The Affordable Care Act (ACA) is a comprehensive health care reform law enacted in March 2010 that reshaped how Americans get and pay for health insurance. Often called “Obamacare,” its formal name is the Patient Protection and Affordable Care Act. The law created online insurance marketplaces, expanded Medicaid, and put new rules on insurance companies to protect consumers. As of early 2025, more than 24 million people are enrolled in marketplace plans alone.
The Three Core Goals
The ACA was built around three pillars. First, it aimed to make health insurance affordable for more people by offering subsidies (called premium tax credits) that lower monthly costs for households earning between 100% and 400% of the federal poverty level. Second, it expanded Medicaid to cover adults earning below 138% of the federal poverty level, though not all states have adopted the expansion. Third, it pushed for new ways of delivering medical care designed to bring down health care costs overall.
Before the ACA, millions of Americans were either uninsured or stuck with plans that could drop them when they got sick. The law addressed both problems simultaneously: it made coverage easier to get and set minimum standards for what that coverage actually included.
Pre-Existing Condition Protections
One of the most significant changes the ACA introduced is that health insurance companies cannot refuse coverage or charge you more because of a pre-existing condition. That includes asthma, diabetes, cancer, pregnancy, and any other health problem you had before your new coverage started. Insurers also cannot limit benefits for those conditions. Once you have a plan, they cannot refuse to cover treatment for something you were already dealing with.
Before 2010, insurers routinely denied applications or charged dramatically higher premiums based on medical history. The ACA eliminated that practice for nearly all plans, with a narrow exception for certain “grandfathered” plans that existed before the law took effect.
Essential Health Benefits
The ACA requires all individual and small group market plans to cover 10 categories of services. These include doctors’ visits, inpatient and outpatient hospital care, prescription drugs, pregnancy and childbirth, mental health services, rehabilitative services, lab tests, preventive care, pediatric services (including dental and vision for children), and emergency services. Before the ACA, many cheaper plans excluded entire categories, leaving people exposed to enormous bills for things like maternity care or mental health treatment.
On top of these essential benefits, most plans must cover a set of preventive services at no cost to you when you see an in-network provider. That means no copay, no coinsurance, and no deductible for things like immunizations, cancer screenings, blood pressure checks, and annual wellness visits.
How the Insurance Marketplace Works
The ACA created the Health Insurance Marketplace (sometimes called the “exchange”), an online platform where individuals and families can compare and buy health insurance plans. Plans are organized into four tiers based on how they split costs between you and the insurer:
- Bronze: The plan covers about 60% of costs, you pay 40%. Monthly premiums are lowest, but out-of-pocket costs when you use care are highest.
- Silver: The plan covers about 70%, you pay 30%. If you qualify for extra savings based on income, Silver plans can cover anywhere from 73% to 94% of costs.
- Gold: The plan covers about 80%, you pay 20%.
- Platinum: The plan covers about 90%, you pay 10%. Premiums are highest, but you pay the least when you actually need care.
All four tiers cover the same essential health benefits. The difference is purely in how costs are shared. Someone who rarely sees a doctor might prefer a Bronze plan with lower premiums. Someone managing a chronic condition might save money overall with Gold or Platinum despite higher monthly payments.
Subsidies and Financial Help
The ACA’s premium tax credits reduce the monthly cost of marketplace plans for people who qualify based on income. Originally, these subsidies were available only to households earning up to 400% of the federal poverty level. In 2021 and again in 2022, Congress expanded the subsidies so that middle-income earners above that threshold (for example, a family of three earning more than roughly $103,000 a year) could also receive help. These enhanced subsidies are currently set to expire at the end of 2025.
If the enhanced subsidies aren’t renewed, millions of people will see their premiums rise significantly, and those earning above 400% of the poverty level will lose eligibility for financial assistance entirely. Insurers and regulators need to know the outcome well in advance to set accurate premiums for the following year, making this one of the most consequential policy decisions affecting the ACA’s near-term future.
Medicaid Expansion
The ACA extended Medicaid eligibility to all adults under 65 with incomes below 133% of the federal poverty level. A built-in income disregard of 5 percentage points means the effective threshold is 138% of the poverty level. This was a major shift because, before the ACA, Medicaid in most states covered only specific groups like children, pregnant women, and people with disabilities. Adults without dependent children were largely excluded regardless of how little they earned.
The Supreme Court ruled in 2012 that states could not be forced to expand Medicaid, making it optional. As a result, expansion has been uneven. In states that have not expanded, some low-income adults fall into a “coverage gap” where they earn too much for traditional Medicaid but too little to qualify for marketplace subsidies.
Coverage for Young Adults
The ACA requires plans that offer dependent coverage to let adult children stay on a parent’s plan until age 26. This applies regardless of whether the young adult lives with their parents, is claimed as a tax dependent, or is still in school. It covers both married and unmarried children, though the young adult’s own spouse and children do not qualify for coverage under the parent’s plan.
This provision was one of the first ACA benefits to take effect and quickly became one of its most popular. It gave millions of young adults coverage during a period of life when they were often between jobs or in entry-level positions that didn’t offer insurance.
Requirements for Employers
Businesses with 50 or more full-time employees (called “applicable large employers”) are required to offer health insurance to at least 95% of their full-time workers and those workers’ dependents. If they don’t, and even one employee ends up getting a subsidized marketplace plan, the employer faces a penalty. For 2024, that penalty is $2,970 per full-time employee annually, with the first 30 employees excluded from the calculation.
Even employers that do offer coverage can face a separate penalty if the insurance is considered unaffordable or doesn’t meet minimum standards. In that case, the penalty for 2024 is $4,460 for each employee who receives a marketplace subsidy instead. Small businesses with fewer than 50 full-time employees have no obligation to provide coverage, though many do voluntarily.