Short answer: Open enrollment is the once-a-year window when you can enroll in or change your coverage. A special enrollment period (SEP) lets you enroll outside that window after a qualifying life event, such as marriage, a new baby, or losing other coverage, usually within 30 days (employer plans) or 60 days (the Marketplace).
Open enrollment is the annual period when employees can join the health plan, drop it, switch options, or add/remove dependents. Outside that window, your elections are generally locked in for the plan year.
A special enrollment period (SEP) is the exception. Federal HIPAA special-enrollment rules and the ACA let you make changes mid-year after a qualifying life event, including:
- Marriage, divorce, or legal separation
- Birth, adoption, or placement for adoption of a child
- Loss of other coverage (for example, a spouse’s job loss, or aging off a parent’s plan)
- A court order requiring coverage of a dependent
Timing matters: employer plans typically give you 30 days from the event to act, while the Health Insurance Marketplace generally gives 60 days. Be ready to document the event (a marriage certificate, birth record, or loss-of-coverage letter).
Sources
- HIPAA special enrollment rights, 29 CFR §2590.701-6; CMS, HealthCare.gov (special enrollment periods).
Content history
Originally published: June 16, 2026
Last reviewed: June 16, 2026