Who has to pay after a code 28 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 28

Denial code 28: what it means — and how to fight it

Denial code 28 (shown on your EOB as CO-28 or PR-28) means: “Coverage not in effect at the time the service was provided.” In plain English: The plan says you were not covered on the day you got care. Sometimes true, often a start-date or termination-date error.

high appealability Who owes depends on the details

What they're really saying

“Coverage not in effect at the time the service was provided.”

The plan says you were not covered on the day you got care. Sometimes true, often a start-date or termination-date error.

Your odds

Strong — this type of denial has real weaknesses.

Frequently overturned when you can show you were enrolled that day.

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 28 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.
Find something in writing that shows you were enrolled on the date you got care. Get proof of coverage for the date of service: an ID card with effective dates, an enrollment confirmation, a pay stub showing a premium deduction, or a Marketplace eligibility notice. If you switched plans mid-month, ask which plan was active that day and have the office rebill the right one. If your employer reported the wrong start date, HR can correct it with the carrier.
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 28 mean?: The plan says you were not covered on the day you got care. Sometimes true, often a start-date or termination-date error.
Can I appeal a CO-28 or PR-28 denial?: Yes. Appealing is free and it is your legal right. For this code the odds are high: Frequently overturned when you can show you were enrolled that day. Fewer than 1 in 100 denials are ever appealed — insurers count on silence.
Who has to pay after a code 28 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.