The Affordable Care Act (ACA), also known as Obamacare, is a federal health care law enacted in 2010 that expanded access to health insurance, created health insurance marketplaces and premium subsidies, expanded Medicaid in participating states, and established consumer protections for people with private health coverage.
The Affordable Care Act is a federal law that changed how health insurance is sold, regulated, and subsidized in the United States. Its formal name is the Patient Protection and Affordable Care Act, or PPACA.
President Barack Obama signed the Patient Protection and Affordable Care Act into law on March 23, 2010. Congress amended it one week later through the Health Care and Education Reconciliation Act of 2010. The term “Affordable Care Act” generally refers to the law as amended.
The ACA affects individual health insurance, employer-sponsored coverage, Medicaid, taxes, insurance regulation, and the way people obtain financial assistance for coverage. Some of its provisions apply broadly across the health insurance market, while others apply only to particular plans, employers, or individuals.
Before the ACA, insurers in the individual health insurance market could commonly deny coverage or charge higher premiums based on a person's medical history. Policies could also contain limits that restricted how much an insurer would pay for certain benefits over a year or a person's lifetime.
The ACA imposed a series of federal insurance protections. Marketplace plans generally cannot deny coverage, charge higher premiums, or refuse to cover essential health benefits because someone has a preexisting medical condition. The law also restricts annual and lifetime dollar limits on essential health benefits and provides protections against certain cancellations of coverage.
The law also created health insurance marketplaces, provided financial assistance to qualifying consumers, expanded Medicaid eligibility in states that elected to participate, and established coverage requirements and reporting obligations for certain large employers.
The ACA created health insurance exchanges, commonly called Health Insurance Marketplaces, where individuals and families can compare and purchase private health insurance.
Some states operate their own marketplaces. The federal government operates HealthCare.gov for states that use the federal Marketplace.
Plans sold through the Marketplace must comply with ACA requirements, including protections for preexisting conditions and coverage of specified categories of essential health benefits. Depending on income and other eligibility rules, consumers who purchase coverage through a Marketplace can also qualify for federal financial assistance.
The Supreme Court addressed an important question about federal Marketplace subsidies in King v. Burwell in 2015. The Court held that the ACA's premium tax credits are available to qualifying consumers in states using a federally operated exchange, as well as in states operating their own exchanges.
The premium tax credit is a federal tax credit designed to reduce the cost of health insurance purchased through the Marketplace.
Eligibility depends on household income, family size, access to other qualifying coverage, and several tax-related requirements. The credit can generally be paid in advance to an insurer to reduce monthly premiums or claimed when a taxpayer files a federal income tax return.
For 2026, the general income range for premium tax credit eligibility is between 100% and 400% of the federal poverty level, subject to other eligibility requirements. Congress temporarily removed the 400% upper income limit for tax years 2021 through 2025, but that temporary expansion expired at the end of 2025.
Eligibility rules and subsidy amounts can change through federal legislation, so the applicable rules depend on the coverage and tax year involved.
One of the ACA's central insurance reforms concerns preexisting medical conditions.
Marketplace insurers generally cannot refuse to cover someone because of a condition that existed before the policy began. They also cannot charge a person more or refuse to pay for essential health benefits solely because of that person's health history. Pregnancy is also treated as a covered condition rather than a basis for denying coverage or imposing a higher premium.
Some older grandfathered health plans are treated differently under the law and are exempt from certain ACA requirements. As a result, the specific protections that apply can depend on the type of health plan involved.
The ACA requires individual and small-group plans subject to its essential health benefits rules, including Marketplace plans, to provide coverage within 10 general categories of medical services.
Those categories include outpatient care, emergency services, hospitalization, maternity and newborn care, mental health and substance use disorder treatment, prescription drugs, rehabilitation and habilitation services, laboratory services, preventive and wellness care, and pediatric services.
The law establishes broad categories rather than requiring every health plan to cover every treatment in exactly the same way. Specific covered services, provider networks, deductibles, copayments, and other plan terms can vary by state and insurer.
Large self-insured employer plans are generally not required to provide the ACA's complete package of essential health benefits, although other ACA protections can still apply to them.
The ACA expanded dependent coverage by allowing many young adults to remain on a parent's health insurance plan until age 26.
The rule applies broadly to eligible dependent coverage and is one of the ACA provisions that also applies to many grandfathered plans.
After a person ages out of parental coverage, other coverage options can include employer-sponsored insurance, Marketplace coverage, Medicaid, or a student health plan, depending on the person's circumstances.
The ACA sought to expand Medicaid eligibility to nearly all nonelderly adults with incomes up to an effective level of 138% of the federal poverty level.
The original law attempted to require participating states to adopt the expansion by placing their existing federal Medicaid funding at risk if they refused.
The Supreme Court changed how that provision operates in National Federation of Independent Business v. Sebelius in 2012. The Court concluded that Congress could not threaten states with the loss of their existing Medicaid funding in order to compel participation in the expansion. The expansion remained available, but states had a genuine choice whether to adopt it.
As a result, Medicaid eligibility for low-income adults can differ significantly from one state to another. HealthCare.gov notes that people with incomes below the federal poverty level can still fall into a “coverage gap” in states that have not expanded Medicaid if they do not qualify under another Medicaid eligibility category.
The ACA does not require every employer to provide health insurance.
Its employer shared responsibility provisions generally apply to employers with an average of at least 50 full-time employees, including full-time-equivalent employees, during the preceding year. These employers are known as applicable large employers, or ALEs.
An applicable large employer can face an employer shared responsibility payment if it fails to offer qualifying coverage to enough full-time employees and their dependents and at least one full-time employee receives a premium tax credit for Marketplace coverage.
The law also contains detailed standards involving affordability, minimum value, employee status, and employer reporting. Employer coverage provides “minimum value” for these purposes when it generally covers at least 60% of the expected total allowed cost of benefits under the plan.
The ACA originally required most Americans to maintain minimum essential health coverage or potentially make an individual shared responsibility payment to the federal government.
The Supreme Court considered that requirement in National Federation of Independent Business v. Sebelius. The Court concluded that the mandate could not be sustained under Congress's Commerce Clause authority, but the payment associated with going without coverage could constitutionally be treated as an exercise of Congress's taxing power.
Congress later reduced the federal shared responsibility payment to $0 beginning in 2019. The statutory minimum-coverage language remained in federal law, but there is no current federal financial penalty for going without qualifying health insurance.
Some states have adopted their own health insurance mandates and penalties, so a person can still face state-law requirements even though the federal payment is zero.
No. The Supreme Court has decided several major cases involving the ACA, but the law remains in effect.
In NFIB v. Sebelius, the Court upheld the individual mandate's payment under Congress's taxing power while limiting the federal government's ability to compel states to expand Medicaid.
In King v. Burwell, the Court held that qualifying consumers could receive premium tax credits through federally operated health insurance exchanges.
In California v. Texas in 2021, states and individuals challenged the ACA after Congress reduced the individual mandate penalty to zero. The Supreme Court did not decide whether the mandate was constitutional in its altered form. Instead, the Court held that the plaintiffs lacked Article III standing to bring the challenge because they had not shown an injury traceable to government enforcement of the provision.
No. The ACA regulates different types of health coverage in different ways.
Marketplace plans and most individual and small-group plans are subject to many of the law's central requirements. Employer-sponsored plans can be subject to a different combination of federal rules, and self-insured employer plans are treated differently in several areas.
Grandfathered plans—generally plans that existed when the ACA was enacted and have maintained that status—are exempt from certain requirements. Some ACA protections nevertheless apply to them, including the ability of eligible adult children to remain on a parent's plan until age 26 and restrictions on lifetime limits for essential health benefits.
Determining which ACA protections apply can therefore require looking at the particular insurance plan, the type of coverage, and the provision involved.
The ACA reaches far beyond the Health Insurance Marketplace.
Its provisions affect how insurers treat preexisting conditions, which benefits many plans must cover, how low- and moderate-income consumers can receive financial assistance, who can qualify for Medicaid, how certain employers offer and report health coverage, and how consumers can challenge some insurance decisions.
The law has also generated major questions involving constitutional law, federalism, taxation, administrative law, insurance regulation, and the relationship between federal and state authority.
For consumers, the practical effect often comes down to a more immediate question: whether coverage is available, what it must include, how much assistance is available to pay for it, and what legal protections apply when an insurer denies or limits coverage.
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