Getting married, having a baby, adopting a child, or a death in the family that causes a loss of coverage.

Gaining U.S. citizenship, leaving incarceration, or changes in income that affect your subsidy eligibility.

This includes losing job-based insurance (even if you quit or were fired), turning 26 and "aging out" of a parent's plan, or losing Medicaid/CHIP eligibility.

Special Enrollment Period - the Health Insurance Marketplace

The Calendar Closed, But the Door Isn't: Buying Health Insurance After Open Enrollment