This guide describes the interface that states with Financial Alignment Initiative Demonstrations use to conduct Medicare eligibility verification and MMP enrollment submission to the CMS MARx systems. Version 3.1 of the Guide reflects the addition of historical Medicare beneficiary Part A and Part B entitlement start and end dates on all Medicare Eligibility query mediums produced by Infocrossing. This change is effective October 1, 2019. Version 3.1 of the Guide also introduces Infocrossing’s new RESTful Eligibility Web Service. MMPs and state agencies can now use the RESTful Eligbility web service in conjunction with or as a replacement to the existing web service tool, at their own discretion. The revision history section of the document details these changes.