Effective December 1, 2015 Medicare Part D prescription claims will only be covered if the prescriber is enrolled in Medicare or has a valid opt-out affidavit on file with his/her Medicare Administrative Contractors (MAC). Based on CMS' evaluation of Part D claim data, 30% of the prescribers are not currently enrolled. To mitigate point of service rejections and patient care delays as of December 1, 2015, prescriber outreach is necessary. The Definition of a Valid Prescriber Task Group has developed a prescriber outreach letter template to assist with this effort. This letter may be used by pharmacy providers, PBMs, plan sponsors, and other impacted entities.