The Medicare 72-hour rule, or 3-day rule, states that all services provided for a Medicare beneficiary within a 72-hour period before, during, or after admittance to a hospital be bundled together as one claim for billing. Many non-acute care hospitals and facilities require a 24-hour or 1-day rule.
Medicare pays hospitals a pre-determined rate for each hospital admission. Patients are classified into a Diagnosis Related Group based on statistics such as the principal diagnosis, the patient's age, complications, surgical procedures and other classifications. Medicare pays the hospital a flat rate for each DRG, regardless of the services provided. The 3-day rule requires any outpatient procedures related to the reason for admittance or diagnostic services, related or unrelated to the reason for admittance, to be bundled with any inpatient services when the out-patient procedures or services occur within 72-hours of admittance to a hospital that receives payments through the Inpatient Prospective Payment System.
Alternatively, psychiatric hospitals, rehab facilities, cancer hospitals, long-term care hospitals, and other non-acute facilities have a 24-hour window for bundling service claims. Critical Access Hospitals are not subject to either rule, unless wholly owned by an acute hospital that receives payment through the Inpatient Prospective Payment System. Some other services are also not subject to either rule, including ambulance service and maintenance dialysis.