1. Short title This Act may be cited as the Improving Transparency and Accuracy in Medicare Part D Spending Act . 2. Prohibiting Medicare PDP sponsors and MA–PD organizations from retroactively reducing payment on clean claims submitted by pharmacies (a) 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. . (b) Effective date The amendment made by subsection (a) shall apply with respect to contracts entered into on or after January 1, 2018.