42 CFR §412.120

1. (a)Deductible and coinsurance. Subject to paragraph (a)(2) of this section, the total Medicare payments otherwise payable to a hospital are reduced by the applicable deductible and coinsurance amounts related to inpatient hospital services as determined in accordance with §§ 409.82, 409.83, and 409.87 of this chapter.
2. (b)Payment by workers' compensation, automobile medical, no-fault or liability insurance or an employer group health plan primary to Medicare. If workers' compensation, automobile medical, no-fault, or liability insurance or an employer group health plan which is primary to Medicare pays in full or in part, the Medicare payment is determined in accordance with the following guidelines:
   1. (1)If workers' compensation pays, in accordance with the applicable provisions of §§ 405.316 through 405.321 of this chapter.
   2. (2)If automobile medical, no-fault, or liability insurance pays, in accordance with the applicable provisions of §§ 405.322 through 405.325 of this chapter.
   3. (3)If an employer group health plan which is primary to Medicare pays for services to ESRD beneficiaries, in accordance with the applicable provisions of §§ 405.326 through 405.329 of this chapter.
   4. (4)If an employer group health plan which is primary to Medicare pays for services to employees age 65-69 and their spouses age 65-69, in accordance with the applicable provisions of §§ 405.340 through 405.344 of this chapter.