RemitBench/Denial codes

Denial codes, in plain words

A denial code tells you why a payer did not pay a line. This reference answers the part you need first: what the code means, who owes the money, and whether an appeal is worth your afternoon.

Read the two letters first

A code on a remittance has two parts. The letters are the group code, and they say who is out the money. The number is the reason code, and it says why. Most people read the number and skip the letters. That is the mistake that gets a patient billed for money the practice already agreed to write off.

The same number can carry any of these letters. They are not interchangeable.

CO: Contractual obligation. The practice absorbs it. This is a write-off you agreed to when you signed the contract, so you do not bill the patient for it.
PR: Patient responsibility. The patient owes it. This is the amount you put on their statement.
OA: Other adjustment. It does not put the money on either side. Payers use it for bookkeeping lines, such as a bundling note, a predetermination, or the part another payer already handled.
PI: Payer initiated reduction. The payer cut the line on its own and the patient does not owe it. Medicare is not allowed to use PI at all. Dental plans use it heavily, often where a medical payer would have said CO.

CO never creates a patient balance. If you read a page that says a CO code can be billed to the patient, close it. Under a participating contract, CO is your write-off.

CO-27 and PR-27 carry the same reason and the opposite bill. Check the letters before you post.

Dental billers, one extra warning. Dental plans barely use CO. They lean on PR and PI instead, and which one you get can depend on whether you are in that plan's network. So the medical habit of reading the number and assuming the letters is even riskier here.

Codes with a full page

These three are written out: what the payer meant, what to do next, and when to stop.

CO-16 Something on the claim was missing or wrong, so the payer would not process it. The code itself does not say what. The remark code next to it does. Read that first.
CO-97 The payer says this service is already paid for inside another service on the claim. Often a bundling edit or a global period. The practice writes it off, not the patient.
PR-27 Coverage had ended by the date of service. Find the right payer before you bill the patient, because there usually is one.

Other codes you will see

These do not have a page yet. The plain meaning is below so the list is still useful. Ask for the ones you hit most and they go next.

CO-4The modifier you used does not go with that procedure code.
CO-11The diagnosis you billed does not support the procedure you billed.
CO-18The payer already has this exact claim line. It is a duplicate.
CO-22Another plan is primary. Bill that one first and send the remittance with the second claim.
CO-29The claim arrived after the filing deadline.
CO-45You billed more than the contracted rate. The difference is your write-off, not a patient balance.
CO-50The payer decided the service was not medically necessary.
CO-109Wrong payer. Send the claim to the right one.
CO-119The plan maximum for the period is used up. Common in dental when the annual maximum runs out.
CO-151You billed more units or visits than the payer will pay for.
CO-167That diagnosis is not covered by the plan.
CO-197Prior authorization was required and the payer has none on file.
CO-204The plan does not cover this service at all.
CO-234The service is real, but this payer never pays it as its own line.
CO-B15Another service had to be billed and covered first, and it was not.
PR-1Deductible. The patient owes it.
PR-2Coinsurance. The patient owes it.
PR-3Copay. The patient owes it.
PR-26The date of service was before coverage started.
PR-49A routine or preventive visit the plan does not cover.
PR-96Not a covered charge, and the plan puts it on the patient. Check for CO-96 instead, which is yours.

One caution on the short list above. A payer picks the group code, and payers are not always consistent. Read the letters printed on your own remittance rather than assuming the pairing above. Where a code commonly appears with more than one group code, the full page says so.

RemitBench reads dental EOB PDFs and turns them into posting-ready lines, in your browser, with no upload. It does not read medical remittances today.

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