Involuntary loss of coverage is a qualifying event that triggers a special enrollment period. If you lose your plan, you’ll have a chance to enroll in a new plan, either on or off the exchange in your state.
The effective date is the date your insurance coverage commences. In most cases, this will always be the first of a future month, although a newborn baby or newly adopted child can have coverage retroactive to the date of birth or adoption.
In most cases, employer-sponsored coverage will be effective the first of the month following your enrollment, or the first of the coming plan year if you enroll or make a plan change during your employer’s open enrollment period.
If you enroll through your marketplace your coverage effective date mostly depends on whether you're enrolling during open enrollment or a special enrollment period.