The individual mandate, requiring most Americans to have health insurance or pay a penalty, was a central but controversial component of the ACA, though its penalty was later repealed.

To ensure a balanced risk pool — meaning enough healthy people enrolled to offset the costs of sicker individuals — the ACA included an 'individual mandate.' This provision required most Americans to obtain minimum essential health coverage or pay a tax penalty. The idea was to prevent a scenario where only sick individuals purchased insurance, driving up premiums for everyone. While crucial to the law's economic model, the individual mandate was highly contentious, leading to a Supreme Court challenge that upheld its constitutionality as a tax. However, as part of the Tax Cuts and Jobs Act of 2017, the penalty for not having insurance was reduced to $0, effectively repealing the enforcement mechanism of the individual mandate starting in 2019. Despite the removal of the federal penalty, some states have since implemented their own individual mandates.