More than a decade and a half after its passage, the Affordable Care Act remains the backbone of health coverage for tens of millions of Americans. The ACA’s marketplaces, subsidies, Medicaid expansion, and consumer protections have reshaped how people buy insurance — and the law continues to evolve through legislation and court challenges. Here is how the Affordable Care Act works in 2026, who it covers, and what to know if you are shopping for a plan.
Table of Contents
- What the ACA Does: The Big Picture
- The Health Insurance Marketplaces
- Subsidies: Premium Tax Credits and Cost-Sharing
- Medicaid Expansion
- Consumer Protections That Apply to Everyone
- Enrollment in 2026: What to Know
- Key Takeaways
What the ACA Does: The Big Picture
The Affordable Care Act, signed in 2010, attacked the uninsured problem from three directions at once. First, it created regulated marketplaces where individuals and small businesses can shop for coverage. Second, it offered financial help — premium tax credits and cost-sharing reductions — to make that coverage affordable. Third, it expanded Medicaid to cover low-income adults in participating states.
Around those pillars, the law layered sweeping consumer protections: insurers can no longer deny coverage or charge more based on pre-existing conditions, plans must cover a set of essential health benefits, and young adults can stay on a parent’s plan until age 26. The law also required most plans to cover preventive services — vaccinations, screenings, contraception — with no cost-sharing.
The result: the uninsured rate fell dramatically after the law’s main provisions took effect in 2014, and marketplace enrollment has grown in recent years as subsidies were expanded. According to the Centers for Medicare and Medicaid Services, marketplace sign-ups have reached record levels in recent open enrollment periods. Official program data and rules are published by cms.gov.
The Health Insurance Marketplaces
The marketplaces — HealthCare.gov in most states, with some states running their own exchanges — are online shops where individuals and families buy coverage. Plans are organized into metal tiers: Bronze (lowest premiums, highest out-of-pocket costs), Silver, Gold, and Platinum (highest premiums, lowest out-of-pocket costs). Catastrophic plans with very low premiums are available to people under 30 and those with hardship exemptions.
Every marketplace plan must cover ten categories of essential health benefits, including hospitalization, prescription drugs, maternity care, mental health services, and emergency care. Plans cannot impose annual or lifetime dollar limits on these benefits. This standardization makes comparison shopping possible: within a metal tier, the differences between plans come down to networks, formularies, and cost-sharing details.
Open enrollment runs once a year, typically November through mid-January, and coverage bought then starts January 1. Outside that window, you can only enroll if you qualify for a special enrollment period — triggered by events like losing job-based coverage, moving, getting married, or having a baby. For step-by-step help picking a plan, see our guide on how to choose health insurance during open enrollment.
Subsidies: Premium Tax Credits and Cost-Sharing
Subsidies are what make marketplace coverage affordable for most enrollees. Premium tax credits cap what eligible households pay for a benchmark Silver plan as a percentage of income, with the government paying the rest directly to the insurer. Enhanced subsidies enacted in recent years extended eligibility further up the income scale and lowered the percentage-of-income caps — changes that substantially reduced premiums for middle-income buyers.
A second form of help, cost-sharing reductions, lowers deductibles, copays, and out-of-pocket maximums — but only for Silver plans purchased by lower-income enrollees. Together, the two subsidies mean that many marketplace shoppers pay far less than the plan’s sticker price. Whether the enhanced subsidies continue beyond their current authorization is one of the biggest open questions in health policy, with major implications for premiums.
Eligibility depends on income, household size, and access to other coverage. People offered “affordable” job-based insurance generally cannot get marketplace subsidies, though the definition of affordable has been refined over the years. The marketplace application itself determines eligibility and applies the credits automatically.
Medicaid Expansion
The ACA originally required states to expand Medicaid to adults earning up to 138 percent of the federal poverty level, but a 2012 Supreme Court decision made expansion optional. Most states have now adopted it, covering millions of low-income adults who previously fell into a gap — too poor for marketplace subsidies but ineligible for traditional Medicaid.
In states that have not expanded, that coverage gap persists: childless adults with very low incomes often qualify for neither Medicaid nor subsidized marketplace coverage. Expansion remains one of the most studied provisions in health policy, with research generally finding improved access to care, better financial security, and even reduced mortality among the expansion population.
Medicaid itself is a joint federal-state program covering well over 70 million Americans, including children, pregnant women, seniors, and people with disabilities. The federal government pays the lion’s share of expansion costs — 90 percent — which is why the fiscal argument for holdout states centers on the remaining state share and on political opposition to the ACA itself.
Consumer Protections That Apply to Everyone
Many of the ACA’s most popular provisions apply beyond the marketplaces, including to job-based plans. Insurers cannot deny coverage or charge higher premiums because of pre-existing conditions — a protection that polls consistently show is among the law’s most valued. Women cannot be charged more than men for the same coverage. Plans must allow young adults to stay on parental coverage until 26.
The law also ended “rescissions” — the practice of canceling a sick person’s policy over minor application errors — and required insurers to spend at least 80 to 85 percent of premium dollars on medical care rather than administration and profit, with rebates to consumers when they fall short. These rules reshaped the individual market from one where insurers competed by avoiding sick people to one where they compete on price and networks.
For readers comparing plan types more broadly, our breakdown of HMO vs. PPO vs. EPO plans explains how networks and referrals work across all kinds of coverage, and our guide to understanding health insurance metal tiers covers Bronze through Platinum.
Enrollment in 2026: What to Know
If you are shopping for 2026 coverage, start at HealthCare.gov (or your state’s exchange) during open enrollment. Have your income estimate, household information, and current coverage details ready. Compare plans on total cost — premiums plus expected out-of-pocket spending — not premiums alone, and check that your doctors and prescriptions are covered before you commit.
Beware of lookalike plans sold outside the marketplace: short-term and fixed-indemnity plans are cheaper but do not have to cover pre-existing conditions or essential benefits. They can leave buyers exposed to catastrophic bills. Marketplace plans are the only ones eligible for subsidies and the only individual-market plans guaranteed to meet ACA standards.
Free, unbiased help is available: navigators and certified assisters in every state help with applications at no charge. Given how much subsidies can change year to year, even current enrollees should shop actively rather than auto-renewing — a better or cheaper plan may be waiting. Official enrollment resources are maintained by usa.gov.
