An individual mandate is a requirement that all persons procure a particular good or service. In health care, it refers to the requirement within the Affordable Care Act that most Americans carry health insurance or pay a tax penalty. The 2018 tax penalty is the greater of either $695 per uninsured adult (and half that amount for a child), or 2.5 percent of household income.
The Supreme Court upheld the ACA’s individual mandate in 2012, although the 2017 tax bill will eliminate the penalty in 2019. 2018 tax returns (filed in 2019) will still include the penalty. Lacking a federal individual mandate, states can implement their own, as Massachusetts did prior to the ACA.