The window is 60 days and it is strict
A qualifying life event gives you 60 days to enroll outside Open Enrollment. It is a hard edge, not a guideline, and it does not reopen because you were busy. The single most useful thing in this article is this: the day the event happens, put a reminder in your phone for two weeks later, not for day 59.
Losing coverage is the common one
A job ending, a plan ending, ageing off a parent's policy at 26, a divorce that ends your access to a spouse's plan, or the end of COBRA when it runs out on its own. Note that voluntarily dropping COBRA, or being dropped for not paying it, does not qualify. Neither does choosing to end a plan you could have kept.
Apply before, not after
For a loss of coverage you can usually apply up to 60 days before it happens. This is much better than waiting. Applying early lets you set the new coverage to begin the day after the old plan ends, with no gap. Applying after the fact often means a start date at the beginning of the following month, and a stretch of weeks uninsured.
The other events
Marriage. The birth or adoption of a child, or placement in foster care. A permanent move to an area with different plans available, provided you had coverage for at least one of the previous 60 days. Gaining citizenship or lawfully present status. Leaving incarceration. Certain income changes that alter your eligibility for help. There are also errors and exceptional-circumstance cases the Marketplace can grant.
What does not qualify
Getting sick. Pregnancy on its own, in most cases, although the birth itself does qualify. Missing Open Enrollment. Deciding your current plan is too expensive. These are the conversations we least enjoy having, and they are the reason we would rather field an unnecessary call in November than a necessary one in March.
Have the proof ready
The Marketplace usually asks for documentation and will hold your enrollment until it arrives. A termination letter from the previous carrier for a loss of coverage. A lease, deed or utility bill for a move. A marriage certificate or a birth certificate. Knowing which document will be accepted before you go looking saves the most common delay we see.