42 CFR 424.16 - Timing of certification for individual admitted to a hospital before entitlement to Medicare benefits.
(a)Basic rule. If an indivdual is admitted to a hospital before becoming entitled to Medicare benefits (for instance, before attaining age 65), the day of entitlement (instead of the day of admission) is the starting point for the time limits specified in subpart B of this part for certification and recertification.
(b)Example. (Hospital that is not a psychiatric hospital and is not subject to PPS). For a patient who is admitted on August 15 and becomes entitled on September 1 -
(1) The certification is required no later than September 12;
(2) The first recertification is required no later than September 18; and
(3) Subsequent recertifications are required at least every 30 days after September 18.