42 C.F.R. § 411.30 – Effect of primary payment on benefit utilization and deductibles.

(a) Benefit utilization. Inpatient psychiatric hospital and SNF care that is paid for by a primary payer is not counted against the number of inpatient care days available to the beneficiary under Medicare Part A.
(b) Deductibles. Expenses for Medicare covered services that are paid for by primary payers are credited toward the Medicare Part A and Part B deductibles.