Outside of Annual Benefits Enrollment, you can only make changes to your medical, dental, and vision plans, or your health care or day care flexible spending accounts, if you experience a Qualified Event, such as:
You get married, divorced, or begin or end a domestic partnership.
You have a baby or adopt a child.
Your spouse loses or gains employment.
The Health Plans Overview chapter of the Benefits Book contains a table listing all Qualified Events and the changes you may make as a result of each event. Changes must be consistent with the event. In addition, see the same chapter for HIPAA Special Enrollment rights.