42 CFR §424.127

1. (a)Conditions for payment of inpatient hospital services. Medicare pays the beneficiary if—
   1. (1)The hospital does not have in effect an election to claim payment; and
   2. (2)The beneficiary, or someone on his or her behalf, submits—
      1. (i)A claim in accordance with § 424.32;
      2. (ii)An itemized hospital bill; and
      3. (iii)Evidence requested by CMS to establish that the services meet the requirements of this subpart.
2. (b)Amount payable for inpatient hospital services. The amount payable to the beneficiary is determined in accordance with § 424.109(b).
3. (c)Conditions for payment for Part B services. Medicare pays the beneficiary for physicians' services and ambulance services as specified in § 424.121, if an itemized bill for the services is submitted by the beneficiary or someone on his or her behalf and the conditions of § 424.126(a) (2) and (3) are met.
4. (d)The amount payable to the beneficiary is determined in accordance with § 410.152 of this chapter.