42 CFR §424.108

1. (a)Conditions for payment. Medicare pays the hospital for emergency services if the hospital—
   1. (1)Has in effect a statement of election to claim payment for all covered emergency services furnished during a calendar year, in accordance with § 424.104;
   2. (2)Claims payment in accordance with § 424.32; and
   3. (3)Submits evidence requested by CMS to establish that the services meet the requirements of this subpart.
2. (b)Subsequent claims. If the hospital files subsequent claims because the initial claim did not include all the services furnished, those claims must include physicians' statements that—
   1. (1)Contain sufficient information to clearly establish that, when the additional services were furnished, the emergency still existed; and
   2. (2)Indicate when the emergency ended, which, for inpatient hospital services, is the earliest date on which the beneficiary could be safely discharged or transferred to a participating hospital or other institution.