42 CFR §427.505

1. (a)Rebate amounts owed by a manufacturer. For a rebate amount owed by a manufacturer, payment is due no later than 11:59 p.m. Pacific Time (PT) on the 30th calendar day after the date of receipt of information regarding the rebate amount on—
   1. (1)A Rebate Report as set forth in § 427.501(c) or § 427.502(c)(1) or (2); or
   2. (2)A report of a reconciled rebate amount as set forth in § 427.501(d) or § 427.502(c)(2)(ii).
2. (b)Failure to pay a rebate amount. Failure to pay a rebate amount due timely and in full may result in an enforcement action as described in subpart G of this part.
3. (c)Refund to the manufacturer. If a reconciled rebate amount for an applicable calendar quarter as set forth in § 427.501(d) or § 427.502(c)(2)(ii) is less than what the manufacturer paid for that applicable calendar quarter, CMS will initiate the process to provide a refund equal to the excess amount paid within 60 days of the date of receipt of the report with such reconciled rebate amount.