A cost-sharing subsidy – also known as a cost-sharing reduction (CSR) – is a provision of the Affordable Care Act that allows people with modest incomes (up to 250 percent of the federal poverty level), to enroll in Silver-level health plans that have more robust benefits than a normal Silver plan.
The federal government used to pay insurers directly for the cost of providing cost-sharing subsidies, but that ended in late 2017. Since then, insurers have added the cost of this benefit to the premiums they charge, but they mostly add it only to the cost of Silver plans. This results in larger premium subsidies (which most enrollees receive) and has made coverage more affordable for most people in most areas.
Read more about CSRs.