Claims · Updated 2026-09-08 · 6 min read

Can I bill the patient for this denial?

The group code decides, not the reason code. CO and PI are the office's write-off and PR is the patient's, and the same denial can be either one.

The reason code never answers this question. The group code does. Every Claim Adjustment Reason Code on a dental Explanation of Benefits arrives with a group letter — CO for contractual obligation, PR for patient responsibility, PI for a payer-initiated reduction, OA for other adjustment — and that letter is what says whose money the unpaid difference is. CO means the dentist agreed to the reduction by signing the network contract, so it is written off. PI means the payer decided not to pay it and no contract or patient liability covers it, so it is also written off. PR means the plan says the amount is the patient's. OA usually means another carrier's payment moved the money. The complication is that the same denial, on the same carrier, with the same sentence, can arrive as PR for one dentist and PI for another — the difference being whether the dentist participates in that network. As of September 2026 Delta Dental publishes both columns side by side, which makes it the clearest published proof of the rule.

What we measured

Code tokens on dental EOB lines and whether the group letter was printed with them, measured September 2026, only tokens seen at five or more practices.

The shape of that table is the practical problem. The tokens that carry a group letter — CO45, CO-45, PR2 — are a small minority of the lines. On most lines the number arrives bare, which means the field that answers "can I bill this?" is not printed where you are looking. It is in the money columns and in the carrier's own par and non-par mapping.

What the carriers' own documents say

Delta Dental of California's published mapping carries two group columns, one for a non-participating dentist and one for a participating one. The same policy code, the same sentence, two answers.

Delta writes the participating dentist's obligation into the description itself. From Delta Dental – Policy ID Mapping for CARC/RARC Health Care Policy Codes:

"The submitted documentation does not support the payment of benefits for the procedure. Contracting providers agree to charge the patient only the amount indicated as 'Patient Pays.'" (policy code 504)

Two of its non-covered codes make the same point under a single reason code. Policy code FLK is patient responsibility both ways — "this service is not allowable. The patient is responsible for the amount indicated as 'Patient Pays'" — while policy code FLL carries the same reason code with the opposite group letter:

"According to our guidelines, the fee for this procedure is considered to be part of, and included in the fee for a completed service."

MetLife states the ceiling that applies even when the plan pays nothing, in its MetLife Preferred Dentist Program (PDP) Resource Manual:

"When the plan allowance is not reimbursed in full or in part by the benefit plan, any difference is the responsibility of the participant up to the plan allowance. The participant is not responsible for any amount that exceeds the plan allowance."

And on a downgraded service, the same manual caps the charge at the contracted fee for what was actually submitted:

"If a benefit determination is made that an alternate dental service meets the plan design contract provisions then the participating dentist can only charge up to the contracted schedule amount for the originally submitted service. The plan benefit will be based upon the alternate procedure."

One public programme forbids the bill outright when the office filed late. From the Renaissance TennCare Provider Manual, Adults, v8, 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

Three separate contracts decide the answer and none of them is the code.

The network agreement. Participation is what converts a PR into a PI on many carriers' mappings. The dentist who signed the contract agreed to absorb specific categories of refusal, and the carrier's remittance mapping is the list.

The plan design. A service the plan simply does not buy is normally the patient's, and a service the plan buys but will not pay on this claim often is not. That is why 204, "not covered under the patient's current benefit plan", is worth reading twice: on one carrier's own codes it is patient responsibility on one code and a write-off on another.

State law and programme rules. Public programmes routinely bar balance billing where a commercial contract would allow it, as the TennCare Adult manual does for late filing.

What to do

• Find the group letter before quoting the patient anything. If the remittance prints only a bare number, read the money columns: an amount landing in patient responsibility is the plan's answer.
• Check the office's participation status with the specific network that adjudicated the claim, not with the carrier generally. Carriers run several networks and the mapping follows the network.
• On an in-network denial of a covered service, bill the contracted allowance and not the full fee. That is a contract term, not a courtesy.
• Where an alternate benefit was applied in network, charge no more than the contracted fee for the procedure that was submitted, and tell the patient which two numbers you subtracted.
• Never bill a patient for a late-filed claim without reading the contract and the programme rules. On at least one public programme it is prohibited outright.
• Write the group letter into the ledger note alongside the reason, so whoever answers the patient's call has the answer in front of them.

Numbers last refreshed September 2026.

All articles · Kaylie