RemitBench/Denial codes/CO-23

CO-23 denial code

Code 23 is bookkeeping, not a denial. It records what the previous payer already did to the claim so the arithmetic on the secondary remittance adds up.

The code list's own wording: The impact of prior payer(s) adjudication including payments and/or adjustments. (Use only with Group Code OA)

What it means: You billed a secondary payer. This line carries the primary payer's payments and adjustments across so the secondary's maths balances. Nothing was refused.
Who owes the money: Nobody There is no new money being allocated here. It is a restatement of what already happened at the first payer.
Is appealing worth it: Nothing to appeal. If the secondary paid less than you expected, the reason will be elsewhere on the remittance, not on this line.

The code list restricts this one. Code 23 carries the note "Use only with Group Code OA". So OA-23 is the correct form. If you receive a CO-23 or a PR-23, the payer has used a group code the code list does not allow with this reason, and that is worth a call, especially if it is being treated as a write-off or a patient balance.

What the line is doing

Secondary claims have to reconcile against what the primary did. Without a line like this, the amounts on a secondary remittance would not add up to the charge.

The primary payer's payment amount.
Contractual adjustments the primary applied.
Patient responsibility the primary assigned.
The net position the secondary is starting from.

Because it is a summary of somebody else's decisions, nothing on this line is arguable with the secondary payer.

Remark codes you will see with it

Remark code	What it adds
MA04	Secondary payment cannot be considered without the primary payer's information. If this appears, the primary details did not arrive. Its own page.
N4	Missing, incomplete or invalid prior insurance carrier remittance.

Remark code

What it adds

MA04

Secondary payment cannot be considered without the primary payer's information. If this appears, the primary details did not arrive. Its own page.

Missing, incomplete or invalid prior insurance carrier remittance.

The one group code allowed

Most codes in this reference can carry any of the four letters. This one is different, and it says so in the code list itself.

OA-23: Other adjustment. The correct and only approved pairing. It puts the amount on neither side.
CO-23: Not an approved pairing. If you see it, the amount is being pushed into your write-offs by a code that should not carry it. Worth a call.
PR-23: Not an approved pairing, and worse, because it puts money on the patient that the primary already accounted for. Do not post it to a statement without checking.

What to do next

Reconcile the secondary against the primary

The whole purpose of the line. Charge, primary payment, primary adjustments, patient responsibility, secondary payment. If those do not sum, something else on the remittance is wrong.
Check the group code

OA is the approved one. Anything else means the amount is being allocated in a way the code list does not sanction.
Do not route it to the denial queue

Like CO-45 and CO-253, this is an adjustment code that inflates denial statistics and wastes follow up time.

Codes that get mixed up with 23

Code	How it differs from 23
22	Another payer may be primary. That is the denial you get for billing out of order. This is what a correctly ordered claim looks like. See CO-22.
45	Charge exceeds the fee schedule. A real contractual write-off. See CO-45.
109	Wrong payer entirely. See CO-109.

Code 23 in dental

You will see this on every properly ordered secondary dental claim. It is a sign the sequence worked rather than a sign of a problem.

It is where dual coverage disappointment becomes visible

Patients with two dental plans often expect the second to cover everything the first did not. This line is where you can see how the secondary actually coordinated, and it is worth reading before you tell the patient what they owe.

Questions people ask about CO-23

Is code 23 a denial?

No. It records what the primary payer already paid and adjusted, so that the secondary payer's remittance reconciles against the original charge. Nothing was refused on this line.

Why did I receive a CO-23 instead of OA-23?

The code list says code 23 is to be used only with group code OA. A CO-23 pushes the amount into your contractual write-offs, and a PR-23 puts it on the patient, neither of which the code list sanctions. Both are worth a call to the payer.

Related codes

Back to all denial codes

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