Under the Affordable Care Act, most plans must have an out-of-pocket maximum (referred to as maximum OOP, or MOOP) of no more than $8,550 in cost-sharing for a single individual in 2021 (this limit is indexed each year in the annual Notice of Benefit and Payment Parameters). Many plans have out-of-pocket limits below this level, but they cannot be higher. Once your cost-sharing amounts have reached your plan's maximum out-of-pocket limit for the year, the health insurance plan will pay 100% of your remaining covered costs that year. The ACA's limits on out-of-pocket costs only applies to in-network services that fall within the umbrella of essential health benefits. And it does not apply to grandmothered or grandfathered plans, or to plans that aren't regulated by the ACA at all, such as short-term health insurance. Original Medicare does not have a cap on cost-sharing amounts, although most enrollees have supplemental coverage (from an employer, Medicaid, or a Medigap plan) that covers some or all of their cost-sharing expenses. Medicare Advantage plans cannot require members to pay cost-sharing in excess of $7,550 in 2021, although many plans have cost-sharing limits below this (note that the out-of-pocket limits for Medicare Advantage plans do not include the cost of prescription drugs, which are covered separately and have separate — and unlimited — cost-sharing).