buy it — so the only questions left are whether a covered alternative code exists, and who absorbs the charge. That second question is answered by the two letters, not the number. PR-204 makes it the patient's, billed at the contracted allowance for an in-network dentist. CO-204 or PI-204 makes it the office's write-off. As of September 2026, across 37 dental practices, procedures denied as not covered by the plan were 14,609 lines from 172 different payers — 22.3% of every denied line, the largest single class of denial in what we measured across 37 practices.
What we measured
| denial reason as it reached the office | denied lines | practices | payers | share of denials |
|---|---|---|---|---|
| Procedure not covered by the plan | 14,609 | 37 | 172 | 22.3% |
| Plan limitation (other) | 2,828 | 32 | 77 | 4.3% |
| Waiting period not met | 291 | 16 | 30 | 0.4% |
| Provider out of network | 238 | 12 | 9 | 0.4% |
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.
Two things in that table. First, non-coverage is not a niche outcome — it is more than one denied line in five, and it reached every one of the 37 practices from 172 different insurance companies. Second, the reasons offices worry about are far below it: an unmet waiting period and an out-of-network provider together are under 1%. Most "not covered" is exactly what it says, a benefit the employer group did not buy.
Not every carrier prints the code as CO-204. Some spell it out in words on the line as CARC 204, and on those remittances a code beside a line does not by itself mean the line was denied — codes ride approved lines as informational overrides too. Read the paid amount, not the presence of a code.
What the carriers' own documents say
Delta Dental's published crosswalk contains two policy codes mapped to CARC 204, and they are the cleanest demonstration in dentistry that the number is not the answer. FLK is PR for participating and non-participating dentists alike — the patient's bill:
"According to our guidelines, this service is not allowable. The patient is responsible for the amount indicated as 'Patient Pays'."
FLL is PI both ways — the office's write-off:
"According to our guidelines, the fee for this procedure is considered to be part of, and included in the fee for a completed service."
Both from Delta Dental — Policy ID Mapping for CARC/RARC Health Care Policy Codes, pinned at Delta Dental of California network scope. Same reason code, opposite group letters, opposite answers to the only question that matters at the front desk.
On public programmes the non-coverage decision is made above the claim entirely. The Alabama Medicaid Non-Covered Services List (May 2023) states the scope in one line: no coverage for "dental services for adults (age 21 and older), except pregnant adult recipients through 60 days postpartum", nor for "routine orthodontic care (braces), routine partials, dentures or bridgework, gold caps or crowns, periodontal or gum surgery". That is a programme design decision, not a judgment about the patient's teeth, and there is no clinical argument that moves it.
Why it depends on the contract
"Not covered" is a fact about the employer group's purchase, not about the carrier. The same carrier sells plans that cover implants and plans that do not, plans with an adult fluoride benefit and plans without. So a 204 tells you what this plan bought, and next year's renewal can change it.
The group letters then depend on a second contract — the dentist's. Where the carrier's own rules say a contracted dentist may not bill for a service, the code arrives as PI even though the plan simply does not cover it. Where the patient has agreed in advance to a non-covered service, it arrives as PR. And for an in-network dentist a PR-204 is still capped: MetLife's Preferred Dentist Program Resource Manual states that "The participant is not responsible for any amount that exceeds the plan allowance", which holds when the plan pays nothing.
What to do
- Read the group letters first. PR is billable, CO and PI are not, and no amount of reading the sentence changes that.
- Check whether a covered alternative code exists for the same clinical outcome before you write the charge off or bill it.
- Where the patient is going ahead with a non-covered service, get the consent to the charge signed before treatment, not after the EOB arrives.
- On a public programme, look up the programme's own non-covered list rather than appealing. Adult scope exclusions are set at state level.
- Quote an in-network PR-204 at the contracted allowance, never the office's full fee.
- Record the non-covered finding against the plan, not the patient, so the next patient from the same employer group is quoted correctly the first time.
Numbers last refreshed September 2026.