Who has to pay after a code 101 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.

All denial codes · code 101

Denial code 101: what it means — and how to fight it

Denial code 101 (shown on your EOB as CO-101 or PR-101) means: “Predetermination: anticipated payment upon completion of services or claim adjudication.” In plain English: This is not a denial. It is an estimate of what your plan expects to pay once the care actually happens and gets billed.

low appealability Who owes depends on the details

What they're really saying

“Predetermination: anticipated payment upon completion of services or claim adjudication.”

This is not a denial. It is an estimate of what your plan expects to pay once the care actually happens and gets billed.

Your odds

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

Nothing to appeal yet — but an estimate is not a guarantee of payment.

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 101 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.
Save this letter — you have not been denied, but you will want it later. Keep this letter. It is useful evidence later if the plan pays less than it estimated. Read it for conditions attached to the estimate — prior authorization still required, in-network provider required, benefit limits — and satisfy them before the service. If the final payment comes in lower than the predetermination, quote the letter by date and reference number in your appeal.
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 101 mean?: This is not a denial. It is an estimate of what your plan expects to pay once the care actually happens and gets billed.
Can I appeal a CO-101 or PR-101 denial?: Yes. Appealing is free and it is your legal right. For this code the odds are low: Nothing to appeal yet — but an estimate is not a guarantee of payment. Fewer than 1 in 100 denials are ever appealed — insurers count on silence.
Who has to pay after a code 101 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.