What Is Open Enrollment for Health Insurance?

Every fall, millions of Americans face a flurry of emails, mailers, and HR reminders about open enrollment — and every year, a significant number of people miss the window or make hasty decisions they regret for the next 12 months. So what is open enrollment, exactly? It is the designated period each year when you can enroll in a new health insurance plan, switch plans, or make changes to your existing coverage without needing a qualifying life event. Miss this window and you are generally locked into your current coverage — or locked out of coverage entirely — until the next year. Understanding how open enrollment works, when it happens, and what to look for can save you hundreds or even thousands of dollars. For more on navigating health insurance in the US, see our healthcare policy guide.

It helps to separate two related ideas. Open enrollment is the when — the time period during which you can act. The health insurance marketplace is the where — the platform on which individuals shop for and buy ACA plans, often with subsidies. This article focuses on the timing and the decisions; if you want a deeper look at the platform itself, our marketplace guide covers that ground.

How Open Enrollment Works

Open enrollment exists because health insurance operates on an annual cycle. Insurers set premiums and plan designs each year based on projected costs for the covered population. Allowing people to sign up only during a defined window helps prevent adverse selection — the scenario where people wait until they are sick to buy coverage, which would drive premiums up for everyone.

During open enrollment, you can enroll in a health plan for the first time, switch from one plan to another (even a different insurer), change your coverage level (individual to family, or vice versa), add or remove dependents, and drop coverage. Outside of open enrollment, changes are generally permitted only if you experience a qualifying life event — such as marriage, divorce, the birth of a child, loss of other coverage, moving to a new area, or certain changes in household income that affect subsidy eligibility.

There are several distinct open enrollment periods that affect different groups: the federal and state health insurance marketplace open enrollment, employer-sponsored open enrollment, and — for those 65 and older or otherwise eligible — Medicare’s Annual Enrollment Period. The dates and rules differ, so knowing which one applies to you is the first step.

Marketplace Open Enrollment Dates

For plans sold through the Affordable Care Act marketplace (HealthCare.gov or a state-run exchange), open enrollment generally runs from about November 1 through January 15 for the following year’s coverage. Based on the current HealthCare.gov schedule, you typically must enroll by December 15 for coverage that starts January 1; enrolling between mid-December and January 15 usually means coverage begins February 1. Dates can vary by state, and states that run their own exchanges — including California (Covered California), New York, Colorado, Massachusetts, and others — sometimes use different or extended windows. Because deadlines shift and states differ, always confirm the current dates on HealthCare.gov or your state exchange before you rely on them.

Marketplace enrollment has grown substantially in recent years. During the 2025 open enrollment period, a record number of people — more than 24 million, according to the Centers for Medicare & Medicaid Services — selected marketplace coverage. Enrollment figures for later years depend heavily on premiums and subsidy policy, which is why the next section matters so much for 2026 and beyond.

If you miss marketplace open enrollment, you generally cannot enroll until the next year unless you qualify for a Special Enrollment Period (SEP). Common qualifying events include losing employer-sponsored coverage, getting married or divorced, having a baby, moving to a new coverage area, or experiencing a significant change in household income. Medicaid and the Children’s Health Insurance Program (CHIP), by contrast, accept enrollment year-round — there is no open enrollment restriction for those programs.

A 2026 Watch Item: Enhanced Premium Subsidies

One policy question looms over recent and upcoming open enrollment seasons: the enhanced premium tax credits that have lowered marketplace premiums since 2021. These enhanced subsidies were scheduled to expire after the 2025 plan year unless Congress extended them. Whether they are extended, allowed to lapse, or modified directly affects how much you pay, and if they phase down, many enrollees could see noticeably higher net premiums.

Because this is an active and changing policy area, do not assume last year’s subsidy amount will carry over. Before you choose a plan, log in to HealthCare.gov or your state exchange, update your household and income information, and look at your actual current-year premium after any credits — not a prior year’s figure. If your subsidy has changed, a plan that was affordable last year may not be this year, and a different plan may now be the better value. Our healthcare policy guide tracks how these rules fit into the broader system.

Employer Open Enrollment

If you get health insurance through your job, your employer sets its own open enrollment period — usually two to four weeks, often in the fall, though the exact dates vary by company. Most employers align their plan year with the calendar year (a January 1 start), but some use a fiscal year or another schedule. HR departments typically announce open enrollment dates several weeks in advance, along with plan options and any cost changes for the coming year.

During employer open enrollment, review any changes to premiums, deductibles, copays, and coinsurance from the current year. Employers often adjust their offerings annually, and the cheapest option last year may not be the cheapest this year. Check whether your doctors and preferred hospitals remain in-network, especially if your employer is switching insurance carriers. If a high-deductible health plan (HDHP) with a health savings account (HSA) is offered, evaluate whether it fits your situation — particularly if your employer contributes to the HSA.

A common and costly mistake is doing nothing during open enrollment. Many employer plans auto-renew your current selection if you take no action, but not all do — some require active enrollment each year, and failing to act can leave you without coverage. Even when auto-renewal applies, skipping the review means you may miss a better plan, a new HSA contribution, or changes that make your current plan more expensive. According to a SHRM survey, many employees spend very little time reviewing their benefits during open enrollment — often less than half an hour — which is rarely enough to make a well-informed choice.

Medicare’s Annual Enrollment Period

If you are on Medicare, you have your own yearly window. Medicare’s Annual Enrollment Period (also called the Annual Election Period, or AEP) runs each year from October 15 through December 7, with changes generally taking effect January 1. During AEP you can switch between Original Medicare and Medicare Advantage, change Medicare Advantage or Part D prescription drug plans, and make other adjustments. Medicare Advantage also has a separate Open Enrollment Period early in the year (generally January 1 through March 31) that allows certain changes. Confirm current dates and rules at Medicare.gov, since Medicare’s windows are separate from the ACA marketplace and employer schedules.

What to Look for During Open Enrollment

Choosing a health plan is more than comparing monthly premiums. The lowest premium is not always the cheapest plan once you factor in deductibles, copays, coinsurance, and your expected healthcare usage. Here is a framework for evaluating your options.

Start by estimating your total annual cost: 12 months of premiums (after any subsidy) plus expected out-of-pocket spending based on your typical healthcare use. If you take a maintenance medication, check each plan’s formulary to see whether it is covered and at what tier. If you have a preferred doctor or hospital, verify they are in-network under each plan you are considering. Compare the out-of-pocket maximums — that figure is your worst-case exposure in a year with a major medical event.

Do not overlook plan-type differences. HMOs generally require referrals and limit you to in-network providers but often have lower premiums. PPOs offer broader network access and no referral requirements but usually cost more. EPOs blend elements of both. HDHPs pair lower premiums with HSA eligibility. The right answer depends on how you use healthcare — a healthy 28-year-old and a 55-year-old managing multiple chronic conditions should approach the decision very differently.

Special Enrollment Periods: What Qualifies

Life does not always align with open enrollment windows. The ACA created Special Enrollment Periods (SEPs) to allow marketplace enrollment outside the standard window when certain life events occur. According to HealthCare.gov, qualifying events include:

• Losing health coverage (job loss, aging off a parent’s plan, COBRA expiration)
• Getting married or divorced
• Having a baby or adopting a child
• Moving to a new state or county with different plan options
• Gaining citizenship or lawful presence
• Leaving incarceration
• Significant income changes affecting subsidy eligibility

Most SEPs give you 60 days from the qualifying event to enroll. You will typically need to provide documentation — a termination letter, marriage certificate, or birth certificate, for example. Do not wait until the 60-day window is nearly closed; processing delays can cause gaps in coverage if you enroll at the last minute. Employer-sponsored plans also offer SEPs for similar life events, usually with a 30-day enrollment window, so check your HR deadlines quickly.

Common Open Enrollment Mistakes

The biggest mistake is not participating at all. But even active participants make errors that cost them. Choosing the cheapest premium without calculating total cost of care is the most common — a low-premium plan with a very high deductible can be far more expensive than a higher-premium plan with a low deductible if you use healthcare regularly. Run the numbers for your own expected usage rather than defaulting to the smallest monthly payment.

Failing to check provider networks is another frequent error. Plans change their networks annually, and a doctor who was in-network last year may not be this year. Similarly, people forget to review prescription drug formularies — your medication might move to a higher (more expensive) tier or be dropped entirely. Not updating your household information (income, dependents) on the marketplace can result in the wrong subsidy amount, which can lead to a tax surprise when you reconcile your premium tax credit on your federal return.

Finally, overlooking ancillary benefits like dental, vision, life insurance, and disability coverage during open enrollment can mean missing the only chance to enroll in or change these benefits until the next year. Many employers bundle these with medical enrollment, and it is easy to skip them when you are focused solely on health insurance premiums.

Frequently Asked Questions

What happens if I miss open enrollment?

If you miss employer open enrollment, you are generally stuck with your current plan (or no coverage) until the next enrollment period, unless you experience a qualifying life event. If you miss marketplace open enrollment, you cannot buy an ACA plan until the following year’s window unless you qualify for a Special Enrollment Period. Medicaid and CHIP enrollment remain available year-round.

Can I change my health insurance plan outside of open enrollment?

Only if you experience a qualifying life event — such as marriage, birth of a child, job loss, or a move to a new coverage area. These events trigger a Special Enrollment Period, typically 30 to 60 days, during which you can enroll in or change plans. Without a qualifying event, you generally must wait until the next open enrollment.

Is open enrollment the same as the ACA marketplace?

Not exactly. Open enrollment is the time period during which you can enroll. The ACA marketplace is the platform where you shop for and buy individual health insurance plans, often with subsidies. Employer-sponsored plans and Medicare also have their own enrollment windows, separate from the marketplace. The term “open enrollment” applies across all of these contexts, which is why it helps to identify which one is relevant to you.

Do I have to re-enroll every year?

On the marketplace, your plan generally auto-renews if you take no action, but your subsidy amount can change based on updated income data, plan pricing, and current subsidy rules. Actively re-enrolling helps ensure you get the best available plan and an accurate subsidy. For employer plans, policies vary — some auto-renew while others require active enrollment each year. Check with your HR department.

What to Do Next

Mark your calendar for open enrollment — your employer’s window, the marketplace dates if applicable, and Medicare’s AEP if you are eligible. Gather your current plan documents, review last year’s medical expenses, and list any expected changes (new medications, planned procedures, changes in dependents). Compare at least three plan options on total annual cost, not just premiums. If you are shopping on the marketplace, update your income information to get an accurate, current subsidy estimate — especially given ongoing changes to enhanced subsidies. And if you have already missed this year’s window, check whether a qualifying life event gives you access to a Special Enrollment Period. The decision you make during these few weeks affects your healthcare costs and access for the entire year ahead — it is worth the time to get it right.

Sources

• HealthCare.gov — Open Enrollment dates and deadlines; Special Enrollment Period glossary (healthcare.gov)
• Centers for Medicare & Medicaid Services — Marketplace enrollment reports (cms.gov)
• Medicare.gov — Medicare Annual Enrollment Period and Open Enrollment Period (medicare.gov)
• Internal Revenue Service — Premium Tax Credit (irs.gov)
• SHRM — employee benefits and open enrollment survey data (shrm.org)