CO-A6: Prior Hospitalization or 30-Day Transfer Requirement Not Met

What Does CO-A6 Mean?

CO-A6 is the standard pairing, indicating the denial is a contractual obligation because the prior hospitalization or transfer requirement was not met. Under the provider's participation agreement with Medicare, SNF coverage requires a qualifying prior stay. When this requirement is not satisfied, the claim is denied as a contractual matter. The provider should first attempt to verify and document the qualifying stay before accepting the write-off.

When CARC A6 appears on a remittance, the payer is denying the claim because the patient did not meet the required prior hospitalization or 30-day transfer criterion. This code is most commonly associated with Medicare skilled nursing facility (SNF) coverage, which requires the patient to have had a qualifying inpatient hospital stay of at least 3 consecutive days within 30 days before the SNF admission.

The 3-day rule is a frequent source of A6 denials. Under traditional Medicare, observation stays do not count toward the 3-day requirement — only formally admitted inpatient days qualify. A patient who spent 4 days in the hospital under observation status and then transferred to a SNF would trigger CARC A6 because those observation days do not satisfy the inpatient stay requirement. The distinction between observation and inpatient status is critical and often the root cause of this denial.

Beyond the 3-day stay, the 30-day transfer window is the second common trigger. Even if the patient had a qualifying inpatient stay, the SNF admission must occur within 30 days of the hospital discharge date. Delays in transfer — whether due to bed availability, patient recovery, or administrative issues — can push the admission past the 30-day window and result in a CARC A6 denial.

Common Causes

How to Resolve

Verify whether the patient had a qualifying inpatient stay within 30 days of admission, then appeal with documentation or determine patient liability.

1. Document the qualifying stay Obtain the prior hospital's admission records confirming inpatient status, length of stay, and discharge date. Calculate whether the dates satisfy the 3-day and 30-day requirements.
2. Appeal with supporting documentation If the requirements were met, submit an appeal with admission records, discharge summaries, and transfer documentation proving the qualifying stay and timely transfer.
3. Write off or bill the patient If the requirements were not met, determine whether to write off the charges or transfer them to patient responsibility based on the payer contract and ABN (Advance Beneficiary Notice) status.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-A6:

How to Prevent CO-A6

• Verify qualifying inpatient stay status and dates with the referring hospital before admitting patients to the SNF
• Confirm the admission date falls within the 30-day transfer window before proceeding with the SNF admission
• Implement admission screening that automatically checks for qualifying prior hospitalizations and flags cases where the requirement may not be met
• Train admissions staff on the distinction between inpatient and observation status and its impact on SNF coverage eligibility

General Prevention

• Verify the patient's prior inpatient hospital stay status (not observation) and dates before admitting to SNF or post-acute care to ensure the 3-day qualifying stay requirement is met
• Confirm the admission date falls within 30 days of the qualifying hospital discharge date before proceeding with the SNF or post-acute admission
• Establish communication channels with referring hospitals to obtain and verify prior hospitalization documentation before admission
• Implement admission screening workflows that automatically check for qualifying prior hospitalizations and flag cases where the requirement may not be met
• Maintain thorough documentation of the prior hospitalization including admission type, dates, and discharge status to support claims processing
• Train admissions staff on Medicare SNF qualifying stay requirements and the distinction between inpatient and observation status

Also Filed As

The same CARC A6 may appear with different Group Codes:

Related Denial Codes