42 C.F.R. § 600.510 – Cost-sharing.

(a) Cost-sharing requirements.
1. (1) For cost sharing imposed on enrollees, the State must assure the following:
  1. (i) The cost sharing imposed on enrollees meet the standards detailed in § 600.520(c).
  2. (ii) The establishment of an effective system to monitor and track the cost-sharing standards consistent with § 600.520(b) through (d).
2. (2) This assurance must be reflected in the BHP Blueprint, which shall also include the group or groups of enrollees subject to the cost sharing.
(b) Cost sharing for preventive health services. A State may not impose cost sharing with respect to the preventive health services or items, as defined in, and in accordance with 45 CFR 147.130.