(1) Payment for hospital residents will be made as follows:

(a) prior to obtaining hospital residency status, claims for that recipient may be billed on an interim basis as provided in ARM 37.86.2905(4);

(b) final payment for the first 180 days of inpatient care will be the APR-DRG payment for the case as computed in ARM 37.86.2907 plus any appropriate outlier and add-on payment;

(c) final payment for all patient care subsequent to 180 days will be reimbursed at 80% of the hospital specific estimated cost to charge ratio as computed by the department without cost settlement; and

(d) the hospital must obtain authorization to bill prior to submission of the first claim and must provide medical records upon request of the department or its designated review organization for continued stay reviews.