42 C.F.R. § 423.343 : Public Health — CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES — MEDICARE PROGRAM — VOLUNTARY MEDICARE PRESCRIPTION DRUG BENEFIT — PAYMENTS TO PART D PLAN SPONSORS FOR QUALIFIED PRESCRIPTION DRUG COVERAGE — Retroactive adjustments and reconciliations

(a) Application of enrollee adjustment. The provisions of §422.308(f) of this chapter apply to payments to Part D sponsors under this section in the same manner as they apply to payments to MA organizations under section 1853(a) of the Act.
(b) Health status. CMS makes adjustments to payments made under §423.329(a)(1) to account for updated health status risk adjustment data as provided under §422.310(g)(2) of this chapter. CMS may recover payments associated with health status adjustments if the Part D sponsor fails to provide the information described in §423.329(b)(3).
(c) Reinsurance. CMS makes final payment for reinsurance after a coverage year after obtaining all of the information necessary to determine the amount of payment.
(1) Submission of cost data. Within 6 months of the end of a coverage year, the Part D sponsor must provide the information that CMS requires.
(2) Payments. CMS at its discretion either makes lump-sum payments or adjusts monthly payments throughout the remainder of the payment year following the coverage year based on the difference between monthly reinsurance payments made during the coverage year and the amount payable in §423.329(c) for the coverage year. CMS may recover payments made through a lump sum recovery or by adjusting monthly payments throughout the remainder of the coverage year if the monthly reinsurance payments made during the coverage year exceed the amount payable under §423.329(c) or if the Part D sponsor does not provide the data in paragraph (c)(1) of this section.
(d) Low-income cost-sharing subsidy. CMS makes final payment for low-income cost-sharing subsidies after a coverage year after obtaining all of the information necessary to determine the amount of payment.
(1) Submission of cost data. Within 6 months of the end of a coverage year, the Part D sponsor must provide the information that CMS requires.
(2) Payments. CMS at its discretion either makes lump-sum payments or adjusts monthly payments throughout the remainder of the payment year following the coverage year based on the difference between interim low-income cost-sharing subsidy payments and total low-income cost-sharing subsidy costs eligible for subsidy under §423.782 submitted by the plan for the coverage year. CMS may recover payments made through a lump sum recovery or by adjusting monthly payments throughout the remainder of the coverage year if interim low-income cost-sharing subsidy payments exceed the amount payable under §423.782 or if the Part D sponsor does not provide the data in paragraph (d)(1) of this section. In the event adequate data is not provided for risk corridor costs, CMS assumes that the Part D plan's adjusted allowable risk corridor costs are 50 percent of the target amount.

42 C.F.R. §423.343