New guidance issued June 20 are designed to reduce improper federal Medicaid payments in states that are expanding the program to more adults.

Medicaid has added over 15 million new adult enrollees since the Affordable Care Act allowed expansion of the low-income program to people who earn slightly more than the federal poverty level. A recent audit from the Health and Human Services Office of the Inspector General found some states failed to follow federal and state guidelines when determining eligibility for the new beneficiaries.

States are now required to update their eligibility policies for adult recipients and describe the...