"Since January 1, 2014, most individuals have had to maintain health insurance coverage or pay a penalty for noncompliance implemented through the Internal Revenue Code (IRC). To comply with this individual mandate, individuals need to maintain minimum essential coverage, which includes most types of public and private health insurance coverage. Some individuals are exempt from the mandate and not subject to its associated penalty. The individual mandate was established under the Patient Protection and Affordable Care Act (ACA; P.L. 111-148, as amended) and works in conjunction with other ACA provisions. Under the ACA, a number of federal requirements applicable to private health insurance issuers went into effect intending to improve access to private health insurance for sick individuals or those at high risk of becoming ill. The individual mandate works in tandem with the requirements by encouraging healthy individuals to participate in the market so that insurers' risk pools are not entirely composed of individuals who are at high risk of using health care services."
CRS Report for Congress, R44438
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html