When Can I Buy Health Insurance: Open Enrollment, SEPs, Medicare

You can buy health insurance whenever you have an open window, and the window depends on where you’re getting your coverage. For most people shopping on their own, open enrollment on HealthCare.gov runs from November 1 through January 15.¹ Outside that window, you generally need a qualifying life event to enroll in a marketplace plan. Employer plans, Medicare, Medicaid, and CHIP each run on their own calendars, and some of those calendars never close.

Marketplace Open Enrollment: November 1 to January 15

Open Enrollment is the annual window when anyone can sign up for, renew, or change a plan through the federal marketplace or a state-based exchange. On HealthCare.gov, the window runs November 1 through January 15.¹ Some states that operate their own exchanges set slightly different dates, so check your state’s marketplace if you don’t use HealthCare.gov.

When your coverage starts depends on when you enroll. Pick a plan by December 15 and coverage begins January 1. Enroll between December 16 and January 15 and coverage starts February 1.¹ That gap matters if you take ongoing prescriptions or have a procedure scheduled in January.

One thing to know about pricing in the current window: premium tax credits are still available for households between 100% and 400% of the federal poverty level.² The enhanced subsidies that removed the 400% income cap from 2021 through 2025 expired at the start of 2026, so the ceiling is back in place.

Buying Outside Open Enrollment: Special Enrollment Periods

If you miss Open Enrollment, you can still buy a marketplace plan when a qualifying life event opens a Special Enrollment Period. The common triggers are losing existing coverage, moving to a new area, getting married, having a baby, or adopting a child.³ Less obvious events also qualify: gaining a dependent through a court order, being a survivor of domestic violence who needs a separate plan, or being affected by a natural disaster in a FEMA-designated area.⁴

You typically have 60 days from the event to enroll.⁵ Miss that deadline and you’ll usually wait until the next Open Enrollment. The marketplace will ask for documentation such as a coverage termination letter or proof of your new address before confirming enrollment.

Start dates vary by event. If you’re losing employer coverage, you can line up a new plan so it begins the day after your old one ends. For newborns and adopted children, coverage applies retroactively to the date of birth or placement, so the child is covered from day one even if you take a few weeks to enroll.⁵

Buying Coverage After a Job Loss

Losing a job with health benefits gives you a choice: continue your employer plan through COBRA, buy a marketplace plan through your Special Enrollment Period, or use one as a bridge to the other.

COBRA lets you stay on your former employer’s group plan for up to 18 months after a job loss or reduction in hours. Spouses and dependents who lose coverage due to events like divorce or a worker’s death can keep COBRA for up to 36 months. The catch is cost: you pay the full premium plus a 2% administrative fee, for a total of up to 102% of the plan’s cost.⁶ That’s often hundreds of dollars more per month than what you paid as an employee.

Losing job-based coverage also qualifies you for a 60-day marketplace Special Enrollment Period. If your income now qualifies you for premium tax credits, a marketplace plan may be substantially cheaper than COBRA. Here is where people get tripped up: if you elect COBRA and then drop it early without another qualifying event, you generally cannot enroll in a marketplace plan until the next Open Enrollment. Exhausting the full COBRA term does trigger a new Special Enrollment Period; voluntarily canceling early does not.⁶

Enrolling Through an Employer

Most workers with job-based insurance can only enroll or make changes during their company’s annual enrollment window, which employers typically schedule in the fall for coverage starting January 1. The exact dates are set by each employer, not by federal law, so they vary.

New hires get a separate enrollment window. Federal regulations prohibit employer plans from imposing a waiting period longer than 90 days before coverage begins.⁷ In practice, most employers start coverage within 30 to 60 days. Some plans also require minimum weekly hours for eligibility.

Outside annual enrollment, employer plans must let you make changes when you experience certain life events. Under federal law, you have 30 days after getting married, having a baby, adopting a child, or losing other coverage to request changes through your employer. That window is tighter than the marketplace’s 60-day window, so act quickly. If you or a dependent loses Medicaid or CHIP eligibility, the federal deadline is 60 days.⁸

Medicare Has Its Own Calendar

Medicare runs on a separate schedule from the marketplace, and getting the timing right matters because late enrollment carries permanent premium penalties.

Initial Enrollment Period

When you first become eligible for Medicare, usually at age 65, you get a seven-month Initial Enrollment Period. It starts three months before your 65th birthday month, includes your birthday month, and runs three months after.⁹ Enrolling in the three months before your birthday month gives you coverage starting on the first day of your birthday month. Waiting until the months after delays your start date.

General Enrollment Period

If you miss your Initial Enrollment Period, you can sign up for Medicare Part A and Part B during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage begins the month after you enroll.⁹

Medicare Advantage and Part D

Medicare Advantage (Part C) and prescription drug plans (Part D) have their own annual window: October 15 through December 7. Changes take effect January 1 of the following year.¹⁰ During this period you can join, switch, or drop a Medicare Advantage or drug plan. Certain life events, such as moving or losing employer coverage, may also open a Medicare Special Enrollment Period outside this window.

Late Enrollment Penalties

Delaying Medicare enrollment without qualifying coverage elsewhere triggers penalties that permanently increase your premiums. For Part B, the penalty is an extra 10% of the standard monthly premium ($202.90 in 2026) for each full 12-month period you could have had Part B but didn’t sign up. Someone who delays two years would pay an extra $40.58 per month on top of the standard premium, and that surcharge continues for as long as they have Part B.¹¹

Part D carries a similar penalty: 1% of the national base beneficiary premium ($38.99 in 2026) for each month you went without creditable drug coverage. Going without drug coverage for two years produces a penalty of roughly $9.36 per month, added to your plan premium indefinitely.¹¹ If you have creditable drug coverage through an employer or union, you’re exempt as long as you enroll in Part D within 63 days of losing that coverage.

Part A penalties apply only to people who must pay a Part A premium; most people qualify for premium-free Part A through work history.

Medicaid and CHIP: Any Time of Year

Medicaid and the Children’s Health Insurance Program have no enrollment season. You can apply any time, and if you qualify, coverage can begin immediately.¹² Eligibility is based on household income and varies by state. In states that expanded Medicaid under the Affordable Care Act, adults generally qualify with income up to 138% of the federal poverty level, about $22,024 for a single person in 2026.¹³ States that haven’t expanded Medicaid have much narrower eligibility, often limited to very low-income parents, pregnant women, and people with disabilities.

CHIP covers children in families that earn too much for Medicaid but can’t afford private insurance. Income limits are higher than Medicaid and vary by state. If you apply for marketplace coverage and the application flags possible Medicaid or CHIP eligibility, your information gets forwarded to your state agency for a determination. Applying costs nothing and can be done any time.¹²

Short-Term Plans as a Stopgap

Short-term health plans are sold year-round and don’t require a qualifying life event. They’re designed as temporary coverage between jobs or while you wait for other benefits to begin. These plans are not regulated under the Affordable Care Act, so they can deny applicants based on health history, exclude pre-existing conditions, skip services like maternity or mental health care, and impose annual or lifetime benefit caps.

Federal rules finalized in 2024 limited short-term plans to an initial term of three months and a maximum of four months including renewals. Federal agencies announced in August 2025 that they will not prioritize enforcement of those limits while new rulemaking is underway, expected to conclude in 2026. The effective duration now depends on what your state allows: some states cap short-term plans at three or six months, others permit terms up to a year with renewal, and a few ban them outright.

Premiums are lower than ACA-compliant coverage, but the tradeoff is real. If you develop a serious illness or need surgery, a short-term plan’s exclusions and benefit caps can leave you with tens of thousands of dollars in bills. These plans also don’t count as minimum essential coverage, so they won’t shield you from late enrollment penalties for programs like Medicare Part D. Use one as a stopgap, not a substitute.

1
HealthCare.gov. When Can You Get Health Insurance?
2
Internal Revenue Service. Eligibility for the Premium Tax Credit
3
HealthCare.gov. Special Enrollment Period
4
HealthCare.gov. Special Enrollment Periods for Complex Issues
5
HealthCare.gov. Getting Health Coverage Outside Open Enrollment
6
U.S. Department of Labor. FAQs on COBRA Continuation Health Coverage for Workers
7
eCFR. 45 CFR 147.116 – Prohibition on Waiting Periods That Exceed 90 Days
8
U.S. Department of Labor. FAQs on HIPAA Portability and Nondiscrimination Requirements for Workers
9
Medicare. When Does Medicare Coverage Start
10
Medicare. Open Enrollment
11
Medicare. Avoid Late Enrollment Penalties
12
HealthCare.gov. Medicaid and CHIP Coverage
13
HealthCare.gov. Federal Poverty Level (FPL)