Health Insurance Learning Center
How Does the ACA Marketplace Work?
Over 21 million Americans enrolled through the ACA marketplace in 2025, and 92% received subsidies that cut premiums by an average of 85%. Here's how it works.
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What Is the ACA Marketplace and Who Is It For?
The Affordable Care Act (ACA) marketplace is where individuals and families buy health insurance that must cover 10 essential health benefits, including hospitalization, prescriptions, maternity, and preventive care. According to CMS, enrollment hit a record 21.4 million in 2025.
Most people apply for premium tax credits based on household income. The IRS describes the credit as generally available between 100% and 400% of the Federal Poverty Level, subject to other rules, and only the Marketplace can determine your amount. Your application is a projection of the coverage year, so you must update it as your income or household changes rather than waiting until you file. If your income is self-employment income, see our guide to estimating Marketplace income when self-employed.
Open Enrollment runs November 1 through January 15 in most states. Outside that window, you need a qualifying life event (losing coverage, marriage, birth, a move) for a 60-day Special Enrollment Period. Enroll by December 15 for January 1 coverage where that deadline applies, and confirm the final date with your Marketplace, since state deadlines can differ.
How Do ACA Subsidies and Cost-Sharing Reductions Work?
Premium Tax Credits
Directly reduce your monthly premium. Based on income relative to the Federal Poverty Level. A household earning 200% FPL pays no more than ~6.5% of income toward a benchmark Silver plan premium (HealthCare.gov).
Cost-Sharing Reductions (CSRs)
Available at 100 to 250% FPL on Silver plans only. CSRs can reduce a $5,000 deductible to $250 and cut the out-of-pocket maximum from $9,200 to as low as $3,050. Per KFF, 60% of eligible enrollees benefit from CSRs.
How to Estimate Your Subsidy
Use HealthCare.gov or work with a licensed agent to enter your income and household size. You'll see estimated monthly costs for each metal level. Subsidy amounts update automatically as income changes.
What Counts as Income?
Modified Adjusted Gross Income (MAGI): wages, self-employment income after allowable expenses, Social Security, unemployment, alimony, and investment income. It does not include gifts, inheritances, or child support. Update your application whenever your expected income changes.
Related tools and guides
Estimate your premium tax credit in under a minute.
See where the 400% FPL cliff hits your household.
Hub for high earners who don't qualify for a premium tax credit.
Business profit, fluctuating months, and repaying excess advance credit.
How affordability is tested for the employee and the family.
Which triggers allow a mid-year switch and which do not.