; and (3) the total estimated economic cost imposed by all such rules. (b) Report Not later than 1 year after the date of the enactment of this Act, the Comptroller General of the United States shall submit a report to Congress that contains the findings of the study conducted under subsection (a). E Medicare Prescription Drug Competition 341. Medicare drug coverage Notwithstanding any other provision of law, the Secretary of Health and Human Services may alter the reimbursement mechanism for prescription drugs provided through the Medicare Part B program by reimbursing at a rate that, based on ASP+6% in the year of implementation of this Act, grows at CPI. 342. PBM transparency and elimination of DIR fees (a) Prohibiting medicare PDP sponsors and MA–PD organizations from retroactively reducing payment on clean claims submitted by pharmacies (1) In general Section 1860D–12(b)(4)(A) of the Social Security Act ( 42 U.S.C. 1395w–112(b)(4)(A) ) is amended by adding at the end the following new clause: (iv) Prohibiting retroactive reductions in payments on clean claims Each contract entered into with a PDP sponsor under this part with respect to a prescription drug plan offered by such sponsor shall provide that after the date of receipt of a clean claim submitted by a pharmacy, the PDP sponsor (or an agent of the PDP sponsor) may not retroactively reduce payment on such claim directly or indirectly through aggregated effective rate or otherwise except in the case such claim is found to not be a clean claim (such as in the case of a claim lacking required substantiating documentation) during the course of a routine audit as permitted pursuant to written agreement between the PDP sponsor (or such an agent) and such pharmacy. The previous sentence shall not prohibit any retroactive increase in payment to a pharmacy pursuant to a written agreement between a PDP sponsor (or an agent of such sponsor) and such pharmacy. . (2) Effective date The amendment made by subsection (a) shall apply with respect to contracts entered