Who has to pay after a code 23 denial?

Who owes depends on the details. The letters in front of the number matter: CO (contractual obligation) usually means an in-network provider must absorb it, while PR (patient responsibility) means the plan says you owe it.

How long do I have to appeal?

It depends on your coverage: 180 days for most employer and marketplace plans, 120 days for Original Medicare, about 90 days for Medicaid (varies by state), and only 65 days for Medicare Advantage. Set your deadline clock before you do anything else.

Denial code 23 · CO-23 / PR-23 · translated

Denial code 23: what it means — and how to fight it

Denial code 23 (shown on your EOB as CO-23 or PR-23) means: “The impact of prior payer(s) adjudication including payments and/or adjustments.” In plain English: Not a denial — this shows how your other insurance's payment affected what this plan paid.

low appealability Who owes depends on the details

What they're really saying

“The impact of prior payer(s) adjudication including payments and/or adjustments.”

Not a denial — this shows how your other insurance's payment affected what this plan paid.

Your odds

Check the math first — this is usually cost-sharing, not a judgment.

Only worth pursuing if the math between the two plans is wrong.

Fewer than 1 in 100 denied claims are ever appealed. When people do appeal, roughly 4 in 10 win the first round — and independent external review overturns 40–50% of what reaches it.

How to appeal a code 23 denial

Decode. You just did — this page is step one.
Set your clock. 180 days for most employer and marketplace plans, 120 for Original Medicare, ~90 for Medicaid, only 65 for Medicare Advantage.
Urgent? If this is care you still need, call and request an expedited appeal — they must decide within 72 hours.
Compare this EOB against the primary plan's EOB line by line. Check both EOBs side by side: primary's payment + secondary's payment + your share should equal the allowed amount.
Send it certified. Letter plus evidence, keep copies of everything.
Escalate. Denied again? Independent external review — a doctor who doesn't work for your insurer decides.

Do it in minutes, free

The AppealClock tool translates your denial, drafts your appeal letter, computes your exact deadline — and watches the clock so you don't have to. No account. Your medical details never leave your device.

Start your appeal & set your clock →

Common questions

What does denial code 23 mean?: Not a denial — this shows how your other insurance's payment affected what this plan paid.
Can I appeal a CO-23 or PR-23 denial?: Yes. Appealing is free and it is your legal right. For this code the odds are low: Only worth pursuing if the math between the two plans is wrong. Fewer than 1 in 100 denials are ever appealed — insurers count on silence.
Who has to pay after a code 23 denial?: Who owes depends on the details. The letters in front of the number matter: CO (contractual obligation) usually means an in-network provider must absorb it, while PR (patient responsibility) means the plan says you owe it.
How long do I have to appeal?: It depends on your coverage: 180 days for most employer and marketplace plans, 120 days for Original Medicare, about 90 days for Medicaid (varies by state), and only 65 days for Medicare Advantage. Set your deadline clock before you do anything else.