Who has to pay after a code A6 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 A6

Denial code A6: what it means — and how to fight it

Denial code A6 (shown on your EOB as CO-A6 or PR-A6) means: “Prior hospitalization or 30 day transfer requirement not met.” In plain English: Medicare will not pay for this nursing-home stay because your hospital stay before it was too short or the wrong kind. This is the three-midnight rule.

high appealability Who owes depends on the details

What they're really saying

“Prior hospitalization or 30 day transfer requirement not met.”

Medicare will not pay for this nursing-home stay because your hospital stay before it was too short or the wrong kind. This is the three-midnight rule.

Your odds

Strong — this type of denial has real weaknesses.

Very much worth appealing — observation status is the usual culprit and it can be challenged.

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 A6 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.
Check your hospital record for whether you were "observation" or "inpatient". The most common cause is being kept in the hospital under "observation" instead of admitted as an inpatient, which does not count toward the three-day requirement even if you were there for days. Get your hospital record and check your status day by day. Ask the hospital whether it issued the required Medicare Outpatient Observation Notice, and request that your status be reviewed and corrected to inpatient. Also check the 30-day rule: if you re-entered a nursing facility within 30 days of a qualifying stay, no new hospital stay is required.
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 A6 mean?: Medicare will not pay for this nursing-home stay because your hospital stay before it was too short or the wrong kind. This is the three-midnight rule.
Can I appeal a CO-A6 or PR-A6 denial?: Yes. Appealing is free and it is your legal right. For this code the odds are high: Very much worth appealing — observation status is the usual culprit and it can be challenged. Fewer than 1 in 100 denials are ever appealed — insurers count on silence.
Who has to pay after a code A6 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.