you can buy a plan on the marketplace but evaluate this decision very carefully. employer health insurance is tax advantaged meaning you receive the benefit without having to pay taxes on its value. if you buy your own coverage you'll lose that as well as whatever portion of your coverage your employer helps pay for (most employers cover 70%-80% of employees' health benefit costs). that's all to say yes you can leave your employer's plan and buy your own coverage but in most cases it's not in your best financial interest to do so. just tread carefully. and you won't be able to make any changes outside of open enrollment unless there's some big event like a job loss.
if i'm dissatisfied with my employer's health insurance over 400% poverty can i leave my plan to sign up under aca? . are there penalties for leaving an insurer outside of enrollment periods or a life changing event?