42 CFR §423.2325

1. (a)General rule. On behalf of the manufacturers, Part D sponsors must provide applicable beneficiaries with applicable discounts on applicable drugs at the point-of-sale.
2. (b)Discount determination.
   1. (1)Part D sponsors must determine the following:
      1. (i)Whether an enrollee is an applicable beneficiary (as defined in § 423.100).
      2. (ii)Whether a Part D drug is an applicable drug (as defined in § 423.100).
      3. (iii)The amount of the applicable discount (as defined in § 423.2305) to be provided at the point-of-sale.
   2. (2)Part D sponsors must make retroactive adjustments to the applicable discount as necessary to reflect changes to the claim or beneficiary eligibility determined after the date of dispensing.
   3. (3)Part D sponsors must determine whether any affected beneficiaries need to be notified by the Part D sponsor that an applicable drug is eligible for Part D coverage whenever CMS specifies a retroactive effective date for a labeler code and notify such beneficiaries.
3. (c)Exception to point-of-sale requirement. Part D sponsors must provide an applicable discount for applicable drugs submitted by applicable beneficiaries via paper claims, including out-of-network and in-network paper claims, if such claims are payable under the Part D plan.
4. (d)Collection of data. Part D sponsors must provide CMS with appropriate data on the applicable discounts provided by the Part D sponsors in a manner specified by CMS.
5. (e)Supplemental benefits.
   1. (1)An applicable discount must be applied to beneficiary cost-sharing after supplemental benefits (as defined in § 423.100) have been applied to the claim for an applicable drug.
   2. (2)No applicable discount is available if supplemental benefits (as defined in § 423.100) eliminate the coverage gap so that a beneficiary has zero cost-sharing.
6. (f)Other health or prescription drug coverage. An applicable discount must be applied to beneficiary cost-sharing when Part D is the primary payer before any other health or prescription drug coverage is applied.
7. (g)Pharmacy prompt payment. Part D sponsors must reimburse a network pharmacy (as defined in § 423.100) the amount of the applicable discount no later than the applicable number of calendar days after the date of dispensing of an applicable drug. For long-term care and home infusion pharmacies, the date of dispensing can be interpreted as the date the pharmacy submits the discounted claim for reimbursement.
8. (h)Treatment of employer group waiver plans. As of 2014, Part D sponsors offering employer group waiver plans must provide applicable discounts to applicable beneficiaries who are employer group waiver plan enrollees as determined consistent with the defined standard benefit.